lib_generic/bzlib_huffman.c

   1 #include <config.h>
   2 #ifdef CONFIG_BZIP2
   3
   4 /*-------------------------------------------------------------*/
   5 /*--- Huffman coding low-level stuff                        ---*/
   6 /*---                                             huffman.c ---*/
   7 /*-------------------------------------------------------------*/
   8
   9 /*--
  10   This file is a part of bzip2 and/or libbzip2, a program and
  11   library for lossless, block-sorting data compression.
  12
  13   Copyright (C) 1996-2002 Julian R Seward.  All rights reserved.
  14
  15   Redistribution and use in source and binary forms, with or without
  16   modification, are permitted provided that the following conditions
  17   are met:
  18
  19   1. Redistributions of source code must retain the above copyright
  20      notice, this list of conditions and the following disclaimer.
  21
  22   2. The origin of this software must not be misrepresented; you must
  23      not claim that you wrote the original software.  If you use this
  24      software in a product, an acknowledgment in the product
  25      documentation would be appreciated but is not required.
  26
  27   3. Altered source versions must be plainly marked as such, and must
  28      not be misrepresented as being the original software.
  29
  30   4. The name of the author may not be used to endorse or promote
  31      products derived from this software without specific prior written
  32      permission.
  33
  34   THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
  35   OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  36   WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  37   ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
  38   DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  39   DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
  40   GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  41   INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
  42   WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
  43   NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  44   SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  45
  46   Julian Seward, Cambridge, UK.
  47   jseward@acm.org
  48   bzip2/libbzip2 version 1.0 of 21 March 2000
  49
  50   This program is based on (at least) the work of:
  51      Mike Burrows
  52      David Wheeler
  53      Peter Fenwick
  54      Alistair Moffat
  55      Radford Neal
  56      Ian H. Witten
  57      Robert Sedgewick
  58      Jon L. Bentley
  59
  60   For more information on these sources, see the manual.
  61 --*/
  62
  63
  64 #include "bzlib_private.h"
  65
  66 /*---------------------------------------------------*/
  67 #define WEIGHTOF(zz0)  ((zz0) & 0xffffff00)
  68 #define DEPTHOF(zz1)   ((zz1) & 0x000000ff)
  69 #define MYMAX(zz2,zz3) ((zz2) > (zz3) ? (zz2) : (zz3))
  70
  71 #define ADDWEIGHTS(zw1,zw2)                           \
  72    (WEIGHTOF(zw1)+WEIGHTOF(zw2)) |                    \
  73    (1 + MYMAX(DEPTHOF(zw1),DEPTHOF(zw2)))
  74
  75 #define UPHEAP(z)                                     \
  76 {                                                     \
  77    Int32 zz, tmp;                                     \
  78    zz = z; tmp = heap[zz];                            \
  79    while (weight[tmp] < weight[heap[zz >> 1]]) {      \
  80       heap[zz] = heap[zz >> 1];                       \
  81       zz >>= 1;                                       \
  82    }                                                  \
  83    heap[zz] = tmp;                                    \
  84 }
  85
  86 #define DOWNHEAP(z)                                   \
  87 {                                                     \
  88    Int32 zz, yy, tmp;                                 \
  89    zz = z; tmp = heap[zz];                            \
  90    while (True) {                                     \
  91       yy = zz << 1;                                   \
  92       if (yy > nHeap) break;                          \
  93       if (yy < nHeap &&                               \
  94           weight[heap[yy+1]] < weight[heap[yy]])      \
  95          yy++;                                        \
  96       if (weight[tmp] < weight[heap[yy]]) break;      \
  97       heap[zz] = heap[yy];                            \
  98       zz = yy;                                        \
  99    }                                                  \
 100    heap[zz] = tmp;                                    \
 101 }
 102
 103
 104 /*---------------------------------------------------*/
 105 void BZ2_hbMakeCodeLengths ( UChar *len,
 106                              Int32 *freq,
 107                              Int32 alphaSize,
 108                              Int32 maxLen )
 109 {
 110    /*--
 111       Nodes and heap entries run from 1.  Entry 0
 112       for both the heap and nodes is a sentinel.
