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/*-------------------------------------------------------------*/
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/*--- Huffman coding low-level stuff                        ---*/
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/*---                                             huffman.c ---*/
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/*-------------------------------------------------------------*/
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/* ------------------------------------------------------------------
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   This file is part of bzip2/libbzip2, a program and library for
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   lossless, block-sorting data compression.
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   bzip2/libbzip2 version 1.0.4 of 20 December 2006
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   Copyright (C) 1996-2006 Julian Seward <jseward@bzip.org>
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   Please read the WARNING, DISCLAIMER and PATENTS sections in the
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   README file.
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   This program is released under the terms of the license contained
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   in the file LICENSE.
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   ------------------------------------------------------------------ */
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#include "bzlib_private.h"
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/*---------------------------------------------------*/
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#define WEIGHTOF(zz0)  ((zz0) & 0xffffff00)
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#define DEPTHOF(zz1)   ((zz1) & 0x000000ff)
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#define MYMAX(zz2,zz3) ((zz2) > (zz3) ? (zz2) : (zz3))
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#define ADDWEIGHTS(zw1,zw2)                           \
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   (WEIGHTOF(zw1)+WEIGHTOF(zw2)) |                    \
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   (1 + MYMAX(DEPTHOF(zw1),DEPTHOF(zw2)))
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#define UPHEAP(z)                                     \
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{                                                     \
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   Int32 zz, tmp;                                     \
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   zz = z; tmp = heap[zz];                            \
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   while (weight[tmp] < weight[heap[zz >> 1]]) {      \
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      heap[zz] = heap[zz >> 1];                       \
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      zz >>= 1;                                       \
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   }                                                  \
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   heap[zz] = tmp;                                    \
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}
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#define DOWNHEAP(z)                                   \
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{                                                     \
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   Int32 zz, yy, tmp;                                 \
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   zz = z; tmp = heap[zz];                            \
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   while (True) {                                     \
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      yy = zz << 1;                                   \
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      if (yy > nHeap) break;                          \
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      if (yy < nHeap &&                               \
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          weight[heap[yy+1]] < weight[heap[yy]])      \
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         yy++;                                        \
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      if (weight[tmp] < weight[heap[yy]]) break;      \
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      heap[zz] = heap[yy];                            \
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      zz = yy;                                        \
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   }                                                  \
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   heap[zz] = tmp;                                    \
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}
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/*---------------------------------------------------*/
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void BZ2_hbMakeCodeLengths ( UChar *len,
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                             Int32 *freq,
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                             Int32 alphaSize,
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                             Int32 maxLen )
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{
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   /*--
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      Nodes and heap entries run from 1.  Entry 0
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      for both the heap and nodes is a sentinel.
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   --*/
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   Int32 nNodes, nHeap, n1, n2, i, j, k;
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   Bool  tooLong;
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   Int32 heap   [ BZ_MAX_ALPHA_SIZE + 2 ];
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   Int32 weight [ BZ_MAX_ALPHA_SIZE * 2 ];
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   Int32 parent [ BZ_MAX_ALPHA_SIZE * 2 ];
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   for (i = 0; i < alphaSize; i++)
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      weight[i+1] = (freq[i] == 0 ? 1 : freq[i]) << 8;
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   while (True) {
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      nNodes = alphaSize;
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      nHeap = 0;
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      heap[0] = 0;
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      weight[0] = 0;
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      parent[0] = -2;
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      for (i = 1; i <= alphaSize; i++) {
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         parent[i] = -1;
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         nHeap++;
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         heap[nHeap] = i;
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         UPHEAP(nHeap);
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      }
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      AssertH( nHeap < (BZ_MAX_ALPHA_SIZE+2), 2001 );
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      while (nHeap > 1) {
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         n1 = heap[1]; heap[1] = heap[nHeap]; nHeap--; DOWNHEAP(1);
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         n2 = heap[1]; heap[1] = heap[nHeap]; nHeap--; DOWNHEAP(1);
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         nNodes++;
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         parent[n1] = parent[n2] = nNodes;
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         weight[nNodes] = ADDWEIGHTS(weight[n1], weight[n2]);
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         parent[nNodes] = -1;
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         nHeap++;
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         heap[nHeap] = nNodes;
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         UPHEAP(nHeap);
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      }
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      AssertH( nNodes < (BZ_MAX_ALPHA_SIZE * 2), 2002 );
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      tooLong = False;
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      for (i = 1; i <= alphaSize; i++) {
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         j = 0;
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         k = i;
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         while (parent[k] >= 0) { k = parent[k]; j++; }
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         len[i-1] = j;
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         if (j > maxLen) tooLong = True;
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      }
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      if (! tooLong) break;
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      /* 17 Oct 04: keep-going condition for the following loop used
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         to be 'i < alphaSize', which missed the last element,
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         theoretically leading to the possibility of the compressor
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         looping.  However, this count-scaling step is only needed if
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         one of the generated Huffman code words is longer than
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         maxLen, which up to and including version 1.0.2 was 20 bits,
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         which is extremely unlikely.  In version 1.0.3 maxLen was
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         changed to 17 bits, which has minimal effect on compression
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         ratio, but does mean this scaling step is used from time to
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         time, enough to verify that it works.
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         This means that bzip2-1.0.3 and later will only produce
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         Huffman codes with a maximum length of 17 bits.  However, in
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         order to preserve backwards compatibility with bitstreams
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         produced by versions pre-1.0.3, the decompressor must still
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         handle lengths of up to 20. */
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      for (i = 1; i <= alphaSize; i++) {
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         j = weight[i] >> 8;
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         j = 1 + (j / 2);
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         weight[i] = j << 8;
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      }
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   }
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}
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/*---------------------------------------------------*/
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void BZ2_hbAssignCodes ( Int32 *code,
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                         UChar *length,
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                         Int32 minLen,
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                         Int32 maxLen,
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                         Int32 alphaSize )
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{
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   Int32 n, vec, i;
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   vec = 0;
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   for (n = minLen; n <= maxLen; n++) {
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      for (i = 0; i < alphaSize; i++)
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         if (length[i] == n) { code[i] = vec; vec++; };
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      vec <<= 1;
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   }
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}
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/*---------------------------------------------------*/
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void BZ2_hbCreateDecodeTables ( Int32 *limit,
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                                Int32 *base,
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                                Int32 *perm,
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                                UChar *length,
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                                Int32 minLen,
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                                Int32 maxLen,
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                                Int32 alphaSize )
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{
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   Int32 pp, i, j, vec;
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   pp = 0;
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   for (i = minLen; i <= maxLen; i++)
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      for (j = 0; j < alphaSize; j++)
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         if (length[j] == i) { perm[pp] = j; pp++; };
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   for (i = 0; i < BZ_MAX_CODE_LEN; i++) base[i] = 0;
186
   for (i = 0; i < alphaSize; i++) base[length[i]+1]++;
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   for (i = 1; i < BZ_MAX_CODE_LEN; i++) base[i] += base[i-1];
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190
   for (i = 0; i < BZ_MAX_CODE_LEN; i++) limit[i] = 0;
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   vec = 0;
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193
   for (i = minLen; i <= maxLen; i++) {
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      vec += (base[i+1] - base[i]);
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      limit[i] = vec-1;
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      vec <<= 1;
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   }
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   for (i = minLen + 1; i <= maxLen; i++)
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      base[i] = ((limit[i-1] + 1) << 1) - base[i];
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}
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/*-------------------------------------------------------------*/
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/*--- end                                         huffman.c ---*/
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/*-------------------------------------------------------------*/