308 lines
9.4 KiB
C
308 lines
9.4 KiB
C
/*
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Routines in this file are based on:
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Zlib (RFC1950 / RFC1951) compression for PuTTY.
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PuTTY is copyright 1997-2014 Simon Tatham.
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Portions copyright Robert de Bath, Joris van Rantwijk, Delian
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Delchev, Andreas Schultz, Jeroen Massar, Wez Furlong, Nicolas Barry,
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Justin Bradford, Ben Harris, Malcolm Smith, Ahmad Khalifa, Markus
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Kuhn, Colin Watson, and CORE SDI S.A.
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Permission is hereby granted, free of charge, to any person
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obtaining a copy of this software and associated documentation files
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(the "Software"), to deal in the Software without restriction,
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including without limitation the rights to use, copy, modify, merge,
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publish, distribute, sublicense, and/or sell copies of the Software,
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and to permit persons to whom the Software is furnished to do so,
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subject to the following conditions:
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The above copyright notice and this permission notice shall be
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included in all copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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NONINFRINGEMENT. IN NO EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE
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FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF
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CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
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WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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*/
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#include <stdlib.h>
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#include <string.h>
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#include <assert.h>
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#include "defl_static.h"
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#define snew(type) ( (type *) malloc(sizeof(type)) )
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#define snewn(n, type) ( (type *) malloc((n) * sizeof(type)) )
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#define sresize(x, n, type) ( (type *) realloc((x), (n) * sizeof(type)) )
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#define sfree(x) ( free((x)) )
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#ifndef FALSE
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#define FALSE 0
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#define TRUE (!FALSE)
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#endif
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/* ----------------------------------------------------------------------
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* Zlib compression. We always use the static Huffman tree option.
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* Mostly this is because it's hard to scan a block in advance to
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* work out better trees; dynamic trees are great when you're
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* compressing a large file under no significant time constraint,
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* but when you're compressing little bits in real time, things get
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* hairier.
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*
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* I suppose it's possible that I could compute Huffman trees based
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* on the frequencies in the _previous_ block, as a sort of
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* heuristic, but I'm not confident that the gain would balance out
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* having to transmit the trees.
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*/
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void outbits(struct Outbuf *out, unsigned long bits, int nbits)
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{
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assert(out->noutbits + nbits <= 32);
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out->outbits |= bits << out->noutbits;
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out->noutbits += nbits;
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while (out->noutbits >= 8) {
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if (out->outlen >= out->outsize) {
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out->outsize = out->outlen + 64;
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out->outbuf = sresize(out->outbuf, out->outsize, unsigned char);
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}
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out->outbuf[out->outlen++] = (unsigned char) (out->outbits & 0xFF);
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out->outbits >>= 8;
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out->noutbits -= 8;
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}
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}
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static const unsigned char mirrorbytes[256] = {
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0x00, 0x80, 0x40, 0xc0, 0x20, 0xa0, 0x60, 0xe0,
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0x10, 0x90, 0x50, 0xd0, 0x30, 0xb0, 0x70, 0xf0,
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0x08, 0x88, 0x48, 0xc8, 0x28, 0xa8, 0x68, 0xe8,
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0x18, 0x98, 0x58, 0xd8, 0x38, 0xb8, 0x78, 0xf8,
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0x04, 0x84, 0x44, 0xc4, 0x24, 0xa4, 0x64, 0xe4,
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0x14, 0x94, 0x54, 0xd4, 0x34, 0xb4, 0x74, 0xf4,
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0x0c, 0x8c, 0x4c, 0xcc, 0x2c, 0xac, 0x6c, 0xec,
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0x1c, 0x9c, 0x5c, 0xdc, 0x3c, 0xbc, 0x7c, 0xfc,
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0x02, 0x82, 0x42, 0xc2, 0x22, 0xa2, 0x62, 0xe2,
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0x12, 0x92, 0x52, 0xd2, 0x32, 0xb2, 0x72, 0xf2,
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0x0a, 0x8a, 0x4a, 0xca, 0x2a, 0xaa, 0x6a, 0xea,
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0x1a, 0x9a, 0x5a, 0xda, 0x3a, 0xba, 0x7a, 0xfa,
