lib/bzlib_huffman.c

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