code:
#include "config.h"
#include "local-store.hh"
#include "globals.hh"
#include "archive.hh"
#include "pathlocks.hh"
#include "worker-protocol.hh"
#include "derivations.hh"
#include "affinity.hh"

#include <iostream>
#include <algorithm>
#include <cstring>

#include <sys/types.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <unistd.h>
#include <utime.h>
#include <fcntl.h>
#include <errno.h>
#include <stdio.h>
#include <time.h>
#include <grp.h>
#include <ctype.h>

#if HAVE_UNSHARE && HAVE_STATVFS && HAVE_SYS_MOUNT_H
#include <sched.h>
#include <sys/statvfs.h>
#include <sys/mount.h>
#endif

#include <sys/ioctl.h>
#include <errno.h>

#include <sqlite3.h>

namespace nix {

void checkStoreNotSymlink()
{
    if (getEnv("NIX_IGNORE_SYMLINK_STORE") == "1") return;
    Path path = settings.nixStore;
    struct stat st;
    while (path != "/") {
        if (lstat(path.c_str(), &st))
            throw SysError(format("getting status of `%1%'") % path);
        if (S_ISLNK(st.st_mode))
            throw Error(format(
                "the path `%1%' is a symlink; "
                "this is not allowed for the store and its parent directories")
                % path);
        path = dirOf(path);
    }
}

LocalStore::LocalStore(bool reserveSpace)
{
    schemaPath = settings.nixDBPath + "/schema";

    if (settings.readOnlyMode) {
        openDB(false);
        return;
    }

    /* Create missing state directories if they don't already exist. */
    createDirs(settings.nixStore);
    makeStoreWritable();
    createDirs(linksDir = settings.nixStore + "/.links");
    Path profilesDir = settings.nixStateDir + "/profiles";
    createDirs(profilesDir);
    createDirs(settings.nixStateDir + "/temproots");
    createDirs(settings.nixDBPath);
    Path gcRootsDir = settings.nixStateDir + "/gcroots";
    if (!pathExists(gcRootsDir)) {
        createDirs(gcRootsDir);
        createSymlink(profilesDir, gcRootsDir + "/profiles");
    }

    /* Optionally, create directories and set permissions for a
       multi-user install. */
    if (getuid() == 0 && settings.buildUsersGroup != "") {

        Path perUserDir = profilesDir + "/per-user";
        createDirs(perUserDir);
        if (chmod(perUserDir.c_str(), 0755) == -1)
            throw SysError(format("could not set permissions on '%1%' to 755")
                           % perUserDir);

        mode_t perm = 01775;

        struct group * gr = getgrnam(settings.buildUsersGroup.c_str());
        if (!gr)
            throw Error(format("the group `%1%' specified in `build-users-group' does not exist")
                % settings.buildUsersGroup);
        else {
            struct stat st;
            if (stat(settings.nixStore.c_str(), &st))
                throw SysError(format("getting attributes of path '%1%'") % settings.nixStore);

            if (st.st_uid != 0 || st.st_gid != gr->gr_gid || (st.st_mode & ~S_IFMT) != perm) {
                if (chown(settings.nixStore.c_str(), 0, gr->gr_gid) == -1)
                    throw SysError(format("changing ownership of path '%1%'") % settings.nixStore);
                if (chmod(settings.nixStore.c_str(), perm) == -1)
                    throw SysError(format("changing permissions on path '%1%'") % settings.nixStore);
            }
        }
    }

    checkStoreNotSymlink();

    /* We can't open a SQLite database if the disk is full.  Since
       this prevents the garbage collector from running when it's most
       needed, we reserve some dummy space that we can free just
       before doing a garbage collection. */
    try {
        Path reservedPath = settings.nixDBPath + "/reserved";
        if (reserveSpace) {
            struct stat st;
            if (stat(reservedPath.c_str(), &st) == -1 ||
                st.st_size != settings.reservedSize)
            {
                AutoCloseFD fd = open(reservedPath.c_str(), O_WRONLY | O_CREAT, 0600);
                int res = -1;
#if HAVE_POSIX_FALLOCATE
                res = posix_fallocate(fd, 0, settings.reservedSize);
#endif
                if (res == -1) {
                    writeFull(fd, string(settings.reservedSize, 'X'));
                    ftruncate(fd, settings.reservedSize);
                }
            }
        }
        else
            deletePath(reservedPath);
    } catch (SysError & e) { /* don't care about errors */
    }

    /* Acquire the big fat lock in shared mode to make sure that no
       schema upgrade is in progress. */
    try {
        Path globalLockPath = settings.nixDBPath + "/big-lock";
        globalLock = openLockFile(globalLockPath.c_str(), true);
    } catch (SysError & e) {
        if (e.errNo != EACCES) throw;
        settings.readOnlyMode = true;
        openDB(false);
        return;
    }

    if (!lockFile(globalLock, ltRead, false)) {
        printMsg(lvlError, "waiting for the big store lock...");
        lockFile(globalLock, ltRead, true);
    }

    /* Check the current database schema and if necessary do an
       upgrade.  */
    int curSchema = getSchema();
    if (curSchema > nixSchemaVersion)
        throw Error(format("current store schema is version %1%, but I only support %2%")
            % curSchema % nixSchemaVersion);

    else if (curSchema == 0) { /* new store */
        curSchema = nixSchemaVersion;
        openDB(true);
        writeFile(schemaPath, (format("%1%") % nixSchemaVersion).str());
    }

    else if (curSchema < nixSchemaVersion) {
	/* Guix always used version 7 of the schema.  */
	throw Error(
	    format("Your store database uses an implausibly old schema, version %1%.")
	    % curSchema);
    }

    else openDB(false);
}

LocalStore::~LocalStore()
{
    try {
        if (fdTempRoots != -1) {
            fdTempRoots.close();
            unlink(fnTempRoots.c_str());
        }
    } catch (...) {
        ignoreException();
    }
}

int LocalStore::getSchema()
{
    int curSchema = 0;
    if (pathExists(schemaPath)) {
        string s = readFile(schemaPath);
        if (!string2Int(s, curSchema))
            throw Error(format("`%1%' is corrupt") % schemaPath);
    }
    return curSchema;
}

void LocalStore::openDB(bool create)
{
    if (access(settings.nixDBPath.c_str(), R_OK | W_OK))
        throw SysError(format("store database directory `%1%' is not writable") % settings.nixDBPath);

    /* Open the store database. */
    string dbPath = settings.nixDBPath + "/db.sqlite";
    if (sqlite3_open_v2(dbPath.c_str(), &db.db,
            SQLITE_OPEN_READWRITE | (create ? SQLITE_OPEN_CREATE : 0), 0) != SQLITE_OK)
        throw Error(format("cannot open store database `%1%'") % dbPath);

    if (sqlite3_busy_timeout(db, 60 * 60 * 1000) != SQLITE_OK)
        throwSQLiteError(db, "setting timeout");

    if (sqlite3_exec(db, "pragma foreign_keys = 1;", 0, 0, 0) != SQLITE_OK)
        throwSQLiteError(db, "enabling foreign keys");

    /* !!! check whether sqlite has been built with foreign key
       support */

    /* Whether SQLite should fsync().  "Normal" synchronous mode
       should be safe enough.  If the user asks for it, don't sync at
       all.  This can cause database corruption if the system
       crashes. */
    string syncMode = settings.fsyncMetadata ? "normal" : "off";
    if (sqlite3_exec(db, ("pragma synchronous = " + syncMode + ";").c_str(), 0, 0, 0) != SQLITE_OK)
        throwSQLiteError(db, "setting synchronous mode");

    /* Set the SQLite journal mode.  WAL mode is fastest, so it's the
       default. */
    string mode = settings.useSQLiteWAL ? "wal" : "truncate";
    string prevMode;
    {
        SQLiteStmt stmt;
        stmt.create(db, "pragma main.journal_mode;");
        if (sqlite3_step(stmt) != SQLITE_ROW)
            throwSQLiteError(db, "querying journal mode");
        prevMode = string((const char *) sqlite3_column_text(stmt, 0));
    }
    if (prevMode != mode &&
        sqlite3_exec(db, ("pragma main.journal_mode = " + mode + ";").c_str(), 0, 0, 0) != SQLITE_OK)
        throwSQLiteError(db, "setting journal mode");

    /* Increase the auto-checkpoint interval to 40000 pages.  This
       seems enough to ensure that instantiating the NixOS system
       derivation is done in a single fsync(). */
    if (mode == "wal" && sqlite3_exec(db, "pragma wal_autocheckpoint = 40000;", 0, 0, 0) != SQLITE_OK)
        throwSQLiteError(db, "setting autocheckpoint interval");

    /* Initialise the database schema, if necessary. */
    if (create) {
        const char * schema =
#include "schema.sql.hh"
            ;
        if (sqlite3_exec(db, (const char *) schema, 0, 0, 0) != SQLITE_OK)
            throwSQLiteError(db, "initialising database schema");
    }

    /* Prepare SQL statements. */
    stmtRegisterValidPath.create(db,
        "insert into ValidPaths (path, hash, registrationTime, deriver, narSize) values (?, ?, ?, ?, ?);");
    stmtUpdatePathInfo.create(db,
        "update ValidPaths set narSize = ?, hash = ? where path = ?;");
    stmtAddReference.create(db,
        "insert or replace into Refs (referrer, reference) values (?, ?);");
    stmtQueryPathInfo.create(db,
        "select id, hash, registrationTime, deriver, narSize from ValidPaths where path = ?;");
    stmtQueryReferences.create(db,
        "select path from Refs join ValidPaths on reference = id where referrer = ?;");
    stmtQueryReferrers.create(db,
        "select path from Refs join ValidPaths on referrer = id where reference = (select id from ValidPaths where path = ?);");
    stmtInvalidatePath.create(db,
        "delete from ValidPaths where path = ?;");
    stmtRegisterFailedPath.create(db,
        "insert or ignore into FailedPaths (path, time) values (?, ?);");
    stmtHasPathFailed.create(db,
        "select time from FailedPaths where path = ?;");
    stmtQueryFailedPaths.create(db,
        "select path from FailedPaths;");
    // If the path is a derivation, then clear its outputs.
    stmtClearFailedPath.create(db,
        "delete from FailedPaths where ?1 = '*' or path = ?1 "
        "or path in (select d.path from DerivationOutputs d join ValidPaths v on d.drv = v.id where v.path = ?1);");
    stmtAddDerivationOutput.create(db,
        "insert or replace into DerivationOutputs (drv, id, path) values (?, ?, ?);");
    stmtQueryValidDerivers.create(db,
        "select v.id, v.path from DerivationOutputs d join ValidPaths v on d.drv = v.id where d.path = ?;");
    stmtQueryDerivationOutputs.create(db,
        "select id, path from DerivationOutputs where drv = ?;");
    // Use "path >= ?" with limit 1 rather than "path like '?%'" to
    // ensure efficient lookup.
    stmtQueryPathFromHashPart.create(db,
        "select path from ValidPaths where path >= ? limit 1;");
    stmtQueryValidPaths.create(db, "select path from ValidPaths");
}

/* To improve purity, users may want to make the store a read-only
   bind mount.  So make the store writable for this process. */
void LocalStore::makeStoreWritable()
{
#if HAVE_UNSHARE && HAVE_STATVFS && HAVE_SYS_MOUNT_H && defined(MS_BIND) && defined(MS_REMOUNT)
    if (getuid() != 0) return;
    /* Check if /nix/store is on a read-only mount. */
    struct statvfs stat;
    if (statvfs(settings.nixStore.c_str(), &stat) != 0)
        throw SysError("getting info about the store mount point");

    if (stat.f_flag & ST_RDONLY) {
        if (unshare(CLONE_NEWNS) == -1)
            throw SysError("setting up a private mount namespace");

        if (mount(0, settings.nixStore.c_str(), "none", MS_REMOUNT | MS_BIND, 0) == -1)
            throw SysError(format("remounting %1% writable") % settings.nixStore);
    }
#endif
}

const time_t mtimeStore = 1; /* 1 second into the epoch */

static void canonicaliseTimestampAndPermissions(const Path & path, const struct stat & st)
{
    if (!S_ISLNK(st.st_mode)) {