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0x06, 0x86, 0x46, 0xc6, 0x26, 0xa6, 0x66, 0xe6,
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0x16, 0x96, 0x56, 0xd6, 0x36, 0xb6, 0x76, 0xf6,
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0x0e, 0x8e, 0x4e, 0xce, 0x2e, 0xae, 0x6e, 0xee,
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0x1e, 0x9e, 0x5e, 0xde, 0x3e, 0xbe, 0x7e, 0xfe,
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0x01, 0x81, 0x41, 0xc1, 0x21, 0xa1, 0x61, 0xe1,
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0x11, 0x91, 0x51, 0xd1, 0x31, 0xb1, 0x71, 0xf1,
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0x09, 0x89, 0x49, 0xc9, 0x29, 0xa9, 0x69, 0xe9,
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0x19, 0x99, 0x59, 0xd9, 0x39, 0xb9, 0x79, 0xf9,
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0x05, 0x85, 0x45, 0xc5, 0x25, 0xa5, 0x65, 0xe5,
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0x15, 0x95, 0x55, 0xd5, 0x35, 0xb5, 0x75, 0xf5,
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0x0d, 0x8d, 0x4d, 0xcd, 0x2d, 0xad, 0x6d, 0xed,
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0x1d, 0x9d, 0x5d, 0xdd, 0x3d, 0xbd, 0x7d, 0xfd,
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0x03, 0x83, 0x43, 0xc3, 0x23, 0xa3, 0x63, 0xe3,
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0x13, 0x93, 0x53, 0xd3, 0x33, 0xb3, 0x73, 0xf3,
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0x0b, 0x8b, 0x4b, 0xcb, 0x2b, 0xab, 0x6b, 0xeb,
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0x1b, 0x9b, 0x5b, 0xdb, 0x3b, 0xbb, 0x7b, 0xfb,
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0x07, 0x87, 0x47, 0xc7, 0x27, 0xa7, 0x67, 0xe7,
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0x17, 0x97, 0x57, 0xd7, 0x37, 0xb7, 0x77, 0xf7,
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0x0f, 0x8f, 0x4f, 0xcf, 0x2f, 0xaf, 0x6f, 0xef,
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0x1f, 0x9f, 0x5f, 0xdf, 0x3f, 0xbf, 0x7f, 0xff,
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};
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typedef struct {
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short code, extrabits;
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int min, max;
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} coderecord;
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static const coderecord lencodes[] = {
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{257, 0, 3, 3},
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{258, 0, 4, 4},
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{259, 0, 5, 5},
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{260, 0, 6, 6},
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{261, 0, 7, 7},
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{262, 0, 8, 8},
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{263, 0, 9, 9},
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{264, 0, 10, 10},
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{265, 1, 11, 12},
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{266, 1, 13, 14},
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{267, 1, 15, 16},
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{268, 1, 17, 18},
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{269, 2, 19, 22},
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{270, 2, 23, 26},
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{271, 2, 27, 30},
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{272, 2, 31, 34},
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{273, 3, 35, 42},
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{274, 3, 43, 50},
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{275, 3, 51, 58},
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{276, 3, 59, 66},
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{277, 4, 67, 82},
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{278, 4, 83, 98},
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{279, 4, 99, 114},
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{280, 4, 115, 130},
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{281, 5, 131, 162},
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{282, 5, 163, 194},
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{283, 5, 195, 226},
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{284, 5, 227, 257},
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{285, 0, 258, 258},
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};
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static const coderecord distcodes[] = {
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{0, 0, 1, 1},
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{1, 0, 2, 2},
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{2, 0, 3, 3},
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{3, 0, 4, 4},
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{4, 1, 5, 6},
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{5, 1, 7, 8},
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{6, 2, 9, 12},
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{7, 2, 13, 16},
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{8, 3, 17, 24},
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{9, 3, 25, 32},
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{10, 4, 33, 48},
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{11, 4, 49, 64},
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{12, 5, 65, 96},
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{13, 5, 97, 128},
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{14, 6, 129, 192},
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{15, 6, 193, 256},
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{16, 7, 257, 384},
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{17, 7, 385, 512},
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{18, 8, 513, 768},
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{19, 8, 769, 1024},
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{20, 9, 1025, 1536},
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{21, 9, 1537, 2048},
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{22, 10, 2049, 3072},
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{23, 10, 3073, 4096},
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{24, 11, 4097, 6144},
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{25, 11, 6145, 8192},
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{26, 12, 8193, 12288},
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{27, 12, 12289, 16384},
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{28, 13, 16385, 24576},
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{29, 13, 24577, 32768},
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};
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void zlib_literal(struct Outbuf *out, unsigned char c)
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{
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if (out->comp_disabled) {
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/*
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* We're in an uncompressed block, so just output the byte.
