huffman.c - vx32 - Local 9vx git repository for patches.
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---
huffman.c (8571B)
---
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) 1996-2005 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@bzip.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 /* 17 Oct 04: keep-going condition for the following loop used
166 to be 'i < alphaSize', which missed the last element,
167 theoretically leading to the possibility of the compressor
168 looping. However, this count-scaling step is only needed if
169 one of the generated Huffman code words is longer than
170 maxLen, which up to and including version 1.0.2 was 20 bits,
171 which is extremely unlikely. In version 1.0.3 maxLen was
172 changed to 17 bits, which has minimal effect on compression
173 ratio, but does mean this scaling step is used from time to
174 time, enough to verify that it works.
175
176 This means that bzip2-1.0.3 and later will only produce
177 Huffman codes with a maximum length of 17 bits. However, in
178 order to preserve backwards compatibility with bitstreams
179 produced by versions pre-1.0.3, the decompressor must still
180 handle lengths of up to 20. */
181
182 for (i = 1; i <= alphaSize; i++) {
183 j = weight[i] >> 8;
184 j = 1 + (j / 2);
185 weight[i] = j << 8;
186 }
187 }
188 }
189
190
191 /*---------------------------------------------------*/
192 void BZ2_hbAssignCodes ( Int32 *code,
193 UChar *length,
194 Int32 minLen,
195 Int32 maxLen,
196 Int32 alphaSize )
197 {
198 Int32 n, vec, i;
199
200 vec = 0;
201 for (n = minLen; n <= maxLen; n++) {
202 for (i = 0; i < alphaSize; i++)
203 if (length[i] == n) { code[i] = vec; vec++; };
204 vec <<= 1;
205 }
206 }
207
208
209 /*---------------------------------------------------*/
210 void BZ2_hbCreateDecodeTables ( Int32 *limit,
211 Int32 *base,
212 Int32 *perm,
213 UChar *length,
214 Int32 minLen,
215 Int32 maxLen,
216 Int32 alphaSize )
217 {
218 Int32 pp, i, j, vec;
219
220 pp = 0;
221 for (i = minLen; i <= maxLen; i++)
222 for (j = 0; j < alphaSize; j++)
223 if (length[j] == i) { perm[pp] = j; pp++; };
224
225 for (i = 0; i < BZ_MAX_CODE_LEN; i++) base[i] = 0;
226 for (i = 0; i < alphaSize; i++) base[length[i]+1]++;
227
228 for (i = 1; i < BZ_MAX_CODE_LEN; i++) base[i] += base[i-1];
229
230 for (i = 0; i < BZ_MAX_CODE_LEN; i++) limit[i] = 0;
231 vec = 0;
232
233 for (i = minLen; i <= maxLen; i++) {
234 vec += (base[i+1] - base[i]);
235 limit[i] = vec-1;
236 vec <<= 1;
237 }
238 for (i = minLen + 1; i <= maxLen; i++)
239 base[i] = ((limit[i-1] + 1) << 1) - base[i];
240 }
241
242
243 /*-------------------------------------------------------------*/
244 /*--- end huffman.c ---*/
245 /*-------------------------------------------------------------*/