        /* Mask out all type related bits. */
        mode_t mode = st.st_mode & ~S_IFMT;

        if (mode != 0444 && mode != 0555) {
            mode = (st.st_mode & S_IFMT)
                 | 0444
                 | (st.st_mode & S_IXUSR ? 0111 : 0);
            if (chmod(path.c_str(), mode) == -1)
                throw SysError(format("changing mode of `%1%' to %2$o") % path % mode);
        }

    }

    if (st.st_mtime != mtimeStore) {
        struct timeval times[2];
        times[0].tv_sec = st.st_atime;
        times[0].tv_usec = 0;
        times[1].tv_sec = mtimeStore;
        times[1].tv_usec = 0;
#if HAVE_LUTIMES
        if (lutimes(path.c_str(), times) == -1)
            if (errno != ENOSYS ||
                (!S_ISLNK(st.st_mode) && utimes(path.c_str(), times) == -1))
#else
        if (!S_ISLNK(st.st_mode) && utimes(path.c_str(), times) == -1)
#endif
            throw SysError(format("changing modification time of `%1%'") % path);
    }
}

void canonicaliseTimestampAndPermissions(const Path & path)
{
    struct stat st;
    if (lstat(path.c_str(), &st))
        throw SysError(format("getting attributes of path `%1%'") % path);
    canonicaliseTimestampAndPermissions(path, st);
}

static void canonicalisePathMetaData_(const Path & path, uid_t fromUid, InodesSeen & inodesSeen)
{
    checkInterrupt();

    struct stat st;
    if (lstat(path.c_str(), &st))
        throw SysError(format("getting attributes of path `%1%'") % path);

    /* Really make sure that the path is of a supported type. */
    if (!(S_ISREG(st.st_mode) || S_ISDIR(st.st_mode) || S_ISLNK(st.st_mode)))
        throw Error(format("file ‘%1%’ has an unsupported type") % path);

    /* Fail if the file is not owned by the build user.  This prevents
       us from messing up the ownership/permissions of files
       hard-linked into the output (e.g. "ln /etc/shadow $out/foo").
       However, ignore files that we chown'ed ourselves previously to
       ensure that we don't fail on hard links within the same build
       (i.e. "touch $out/foo; ln $out/foo $out/bar"). */
    if (fromUid != (uid_t) -1 && st.st_uid != fromUid) {
        assert(!S_ISDIR(st.st_mode));
        if (inodesSeen.find(Inode(st.st_dev, st.st_ino)) == inodesSeen.end())
            throw BuildError(format("invalid ownership on file `%1%'") % path);
        mode_t mode = st.st_mode & ~S_IFMT;
        assert(S_ISLNK(st.st_mode) || (st.st_uid == geteuid() && (mode == 0444 || mode == 0555) && st.st_mtime == mtimeStore));
        return;
    }

    inodesSeen.insert(Inode(st.st_dev, st.st_ino));

    canonicaliseTimestampAndPermissions(path, st);

    /* Change ownership to the current uid.  If it's a symlink, use
       lchown if available, otherwise don't bother.  Wrong ownership
       of a symlink doesn't matter, since the owning user can't change
       the symlink and can't delete it because the directory is not
       writable.  The only exception is top-level paths in the
       store (since that directory is group-writable for the build
       users group); we check for this case below. */
    if (st.st_uid != geteuid()) {
#if HAVE_LCHOWN
        if (lchown(path.c_str(), geteuid(), getegid()) == -1)
#else
        if (!S_ISLNK(st.st_mode) &&
            chown(path.c_str(), geteuid(), getegid()) == -1)
#endif
            throw SysError(format("changing owner of `%1%' to %2%")
                % path % geteuid());
    }

    if (S_ISDIR(st.st_mode)) {
        DirEntries entries = readDirectory(path);
        for (auto & i : entries)
            canonicalisePathMetaData_(path + "/" + i.name, fromUid, inodesSeen);
    }
}

void canonicalisePathMetaData(const Path & path, uid_t fromUid, InodesSeen & inodesSeen)
{
    canonicalisePathMetaData_(path, fromUid, inodesSeen);

    /* On platforms that don't have lchown(), the top-level path can't
       be a symlink, since we can't change its ownership. */
    struct stat st;
    if (lstat(path.c_str(), &st))
        throw SysError(format("getting attributes of path `%1%'") % path);

    if (st.st_uid != geteuid()) {
        assert(S_ISLNK(st.st_mode));
        throw Error(format("wrong ownership of top-level store path `%1%'") % path);
    }
}

void canonicalisePathMetaData(const Path & path, uid_t fromUid)
{
    InodesSeen inodesSeen;
    canonicalisePathMetaData(path, fromUid, inodesSeen);
}

void LocalStore::checkDerivationOutputs(const Path & drvPath, const Derivation & drv)
{
    string drvName = storePathToName(drvPath);
    assert(isDerivation(drvName));
    drvName = string(drvName, 0, drvName.size() - drvExtension.size());

    if (isFixedOutputDrv(drv)) {
        DerivationOutputs::const_iterator out = drv.outputs.find("out");
        if (out == drv.outputs.end())
            throw Error(format("derivation `%1%' does not have an output named `out'") % drvPath);

        bool recursive; HashType ht; Hash h;
        out->second.parseHashInfo(recursive, ht, h);
        Path outPath = makeFixedOutputPath(recursive, ht, h, drvName);

        StringPairs::const_iterator j = drv.env.find("out");
        if (out->second.path != outPath || j == drv.env.end() || j->second != outPath)
            throw Error(format("derivation `%1%' has incorrect output `%2%', should be `%3%'")
                % drvPath % out->second.path % outPath);
    }

    else {
        Derivation drvCopy(drv);
        foreach (DerivationOutputs::iterator, i, drvCopy.outputs) {
            i->second.path = "";
            drvCopy.env[i->first] = "";
        }

        Hash h = hashDerivationModulo(*this, drvCopy);

        foreach (DerivationOutputs::const_iterator, i, drv.outputs) {
            Path outPath = makeOutputPath(i->first, h, drvName);
            StringPairs::const_iterator j = drv.env.find(i->first);
            if (i->second.path != outPath || j == drv.env.end() || j->second != outPath)
                throw Error(format("derivation `%1%' has incorrect output `%2%', should be `%3%'")
                    % drvPath % i->second.path % outPath);
        }
    }
}

uint64_t LocalStore::addValidPath(const ValidPathInfo & info, bool checkOutputs)
{
    stmtRegisterValidPath.use()
        (info.path)
        ("sha256:" + printHash(info.hash))
        (info.registrationTime == 0 ? time(0) : info.registrationTime)
        (info.deriver, info.deriver != "")
        (info.narSize, info.narSize != 0)
        .exec();
    uint64_t id = sqlite3_last_insert_rowid(db);

    /* If this is a derivation, then store the derivation outputs in
       the database.  This is useful for the garbage collector: it can
       efficiently query whether a path is an output of some
       derivation. */
    if (isDerivation(info.path)) {
        Derivation drv = readDerivation(info.path);

        /* Verify that the output paths in the derivation are correct
           (i.e., follow the scheme for computing output paths from
           derivations).  Note that if this throws an error, then the
           DB transaction is rolled back, so the path validity
           registration above is undone. */
        if (checkOutputs) checkDerivationOutputs(info.path, drv);

        for (auto & i : drv.outputs) {
            stmtAddDerivationOutput.use()
                (id)
                (i.first)
                (i.second.path)
                .exec();
        }
    }

    return id;
}

void LocalStore::addReference(uint64_t referrer, uint64_t reference)
{
    stmtAddReference.use()(referrer)(reference).exec();
}

void LocalStore::registerFailedPath(const Path & path)
{
    retrySQLite<void>([&]() {
        stmtRegisterFailedPath.use()(path)(time(0)).step();
    });
}

bool LocalStore::hasPathFailed(const Path & path)
{
    return retrySQLite<bool>([&]() {
        return stmtHasPathFailed.use()(path).next();
    });
}

PathSet LocalStore::queryFailedPaths()
{
    return retrySQLite<PathSet>([&]() {
        auto useQueryFailedPaths(stmtQueryFailedPaths.use());

        PathSet res;
        while (useQueryFailedPaths.next())
            res.insert(useQueryFailedPaths.getStr(0));

        return res;
    });
}

void LocalStore::clearFailedPaths(const PathSet & paths)
{
    retrySQLite<void>([&]() {
        SQLiteTxn txn(db);

        for (auto & path : paths)
            stmtClearFailedPath.use()(path).exec();

        txn.commit();
    });
}

Hash parseHashField(const Path & path, const string & s)
{
    string::size_type colon = s.find(':');
    if (colon == string::npos)
        throw Error(format("corrupt hash `%1%' in valid-path entry for `%2%'")
            % s % path);
    HashType ht = parseHashType(string(s, 0, colon));
    if (ht == htUnknown)
        throw Error(format("unknown hash type `%1%' in valid-path entry for `%2%'")
            % string(s, 0, colon) % path);
    return parseHash(ht, string(s, colon + 1));
}

ValidPathInfo LocalStore::queryPathInfo(const Path & path)
{
    ValidPathInfo info;
    info.path = path;

    assertStorePath(path);

    return retrySQLite<ValidPathInfo>([&]() {

        /* Get the path info. */
        auto useQueryPathInfo(stmtQueryPathInfo.use()(path));

        if (!useQueryPathInfo.next())
            throw Error(format("path `%1%' is not valid") % path);

        info.id = useQueryPathInfo.getInt(0);

        info.hash = parseHashField(path, useQueryPathInfo.getStr(1));

        info.registrationTime = useQueryPathInfo.getInt(2);

        auto s = (const char *) sqlite3_column_text(stmtQueryPathInfo, 3);
        if (s) info.deriver = s;

        /* Note that narSize = NULL yields 0. */
        info.narSize = useQueryPathInfo.getInt(4);

        /* Get the references. */
        auto useQueryReferences(stmtQueryReferences.use()(info.id));

        while (useQueryReferences.next())
            info.references.insert(useQueryReferences.getStr(0));

        return info;
    });
}

/* Update path info in the database.  Currently only updates the
   narSize field. */
void LocalStore::updatePathInfo(const ValidPathInfo & info)
{
    stmtUpdatePathInfo.use()
        (info.narSize, info.narSize != 0)
        ("sha256:" + printHash(info.hash))
        (info.path)
        .exec();
}

uint64_t LocalStore::queryValidPathId(const Path & path)
{
    auto use(stmtQueryPathInfo.use()(path));
    if (!use.next())
        throw Error(format("path ‘%1%’ is not valid") % path);
    return use.getInt(0);
}

bool LocalStore::isValidPath_(const Path & path)
{
    return stmtQueryPathInfo.use()(path).next();
}

bool LocalStore::isValidPath(const Path & path)
{
    return retrySQLite<bool>([&]() {
        return isValidPath_(path);
    });
}

PathSet LocalStore::queryValidPaths(const PathSet & paths)
{
    return retrySQLite<PathSet>([&]() {
        PathSet res;
        foreach (PathSet::const_iterator, i, paths)
            if (isValidPath_(*i)) res.insert(*i);
        return res;
    });
}

PathSet LocalStore::queryAllValidPaths()
{
    return retrySQLite<PathSet>([&]() {
        auto use(stmtQueryValidPaths.use());
        PathSet res;
        while (use.next()) res.insert(use.getStr(0));
        return res;
    });
}

void LocalStore::queryReferences(const Path & path,
    PathSet & references)
{
    ValidPathInfo info = queryPathInfo(path);
    references.insert(info.references.begin(), info.references.end());
}

void LocalStore::queryReferrers_(const Path & path, PathSet & referrers)
{
    auto useQueryReferrers(stmtQueryReferrers.use()(path));

    while (useQueryReferrers.next())
        referrers.insert(useQueryReferrers.getStr(0));
}

void LocalStore::queryReferrers(const Path & path, PathSet & referrers)
{
    assertStorePath(path);
    return retrySQLite<void>([&]() {
        queryReferrers_(path, referrers);
    });
}

