lib/Support/bzip2/huffman.c

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