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/*-------------------------------------------------------------*//*--- Huffman coding low-level stuff ---*//*--- huffman.c ---*//*-------------------------------------------------------------*/
/*--
This file is a part of bzip2 and/or libbzip2, a program and library for lossless, block-sorting data compression.
Copyright (C) 1996-2002 Julian R Seward. All rights reserved.
Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:
1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
2. The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgment in the product documentation would be appreciated but is not required.
3. Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.
4. The name of the author may not be used to endorse or promote products derived from this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
Julian Seward, Cambridge, UK. jseward@acm.org bzip2/libbzip2 version 1.0 of 21 March 2000
This program is based on (at least) the work of: Mike Burrows David Wheeler Peter Fenwick Alistair Moffat Radford Neal Ian H. Witten Robert Sedgewick Jon L. Bentley
For more information on these sources, see the manual.--*/
#include "bzlib_private.h"
/*---------------------------------------------------*/#define WEIGHTOF(zz0) ((zz0) & 0xffffff00)
#define DEPTHOF(zz1) ((zz1) & 0x000000ff)
#define MYMAX(zz2,zz3) ((zz2) > (zz3) ? (zz2) : (zz3))
#define ADDWEIGHTS(zw1,zw2) \
(WEIGHTOF(zw1)+WEIGHTOF(zw2)) | \ (1 + MYMAX(DEPTHOF(zw1),DEPTHOF(zw2)))
#define UPHEAP(z) \
{ \ Int32 zz, tmp; \ zz = z; tmp = heap[zz]; \ while (weight[tmp] < weight[heap[zz >> 1]]) { \ heap[zz] = heap[zz >> 1]; \ zz >>= 1; \ } \ heap[zz] = tmp; \}
#define DOWNHEAP(z) \
{ \ Int32 zz, yy, tmp; \ zz = z; tmp = heap[zz]; \ while (True) { \ yy = zz << 1; \ if (yy > nHeap) break; \ if (yy < nHeap && \ weight[heap[yy+1]] < weight[heap[yy]]) \ yy++; \ if (weight[tmp] < weight[heap[yy]]) break; \ heap[zz] = heap[yy]; \ zz = yy; \ } \ heap[zz] = tmp; \}
/*---------------------------------------------------*/void BZ2_hbMakeCodeLengths ( UChar *len, Int32 *freq, Int32 alphaSize, Int32 maxLen ){ /*--
Nodes and heap entries run from 1. Entry 0 for both the heap and nodes is a sentinel. --*/ Int32 nNodes, nHeap, n1, n2, i, j, k; Bool tooLong;
Int32 heap [ BZ_MAX_ALPHA_SIZE + 2 ]; Int32 weight [ BZ_MAX_ALPHA_SIZE * 2 ]; Int32 parent [ BZ_MAX_ALPHA_SIZE * 2 ];
for (i = 0; i < alphaSize; i++) weight[i+1] = (freq[i] == 0 ? 1 : freq[i]) << 8;
while (True) {
nNodes = alphaSize; nHeap = 0;
heap[0] = 0; weight[0] = 0; parent[0] = -2;
for (i = 1; i <= alphaSize; i++) { parent[i] = -1; nHeap++; heap[nHeap] = i; UPHEAP(nHeap); }
AssertH( nHeap < (BZ_MAX_ALPHA_SIZE+2), 2001 ); while (nHeap > 1) { n1 = heap[1]; heap[1] = heap[nHeap]; nHeap--; DOWNHEAP(1); n2 = heap[1]; heap[1] = heap[nHeap]; nHeap--; DOWNHEAP(1); nNodes++; parent[n1] = parent[n2] = nNodes; weight[nNodes] = ADDWEIGHTS(weight[n1], weight[n2]); parent[nNodes] = -1; nHeap++; heap[nHeap] = nNodes; UPHEAP(nHeap); }
AssertH( nNodes < (BZ_MAX_ALPHA_SIZE * 2), 2002 );
tooLong = False; for (i = 1; i <= alphaSize; i++) { j = 0; k = i; while (parent[k] >= 0) { k = parent[k]; j++; } len[i-1] = j; if (j > maxLen) tooLong = True; } if (! tooLong) break;
for (i = 1; i < alphaSize; i++) { j = weight[i] >> 8; j = 1 + (j / 2); weight[i] = j << 8; } }}
/*---------------------------------------------------*/void BZ2_hbAssignCodes ( Int32 *code, UChar *length, Int32 minLen, Int32 maxLen, Int32 alphaSize ){ Int32 n, vec, i;
vec = 0; for (n = minLen; n <= maxLen; n++) { for (i = 0; i < alphaSize; i++) if (length[i] == n) { code[i] = vec; vec++; }; vec <<= 1; }}
/*---------------------------------------------------*/void BZ2_hbCreateDecodeTables ( Int32 *limit, Int32 *base, Int32 *perm, UChar *length, Int32 minLen, Int32 maxLen, Int32 alphaSize ){ Int32 pp, i, j, vec;
pp = 0; for (i = minLen; i <= maxLen; i++) for (j = 0; j < alphaSize; j++) if (length[j] == i) { perm[pp] = j; pp++; };
for (i = 0; i < BZ_MAX_CODE_LEN; i++) base[i] = 0; for (i = 0; i < alphaSize; i++) base[length[i]+1]++;
for (i = 1; i < BZ_MAX_CODE_LEN; i++) base[i] += base[i-1];
for (i = 0; i < BZ_MAX_CODE_LEN; i++) limit[i] = 0; vec = 0;
for (i = minLen; i <= maxLen; i++) { vec += (base[i+1] - base[i]); limit[i] = vec-1; vec <<= 1; } for (i = minLen + 1; i <= maxLen; i++) base[i] = ((limit[i-1] + 1) << 1) - base[i];}
/*-------------------------------------------------------------*//*--- end huffman.c ---*//*-------------------------------------------------------------*/
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