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*/
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outbits(out, c, 8);
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return;
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}
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if (c <= 143) {
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/* 0 through 143 are 8 bits long starting at 00110000. */
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outbits(out, mirrorbytes[0x30 + c], 8);
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} else {
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/* 144 through 255 are 9 bits long starting at 110010000. */
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outbits(out, 1 + 2 * mirrorbytes[0x90 - 144 + c], 9);
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}
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}
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void zlib_match(struct Outbuf *out, int distance, int len)
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{
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const coderecord *d, *l;
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int i, j, k;
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assert(!out->comp_disabled);
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while (len > 0) {
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int thislen;
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/*
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* We can transmit matches of lengths 3 through 258
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* inclusive. So if len exceeds 258, we must transmit in
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* several steps, with 258 or less in each step.
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*
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* Specifically: if len >= 261, we can transmit 258 and be
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* sure of having at least 3 left for the next step. And if
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* len <= 258, we can just transmit len. But if len == 259
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* or 260, we must transmit len-3.
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*/
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thislen = (len > 260 ? 258 : len <= 258 ? len : len - 3);
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len -= thislen;
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/*
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* Binary-search to find which length code we're
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* transmitting.
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*/
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i = -1;
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j = sizeof(lencodes) / sizeof(*lencodes);
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while (1) {
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assert(j - i >= 2);
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k = (j + i) / 2;
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if (thislen < lencodes[k].min)
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j = k;
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else if (thislen > lencodes[k].max)
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i = k;
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else {
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l = &lencodes[k];
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break; /* found it! */
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}
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}
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/*
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* Transmit the length code. 256-279 are seven bits
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* starting at 0000000; 280-287 are eight bits starting at
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* 11000000.
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*/
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if (l->code <= 279) {
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outbits(out, mirrorbytes[(l->code - 256) * 2], 7);
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} else {
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outbits(out, mirrorbytes[0xc0 - 280 + l->code], 8);
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}
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/*
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* Transmit the extra bits.
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*/
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if (l->extrabits)
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outbits(out, thislen - l->min, l->extrabits);
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/*
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* Binary-search to find which distance code we're
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* transmitting.
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*/
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i = -1;
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j = sizeof(distcodes) / sizeof(*distcodes);
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while (1) {
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assert(j - i >= 2);
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k = (j + i) / 2;
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if (distance < distcodes[k].min)
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j = k;
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else if (distance > distcodes[k].max)
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i = k;
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else {
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d = &distcodes[k];
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break; /* found it! */
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}
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}
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/*
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* Transmit the distance code. Five bits starting at 00000.
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*/
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outbits(out, mirrorbytes[d->code * 8], 5);
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/*
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* Transmit the extra bits.
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*/
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if (d->extrabits)
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outbits(out, distance - d->min, d->extrabits);
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}
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}
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void zlib_start_block(struct Outbuf *out)
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{
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// outbits(out, 0x9C78, 16);
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outbits(out, 1, 1); /* Final block */
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outbits(out, 1, 2); /* Static huffman block */
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}
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void zlib_finish_block(struct Outbuf *out)
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{
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outbits(out, 0, 7); /* close block */
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outbits(out, 0, 7); /* Make sure all bits are flushed */
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}
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void zlib_free_block(struct Outbuf *out) {
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sfree(out->outbuf);
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}
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