Path LocalStore::queryDeriver(const Path & path)
{
    return queryPathInfo(path).deriver;
}

PathSet LocalStore::queryValidDerivers(const Path & path)
{
    assertStorePath(path);

    return retrySQLite<PathSet>([&]() {
        auto useQueryValidDerivers(stmtQueryValidDerivers.use()(path));

        PathSet derivers;
        while (useQueryValidDerivers.next())
            derivers.insert(useQueryValidDerivers.getStr(1));

        return derivers;
    });
}

PathSet LocalStore::queryDerivationOutputs(const Path & path)
{
    return retrySQLite<PathSet>([&]() {
        auto useQueryDerivationOutputs(stmtQueryDerivationOutputs.use()(queryValidPathId(path)));

        PathSet outputs;
        while (useQueryDerivationOutputs.next())
            outputs.insert(useQueryDerivationOutputs.getStr(1));

        return outputs;
    });
}

StringSet LocalStore::queryDerivationOutputNames(const Path & path)
{
    return retrySQLite<StringSet>([&]() {
        auto useQueryDerivationOutputs(stmtQueryDerivationOutputs.use()(queryValidPathId(path)));

        StringSet outputNames;
        while (useQueryDerivationOutputs.next())
            outputNames.insert(useQueryDerivationOutputs.getStr(0));

        return outputNames;
    });
}

Path LocalStore::queryPathFromHashPart(const string & hashPart)
{
    if (hashPart.size() != 32) throw Error("invalid hash part");

    Path prefix = settings.nixStore + "/" + hashPart;

    return retrySQLite<Path>([&]() -> Path {
        auto useQueryPathFromHashPart(stmtQueryPathFromHashPart.use()(prefix));

        if (!useQueryPathFromHashPart.next()) return "";

        const char * s = (const char *) sqlite3_column_text(stmtQueryPathFromHashPart, 0);
        return s && prefix.compare(0, prefix.size(), s, prefix.size()) == 0 ? s : "";
    });
}

/* Read a line from the substituter's reply file descriptor, while also
   processing its stderr. */
string LocalStore::getLineFromSubstituter(Agent & run)
{
    string res, err;

    while (1) {
        checkInterrupt();

        fd_set fds;
        FD_ZERO(&fds);
        FD_SET(run.fromAgent.readSide, &fds);
        FD_SET(run.builderOut.readSide, &fds);

        /* Wait for data to appear on the substituter's stdout or
           stderr. */
        if (select(std::max(run.fromAgent.readSide, run.builderOut.readSide) + 1, &fds, 0, 0, 0) == -1) {
            if (errno == EINTR) continue;
            throw SysError("waiting for input from the substituter");
        }

        /* Completely drain stderr before dealing with stdout. */
        if (FD_ISSET(run.fromAgent.readSide, &fds)) {
            char buf[4096];
            ssize_t n = read(run.fromAgent.readSide, (unsigned char *) buf, sizeof(buf));
            if (n == -1) {
                if (errno == EINTR) continue;
                throw SysError("reading from substituter's stderr");
            }
            if (n == 0) throw EndOfFile(format("`%1% substitute' died unexpectedly")
					% settings.guixProgram);
            err.append(buf, n);
            string::size_type p;
            while (((p = err.find('\n')) != string::npos)
		   || ((p = err.find('\r')) != string::npos)) {
	        string thing(err, 0, p + 1);
	        writeToStderr("substitute: " + thing);
                err = string(err, p + 1);
            }
        }

        /* Read from stdout until we get a newline or the buffer is empty. */
        else if (FD_ISSET(run.builderOut.readSide, &fds)) {
	    unsigned char c;
	    readFull(run.builderOut.readSide, (unsigned char *) &c, 1);
	    if (c == '\n') {
		if (!err.empty()) printMsg(lvlError, "substitute: " + err);
		return res;
	    }
	    res += c;
        }
    }
}

template<class T> T LocalStore::getIntLineFromSubstituter(Agent & run)
{
    string s = getLineFromSubstituter(run);
    T res;
    if (!string2Int(s, res)) throw Error("integer expected from stream");
    return res;
}

PathSet LocalStore::querySubstitutablePaths(const PathSet & paths)
{
    PathSet res;

    if (!settings.useSubstitutes || paths.empty()) return res;

    Agent & run = *substituter();

    string s = "have ";
    foreach (PathSet::const_iterator, j, paths)
	if (res.find(*j) == res.end()) { s += *j; s += " "; }
    writeLine(run.toAgent.writeSide, s);
    while (true) {
	/* FIXME: we only read stderr when an error occurs, so
	   substituters should only write (short) messages to
	   stderr when they fail.  I.e. they shouldn't write debug
	   output. */
	Path path = getLineFromSubstituter(run);
	if (path == "") break;
	res.insert(path);
    }

    return res;
}

std::shared_ptr<Agent> LocalStore::substituter()
{
    if (!runningSubstituter) {
	const Strings args = { "substitute", "--query" };
	const std::map<string, string> env = { { "_NIX_OPTIONS", settings.pack() } };
	runningSubstituter = std::make_shared<Agent>(settings.guixProgram, args, env);
    }

    return runningSubstituter;
}

void LocalStore::querySubstitutablePathInfos(PathSet & paths, SubstitutablePathInfos & infos)
{
    if (!settings.useSubstitutes) return;

    Agent & run = *substituter();

    string s = "info ";
    foreach (PathSet::const_iterator, i, paths)
        if (infos.find(*i) == infos.end()) { s += *i; s += " "; }
    writeLine(run.toAgent.writeSide, s);

    while (true) {
        Path path = getLineFromSubstituter(run);
        if (path == "") break;
        if (paths.find(path) == paths.end())
            throw Error(format("got unexpected path `%1%' from substituter") % path);
        paths.erase(path);
        SubstitutablePathInfo & info(infos[path]);
        info.deriver = getLineFromSubstituter(run);
        if (info.deriver != "") assertStorePath(info.deriver);
        int nrRefs = getIntLineFromSubstituter<int>(run);
        while (nrRefs--) {
            Path p = getLineFromSubstituter(run);
            assertStorePath(p);
            info.references.insert(p);
        }
        info.downloadSize = getIntLineFromSubstituter<long long>(run);
        info.narSize = getIntLineFromSubstituter<long long>(run);
    }
}

void LocalStore::querySubstitutablePathInfos(const PathSet & paths,
    SubstitutablePathInfos & infos)
{
    if (!paths.empty()) {
	PathSet todo = paths;
	querySubstitutablePathInfos(todo, infos);
    }
}

Hash LocalStore::queryPathHash(const Path & path)
{
    return queryPathInfo(path).hash;
}

void LocalStore::registerValidPath(const ValidPathInfo & info)
{
    ValidPathInfos infos;
    infos.push_back(info);
    registerValidPaths(infos);
}

void LocalStore::registerValidPaths(const ValidPathInfos & infos)
{
    /* SQLite will fsync by default, but the new valid paths may not be fsync-ed.
     * So some may want to fsync them before registering the validity, at the
     * expense of some speed of the path registering operation. */
    if (settings.syncBeforeRegistering) sync();

    return retrySQLite<void>([&]() {
        SQLiteTxn txn(db);
        PathSet paths;

        foreach (ValidPathInfos::const_iterator, i, infos) {
            assert(i->hash.type == htSHA256);
            if (isValidPath_(i->path))
                updatePathInfo(*i);
            else
                addValidPath(*i, false);
            paths.insert(i->path);
        }

        for (auto & i : infos) {
            auto referrer = queryValidPathId(i.path);
            for (auto & j : i.references)
                addReference(referrer, queryValidPathId(j));
        }

        /* Check that the derivation outputs are correct.  We can't do
           this in addValidPath() above, because the references might
           not be valid yet. */
        foreach (ValidPathInfos::const_iterator, i, infos)
            if (isDerivation(i->path)) {
                // FIXME: inefficient; we already loaded the
                // derivation in addValidPath().
                Derivation drv = readDerivation(i->path);
                checkDerivationOutputs(i->path, drv);
            }

        /* Do a topological sort of the paths.  This will throw an
           error if a cycle is detected and roll back the
           transaction.  Cycles can only occur when a derivation
           has multiple outputs. */
        topoSortPaths(*this, paths);

        txn.commit();
    });
}

/* Invalidate a path.  The caller is responsible for checking that
   there are no referrers. */
void LocalStore::invalidatePath(const Path & path)
{
    debug(format("invalidating path `%1%'") % path);

    drvHashes.erase(path);

    stmtInvalidatePath.use()(path).exec();

    /* Note that the foreign key constraints on the Refs table take
       care of deleting the references entries for `path'. */
}

Path LocalStore::addToStoreFromDump(const string & dump, const string & name,
    bool recursive, HashType hashAlgo, bool repair)
{
    Hash h = hashString(hashAlgo, dump);

    Path dstPath = makeFixedOutputPath(recursive, hashAlgo, h, name);

    addTempRoot(dstPath);

    if (repair || !isValidPath(dstPath)) {

        /* The first check above is an optimisation to prevent
           unnecessary lock acquisition. */

        PathLocks outputLock(singleton<PathSet, Path>(dstPath));

        if (repair || !isValidPath(dstPath)) {

            if (pathExists(dstPath)) deletePath(dstPath);

            if (recursive) {
                StringSource source(dump);
                restorePath(dstPath, source);
            } else
                writeFile(dstPath, dump);

            canonicalisePathMetaData(dstPath, -1);

            /* Register the SHA-256 hash of the NAR serialisation of
               the path in the database.  We may just have computed it
               above (if called with recursive == true and hashAlgo ==
               sha256); otherwise, compute it here. */
            HashResult hash;
            if (recursive) {
                hash.first = hashAlgo == htSHA256 ? h : hashString(htSHA256, dump);
                hash.second = dump.size();
            } else
                hash = hashPath(htSHA256, dstPath);

            optimisePath(dstPath); // FIXME: combine with hashPath()

            ValidPathInfo info;
            info.path = dstPath;
            info.hash = hash.first;
            info.narSize = hash.second;
            registerValidPath(info);
        }

        outputLock.setDeletion(true);
    }

    return dstPath;
}

Path LocalStore::addToStore(const string & name, const Path & _srcPath,
    bool recursive, HashType hashAlgo, PathFilter & filter, bool repair)
{
    Path srcPath(absPath(_srcPath));
    debug(format("adding `%1%' to the store") % srcPath);

    /* Read the whole path into memory. This is not a very scalable
       method for very large paths, but `copyPath' is mainly used for
       small files. */
    StringSink sink;
    if (recursive)
        dumpPath(srcPath, sink, filter);
    else
        sink.s = readFile(srcPath);

    return addToStoreFromDump(sink.s, name, recursive, hashAlgo, repair);
}

Path LocalStore::addTextToStore(const string & name, const string & s,
    const PathSet & references, bool repair)
{
    Path dstPath = computeStorePathForText(name, s, references);

    addTempRoot(dstPath);

    if (repair || !isValidPath(dstPath)) {

        PathLocks outputLock(singleton<PathSet, Path>(dstPath));

        if (repair || !isValidPath(dstPath)) {

            if (pathExists(dstPath)) deletePath(dstPath);

            writeFile(dstPath, s);

            canonicalisePathMetaData(dstPath, -1);

            HashResult hash = hashPath(htSHA256, dstPath);

            optimisePath(dstPath);

            ValidPathInfo info;
            info.path = dstPath;
            info.hash = hash.first;
            info.narSize = hash.second;
            info.references = references;
            registerValidPath(info);
        }

        outputLock.setDeletion(true);
    }

    return dstPath;
}

struct HashAndWriteSink : Sink
{
    Sink & writeSink;
    HashSink hashSink;
    HashAndWriteSink(Sink & writeSink) : writeSink(writeSink), hashSink(htSHA256)
    {
    }
    virtual void operator () (const unsigned char * data, size_t len)
    {
        writeSink(data, len);
        hashSink(data, len);
    }
    Hash currentHash()
    {
        return hashSink.currentHash().first;
    }
};

