cannam@89: cannam@89: /*-------------------------------------------------------------*/ cannam@89: /*--- Huffman coding low-level stuff ---*/ cannam@89: /*--- huffman.c ---*/ cannam@89: /*-------------------------------------------------------------*/ cannam@89: cannam@89: /* ------------------------------------------------------------------ cannam@89: This file is part of bzip2/libbzip2, a program and library for cannam@89: lossless, block-sorting data compression. cannam@89: cannam@89: bzip2/libbzip2 version 1.0.6 of 6 September 2010 cannam@89: Copyright (C) 1996-2010 Julian Seward cannam@89: cannam@89: Please read the WARNING, DISCLAIMER and PATENTS sections in the cannam@89: README file. cannam@89: cannam@89: This program is released under the terms of the license contained cannam@89: in the file LICENSE. cannam@89: ------------------------------------------------------------------ */ cannam@89: cannam@89: cannam@89: #include "bzlib_private.h" cannam@89: cannam@89: /*---------------------------------------------------*/ cannam@89: #define WEIGHTOF(zz0) ((zz0) & 0xffffff00) cannam@89: #define DEPTHOF(zz1) ((zz1) & 0x000000ff) cannam@89: #define MYMAX(zz2,zz3) ((zz2) > (zz3) ? (zz2) : (zz3)) cannam@89: cannam@89: #define ADDWEIGHTS(zw1,zw2) \ cannam@89: (WEIGHTOF(zw1)+WEIGHTOF(zw2)) | \ cannam@89: (1 + MYMAX(DEPTHOF(zw1),DEPTHOF(zw2))) cannam@89: cannam@89: #define UPHEAP(z) \ cannam@89: { \ cannam@89: Int32 zz, tmp; \ cannam@89: zz = z; tmp = heap[zz]; \ cannam@89: while (weight[tmp] < weight[heap[zz >> 1]]) { \ cannam@89: heap[zz] = heap[zz >> 1]; \ cannam@89: zz >>= 1; \ cannam@89: } \ cannam@89: heap[zz] = tmp; \ cannam@89: } cannam@89: cannam@89: #define DOWNHEAP(z) \ cannam@89: { \ cannam@89: Int32 zz, yy, tmp; \ cannam@89: zz = z; tmp = heap[zz]; \ cannam@89: while (True) { \ cannam@89: yy = zz << 1; \ cannam@89: if (yy > nHeap) break; \ cannam@89: if (yy < nHeap && \ cannam@89: weight[heap[yy+1]] < weight[heap[yy]]) \ cannam@89: yy++; \ cannam@89: if (weight[tmp] < weight[heap[yy]]) break; \ cannam@89: heap[zz] = heap[yy]; \ cannam@89: zz = yy; \ cannam@89: } \ cannam@89: heap[zz] = tmp; \ cannam@89: } cannam@89: cannam@89: cannam@89: /*---------------------------------------------------*/ cannam@89: void BZ2_hbMakeCodeLengths ( UChar *len, cannam@89: Int32 *freq, cannam@89: Int32 alphaSize, cannam@89: Int32 maxLen ) cannam@89: { cannam@89: /*-- cannam@89: Nodes and heap entries run from 1. Entry 0 cannam@89: for both the heap and nodes is a sentinel. cannam@89: --*/ cannam@89: Int32 nNodes, nHeap, n1, n2, i, j, k; cannam@89: Bool tooLong; cannam@89: cannam@89: Int32 heap [ BZ_MAX_ALPHA_SIZE + 2 ]; cannam@89: Int32 weight [ BZ_MAX_ALPHA_SIZE * 2 ]; cannam@89: Int32 parent [ BZ_MAX_ALPHA_SIZE * 2 ]; cannam@89: cannam@89: for (i = 0; i < alphaSize; i++) cannam@89: weight[i+1] = (freq[i] == 0 ? 1 : freq[i]) << 8; cannam@89: cannam@89: while (True) { cannam@89: cannam@89: nNodes = alphaSize; cannam@89: nHeap = 0; cannam@89: cannam@89: heap[0] = 0; cannam@89: weight[0] = 0; cannam@89: parent[0] = -2; cannam@89: cannam@89: for (i = 1; i <= alphaSize; i++) { cannam@89: parent[i] = -1; cannam@89: nHeap++; cannam@89: heap[nHeap] = i; cannam@89: UPHEAP(nHeap); cannam@89: } cannam@89: cannam@89: AssertH( nHeap < (BZ_MAX_ALPHA_SIZE+2), 2001 ); cannam@89: cannam@89: while (nHeap > 1) { cannam@89: n1 = heap[1]; heap[1] = heap[nHeap]; nHeap--; DOWNHEAP(1); cannam@89: n2 = heap[1]; heap[1] = heap[nHeap]; nHeap--; DOWNHEAP(1); cannam@89: nNodes++; cannam@89: parent[n1] = parent[n2] = nNodes; cannam@89: