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/*
* 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 1.17 2001/12/29 21:56:01 stevesk Exp $");
#include "log.h"
#include "buffer.h"
#include "zlib.h"
#include "compress.h"
static z_stream incoming_stream;
static z_stream outgoing_stream;
static int compress_init_send_called = 0;
static int compress_init_recv_called = 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)
inflateEnd(&incoming_stream);
if (compress_init_send_called == 1)
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:
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:
fatal("buffer_uncompress: inflate returned %d", status);
/* NOTREACHED */
}
}
}
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