#define EXPORT_MAGIC 0x4558494e

static void checkSecrecy(const Path & path)
{
    struct stat st;
    if (stat(path.c_str(), &st))
        throw SysError(format("getting status of `%1%'") % path);
    if ((st.st_mode & (S_IRWXG | S_IRWXO)) != 0)
        throw Error(format("file `%1%' should be secret (inaccessible to everybody else)!") % path);
}

/* Return the authentication agent, a "guix authenticate" process started
   lazily.  */
static std::shared_ptr<Agent> authenticationAgent()
{
    static std::shared_ptr<Agent> agent;

    if (!agent) {
	Strings args = { "authenticate" };
	agent = std::make_shared<Agent>(settings.guixProgram, args);
    }

    return agent;
}

/* Read an integer and the byte that immediately follows it from FD.  Return
   the integer.  */
static int readInteger(int fd)
{
    string str;

    while (1) {
        char ch;
        ssize_t rd = read(fd, &ch, 1);
        if (rd == -1) {
            if (errno != EINTR)
                throw SysError("reading an integer");
        } else if (rd == 0)
            throw EndOfFile("unexpected EOF reading an integer");
        else {
	    if (isdigit(ch)) {
		str += ch;
	    } else {
		break;
	    }
        }
    }

    return stoi(str);
}

/* Read from FD a reply coming from 'guix authenticate'.  The reply has the
   form "CODE LEN:STR".  CODE is an integer, where zero indicates success.
   LEN specifies the length in bytes of the string that immediately
   follows.  */
static std::string readAuthenticateReply(int fd)
{
    int code = readInteger(fd);
    int len = readInteger(fd);

    string str;
    str.resize(len);
    readFull(fd, (unsigned char *) &str[0], len);

    if (code == 0)
	return str;
    else
	throw Error(str);
}

/* Sign HASH with the key stored in file SECRETKEY.  Return the signature as a
   string, or raise an exception upon error.  */
static std::string signHash(const string &secretKey, const Hash &hash)
{
    auto agent = authenticationAgent();
    auto hexHash = printHash(hash);

    writeLine(agent->toAgent.writeSide,
	      (format("sign %1%:%2% %3%:%4%")
	       % secretKey.size() % secretKey
	       % hexHash.size() % hexHash).str());

    return readAuthenticateReply(agent->fromAgent.readSide);
}

/* Verify SIGNATURE and return the base16-encoded hash over which it was
   computed.  */
static std::string verifySignature(const string &signature)
{
    auto agent = authenticationAgent();

    writeLine(agent->toAgent.writeSide,
	      (format("verify %1%:%2%")
	       % signature.size() % signature).str());

    return readAuthenticateReply(agent->fromAgent.readSide);
}

void LocalStore::exportPath(const Path & path, bool sign,
    Sink & sink)
{
    assertStorePath(path);

    printMsg(lvlInfo, format("exporting path `%1%'") % path);

    if (!isValidPath(path))
        throw Error(format("path `%1%' is not valid") % path);

    HashAndWriteSink hashAndWriteSink(sink);

    dumpPath(path, hashAndWriteSink);

    /* Refuse to export paths that have changed.  This prevents
       filesystem corruption from spreading to other machines.
       Don't complain if the stored hash is zero (unknown). */
    Hash hash = hashAndWriteSink.currentHash();
    Hash storedHash = queryPathHash(path);
    if (hash != storedHash && storedHash != Hash(storedHash.type))
        throw Error(format("hash of path `%1%' has changed from `%2%' to `%3%'!") % path
            % printHash(storedHash) % printHash(hash));

    writeInt(EXPORT_MAGIC, hashAndWriteSink);

    writeString(path, hashAndWriteSink);

    PathSet references;
    queryReferences(path, references);
    writeStrings(references, hashAndWriteSink);

    Path deriver = queryDeriver(path);
    writeString(deriver, hashAndWriteSink);

    if (sign) {
        Hash hash = hashAndWriteSink.currentHash();

        writeInt(1, hashAndWriteSink);

        Path secretKey = settings.nixConfDir + "/signing-key.sec";
        checkSecrecy(secretKey);

	string signature = signHash(secretKey, hash);

        writeString(signature, hashAndWriteSink);

    } else
        writeInt(0, hashAndWriteSink);
}

struct HashAndReadSource : Source
{
    Source & readSource;
    HashSink hashSink;
    bool hashing;
    HashAndReadSource(Source & readSource) : readSource(readSource), hashSink(htSHA256)
    {
        hashing = true;
    }
    size_t read(unsigned char * data, size_t len)
    {
        size_t n = readSource.read(data, len);
        if (hashing) hashSink(data, n);
        return n;
    }
};

/* Create a temporary directory in the store that won't be
   garbage-collected. */
Path LocalStore::createTempDirInStore()
{
    Path tmpDir;
    do {
        /* There is a slight possibility that `tmpDir' gets deleted by
           the GC between createTempDir() and addTempRoot(), so repeat
           until `tmpDir' exists. */
        tmpDir = createTempDir(settings.nixStore);
        addTempRoot(tmpDir);
    } while (!pathExists(tmpDir));
    return tmpDir;
}

Path LocalStore::importPath(bool requireSignature, Source & source)
{
    HashAndReadSource hashAndReadSource(source);

    /* We don't yet know what store path this archive contains (the
       store path follows the archive data proper), and besides, we
       don't know yet whether the signature is valid. */
    Path tmpDir = createTempDirInStore();
    AutoDelete delTmp(tmpDir);
    Path unpacked = tmpDir + "/unpacked";

    restorePath(unpacked, hashAndReadSource);

    unsigned int magic = readInt(hashAndReadSource);
    if (magic != EXPORT_MAGIC)
        throw Error("normalized archive cannot be imported; wrong format");

    Path dstPath = readStorePath(hashAndReadSource);

    PathSet references = readStorePaths<PathSet>(hashAndReadSource);

    Path deriver = readString(hashAndReadSource);
    if (deriver != "") assertStorePath(deriver);

    Hash hash = hashAndReadSource.hashSink.finish().first;
    hashAndReadSource.hashing = false;

    bool haveSignature = readInt(hashAndReadSource) == 1;

    if (requireSignature && !haveSignature)
        throw Error(format("imported archive of `%1%' lacks a signature") % dstPath);

    if (haveSignature) {
        string signature = readString(hashAndReadSource);

        if (requireSignature) {
	    string hash2 = verifySignature(signature);

            /* Note: runProgram() throws an exception if the signature
               is invalid. */

            if (printHash(hash) != hash2)
                throw Error(
                    "signed hash doesn't match actual contents of imported "
                    "archive; archive could be corrupt, or someone is trying "
                    "to import a Trojan horse");
        }
    }

    /* Do the actual import. */

    /* !!! way too much code duplication with addTextToStore() etc. */
    addTempRoot(dstPath);

    if (!isValidPath(dstPath)) {

        PathLocks outputLock;

        /* Lock the output path.  But don't lock if we're being called
           from a build hook (whose parent process already acquired a
           lock on this path). */
        Strings locksHeld = tokenizeString<Strings>(getEnv("NIX_HELD_LOCKS"));
        if (find(locksHeld.begin(), locksHeld.end(), dstPath) == locksHeld.end())
            outputLock.lockPaths(singleton<PathSet, Path>(dstPath));

        if (!isValidPath(dstPath)) {

            if (pathExists(dstPath)) deletePath(dstPath);

            if (rename(unpacked.c_str(), dstPath.c_str()) == -1)
                throw SysError(format("cannot move `%1%' to `%2%'")
                    % unpacked % dstPath);

            canonicalisePathMetaData(dstPath, -1);

            /* !!! if we were clever, we could prevent the hashPath()
               here. */
            HashResult hash = hashPath(htSHA256, dstPath);

            optimisePath(dstPath); // FIXME: combine with hashPath()

            ValidPathInfo info;
            info.path = dstPath;
            info.hash = hash.first;
            info.narSize = hash.second;
            info.references = references;
            info.deriver = deriver != "" && isValidPath(deriver) ? deriver : "";
            registerValidPath(info);
        }

        outputLock.setDeletion(true);
    }

    return dstPath;
}

Paths LocalStore::importPaths(bool requireSignature, Source & source)
{
    Paths res;
    while (true) {
        unsigned long long n = readLongLong(source);
        if (n == 0) break;
        if (n != 1) throw Error("input doesn't look like something created by `nix-store --export'");
        res.push_back(importPath(requireSignature, source));
    }
    return res;
}

void LocalStore::invalidatePathChecked(const Path & path)
{
    assertStorePath(path);

    retrySQLite<void>([&]() {
        SQLiteTxn txn(db);

        if (isValidPath_(path)) {
            PathSet referrers; queryReferrers_(path, referrers);
            referrers.erase(path); /* ignore self-references */
            if (!referrers.empty())
                throw PathInUse(format("cannot delete path `%1%' because it is in use by %2%")
                    % path % showPaths(referrers));
            invalidatePath(path);
        }

        txn.commit();
    });
}

bool LocalStore::verifyStore(bool checkContents, bool repair)
{
    printMsg(lvlError, format("reading the store..."));

    bool errors = false;

    /* Acquire the global GC lock to prevent a garbage collection. */
    AutoCloseFD fdGCLock = openGCLock(ltWrite);

    PathSet store;
    for (auto & i : readDirectory(settings.nixStore)) store.insert(i.name);

    /* Check whether all valid paths actually exist. */
    printMsg(lvlInfo, "checking path existence...");

    PathSet validPaths2 = queryAllValidPaths(), validPaths, done;

    foreach (PathSet::iterator, i, validPaths2)
        verifyPath(*i, store, done, validPaths, repair, errors);

    /* Release the GC lock so that checking content hashes (which can
       take ages) doesn't block the GC or builds. */
    fdGCLock.close();

    /* Optionally, check the content hashes (slow). */
    if (checkContents) {
        printMsg(lvlInfo, "checking hashes...");

        Hash nullHash(htSHA256);

        foreach (PathSet::iterator, i, validPaths) {
            try {
                ValidPathInfo info = queryPathInfo(*i);

                /* Check the content hash (optionally - slow). */
                printMsg(lvlTalkative, format("checking contents of `%1%'") % *i);
                HashResult current = hashPath(info.hash.type, *i);

                if (info.hash != nullHash && info.hash != current.first) {
                    printMsg(lvlError, format("path `%1%' was modified! "
                            "expected hash `%2%', got `%3%'")
                        % *i % printHash(info.hash) % printHash(current.first));
                    if (repair) repairPath(*i); else errors = true;
                } else {

                    bool update = false;

                    /* Fill in missing hashes. */
                    if (info.hash == nullHash) {
                        printMsg(lvlError, format("fixing missing hash on `%1%'") % *i);
                        info.hash = current.first;
                        update = true;
                    }

                    /* Fill in missing narSize fields (from old stores). */
                    if (info.narSize == 0) {
                        printMsg(lvlError, format("updating size field on `%1%' to %2%") % *i % current.second);
                        info.narSize = current.second;
                        update = true;
                    }

                    if (update) updatePathInfo(info);

