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 /*-------------------------------------------------------------*/ 229