source: trunk/third/openssh/compress.c @ 18759

/*
 * Author: Tatu Ylonen <ylo@cs.hut.fi>
 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
 *                    All rights reserved
 * Interface to packet compression for ssh.
 *
 * As far as I am concerned, the code I have written for this software
 * can be used freely for any purpose.  Any derived versions of this
 * software must be clearly marked as such, and if the derived work is
 * incompatible with the protocol description in the RFC file, it must be
 * called by a name other than "ssh" or "Secure Shell".
 */

#include "includes.h"
RCSID("$OpenBSD: compress.c,v 1.19 2002/03/18 17:31:54 provos Exp $");

#include "log.h"
#include "buffer.h"
#include "zlib.h"
#include "compress.h"

z_stream incoming_stream;
z_stream outgoing_stream;
static int compress_init_send_called = 0;
static int compress_init_recv_called = 0;
static int inflate_failed = 0;
static int deflate_failed = 0;

/*
 * Initializes compression; level is compression level from 1 to 9
 * (as in gzip).
 */

void
buffer_compress_init_send(int level)
{
        if (compress_init_send_called == 1)
                deflateEnd(&outgoing_stream);
        compress_init_send_called = 1;
        debug("Enabling compression at level %d.", level);
        if (level < 1 || level > 9)
                fatal("Bad compression level %d.", level);
        deflateInit(&outgoing_stream, level);
}
void
buffer_compress_init_recv(void)
{
        if (compress_init_recv_called == 1)
                inflateEnd(&incoming_stream);
        compress_init_recv_called = 1;
        inflateInit(&incoming_stream);
}

/* Frees any data structures allocated for compression. */

void
buffer_compress_uninit(void)
{
        debug("compress outgoing: raw data %lu, compressed %lu, factor %.2f",
            outgoing_stream.total_in, outgoing_stream.total_out,
            outgoing_stream.total_in == 0 ? 0.0 :
            (double) outgoing_stream.total_out / outgoing_stream.total_in);
        debug("compress incoming: raw data %lu, compressed %lu, factor %.2f",
            incoming_stream.total_out, incoming_stream.total_in,
            incoming_stream.total_out == 0 ? 0.0 :
            (double) incoming_stream.total_in / incoming_stream.total_out);
        if (compress_init_recv_called == 1 && inflate_failed == 0)
                inflateEnd(&incoming_stream);
        if (compress_init_send_called == 1 && deflate_failed == 0)
                deflateEnd(&outgoing_stream);
}

/*
 * Compresses the contents of input_buffer into output_buffer.  All packets
 * compressed using this function will form a single compressed data stream;
 * however, data will be flushed at the end of every call so that each
 * output_buffer can be decompressed independently (but in the appropriate
 * order since they together form a single compression stream) by the
 * receiver.  This appends the compressed data to the output buffer.
 */

void
buffer_compress(Buffer * input_buffer, Buffer * output_buffer)
{
        u_char buf[4096];
        int status;

        /* This case is not handled below. */
        if (buffer_len(input_buffer) == 0)
                return;

        /* Input is the contents of the input buffer. */
        outgoing_stream.next_in = buffer_ptr(input_buffer);
        outgoing_stream.avail_in = buffer_len(input_buffer);

        /* Loop compressing until deflate() returns with avail_out != 0. */
        do {
                /* Set up fixed-size output buffer. */
                outgoing_stream.next_out = buf;
                outgoing_stream.avail_out = sizeof(buf);

                /* Compress as much data into the buffer as possible. */
                status = deflate(&outgoing_stream, Z_PARTIAL_FLUSH);
                switch (status) {
                case Z_OK:
                        /* Append compressed data to output_buffer. */
                        buffer_append(output_buffer, buf,
                            sizeof(buf) - outgoing_stream.avail_out);
                        break;
                default:
                        deflate_failed = 1;
                        fatal("buffer_compress: deflate returned %d", status);
                        /* NOTREACHED */
                }
        } while (outgoing_stream.avail_out == 0);
}

/*
 * Uncompresses the contents of input_buffer into output_buffer.  All packets
 * uncompressed using this function will form a single compressed data
 * stream; however, data will be flushed at the end of every call so that
 * each output_buffer.  This must be called for the same size units that the
 * buffer_compress was called, and in the same order that buffers compressed
 * with that.  This appends the uncompressed data to the output buffer.
 */

void
buffer_uncompress(Buffer * input_buffer, Buffer * output_buffer)
{
        u_char buf[4096];
        int status;

        incoming_stream.next_in = buffer_ptr(input_buffer);
        incoming_stream.avail_in = buffer_len(input_buffer);

        for (;;) {
                /* Set up fixed-size output buffer. */
                incoming_stream.next_out = buf;
                incoming_stream.avail_out = sizeof(buf);

                status = inflate(&incoming_stream, Z_PARTIAL_FLUSH);
                switch (status) {
                case Z_OK:
                        buffer_append(output_buffer, buf,
                            sizeof(buf) - incoming_stream.avail_out);
                        break;
                case Z_BUF_ERROR:
                        /*
                         * Comments in zlib.h say that we should keep calling
                         * inflate() until we get an error.  This appears to
                         * be the error that we get.
                         */
                        return;
                default:
                        inflate_failed = 1;
                        fatal("buffer_uncompress: inflate returned %d", status);
                        /* NOTREACHED */
                }
        }
}