that these are only a subset of the possible return values from <tt>deflate()</tt>
and <tt>inflate()</tt>.
<pre><b>
/* report a zlib or i/o error */
void zerr(int ret)
{
    fputs("zpipe: ", stderr);
    switch (ret) {
    case Z_ERRNO:
        if (ferror(stdin))
            fputs("error reading stdin\n", stderr);
        if (ferror(stdout))
            fputs("error writing stdout\n", stderr);
        break;
    case Z_STREAM_ERROR:
        fputs("invalid compression level\n", stderr);
        break;
    ca