/*= -*- c-basic-offset: 4; indent-tabs-mode: nil; -*- * * librsync -- dynamic caching and delta update in HTTP * $Id$ * * Copyright (C) 2000, 2001 by Martin Pool <mbp@samba.org> * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public License * as published by the Free Software Foundation; either version 2.1 of * the License, or (at your option) any later version. * * This program is distributed in the hope that it will be useful, but * WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with this program; if not, write to the Free Software * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */ /* * Programming languages should be designed not * by piling feature on top of feature, but by * removing the weaknesses and restrictions that * make additional features appear necessary. * -- Revised^5 Report on Scheme */ /* * OK, so I'll admit IO here is a little complex. The most important * player here is the stream, which is an object for managing filter * operations. It has both input and output sides, both of which is * just a (pointer,len) pair into a buffer provided by the client. * The code controlling the stream handles however much data it wants, * and the client provides or accepts however much is convenient. * * At the same time as being friendly to the client, we also try to be * very friendly to the internal code. It wants to be able to ask for * arbitrary amounts of input or output and get it without having to * keep track of partial completion. So there are functions which * either complete, or queue whatever was not sent and return * RS_BLOCKED. * * The output buffer is a little more clever than simply a data * buffer. Instead it knows that we can send either literal data, or * data copied through from the input of the stream. * * In buf.c you will find functions that then map buffers onto stdio * files. * * So on return from an encoding function, either the input or the * output or possibly both will have no more bytes available. */ /* * Manage librsync streams of IO. See scoop.c and tube.c for related * code for input and output respectively. * * librsync never does IO or memory allocation, but relies on the * caller. This is very nice for integration, but means that we have * to be fairly flexible as to when we can `read' or `write' stuff * internally. * * librsync basically does two types of IO. It reads network integers * of various lengths which encode command and control information * such as versions and signatures. It also does bulk data transfer. * * IO of network integers is internally buffered, because higher * levels of the code need to see them transmitted atomically: it's no * good to read half of a uint32. So there is a small and fixed * length internal buffer which accumulates these. Unlike previous * versions of the library, we don't require that the caller hold the * start until the whole thing has arrived, which guarantees that we * can always make progress. * * On each call into a stream iterator, it should begin by trying to * flush output. This may well use up all the remaining stream space, * in which case nothing else can be done. */ /* TODO: Return errors rather than aborting if something goes wrong. */ #include <config_rsync.h> #include <assert.h> #include <stdlib.h> #include <string.h> #include <stdio.h> #include "rsync.h" #include "stream.h" #include "util.h" #include "trace.h" static const int RS_STREAM_DOGTAG = 2001125; /** * \brief Copy up to \p max_len bytes from input of \b stream to its output. * * Return the number of bytes actually copied, which may be less than * LEN if there is not enough space in one or the other stream. * * This always does the copy immediately. Most functions should call * rs_tube_copy() to cause the copy to happen gradually as space * becomes available. */ int rs_buffers_copy(rs_buffers_t *stream, int max_len) { int len = max_len; assert(len > 0); if ((unsigned) len > stream->avail_in) { rs_trace("copy limited to %d available input bytes", stream->avail_in); len = stream->avail_in; } if ((unsigned) len > stream->avail_out) { rs_trace("copy limited to %d available output bytes", stream->avail_out); len = stream->avail_out; } if (!len) return 0; /* rs_trace("stream copied chunk of %d bytes", len); */ memcpy(stream->next_out, stream->next_in, len); stream->next_out += len; stream->avail_out -= len; stream->next_in += len; stream->avail_in -= len; return len; } /** * Whenever a stream processing function exits, it should have done so * because it has either consumed all the input or has filled the * output buffer. This function checks that simple postcondition. */ void rs_buffers_check_exit(rs_buffers_t const *stream) { assert(stream->avail_in == 0 || stream->avail_out == 0); }