                }

            } catch (Error & e) {
                /* It's possible that the path got GC'ed, so ignore
                   errors on invalid paths. */
                if (isValidPath(*i))
                    printMsg(lvlError, format("error: %1%") % e.msg());
                else
                    printMsg(lvlError, format("warning: %1%") % e.msg());
                errors = true;
            }
        }
    }

    return errors;
}

void LocalStore::verifyPath(const Path & path, const PathSet & store,
    PathSet & done, PathSet & validPaths, bool repair, bool & errors)
{
    checkInterrupt();

    if (done.find(path) != done.end()) return;
    done.insert(path);

    if (!isStorePath(path)) {
        printMsg(lvlError, format("path `%1%' is not in the store") % path);
        invalidatePath(path);
        return;
    }

    if (store.find(baseNameOf(path)) == store.end()) {
        /* Check any referrers first.  If we can invalidate them
           first, then we can invalidate this path as well. */
        bool canInvalidate = true;
        PathSet referrers; queryReferrers(path, referrers);
        foreach (PathSet::iterator, i, referrers)
            if (*i != path) {
                verifyPath(*i, store, done, validPaths, repair, errors);
                if (validPaths.find(*i) != validPaths.end())
                    canInvalidate = false;
            }

        if (canInvalidate) {
            printMsg(lvlError, format("path `%1%' disappeared, removing from database...") % path);
            invalidatePath(path);
        } else {
            printMsg(lvlError, format("path `%1%' disappeared, but it still has valid referrers!") % path);
            if (repair)
                try {
                    repairPath(path);
                } catch (Error & e) {
                    printMsg(lvlError, format("warning: %1%") % e.msg());
                    errors = true;
                }
            else errors = true;
        }

        return;
    }

    validPaths.insert(path);
}

bool LocalStore::pathContentsGood(const Path & path)
{
    std::map<Path, bool>::iterator i = pathContentsGoodCache.find(path);
    if (i != pathContentsGoodCache.end()) return i->second;
    printMsg(lvlInfo, format("checking path `%1%'...") % path);
    ValidPathInfo info = queryPathInfo(path);
    bool res;
    if (!pathExists(path))
        res = false;
    else {
        HashResult current = hashPath(info.hash.type, path);
        Hash nullHash(htSHA256);
        res = info.hash == nullHash || info.hash == current.first;
    }
    pathContentsGoodCache[path] = res;
    if (!res) printMsg(lvlError, format("path `%1%' is corrupted or missing!") % path);
    return res;
}

void LocalStore::markContentsGood(const Path & path)
{
    pathContentsGoodCache[path] = true;
}

void LocalStore::vacuumDB()
{
    if (sqlite3_exec(db, "vacuum;", 0, 0, 0) != SQLITE_OK)
        throwSQLiteError(db, "vacuuming SQLite database");
}

void LocalStore::createUser(const std::string & userName, uid_t userId)
{
    auto dir = settings.nixStateDir + "/profiles/per-user/" + userName;

    createDirs(dir);
    if (chmod(dir.c_str(), 0755) == -1)
	throw SysError(format("changing permissions of directory '%s'") % dir);
    if (chown(dir.c_str(), userId, -1) == -1)
	throw SysError(format("changing owner of directory '%s'") % dir);
}

}


code:
#pragma once

#include "sqlite.hh"
#include <string>
#include <unordered_set>

#include "pathlocks.hh"
#include "store-api.hh"
#include "util.hh"

namespace nix {

/* Nix store and database schema version.  Version 1 (or 0) was Nix <=
   0.7.  Version 2 was Nix 0.8 and 0.9.  Version 3 is Nix 0.10.
   Version 4 is Nix 0.11.  Version 5 is Nix 0.12-0.16.  Version 6 is
   Nix 1.0.  Version 7 is Nix 1.3.  Guix has always used version 7.  */
const int nixSchemaVersion = 7;

extern string drvsLogDir;

struct Derivation;

struct OptimiseStats
{
    unsigned long filesLinked;
    unsigned long long bytesFreed;
    unsigned long long blocksFreed;
    OptimiseStats()
    {
        filesLinked = 0;
        bytesFreed = blocksFreed = 0;
    }
};

class LocalStore : public StoreAPI
{
private:
    /* The currently running substituter or empty.  */
    std::shared_ptr<Agent> runningSubstituter;

    /* Ensure the substituter is running and return it.  */
    std::shared_ptr<Agent> substituter();

    Path linksDir;

public:

    /* Initialise the local store, upgrading the schema if
       necessary. */
    LocalStore(bool reserveSpace = true);

    ~LocalStore();

    /* Implementations of abstract store API methods. */

    bool isValidPath(const Path & path);

    PathSet queryValidPaths(const PathSet & paths);

    PathSet queryAllValidPaths();

    ValidPathInfo queryPathInfo(const Path & path);

    Hash queryPathHash(const Path & path);

    void queryReferences(const Path & path, PathSet & references);

    void queryReferrers(const Path & path, PathSet & referrers);

    Path queryDeriver(const Path & path);

    PathSet queryValidDerivers(const Path & path);

    PathSet queryDerivationOutputs(const Path & path);

    StringSet queryDerivationOutputNames(const Path & path);

    Path queryPathFromHashPart(const string & hashPart);

    PathSet querySubstitutablePaths(const PathSet & paths);

    void querySubstitutablePathInfos(PathSet & paths,
        SubstitutablePathInfos & infos);

    void querySubstitutablePathInfos(const PathSet & paths,
        SubstitutablePathInfos & infos);

    Path addToStore(const string & name, const Path & srcPath,
        bool recursive = true, HashType hashAlgo = htSHA256,
        PathFilter & filter = defaultPathFilter, bool repair = false);

    /* Like addToStore(), but the contents of the path are contained
       in `dump', which is either a NAR serialisation (if recursive ==
       true) or simply the contents of a regular file (if recursive ==
       false). */
    Path addToStoreFromDump(const string & dump, const string & name,
        bool recursive = true, HashType hashAlgo = htSHA256, bool repair = false);

    Path addTextToStore(const string & name, const string & s,
        const PathSet & references, bool repair = false);

    void exportPath(const Path & path, bool sign,
        Sink & sink);

    Paths importPaths(bool requireSignature, Source & source);

    void buildPaths(const PathSet & paths, BuildMode buildMode);

    void ensurePath(const Path & path);

    void addTempRoot(const Path & path);

    void addIndirectRoot(const Path & path);

    void syncWithGC();

    Roots findRoots();

    void collectGarbage(const GCOptions & options, GCResults & results);

    /* Optimise the disk space usage of the Nix store by hard-linking
       files with the same contents. */
    void optimiseStore(OptimiseStats & stats);

    /* Generic variant of the above method.  */
    void optimiseStore();

    /* Optimise a single store path. */
    void optimisePath(const Path & path);

    /* Check the integrity of the Nix store.  Returns true if errors
       remain. */
    bool verifyStore(bool checkContents, bool repair);

    /* Register the validity of a path, i.e., that `path' exists, that
       the paths referenced by it exists, and in the case of an output
       path of a derivation, that it has been produced by a successful
       execution of the derivation (or something equivalent).  Also
       register the hash of the file system contents of the path.  The
       hash must be a SHA-256 hash. */
    void registerValidPath(const ValidPathInfo & info);

    void registerValidPaths(const ValidPathInfos & infos);

    /* Register that the build of a derivation with output `path' has
       failed. */
    void registerFailedPath(const Path & path);

    /* Query whether `path' previously failed to build. */
    bool hasPathFailed(const Path & path);

    PathSet queryFailedPaths();

    void clearFailedPaths(const PathSet & paths);

    void vacuumDB();

    /* Repair the contents of the given path by redownloading it using
       a substituter (if available). */
    void repairPath(const Path & path);

    /* Check whether the given valid path exists and has the right
       contents. */
    bool pathContentsGood(const Path & path);

    void markContentsGood(const Path & path);

    void createUser(const std::string & userName, uid_t userId);

private:

    Path schemaPath;

    /* Lock file used for upgrading. */
    AutoCloseFD globalLock;

    /* The SQLite database object. */
    SQLite db;

    /* Some precompiled SQLite statements. */
    SQLiteStmt stmtRegisterValidPath;
    SQLiteStmt stmtUpdatePathInfo;
    SQLiteStmt stmtAddReference;
    SQLiteStmt stmtQueryPathInfo;
    SQLiteStmt stmtQueryReferences;
    SQLiteStmt stmtQueryReferrers;
    SQLiteStmt stmtInvalidatePath;
    SQLiteStmt stmtRegisterFailedPath;
    SQLiteStmt stmtHasPathFailed;
    SQLiteStmt stmtQueryFailedPaths;
    SQLiteStmt stmtClearFailedPath;
    SQLiteStmt stmtAddDerivationOutput;
    SQLiteStmt stmtQueryValidDerivers;
    SQLiteStmt stmtQueryDerivationOutputs;
    SQLiteStmt stmtQueryPathFromHashPart;
    SQLiteStmt stmtQueryValidPaths;

    /* Cache for pathContentsGood(). */
    std::map<Path, bool> pathContentsGoodCache;

    /* The file to which we write our temporary roots. */
    Path fnTempRoots;
    AutoCloseFD fdTempRoots;

    int getSchema();

    void openDB(bool create);

    void makeStoreWritable();

    uint64_t queryValidPathId(const Path & path);

    uint64_t addValidPath(const ValidPathInfo & info, bool checkOutputs = true);

    void addReference(uint64_t referrer, uint64_t reference);

    void appendReferrer(const Path & from, const Path & to, bool lock);

    void rewriteReferrers(const Path & path, bool purge, PathSet referrers);

    void invalidatePath(const Path & path);

    /* Delete a path from the Nix store. */
    void invalidatePathChecked(const Path & path);

    void verifyPath(const Path & path, const PathSet & store,
        PathSet & done, PathSet & validPaths, bool repair, bool & errors);

    void updatePathInfo(const ValidPathInfo & info);

    struct GCState;

    void deleteGarbage(GCState & state, const Path & path);

    void tryToDelete(GCState & state, const Path & path);

    bool canReachRoot(GCState & state, PathSet & visited, const Path & path);

    void deletePathRecursive(GCState & state, const Path & path);

    bool isActiveTempFile(const GCState & state,
        const Path & path, const string & suffix);

    int openGCLock(LockType lockType);

    void removeUnusedLinks(const GCState & state);

    string getLineFromSubstituter(Agent & run);

    template<class T> T getIntLineFromSubstituter(Agent & run);

    Path createTempDirInStore();

    Path importPath(bool requireSignature, Source & source);

    void checkDerivationOutputs(const Path & drvPath, const Derivation & drv);

    typedef std::unordered_set<ino_t> InodeHash;

    InodeHash loadInodeHash();
    Strings readDirectoryIgnoringInodes(const Path & path, const InodeHash & inodeHash);
    void optimisePath_(OptimiseStats & stats, const Path & path, InodeHash & inodeHash);

    // Internal versions that are not wrapped in retry_sqlite.
    bool isValidPath_(const Path & path);
    void queryReferrers_(const Path & path, PathSet & referrers);
};

typedef std::pair<dev_t, ino_t> Inode;
typedef set<Inode> InodesSeen;

/* "Fix", or canonicalise, the meta-data of the files in a store path
   after it has been built.  In particular:
   - the last modification date on each file is set to 1 (i.e.,
     00:00:01 1/1/1970 UTC)
   - the permissions are set of 444 or 555 (i.e., read-only with or
     without execute permission; setuid bits etc. are cleared)
   - the owner and group are set to the Nix user and group, if we're
     running as root. */
void canonicalisePathMetaData(const Path & path, uid_t fromUid, InodesSeen & inodesSeen);
void canonicalisePathMetaData(const Path & path, uid_t fromUid);

void canonicaliseTimestampAndPermissions(const Path & path);

MakeError(PathInUse, Error);

}

repo_name: maximed/guix

license: mit


code:
#include "misc.hh"
#include "store-api.hh"
#include "local-store.hh"
#include "globals.hh"

namespace nix {

Derivation derivationFromPath(StoreAPI & store, const Path & drvPath)
{
    assertStorePath(drvPath);
    store.ensurePath(drvPath);
    return readDerivation(drvPath);
}

void computeFSClosure(StoreAPI & store, const Path & path,
    PathSet & paths, bool flipDirection, bool includeOutputs, bool includeDerivers)
{
    if (paths.find(path) != paths.end()) return;
    paths.insert(path);

