huffman.c (7619B)
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) 1996-2000 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 "os.h" 63 #include "bzlib.h" 64 #include "bzlib_private.h" 65 66 /*---------------------------------------------------*/ 67 #define WEIGHTOF(zz0) ((zz0) & 0xffffff00) 68 #define DEPTHOF(zz1) ((zz1) & 0x000000ff) 69 #define MYMAX(zz2,zz3) ((zz2) > (zz3) ? (zz2) : (zz3)) 70 71 #define ADDWEIGHTS(zw1,zw2) \ 72 (WEIGHTOF(zw1)+WEIGHTOF(zw2)) | \ 73 (1 + MYMAX(DEPTHOF(zw1),DEPTHOF(zw2))) 74 75 #define UPHEAP(z) \ 76 { \ 77 Int32 zz, tmp; \ 78 zz = z; tmp = heap[zz]; \ 79 while (weight[tmp] < weight[heap[zz >> 1]]) { \ 80 heap[zz] = heap[zz >> 1]; \ 81 zz >>= 1; \ 82 } \ 83 heap[zz] = tmp; \ 84 } 85 86 #define DOWNHEAP(z) \ 87 { \ 88 Int32 zz, yy, tmp; \ 89 zz = z; tmp = heap[zz]; \ 90 while (True) { \ 91 yy = zz << 1; \ 92 if (yy > nHeap) break; \ 93 if (yy < nHeap && \ 94 weight[heap[yy+1]] < weight[heap[yy]]) \ 95 yy++; \ 96 if (weight[tmp] < weight[heap[yy]]) break; \ 97 heap[zz] = heap[yy]; \ 98 zz = yy; \ 99 } \ 100 heap[zz] = tmp; \ 101 } 102 103 104 /*---------------------------------------------------*/ 105 void BZ2_hbMakeCodeLengths ( UChar *len, 106 Int32 *freq, 107 Int32 alphaSize, 108 Int32 maxLen ) 109 { 110 /*-- 111 Nodes and heap entries run from 1. Entry 0 112 for both the heap and nodes is a sentinel. 113 --*/ 114 Int32 nNodes, nHeap, n1, n2, i, j, k; 115 Bool tooLong; 116 117 Int32 heap [ BZ_MAX_ALPHA_SIZE + 2 ]; 118 Int32 weight [ BZ_MAX_ALPHA_SIZE * 2 ]; 119 Int32 parent [ BZ_MAX_ALPHA_SIZE * 2 ]; 120 121 for (i = 0; i < alphaSize; i++) 122 weight[i+1] = (freq[i] == 0 ? 1 : freq[i]) << 8; 123 124 while (True) { 125 126 nNodes = alphaSize; 127 nHeap = 0; 128 129 heap[0] = 0; 130 weight[0] = 0; 131 parent[0] = -2; 132 133 for (i = 1; i <= alphaSize; i++) { 134 parent[i] = -1; 135 nHeap++; 136 heap[nHeap] = i; 137 UPHEAP(nHeap); 138 } 139 140 AssertH( nHeap < (BZ_MAX_ALPHA_SIZE+2), 2001 ); 141 142 while (nHeap > 1) { 143 n1 = heap[1]; heap[1] = heap[nHeap]; nHeap--; DOWNHEAP(1); 144 n2 = heap[1]; heap[1] = heap[nHeap]; nHeap--; DOWNHEAP(1); 145 nNodes++; 146 parent[n1] = parent[n2] = nNodes; 147 weight[nNodes] = ADDWEIGHTS(weight[n1], weight[n2]); 148 parent[nNodes] = -1; 149 nHeap++; 150 heap[nHeap] = nNodes; 151 UPHEAP(nHeap); 152 } 153 154 AssertH( nNodes < (BZ_MAX_ALPHA_SIZE * 2), 2002 ); 155 156 tooLong = False; 157 for (i = 1; i <= alphaSize; i++) { 158 j = 0; 159 k = i; 160 while (parent[k] >= 0) { k = parent[k]; j++; } 161 len[i-1] = j; 162 if (j > maxLen) tooLong = True; 163 } 164 165 if (! tooLong) break; 166 167 for (i = 1; i < alphaSize; i++) { 168 j = weight[i] >> 8; 169 j = 1 + (j / 2); 170 weight[i] = j << 8; 171 } 172 } 173 } 174 175 176 /*---------------------------------------------------*/ 177 void BZ2_hbAssignCodes ( Int32 *code, 178 UChar *length, 179 Int32 minLen, 180 Int32 maxLen, 181 Int32 alphaSize ) 182 { 183 Int32 n, vec, i; 184 185 vec = 0; 186 for (n = minLen; n <= maxLen; n++) { 187 for (i = 0; i < alphaSize; i++) 188 if (length[i] == n) { code[i] = vec; vec++; }; 189 vec <<= 1; 190 } 191 } 192 193 194 /*---------------------------------------------------*/ 195 void BZ2_hbCreateDecodeTables ( Int32 *limit, 196 Int32 *base, 197 Int32 *perm, 198 UChar *length, 199 Int32 minLen, 200 Int32 maxLen, 201 Int32 alphaSize ) 202 { 203 Int32 pp, i, j, vec; 204 205 pp = 0; 206 for (i = minLen; i <= maxLen; i++) 207 for (j = 0; j < alphaSize; j++) 208 if (length[j] == i) { perm[pp] = j; pp++; }; 209 210 for (i = 0; i < BZ_MAX_CODE_LEN; i++) base[i] = 0; 211 for (i = 0; i < alphaSize; i++) base[length[i]+1]++; 212 213 for (i = 1; i < BZ_MAX_CODE_LEN; i++) base[i] += base[i-1]; 214 215 for (i = 0; i < BZ_MAX_CODE_LEN; i++) limit[i] = 0; 216 vec = 0; 217 218 for (i = minLen; i <= maxLen; i++) { 219 vec += (base[i+1] - base[i]); 220 limit[i] = vec-1; 221 vec <<= 1; 222 } 223 for (i = minLen + 1; i <= maxLen; i++) 224 base[i] = ((limit[i-1] + 1) << 1) - base[i]; 225 } 226 227 228 /*-------------------------------------------------------------*/ 229 /*--- end huffman.c ---*/ 230 /*-------------------------------------------------------------*/