Method xsgetn

fhstream.cpp:173–216

}

std::streamsize	ifhbuf::xsgetn (char* s, std::streamsize n)
{
	// Use heuristic to decide whether to read directly
	// Read directly only if n >= bytes_available + 4096

	std::streamsize	bytes_available = egptr() - gptr();

	if (n < bytes_available + 4096) {
		// Not worth it to do a direct read
		return std::streambuf::xsgetn(s, n);
	}

	std::streamsize	total_bytes_read = 0;

	// First, copy out the bytes currently in the buffer
	std::memcpy(s, gptr(), bytes_available);

	s += bytes_available;
	n -= bytes_available;
	total_bytes_read += bytes_available;

	// Now do the direct read
	while (n > 0) {
		const size_t	bytes_read = read_fun(handle, s, n);
		if (bytes_read == 0) {
			// EOF
			break;
		}

		s += bytes_read;
		n -= bytes_read;
		total_bytes_read += bytes_read;
	}

	// Fill up the putback area with the most recently read characters
	size_t		nputback = std::min<size_t>(total_bytes_read, putback_size);
	std::memcpy(buffer + (putback_size - nputback), s - nputback, nputback);

	// Reset the buffer with no bytes available for reading, but with some putback characters
	reset_buffer(nputback, 0);

	// Return the total number of bytes read
	return total_bytes_read;
}

std::streambuf*	ifhbuf::setbuf (char* s, std::streamsize n)
{