    PathSet edges;

    if (flipDirection) {
        store.queryReferrers(path, edges);

        if (includeOutputs) {
            PathSet derivers = store.queryValidDerivers(path);
            foreach (PathSet::iterator, i, derivers)
                edges.insert(*i);
        }

        if (includeDerivers && isDerivation(path)) {
            PathSet outputs = store.queryDerivationOutputs(path);
            foreach (PathSet::iterator, i, outputs)
                if (store.isValidPath(*i) && store.queryDeriver(*i) == path)
                    edges.insert(*i);
        }

    } else {
        store.queryReferences(path, edges);

        if (includeOutputs && isDerivation(path)) {
            PathSet outputs = store.queryDerivationOutputs(path);
            foreach (PathSet::iterator, i, outputs)
                if (store.isValidPath(*i)) edges.insert(*i);
        }

        if (includeDerivers) {
            Path deriver = store.queryDeriver(path);
            if (store.isValidPath(deriver)) edges.insert(deriver);
        }
    }

    foreach (PathSet::iterator, i, edges)
        computeFSClosure(store, *i, paths, flipDirection, includeOutputs, includeDerivers);
}

Path findOutput(const Derivation & drv, string id)
{
    foreach (DerivationOutputs::const_iterator, i, drv.outputs)
        if (i->first == id) return i->second.path;
    throw Error(format("derivation has no output `%1%'") % id);
}

static void dfsVisit(StoreAPI & store, const PathSet & paths,
    const Path & path, PathSet & visited, Paths & sorted,
    PathSet & parents)
{
    if (parents.find(path) != parents.end())
        throw BuildError(format("cycle detected in the references of `%1%'") % path);

    if (visited.find(path) != visited.end()) return;
    visited.insert(path);
    parents.insert(path);

    PathSet references;
    if (store.isValidPath(path))
        store.queryReferences(path, references);

    foreach (PathSet::iterator, i, references)
        /* Don't traverse into paths that don't exist.  That can
           happen due to substitutes for non-existent paths. */
        if (*i != path && paths.find(*i) != paths.end())
            dfsVisit(store, paths, *i, visited, sorted, parents);

    sorted.push_front(path);
    parents.erase(path);
}

Paths topoSortPaths(StoreAPI & store, const PathSet & paths)
{
    Paths sorted;
    PathSet visited, parents;
    foreach (PathSet::const_iterator, i, paths)
        dfsVisit(store, paths, *i, visited, sorted, parents);
    return sorted;
}

}


code:
#pragma once

#include "derivations.hh"

namespace nix {

/* Read a derivation, after ensuring its existence through
   ensurePath(). */
Derivation derivationFromPath(StoreAPI & store, const Path & drvPath);

/* Place in `paths' the set of all store paths in the file system
   closure of `storePath'; that is, all paths than can be directly or
   indirectly reached from it.  `paths' is not cleared.  If
   `flipDirection' is true, the set of paths that can reach
   `storePath' is returned; that is, the closures under the
   `referrers' relation instead of the `references' relation is
   returned. */
void computeFSClosure(StoreAPI & store, const Path & path,
    PathSet & paths, bool flipDirection = false,
    bool includeOutputs = false, bool includeDerivers = false);

/* Return the path corresponding to the output identifier `id' in the
   given derivation. */
Path findOutput(const Derivation & drv, string id);

bool willBuildLocally(const Derivation & drv);

bool substitutesAllowed(const Derivation & drv);

}


code:
#include "config.h"

#include "util.hh"
#include "local-store.hh"
#include "globals.hh"

#include <cstdlib>
#include <cstring>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <errno.h>
#include <stdio.h>

namespace nix {

static void makeWritable(const Path & path)
{
    struct stat st;
    if (lstat(path.c_str(), &st))
        throw SysError(format("getting attributes of path `%1%'") % path);
    if (chmod(path.c_str(), st.st_mode | S_IWUSR) == -1)
        throw SysError(format("changing writability of `%1%'") % path);
}

struct MakeReadOnly
{
    Path path;
    MakeReadOnly(const Path & path) : path(path) { }
    ~MakeReadOnly()
    {
        try {
            /* This will make the path read-only. */
            if (path != "") canonicaliseTimestampAndPermissions(path);
        } catch (...) {
            ignoreException();
        }
    }
};

LocalStore::InodeHash LocalStore::loadInodeHash()
{
    printMsg(lvlDebug, "loading hash inodes in memory");
    InodeHash inodeHash;

    AutoCloseDir dir = opendir(linksDir.c_str());
    if (!dir) throw SysError(format("opening directory `%1%'") % linksDir);

    struct dirent * dirent;
    while (errno = 0, dirent = readdir(dir)) { /* sic */
        checkInterrupt();
        // We don't care if we hit non-hash files, anything goes
        inodeHash.insert(dirent->d_ino);
    }
    if (errno) throw SysError(format("reading directory `%1%'") % linksDir);

    printMsg(lvlTalkative, format("loaded %1% hash inodes") % inodeHash.size());

    return inodeHash;
}

Strings LocalStore::readDirectoryIgnoringInodes(const Path & path, const InodeHash & inodeHash)
{
    Strings names;

    AutoCloseDir dir = opendir(path.c_str());
    if (!dir) throw SysError(format("opening directory `%1%'") % path);

    struct dirent * dirent;
    while (errno = 0, dirent = readdir(dir)) { /* sic */
        checkInterrupt();

        if (inodeHash.count(dirent->d_ino)) {
            printMsg(lvlDebug, format("`%1%' is already linked") % dirent->d_name);
            continue;
        }

        string name = dirent->d_name;
        if (name == "." || name == "..") continue;
        names.push_back(name);
    }
    if (errno) throw SysError(format("reading directory `%1%'") % path);

    return names;
}

void LocalStore::optimisePath_(OptimiseStats & stats, const Path & path, InodeHash & inodeHash)
{
    checkInterrupt();

    struct stat st;
    if (lstat(path.c_str(), &st))
        throw SysError(format("getting attributes of path `%1%'") % path);

    if (S_ISDIR(st.st_mode)) {
        Strings names = readDirectoryIgnoringInodes(path, inodeHash);
        foreach (Strings::iterator, i, names)
            optimisePath_(stats, path + "/" + *i, inodeHash);
        return;
    }

    /* We can hard link regular files and maybe symlinks. */
    if (!S_ISREG(st.st_mode)
#if CAN_LINK_SYMLINK
        && !S_ISLNK(st.st_mode)
#endif
        ) return;

    /* Sometimes SNAFUs can cause files in the store to be
       modified, in particular when running programs as root under
       Guix System (example: $fontconfig/var/cache being modified).  Skip
       those files.  FIXME: check the modification time. */
    if (S_ISREG(st.st_mode) && (st.st_mode & S_IWUSR)) {
        printMsg(lvlError, format("skipping suspicious writable file `%1%'") % path);
        return;
    }

    /* This can still happen on top-level files. */
    if (st.st_nlink > 1 && inodeHash.count(st.st_ino)) {
        printMsg(lvlDebug, format("`%1%' is already linked, with %2% other file(s).") % path % (st.st_nlink - 2));
        return;
    }

    /* Hash the file.  Note that hashPath() returns the hash over the
       NAR serialisation, which includes the execute bit on the file.
       Thus, executable and non-executable files with the same
       contents *won't* be linked (which is good because otherwise the
       permissions would be screwed up).

       Also note that if `path' is a symlink, then we're hashing the
       contents of the symlink (i.e. the result of readlink()), not
       the contents of the target (which may not even exist). */
    Hash hash = hashPath(htSHA256, path).first;
    printMsg(lvlDebug, format("`%1%' has hash `%2%'") % path % printHash(hash));

    /* Check if this is a known hash. */
    Path linkPath = linksDir + "/" + printHash32(hash);

 retry:
    if (!pathExists(linkPath)) {
        /* Nope, create a hard link in the links directory. */
        if (link(path.c_str(), linkPath.c_str()) == 0) {
            inodeHash.insert(st.st_ino);
            return;
        }

	switch (errno) {
	case EEXIST:
	    /* Fall through if another process created ‘linkPath’ before
	       we did. */
	    break;

	case ENOSPC:
	    /* On ext4, that probably means the directory index is full.  When
	       that happens, it's fine to ignore it: we just effectively
	       disable deduplication of this file.  */
	    printMsg(lvlInfo, format("cannot link `%1%' to `%2%': %3%")
		     % linkPath % path % strerror(ENOSPC));
	    return;

	default:
            throw SysError(format("cannot link `%1%' to `%2%'") % linkPath % path);
	}
    }

    /* Yes!  We've seen a file with the same contents.  Replace the
       current file with a hard link to that file. */
    struct stat stLink;
    if (lstat(linkPath.c_str(), &stLink))
        throw SysError(format("getting attributes of path `%1%'") % linkPath);

    if (st.st_ino == stLink.st_ino) {
        printMsg(lvlDebug, format("`%1%' is already linked to `%2%'") % path % linkPath);
        return;
    }

    if (st.st_size != stLink.st_size) {
        printMsg(lvlError, format("removing corrupted link ‘%1%’") % linkPath);
        unlink(linkPath.c_str());
        goto retry;
    }

    printMsg(lvlTalkative, format("linking ‘%1%’ to ‘%2%’") % path % linkPath);

    /* Make the containing directory writable, but only if it's not
       the store itself (we don't want or need to mess with its
       permissions). */
    bool mustToggle = !isStorePath(path);
    if (mustToggle) makeWritable(dirOf(path));

    /* When we're done, make the directory read-only again and reset
       its timestamp back to 0. */
    MakeReadOnly makeReadOnly(mustToggle ? dirOf(path) : "");

    Path tempLink = (format("%1%/.tmp-link-%2%-%3%")
        % settings.nixStore % getpid() % rand()).str();

    if (link(linkPath.c_str(), tempLink.c_str()) == -1) {
        if (errno == EMLINK) {
            /* Too many links to the same file (>= 32000 on most file
               systems).  This is likely to happen with empty files.
               Just shrug and ignore. */
            if (st.st_size)
                printMsg(lvlInfo, format("`%1%' has maximum number of links") % linkPath);
            return;
        }
	    throw SysError(format("cannot link `%1%' to `%2%'") % tempLink % linkPath);
	}

    /* Atomically replace the old file with the new hard link. */
    if (rename(tempLink.c_str(), path.c_str()) == -1) {
	int renameErrno = errno;
        if (unlink(tempLink.c_str()) == -1)
            printMsg(lvlError, format("unable to unlink `%1%'") % tempLink);
        if (renameErrno == EMLINK) {
            /* Some filesystems generate too many links on the rename,
               rather than on the original link.  (Probably it
               temporarily increases the st_nlink field before
               decreasing it again.) */
            if (st.st_size)
                printMsg(lvlInfo, format("`%1%' has maximum number of links") % linkPath);
            return;
        }
        throw SysError(format("cannot rename `%1%' to `%2%'") % tempLink % path);
    }

    stats.filesLinked++;
    stats.bytesFreed += st.st_size;
    stats.blocksFreed += st.st_blocks;
}

void LocalStore::optimiseStore(OptimiseStats & stats)
{
    PathSet paths = queryAllValidPaths();
    InodeHash inodeHash = loadInodeHash();

    foreach (PathSet::iterator, i, paths) {
        addTempRoot(*i);
        if (!isValidPath(*i)) continue; /* path was GC'ed, probably */
        startNest(nest, lvlChatty, format("hashing files in `%1%'") % *i);
        optimisePath_(stats, *i, inodeHash);
    }
}

static string showBytes(unsigned long long bytes)
{
    return (format("%.2f MiB") % (bytes / (1024.0 * 1024.0))).str();
}

void LocalStore::optimiseStore()
{
    OptimiseStats stats;

    optimiseStore(stats);

    printMsg(lvlError,
        format("%1% freed by hard-linking %2% files")
        % showBytes(stats.bytesFreed)
        % stats.filesLinked);
}

void LocalStore::optimisePath(const Path & path)
{
    OptimiseStats stats;
    InodeHash inodeHash;

    if (settings.autoOptimiseStore) optimisePath_(stats, path, inodeHash);
}

}


code:
#include "pathlocks.hh"
#include "util.hh"

