 `std::istream`.

    This function attempts to parse a complete HTTP/1 message from the stream.

    @param is The `std::istream` to read from.

    @param buffer The buffer to use.

    @param msg The message to store the result.

    @param ec Set to the error, if any occurred.
*/</span>
<span class="keyword">template</span><span class="special">&lt;</span>
    <span class="keyword">class</span> <span class="identifier">Allocator</span><span class="special">,</span>
    <span class="keyword">bool</span> 