compress.c

   1 /*
   2  *
   3  * compress.c
   4  *
   5  * Author: Tatu Ylonen <ylo@cs.hut.fi>
   6  *
   7  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
   8  *                    All rights reserved
   9  *
  10  * Created: Wed Oct 25 22:12:46 1995 ylo
  11  *
  12  * Interface to packet compression for ssh.
  13  *
  14  */
  15
  16 #include "includes.h"
  17 RCSID("$Id$");
  18
  19 #include "ssh.h"
  20 #include "buffer.h"
  21 #include "zlib.h"
  22
  23 static z_stream incoming_stream;
  24 static z_stream outgoing_stream;
  25
  26 /*
  27  * Initializes compression; level is compression level from 1 to 9
  28  * (as in gzip).
  29  */
  30
  31 void
  32 buffer_compress_init(int level)
  33 {
  34         debug("Enabling compression at level %d.", level);
  35         if (level < 1 || level > 9)
  36                 fatal("Bad compression level %d.", level);
  37         inflateInit(&incoming_stream);
  38         deflateInit(&outgoing_stream, level);
  39 }
  40
  41 /* Frees any data structures allocated for compression. */
  42
  43 void
  44 buffer_compress_uninit()
  45 {
  46         debug("compress outgoing: raw data %lu, compressed %lu, factor %.2f",
  47               outgoing_stream.total_in, outgoing_stream.total_out,
  48               outgoing_stream.total_in == 0 ? 0.0 :
  49               (double) outgoing_stream.total_out / outgoing_stream.total_in);
  50         debug("compress incoming: raw data %lu, compressed %lu, factor %.2f",
  51               incoming_stream.total_out, incoming_stream.total_in,
  52               incoming_stream.total_out == 0 ? 0.0 :
  53               (double) incoming_stream.total_in / incoming_stream.total_out);
  54         inflateEnd(&incoming_stream);
  55         deflateEnd(&outgoing_stream);
  56 }
  57
  58 /*
  59  * Compresses the contents of input_buffer into output_buffer.  All packets
  60  * compressed using this function will form a single compressed data stream;
  61  * however, data will be flushed at the end of every call so that each
  62  * output_buffer can be decompressed independently (but in the appropriate
  63  * order since they together form a single compression stream) by the
  64  * receiver.  This appends the compressed data to the output buffer.
  65  */
  66
  67 void
  68 buffer_compress(Buffer * input_buffer, Buffer * output_buffer)
  69 {
  70         char buf[4096];
  71         int status;
  72
  73         /* This case is not handled below. */
  74         if (buffer_len(input_buffer) == 0)
  75                 return;
  76
  77         /* Input is the contents of the input buffer. */
  78         outgoing_stream.next_in = (unsigned char *) buffer_ptr(input_buffer);
  79         outgoing_stream.avail_in = buffer_len(input_buffer);
  80
  81         /* Loop compressing until deflate() returns with avail_out != 0. */
  82         do {
  83                 /* Set up fixed-size output buffer. */
  84                 outgoing_stream.next_out = (unsigned char *)buf;
  85                 outgoing_stream.avail_out = sizeof(buf);
  86
  87                 /* Compress as much data into the buffer as possible. */
  88                 status = deflate(&outgoing_stream, Z_PARTIAL_FLUSH);
  89                 switch (status) {
  90                 case Z_OK:
  91                         /* Append compressed data to output_buffer. */
  92                         buffer_append(output_buffer, buf,
  93                                       sizeof(buf) - outgoing_stream.avail_out);
  94                         break;
  95                 case Z_STREAM_END:
  96                         fatal("buffer_compress: deflate returned Z_STREAM_END");
  97                         /* NOTREACHED */
  98                 case Z_STREAM_ERROR:
  99                         fatal("buffer_compress: deflate returned Z_STREAM_ERROR");
 100                         /* NOTREACHED */
 101                 case Z_BUF_ERROR:
 102                         fatal("buffer_compress: deflate returned Z_BUF_ERROR");
 103                         /* NOTREACHED */
 104                 default:
 105                         fatal("buffer_compress: deflate returned %d", status);
 106                         /* NOTREACHED */
 107                 }
 108         }
 109         while (outgoing_stream.avail_out == 0);
 110 }
 111
 112 /*
 113  * Uncompresses the contents of input_buffer into output_buffer.  All packets
 114  * uncompressed using this function will form a single compressed data
 115  * stream; however, data will be flushed at the end of every call so that
 116  * each output_buffer.  This must be called for the same size units that the
 117  * buffer_compress was called, and in the same order that buffers compressed
 118  * with that.  This appends the uncompressed data to the output buffer.
 119  */
 120
 121 void
 122 buffer_uncompress(Buffer * input_buffer, Buffer * output_buffer)
 123 {
 124         char buf[4096];
 125         int status;
 126
 127         incoming_stream.next_in = (unsigned char *) buffer_ptr(input_buffer);
 128         incoming_stream.avail_in = buffer_len(input_buffer);
 129
 130         incoming_stream.next_out = (unsigned char *) buf;
 131         incoming_stream.avail_out = sizeof(buf);
 132
 133         for (;;) {
 134                 status = inflate(&incoming_stream, Z_PARTIAL_FLUSH);
 135                 switch (status) {
 136                 case Z_OK:
 137                         buffer_append(output_buffer, buf,
 138                                       sizeof(buf) - incoming_stream.avail_out);
 139                         incoming_stream.next_out = (unsigned char *) buf;
 140                         incoming_stream.avail_out = sizeof(buf);
 141                         break;
 142                 case Z_STREAM_END:
 143                         fatal("buffer_uncompress: inflate returned Z_STREAM_END");
 144                         /* NOTREACHED */
 145                 case Z_DATA_ERROR:
 146                         fatal("buffer_uncompress: inflate returned Z_DATA_ERROR");
 147                         /* NOTREACHED */
 148                 case Z_STREAM_ERROR:
 149                         fatal("buffer_uncompress: inflate returned Z_STREAM_ERROR");
 150                         /* NOTREACHED */
 151                 case Z_BUF_ERROR:
 152                         /*
 153                          * Comments in zlib.h say that we should keep calling
 154                          * inflate() until we get an error.  This appears to
 155                          * be the error that we get.
 156                          */
 157                         return;
 158                 case Z_MEM_ERROR:
 159                         fatal("buffer_uncompress: inflate returned Z_MEM_ERROR");
 160                         /* NOTREACHED */
 161                 default:
 162                         fatal("buffer_uncompress: inflate returned %d", status);
 163                 }
 164         }
 165 }