#include <cerrno>
#include <cstdlib>

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>

namespace nix {

int openLockFile(const Path & path, bool create)
{
    AutoCloseFD fd;

    fd = open(path.c_str(), O_RDWR | (create ? O_CREAT : 0), 0600);
    if (fd == -1 && (create || errno != ENOENT))
        throw SysError(format("opening lock file `%1%'") % path);

    closeOnExec(fd);

    return fd.borrow();
}

void deleteLockFile(const Path & path, int fd)
{
    /* Get rid of the lock file.  Have to be careful not to introduce
       races.  Write a (meaningless) token to the file to indicate to
       other processes waiting on this lock that the lock is stale
       (deleted). */
    unlink(path.c_str());
    writeFull(fd, "d");
    /* Note that the result of unlink() is ignored; removing the lock
       file is an optimisation, not a necessity. */
}

bool lockFile(int fd, LockType lockType, bool wait)
{
    struct flock lock;
    if (lockType == ltRead) lock.l_type = F_RDLCK;
    else if (lockType == ltWrite) lock.l_type = F_WRLCK;
    else if (lockType == ltNone) lock.l_type = F_UNLCK;
    else abort();
    lock.l_whence = SEEK_SET;
    lock.l_start = 0;
    lock.l_len = 0; /* entire file */

    if (wait) {
        while (fcntl(fd, F_SETLKW, &lock) != 0) {
            checkInterrupt();
            if (errno != EINTR)
                throw SysError(format("acquiring/releasing lock"));
        }
    } else {
        while (fcntl(fd, F_SETLK, &lock) != 0) {
            checkInterrupt();
            if (errno == EACCES || errno == EAGAIN) return false;
            if (errno != EINTR)
                throw SysError(format("acquiring/releasing lock"));
        }
    }

    return true;
}

/* This enables us to check whether are not already holding a lock on
   a file ourselves.  POSIX locks (fcntl) suck in this respect: if we
   close a descriptor, the previous lock will be closed as well.  And
   there is no way to query whether we already have a lock (F_GETLK
   only works on locks held by other processes). */
static StringSet lockedPaths; /* !!! not thread-safe */

PathLocks::PathLocks()
    : deletePaths(false)
{
}

PathLocks::PathLocks(const PathSet & paths, const string & waitMsg)
    : deletePaths(false)
{
    lockPaths(paths, waitMsg);
}

bool PathLocks::lockPaths(const PathSet & _paths,
    const string & waitMsg, bool wait)
{
    assert(fds.empty());

    /* Note that `fds' is built incrementally so that the destructor
       will only release those locks that we have already acquired. */

    /* Sort the paths.  This assures that locks are always acquired in
       the same order, thus preventing deadlocks. */
    Paths paths(_paths.begin(), _paths.end());
    paths.sort();

    /* Acquire the lock for each path. */
    foreach (Paths::iterator, i, paths) {
        checkInterrupt();
        Path path = *i;
        Path lockPath = path + ".lock";

        debug(format("locking path `%1%'") % path);

        if (lockedPaths.find(lockPath) != lockedPaths.end())
            throw Error("deadlock: trying to re-acquire self-held lock");

        AutoCloseFD fd;

        while (1) {

            /* Open/create the lock file. */
	    fd = openLockFile(lockPath, true);

            /* Acquire an exclusive lock. */
            if (!lockFile(fd, ltWrite, false)) {
                if (wait) {
                    if (waitMsg != "") printMsg(lvlError, waitMsg);
                    lockFile(fd, ltWrite, true);
                } else {
                    /* Failed to lock this path; release all other
                       locks. */
                    unlock();
                    return false;
                }
            }

            debug(format("lock acquired on `%1%'") % lockPath);

            /* Check that the lock file hasn't become stale (i.e.,
               hasn't been unlinked). */
            struct stat st;
            if (fstat(fd, &st) == -1)
                throw SysError(format("statting lock file `%1%'") % lockPath);
            if (st.st_size != 0)
                /* This lock file has been unlinked, so we're holding
                   a lock on a deleted file.  This means that other
                   processes may create and acquire a lock on
                   `lockPath', and proceed.  So we must retry. */
                debug(format("open lock file `%1%' has become stale") % lockPath);
            else
                break;
        }

        /* Use borrow so that the descriptor isn't closed. */
        fds.push_back(FDPair(fd.borrow(), lockPath));
        lockedPaths.insert(lockPath);
    }

    return true;
}

PathLocks::~PathLocks()
{
    try {
        unlock();
    } catch (...) {
        ignoreException();
    }
}

void PathLocks::unlock()
{
    foreach (list<FDPair>::iterator, i, fds) {
        if (deletePaths) deleteLockFile(i->second, i->first);

        lockedPaths.erase(i->second);
        if (close(i->first) == -1)
            printMsg(lvlError,
                format("error (ignored): cannot close lock file on `%1%'") % i->second);

        debug(format("lock released on `%1%'") % i->second);
    }

    fds.clear();
}

void PathLocks::setDeletion(bool deletePaths)
{
    this->deletePaths = deletePaths;
}

bool pathIsLockedByMe(const Path & path)
{
    Path lockPath = path + ".lock";
    return lockedPaths.find(lockPath) != lockedPaths.end();
}

}


code:
#pragma once

#include "types.hh"

namespace nix {

/* Open (possibly create) a lock file and return the file descriptor.
   -1 is returned if create is false and the lock could not be opened
   because it doesn't exist.  Any other error throws an exception. */
int openLockFile(const Path & path, bool create);

/* Delete an open lock file. */
void deleteLockFile(const Path & path, int fd);

enum LockType { ltRead, ltWrite, ltNone };

bool lockFile(int fd, LockType lockType, bool wait);

class PathLocks
{
private:
    typedef std::pair<int, Path> FDPair;
    list<FDPair> fds;
    bool deletePaths;

public:
    PathLocks();
    PathLocks(const PathSet & paths,
        const string & waitMsg = "");
    bool lockPaths(const PathSet & _paths,
        const string & waitMsg = "",
        bool wait = true);
    ~PathLocks();
    void unlock();
    void setDeletion(bool deletePaths);
};

bool pathIsLockedByMe(const Path & path);

}


code:
#include "references.hh"
#include "hash.hh"
#include "util.hh"
#include "archive.hh"

#include <map>
#include <cstdlib>

namespace nix {

static unsigned int refLength = 32; /* characters */

static void search(const unsigned char * s, unsigned int len,
    StringSet & hashes, StringSet & seen)
{
    static bool initialised = false;
    static bool isBase32[256];
    if (!initialised) {
        for (unsigned int i = 0; i < 256; ++i) isBase32[i] = false;
        for (unsigned int i = 0; i < base32Chars.size(); ++i)
            isBase32[(unsigned char) base32Chars[i]] = true;
        initialised = true;
    }

    for (unsigned int i = 0; i + refLength <= len; ) {
        int j;
        bool match = true;
        for (j = refLength - 1; j >= 0; --j)
            if (!isBase32[(unsigned char) s[i + j]]) {
                i += j + 1;
                match = false;
                break;
            }
        if (!match) continue;
        string ref((const char *) s + i, refLength);
        if (hashes.find(ref) != hashes.end()) {
            debug(format("found reference to `%1%' at offset `%2%'")
                  % ref % i);
            seen.insert(ref);
            hashes.erase(ref);
        }
        ++i;
    }
}

struct RefScanSink : Sink
{
    HashSink hashSink;
    StringSet hashes;
    StringSet seen;

    string tail;

    RefScanSink() : hashSink(htSHA256) { }

    void operator () (const unsigned char * data, size_t len);
};

void RefScanSink::operator () (const unsigned char * data, size_t len)
{
    hashSink(data, len);

    /* It's possible that a reference spans the previous and current
       fragment, so search in the concatenation of the tail of the
       previous fragment and the start of the current fragment. */
    string s = tail + string((const char *) data, len > refLength ? refLength : len);
    search((const unsigned char *) s.data(), s.size(), hashes, seen);

    search(data, len, hashes, seen);

    unsigned int tailLen = len <= refLength ? len : refLength;
    tail =
        string(tail, tail.size() < refLength - tailLen ? 0 : tail.size() - (refLength - tailLen)) +
        string((const char *) data + len - tailLen, tailLen);
}

PathSet scanForReferences(const string & path,
    const PathSet & refs, HashResult & hash)
{
    RefScanSink sink;
    std::map<string, Path> backMap;

    /* For efficiency (and a higher hit rate), just search for the
       hash part of the file name.  (This assumes that all references
       have the form `HASH-bla'). */
    foreach (PathSet::const_iterator, i, refs) {
        string baseName = baseNameOf(*i);
        string::size_type pos = baseName.find('-');
        if (pos == string::npos)
            throw Error(format("bad reference `%1%'") % *i);
        string s = string(baseName, 0, pos);
        assert(s.size() == refLength);
        assert(backMap.find(s) == backMap.end());
        // parseHash(htSHA256, s);
        sink.hashes.insert(s);
        backMap[s] = *i;
    }

    /* Look for the hashes in the NAR dump of the path. */
    dumpPath(path, sink);

    /* Map the hashes found back to their store paths. */
    PathSet found;
    foreach (StringSet::iterator, i, sink.seen) {
        std::map<string, Path>::iterator j;
        if ((j = backMap.find(*i)) == backMap.end()) abort();
        found.insert(j->second);
    }

    hash = sink.hashSink.finish();

    return found;
}

}


code:
#pragma once

#include "types.hh"
#include "hash.hh"

namespace nix {

PathSet scanForReferences(const Path & path, const PathSet & refs,
    HashResult & hash);

}


code:
#include "sqlite.hh"
#include "util.hh"

#include <sqlite3.h>

namespace nix {

[[noreturn]] void throwSQLiteError(sqlite3 * db, const format & f)
{
    int err = sqlite3_errcode(db);
    if (err == SQLITE_BUSY || err == SQLITE_PROTOCOL) {
        if (err == SQLITE_PROTOCOL)
            printMsg(lvlError, "warning: SQLite database is busy (SQLITE_PROTOCOL)");
        else {
            static bool warned = false;
            if (!warned) {
                printMsg(lvlError, "warning: SQLite database is busy");
                warned = true;
            }
        }
        /* Sleep for a while since retrying the transaction right away
           is likely to fail again. */
#if HAVE_NANOSLEEP
        struct timespec t;
        t.tv_sec = 0;
        t.tv_nsec = (random() % 100) * 1000 * 1000; /* <= 0.1s */
        nanosleep(&t, 0);
#else
        sleep(1);
#endif
        throw SQLiteBusy(format("%1%: %2%") % f.str() % sqlite3_errmsg(db));
    }
    else
        throw SQLiteError(format("%1%: %2%") % f.str() % sqlite3_errmsg(db));
}

SQLite::~SQLite()
{
    try {
        if (db && sqlite3_close(db) != SQLITE_OK)
            throwSQLiteError(db, "closing database");
    } catch (...) {
        ignoreException();
    }
}

void SQLiteStmt::create(sqlite3 * db, const string & s)
{
    checkInterrupt();
    assert(!stmt);
    if (sqlite3_prepare_v2(db, s.c_str(), -1, &stmt, 0) != SQLITE_OK)
        throwSQLiteError(db, "creating statement");
    this->db = db;
}

SQLiteStmt::~SQLiteStmt()
{
    try {
        if (stmt && sqlite3_finalize(stmt) != SQLITE_OK)
            throwSQLiteError(db, "finalizing statement");
    } catch (...) {
        ignoreException();
    }
}

SQLiteStmt::Use::Use(SQLiteStmt & stmt)
    : stmt(stmt)
{
    assert(stmt.stmt);
    /* Note: sqlite3_reset() returns the error code for the most
       recent call to sqlite3_step().  So ignore it. */
    sqlite3_reset(stmt);
}