 113    --*/
 114    Int32 nNodes, nHeap, n1, n2, i, j, k;
 115    Bool  tooLong;
 116
 117    Int32 heap   [ BZ_MAX_ALPHA_SIZE + 2 ];
 118    Int32 weight [ BZ_MAX_ALPHA_SIZE * 2 ];
 119    Int32 parent [ BZ_MAX_ALPHA_SIZE * 2 ];
 120
 121    for (i = 0; i < alphaSize; i++)
 122       weight[i+1] = (freq[i] == 0 ? 1 : freq[i]) << 8;
 123
 124    while (True) {
 125
 126       nNodes = alphaSize;
 127       nHeap = 0;
 128
 129       heap[0] = 0;
 130       weight[0] = 0;
 131       parent[0] = -2;
 132
 133       for (i = 1; i <= alphaSize; i++) {
 134          parent[i] = -1;
 135          nHeap++;
 136          heap[nHeap] = i;
 137          UPHEAP(nHeap);
 138       }
 139
 140       AssertH( nHeap < (BZ_MAX_ALPHA_SIZE+2), 2001 );
 141
 142       while (nHeap > 1) {
 143          n1 = heap[1]; heap[1] = heap[nHeap]; nHeap--; DOWNHEAP(1);
 144          n2 = heap[1]; heap[1] = heap[nHeap]; nHeap--; DOWNHEAP(1);
 145          nNodes++;
 146          parent[n1] = parent[n2] = nNodes;
 147          weight[nNodes] = ADDWEIGHTS(weight[n1], weight[n2]);
 148          parent[nNodes] = -1;
 149          nHeap++;
 150          heap[nHeap] = nNodes;
 151          UPHEAP(nHeap);
 152       }
 153
 154       AssertH( nNodes < (BZ_MAX_ALPHA_SIZE * 2), 2002 );
 155
 156       tooLong = False;
 157       for (i = 1; i <= alphaSize; i++) {
 158          j = 0;
 159          k = i;
 160          while (parent[k] >= 0) { k = parent[k]; j++; }
 161          len[i-1] = j;
 162          if (j > maxLen) tooLong = True;
 163       }
 164
 165       if (! tooLong) break;
 166
 167       for (i = 1; i < alphaSize; i++) {
 168          j = weight[i] >> 8;
 169          j = 1 + (j / 2);
 170          weight[i] = j << 8;
 171       }
 172    }
 173 }
 174
 175
 176 /*---------------------------------------------------*/
 177 void BZ2_hbAssignCodes ( Int32 *code,
 178                          UChar *length,
 179                          Int32 minLen,
 180                          Int32 maxLen,
 181                          Int32 alphaSize )
 182 {
 183    Int32 n, vec, i;
 184
 185    vec = 0;
 186    for (n = minLen; n <= maxLen; n++) {
 187       for (i = 0; i < alphaSize; i++)
 188          if (length[i] == n) { code[i] = vec; vec++; };
 189       vec <<= 1;
 190    }
 191 }
 192
 193
 194 /*---------------------------------------------------*/
 195 void BZ2_hbCreateDecodeTables ( Int32 *limit,
 196                                 Int32 *base,
 197                                 Int32 *perm,
 198                                 UChar *length,
 199                                 Int32 minLen,
 200                                 Int32 maxLen,
 201                                 Int32 alphaSize )
 202 {
 203    Int32 pp, i, j, vec;
 204
 205    pp = 0;
 206    for (i = minLen; i <= maxLen; i++)
 207       for (j = 0; j < alphaSize; j++)
 208          if (length[j] == i) { perm[pp] = j; pp++; };
 209
 210    for (i = 0; i < BZ_MAX_CODE_LEN; i++) base[i] = 0;
 211    for (i = 0; i < alphaSize; i++) base[length[i]+1]++;
 212
 213    for (i = 1; i < BZ_MAX_CODE_LEN; i++) base[i] += base[i-1];
 214
 215    for (i = 0; i < BZ_MAX_CODE_LEN; i++) limit[i] = 0;
 216    vec = 0;
 217
 218    for (i = minLen; i <= maxLen; i++) {
 219       vec += (base[i+1] - base[i]);
 220       limit[i] = vec-1;
 221       vec <<= 1;
 222    }
 223    for (i = minLen + 1; i <= maxLen; i++)
 224       base[i] = ((limit[i-1] + 1) << 1) - base[i];
 225 }
 226
 227
 228 /*-------------------------------------------------------------*/
 229 /*--- end                                         huffman.c ---*/
 230 /*-------------------------------------------------------------*/
 231
 232 #endif /* CONFIG_BZIP2 */