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 /*---------------------------------------------------*/
BZ2_hbMakeCodeLengths(UChar * len,Int32 * freq,Int32 alphaSize,Int32 maxLen)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 /*---------------------------------------------------*/
BZ2_hbAssignCodes(Int32 * code,UChar * length,Int32 minLen,Int32 maxLen,Int32 alphaSize)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 /*---------------------------------------------------*/
BZ2_hbCreateDecodeTables(Int32 * limit,Int32 * base,Int32 * perm,UChar * length,Int32 minLen,Int32 maxLen,Int32 alphaSize)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 /*-------------------------------------------------------------*/
231