SQLiteStmt::Use::~Use()
{
    sqlite3_reset(stmt);
}

SQLiteStmt::Use & SQLiteStmt::Use::operator () (const std::string & value, bool notNull)
{
    if (notNull) {
        if (sqlite3_bind_text(stmt, curArg++, value.c_str(), -1, SQLITE_TRANSIENT) != SQLITE_OK)
            throwSQLiteError(stmt.db, "binding argument");
    } else
        bind();
    return *this;
}

SQLiteStmt::Use & SQLiteStmt::Use::operator () (int64_t value, bool notNull)
{
    if (notNull) {
        if (sqlite3_bind_int64(stmt, curArg++, value) != SQLITE_OK)
            throwSQLiteError(stmt.db, "binding argument");
    } else
        bind();
    return *this;
}

SQLiteStmt::Use & SQLiteStmt::Use::bind()
{
    if (sqlite3_bind_null(stmt, curArg++) != SQLITE_OK)
        throwSQLiteError(stmt.db, "binding argument");
    return *this;
}

int SQLiteStmt::Use::step()
{
    return sqlite3_step(stmt);
}

void SQLiteStmt::Use::exec()
{
    int r = step();
    assert(r != SQLITE_ROW);
    if (r != SQLITE_DONE)
        throwSQLiteError(stmt.db, "executing SQLite statement");
}

bool SQLiteStmt::Use::next()
{
    int r = step();
    if (r != SQLITE_DONE && r != SQLITE_ROW)
        throwSQLiteError(stmt.db, "executing SQLite query");
    return r == SQLITE_ROW;
}

std::string SQLiteStmt::Use::getStr(int col)
{
    auto s = (const char *) sqlite3_column_text(stmt, col);
    assert(s);
    return s;
}

int64_t SQLiteStmt::Use::getInt(int col)
{
    // FIXME: detect nulls?
    return sqlite3_column_int64(stmt, col);
}

SQLiteTxn::SQLiteTxn(sqlite3 * db)
{
    this->db = db;
    if (sqlite3_exec(db, "begin;", 0, 0, 0) != SQLITE_OK)
        throwSQLiteError(db, "starting transaction");
    active = true;
}

void SQLiteTxn::commit()
{
    if (sqlite3_exec(db, "commit;", 0, 0, 0) != SQLITE_OK)
        throwSQLiteError(db, "committing transaction");
    active = false;
}

SQLiteTxn::~SQLiteTxn()
{
    try {
        if (active && sqlite3_exec(db, "rollback;", 0, 0, 0) != SQLITE_OK)
            throwSQLiteError(db, "aborting transaction");
    } catch (...) {
        ignoreException();
    }
}

}


code:
#pragma once

#include <functional>
#include <string>

#include "types.hh"

class sqlite3;
class sqlite3_stmt;

namespace nix {

/* RAII wrapper to close a SQLite database automatically. */
struct SQLite
{
    sqlite3 * db;
    SQLite() { db = 0; }
    ~SQLite();
    operator sqlite3 * () { return db; }
};

/* RAII wrapper to create and destroy SQLite prepared statements. */
struct SQLiteStmt
{
    sqlite3 * db = 0;
    sqlite3_stmt * stmt = 0;
    SQLiteStmt() { }
    void create(sqlite3 * db, const std::string & s);
    ~SQLiteStmt();
    operator sqlite3_stmt * () { return stmt; }

    /* Helper for binding / executing statements. */
    class Use
    {
        friend struct SQLiteStmt;
    private:
        SQLiteStmt & stmt;
        unsigned int curArg = 1;
        Use(SQLiteStmt & stmt);

    public:

        ~Use();

        /* Bind the next parameter. */
        Use & operator () (const std::string & value, bool notNull = true);
        Use & operator () (int64_t value, bool notNull = true);
        Use & bind(); // null

        int step();

        /* Execute a statement that does not return rows. */
        void exec();

        /* For statements that return 0 or more rows. Returns true iff
           a row is available. */
        bool next();

        std::string getStr(int col);
        int64_t getInt(int col);
    };

    Use use()
    {
        return Use(*this);
    }
};

/* RAII helper that ensures transactions are aborted unless explicitly
   committed. */
struct SQLiteTxn
{
    bool active = false;
    sqlite3 * db;

    SQLiteTxn(sqlite3 * db);

    void commit();

    ~SQLiteTxn();
};

MakeError(SQLiteError, Error);
MakeError(SQLiteBusy, SQLiteError);

[[noreturn]] void throwSQLiteError(sqlite3 * db, const format & f);

/* Convenience function for retrying a SQLite transaction when the
   database is busy. */
template<typename T>
T retrySQLite(std::function<T()> fun)
{
    while (true) {
        try {
            return fun();
        } catch (SQLiteBusy & e) {
        }
    }
}

}


code:
#include "store-api.hh"
#include "globals.hh"
#include "util.hh"

#include <climits>

namespace nix {

GCOptions::GCOptions()
{
    action = gcDeleteDead;
    ignoreLiveness = false;
    maxFreed = ULLONG_MAX;
}

bool isInStore(const Path & path)
{
    return isInDir(path, settings.nixStore);
}

bool isStorePath(const Path & path)
{
    return isInStore(path)
        && path.find('/', settings.nixStore.size() + 1) == Path::npos;
}

void assertStorePath(const Path & path)
{
    if (!isStorePath(path))
        throw Error(format("path `%1%' is not in the store") % path);
}

Path toStorePath(const Path & path)
{
    if (!isInStore(path))
        throw Error(format("path `%1%' is not in the store") % path);
    Path::size_type slash = path.find('/', settings.nixStore.size() + 1);
    if (slash == Path::npos)
        return path;
    else
        return Path(path, 0, slash);
}

string storePathToName(const Path & path)
{
    assertStorePath(path);
    return string(path, settings.nixStore.size() + 34);
}

void checkStoreName(const string & name)
{
    string validChars = "+-._?=";
    /* Disallow names starting with a dot for possible security
       reasons (e.g., "." and ".."). */
    if (string(name, 0, 1) == ".")
        throw Error(format("invalid name: `%1%'") % name);
    foreach (string::const_iterator, i, name)
        if (!((*i >= 'A' && *i <= 'Z') ||
              (*i >= 'a' && *i <= 'z') ||
              (*i >= '0' && *i <= '9') ||
              validChars.find(*i) != string::npos))
        {
            throw Error(format("invalid character `%1%' in name `%2%'")
                % *i % name);
        }
}

/* Store paths have the following form:

   <store>/<h>-<name>

   where

   <store> = the location of the store, usually /gnu/store

   <name> = a human readable name for the path, typically obtained
     from the name attribute of the derivation, or the name of the
     source file from which the store path is created.  For derivation
     outputs other than the default "out" output, the string "-<id>"
     is suffixed to <name>.

   <h> = base-32 representation of the first 160 bits of a SHA-256
     hash of <s>; the hash part of the store name

   <s> = the string "<type>:sha256:<h2>:<store>:<name>";
     note that it includes the location of the store as well as the
     name to make sure that changes to either of those are reflected
     in the hash (e.g. you won't get /nix/store/<h>-name1 and
     /nix/store/<h>-name2 with equal hash parts).

   <type> = one of:
     "text:<r1>:<r2>:...<rN>"
       for plain text files written to the store using
       addTextToStore(); <r1> ... <rN> are the references of the
       path.
     "source"
       for paths copied to the store using addToStore() when recursive
       = true and hashAlgo = "sha256"
     "output:<id>"
       for either the outputs created by derivations, OR paths copied
       to the store using addToStore() with recursive != true or
       hashAlgo != "sha256" (in that case "source" is used; it's
       silly, but it's done that way for compatibility).  <id> is the
       name of the output (usually, "out").

   <h2> = base-16 representation of a SHA-256 hash of:
     if <type> = "text:...":
       the string written to the resulting store path
     if <type> = "source":
       the serialisation of the path from which this store path is
       copied, as returned by hashPath()
     if <type> = "output:out":
       for non-fixed derivation outputs:
         the derivation (see hashDerivationModulo() in
         primops.cc)
       for paths copied by addToStore() or produced by fixed-output
       derivations:
         the string "fixed:out:<rec><algo>:<hash>:", where
           <rec> = "r:" for recursive (path) hashes, or "" or flat
             (file) hashes
           <algo> = "md5", "sha1" or "sha256"
           <hash> = base-16 representation of the path or flat hash of
             the contents of the path (or expected contents of the
             path for fixed-output derivations)

   It would have been nicer to handle fixed-output derivations under
   "source", e.g. have something like "source:<rec><algo>", but we're
   stuck with this for now...

   The main reason for this way of computing names is to prevent name
   collisions (for security).  For instance, it shouldn't be feasible
   to come up with a derivation whose output path collides with the
   path for a copied source.  The former would have a <s> starting with
   "output:out:", while the latter would have a <2> starting with
   "source:".
*/

Path makeStorePath(const string & type,
    const Hash & hash, const string & name)
{
    /* e.g., "source:sha256:1abc...:/nix/store:foo.tar.gz" */
    string s = type + ":sha256:" + printHash(hash) + ":"
        + settings.nixStore + ":" + name;

    checkStoreName(name);

    return settings.nixStore + "/"
        + printHash32(compressHash(hashString(htSHA256, s), 20))
        + "-" + name;
}

Path makeOutputPath(const string & id,
    const Hash & hash, const string & name)
{
    return makeStorePath("output:" + id, hash,
        name + (id == "out" ? "" : "-" + id));
}

Path makeFixedOutputPath(bool recursive,
    HashType hashAlgo, Hash hash, string name)
{
    return hashAlgo == htSHA256 && recursive
        ? makeStorePath("source", hash, name)
        : makeStorePath("output:out", hashString(htSHA256,
                "fixed:out:" + (recursive ? (string) "r:" : "") +
                printHashType(hashAlgo) + ":" + printHash(hash) + ":"),
            name);
}

Path computeStorePathForText(const string & name, const string & s,
    const PathSet & references)
{
    Hash hash = hashString(htSHA256, s);
    /* Stuff the references (if any) into the type.  This is a bit
       hacky, but we can't put them in `s' since that would be
       ambiguous. */
    string type = "text";
    foreach (PathSet::const_iterator, i, references) {
        type += ":";
        type += *i;
    }
    return makeStorePath(type, hash, name);
}

/* Return a string accepted by decodeValidPathInfo() that
   registers the specified paths as valid.  Note: it's the
   responsibility of the caller to provide a closure. */
string StoreAPI::makeValidityRegistration(const PathSet & paths,
    bool showDerivers, bool showHash)
{
    string s = "";

    foreach (PathSet::iterator, i, paths) {
        s += *i + "\n";

        ValidPathInfo info = queryPathInfo(*i);

        if (showHash) {
            s += printHash(info.hash) + "\n";
            s += (format("%1%\n") % info.narSize).str();
        }

        Path deriver = showDerivers ? info.deriver : "";
        s += deriver + "\n";

        s += (format("%1%\n") % info.references.size()).str();

        foreach (PathSet::iterator, j, info.references)
            s += *j + "\n";
    }

    return s;
}

string showPaths(const PathSet & paths)
{
    string s;
    foreach (PathSet::const_iterator, i, paths) {
        if (s.size() != 0) s += ", ";
        s += "`" + *i + "'";
    }
    return s;
}

void exportPaths(StoreAPI & store, const Paths & paths,
    bool sign, Sink & sink)
{
    foreach (Paths::const_iterator, i, paths) {
        writeInt(1, sink);
        store.exportPath(*i, sign, sink);
    }
    writeInt(0, sink);
}

Path readStorePath(Source & from)
{
    Path path = readString(from);
    assertStorePath(path);
    return path;
}

template<class T> T readStorePaths(Source & from)
{
    T paths = readStrings<T>(from);
    foreach (typename T::iterator, i, paths) assertStorePath(*i);
    return paths;
}

template PathSet readStorePaths(Source & from);

}

#include "local-store.hh"
#include "serialise.hh"

namespace nix {

std::shared_ptr<StoreAPI> store;

std::shared_ptr<StoreAPI> openStore(bool reserveSpace)
{
    return std::shared_ptr<StoreAPI>(new LocalStore(reserveSpace));
}

}