src/lzcommon.c

   1 ////////////////////////////////////////////////////////////////////////////////
   2 // compression code license (ONLY compression code)
   3 //
   4 // Copyright (c) 1997-2001 John Sadler (john_sadler@alum.mit.edu)
   5 // All rights reserved.
   6 //
   7 // Redistribution and use in source and binary forms, with or without
   8 // modification, are permitted provided that the following conditions
   9 // are met:
  10 //
  11 //   * Redistributions of source code must retain the above copyright
  12 //     notice, this list of conditions and the following disclaimer.
  13 //
  14 //   * Redistributions in binary form must reproduce the above copyright
  15 //     notice, this list of conditions and the following disclaimer in the
  16 //     documentation and/or other materials provided with the distribution.
  17 //
  18 // THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  19 // ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  20 // IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  21 // ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  22 // FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  23 // DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  24 // OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  25 // HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  26 // LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  27 // OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  28 // SUCH DAMAGE.
  29 //
  30 static inline uint16_t nwu16 (uint16_t number) {
  31   const uint8_t *pointer = (const uint8_t *)&number;
  32   //
  33   return (uint16_t)(((uint16_t)(pointer[0]<<8))|(pointer[1]));
  34 }
  35
  36
  37 static inline uint32_t nwu32 (uint32_t number) {
  38   const uint16_t *pointer = (const uint16_t *)&number;
  39   //
  40   return ((uint32_t)(nwu16(pointer[0])<<16))|nwu16(pointer[1]);
  41 }
  42
  43
  44 #define BIT_NUMBER(_x)  (1<<(_x))
  45 #define LZ_TYPE_BITS    (1)
  46 #define LZ_OFFSET_BITS  (12)
  47 #define LZ_LENGTH_BITS  (5)
  48 #define LZ_NEXT_BITS    (8)
  49 #define LZ_PHRASE_BITS  (LZ_TYPE_BITS+LZ_OFFSET_BITS+LZ_LENGTH_BITS+LZ_NEXT_BITS)
  50 #define LZ_SYMBOL_BITS  (LZ_TYPE_BITS+LZ_NEXT_BITS)
  51
  52 /*
  53 ** if you match fewer characters than this, don't bother,
  54 ** it's smaller to encode it as a sequence of symbol tokens.
  55 **/
  56 #define LZ_MINIMUM_USEFUL_MATCH  ((int)(LZ_PHRASE_BITS/LZ_SYMBOL_BITS))
  57
  58 #define LZ_WINDOW_SIZE  (BIT_NUMBER(LZ_OFFSET_BITS))
  59 #define LZ_WINDOW_SIZE  (BIT_NUMBER(LZ_OFFSET_BITS))
  60 #define LZ_BUFFER_SIZE  (BIT_NUMBER(LZ_LENGTH_BITS)+LZ_MINIMUM_USEFUL_MATCH)
  61
  62 #define MIN(a,b) \
  63   ({ typeof(a) _a = (a); \
  64      typeof(b) _b = (b); \
  65     _a < _b ? _a : _b; })
  66
  67
  68 static inline void bitSet (unsigned char *bits, size_t index, int value) {
  69   int byteIndex = (index>>3), bitIndex = (index&0x07);
  70   unsigned char mask = (unsigned char)(128>>bitIndex);
  71   //
  72   if (value) bits[byteIndex] |= mask; else bits[byteIndex] &= ~mask;
  73 }
  74
  75
  76 static inline int bitGet (const unsigned char *bits, size_t index) {
  77   int byteIndex = (index>>3), bitIndex = (index&0x07);
  78   //
  79   return ((bits[byteIndex]>>(7-bitIndex))&0x01);
  80 }