weight[nNodes] = ADDWEIGHTS(weight[n1], weight[n2]); cannam@89: parent[nNodes] = -1; cannam@89: nHeap++; cannam@89: heap[nHeap] = nNodes; cannam@89: UPHEAP(nHeap); cannam@89: } cannam@89: cannam@89: AssertH( nNodes < (BZ_MAX_ALPHA_SIZE * 2), 2002 ); cannam@89: cannam@89: tooLong = False; cannam@89: for (i = 1; i <= alphaSize; i++) { cannam@89: j = 0; cannam@89: k = i; cannam@89: while (parent[k] >= 0) { k = parent[k]; j++; } cannam@89: len[i-1] = j; cannam@89: if (j > maxLen) tooLong = True; cannam@89: } cannam@89: cannam@89: if (! tooLong) break; cannam@89: cannam@89: /* 17 Oct 04: keep-going condition for the following loop used cannam@89: to be 'i < alphaSize', which missed the last element, cannam@89: theoretically leading to the possibility of the compressor cannam@89: looping. However, this count-scaling step is only needed if cannam@89: one of the generated Huffman code words is longer than cannam@89: maxLen, which up to and including version 1.0.2 was 20 bits, cannam@89: which is extremely unlikely. In version 1.0.3 maxLen was cannam@89: changed to 17 bits, which has minimal effect on compression cannam@89: ratio, but does mean this scaling step is used from time to cannam@89: time, enough to verify that it works. cannam@89: cannam@89: This means that bzip2-1.0.3 and later will only produce cannam@89: Huffman codes with a maximum length of 17 bits. However, in cannam@89: order to preserve backwards compatibility with bitstreams cannam@89: produced by versions pre-1.0.3, the decompressor must still cannam@89: handle lengths of up to 20. */ cannam@89: cannam@89: for (i = 1; i <= alphaSize; i++) { cannam@89: j = weight[i] >> 8; cannam@89: j = 1 + (j / 2); cannam@89: weight[i] = j << 8; cannam@89: } cannam@89: } cannam@89: } cannam@89: cannam@89: cannam@89: /*---------------------------------------------------*/ cannam@89: void BZ2_hbAssignCodes ( Int32 *code, cannam@89: UChar *length, cannam@89: Int32 minLen, cannam@89: Int32 maxLen, cannam@89: Int32 alphaSize ) cannam@89: { cannam@89: Int32 n, vec, i; cannam@89: cannam@89: vec = 0; cannam@89: for (n = minLen; n <= maxLen; n++) { cannam@89: for (i = 0; i < alphaSize; i++) cannam@89: if (length[i] == n) { code[i] = vec; vec++; }; cannam@89: vec <<= 1; cannam@89: } cannam@89: } cannam@89: cannam@89: cannam@89: /*---------------------------------------------------*/ cannam@89: void BZ2_hbCreateDecodeTables ( Int32 *limit, cannam@89: Int32 *base, cannam@89: Int32 *perm, cannam@89: UChar *length, cannam@89: Int32 minLen, cannam@89: Int32 maxLen, cannam@89: Int32 alphaSize ) cannam@89: { cannam@89: Int32 pp, i, j, vec; cannam@89: cannam@89: pp = 0; cannam@89: for (i = minLen; i <= maxLen; i++) cannam@89: for (j = 0; j < alphaSize; j++) cannam@89: if (length[j] == i) { perm[pp] = j; pp++; }; cannam@89: cannam@89: for (i = 0; i < BZ_MAX_CODE_LEN; i++) base[i] = 0; cannam@89: for (i = 0; i < alphaSize; i++) base[length[i]+1]++; cannam@89: cannam@89: for (i = 1; i < BZ_MAX_CODE_LEN; i++) base[i] += base[i-1]; cannam@89: cannam@89: for (i = 0; i < BZ_MAX_CODE_LEN; i++) limit[i] = 0; cannam@89: vec = 0; cannam@89: cannam@89: for (i = minLen; i <= maxLen; i++) { cannam@89: vec += (base[i+1] - base[i]); cannam@89: limit[i] = vec-1; cannam@89: vec <<= 1; cannam@89: } cannam@89: for (i = minLen + 1; i <= maxLen; i++) cannam@89: base[i] = ((limit[i-1] + 1) << 1) - base[i]; cannam@89: } cannam@89: cannam@89: cannam@89: /*-------------------------------------------------------------*/ cannam@89: /*--- end huffman.c ---*/ cannam@89: /*-------------------------------------------------------------*/