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Source at commit 1079 created 13 years 1 month ago. By meklort, began implimenting Bios disk changes. Code taken from biosfn.c | |
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1 | /* inftrees.c -- generate Huffman trees for efficient decoding␊ |
2 | * Copyright (C) 1995-2010 Mark Adler␊ |
3 | * For conditions of distribution and use, see copyright notice in zlib.h␊ |
4 | */␊ |
5 | ␊ |
6 | #include "zutil.h"␊ |
7 | #include "inftrees.h"␊ |
8 | ␊ |
9 | #define MAXBITS 15␊ |
10 | ␊ |
11 | const char inflate_copyright[] =␊ |
12 | " inflate 1.2.5 Copyright 1995-2010 Mark Adler ";␊ |
13 | /*␊ |
14 | If you use the zlib library in a product, an acknowledgment is welcome␊ |
15 | in the documentation of your product. If for some reason you cannot␊ |
16 | include such an acknowledgment, I would appreciate that you keep this␊ |
17 | copyright string in the executable of your product.␊ |
18 | */␊ |
19 | ␊ |
20 | /*␊ |
21 | Build a set of tables to decode the provided canonical Huffman code.␊ |
22 | The code lengths are lens[0..codes-1]. The result starts at *table,␊ |
23 | whose indices are 0..2^bits-1. work is a writable array of at least␊ |
24 | lens shorts, which is used as a work area. type is the type of code␊ |
25 | to be generated, CODES, LENS, or DISTS. On return, zero is success,␊ |
26 | -1 is an invalid code, and +1 means that ENOUGH isn't enough. table␊ |
27 | on return points to the next available entry's address. bits is the␊ |
28 | requested root table index bits, and on return it is the actual root␊ |
29 | table index bits. It will differ if the request is greater than the␊ |
30 | longest code or if it is less than the shortest code.␊ |
31 | */␊ |
32 | int ZLIB_INTERNAL inflate_table(type, lens, codes, table, bits, work)␊ |
33 | codetype type;␊ |
34 | unsigned short FAR *lens;␊ |
35 | unsigned codes;␊ |
36 | code FAR * FAR *table;␊ |
37 | unsigned FAR *bits;␊ |
38 | unsigned short FAR *work;␊ |
39 | {␊ |
40 | unsigned len; /* a code's length in bits */␊ |
41 | unsigned sym; /* index of code symbols */␊ |
42 | unsigned min, max; /* minimum and maximum code lengths */␊ |
43 | unsigned root; /* number of index bits for root table */␊ |
44 | unsigned curr; /* number of index bits for current table */␊ |
45 | unsigned drop; /* code bits to drop for sub-table */␊ |
46 | int left; /* number of prefix codes available */␊ |
47 | unsigned used; /* code entries in table used */␊ |
48 | unsigned huff; /* Huffman code */␊ |
49 | unsigned incr; /* for incrementing code, index */␊ |
50 | unsigned fill; /* index for replicating entries */␊ |
51 | unsigned low; /* low bits for current root entry */␊ |
52 | unsigned mask; /* mask for low root bits */␊ |
53 | code here; /* table entry for duplication */␊ |
54 | code FAR *next; /* next available space in table */␊ |
55 | const unsigned short FAR *base; /* base value table to use */␊ |
56 | const unsigned short FAR *extra; /* extra bits table to use */␊ |
57 | int end; /* use base and extra for symbol > end */␊ |
58 | unsigned short count[MAXBITS+1]; /* number of codes of each length */␊ |
59 | unsigned short offs[MAXBITS+1]; /* offsets in table for each length */␊ |
60 | static const unsigned short lbase[31] = { /* Length codes 257..285 base */␊ |
61 | 3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 17, 19, 23, 27, 31,␊ |
62 | 35, 43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227, 258, 0, 0};␊ |
63 | static const unsigned short lext[31] = { /* Length codes 257..285 extra */␊ |
64 | 16, 16, 16, 16, 16, 16, 16, 16, 17, 17, 17, 17, 18, 18, 18, 18,␊ |
65 | 19, 19, 19, 19, 20, 20, 20, 20, 21, 21, 21, 21, 16, 73, 195};␊ |
66 | static const unsigned short dbase[32] = { /* Distance codes 0..29 base */␊ |
67 | 1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49, 65, 97, 129, 193,␊ |
68 | 257, 385, 513, 769, 1025, 1537, 2049, 3073, 4097, 6145,␊ |
69 | 8193, 12289, 16385, 24577, 0, 0};␊ |
70 | static const unsigned short dext[32] = { /* Distance codes 0..29 extra */␊ |
71 | 16, 16, 16, 16, 17, 17, 18, 18, 19, 19, 20, 20, 21, 21, 22, 22,␊ |
72 | 23, 23, 24, 24, 25, 25, 26, 26, 27, 27,␊ |
73 | 28, 28, 29, 29, 64, 64};␊ |
74 | ␊ |
75 | /*␊ |
76 | Process a set of code lengths to create a canonical Huffman code. The␊ |
77 | code lengths are lens[0..codes-1]. Each length corresponds to the␊ |
78 | symbols 0..codes-1. The Huffman code is generated by first sorting the␊ |
79 | symbols by length from short to long, and retaining the symbol order␊ |
80 | for codes with equal lengths. Then the code starts with all zero bits␊ |
81 | for the first code of the shortest length, and the codes are integer␊ |
82 | increments for the same length, and zeros are appended as the length␊ |
83 | increases. For the deflate format, these bits are stored backwards␊ |
84 | from their more natural integer increment ordering, and so when the␊ |
85 | decoding tables are built in the large loop below, the integer codes␊ |
86 | are incremented backwards.␊ |
87 | ␊ |
88 | This routine assumes, but does not check, that all of the entries in␊ |
89 | lens[] are in the range 0..MAXBITS. The caller must assure this.␊ |
90 | 1..MAXBITS is interpreted as that code length. zero means that that␊ |
91 | symbol does not occur in this code.␊ |
92 | ␊ |
93 | The codes are sorted by computing a count of codes for each length,␊ |
94 | creating from that a table of starting indices for each length in the␊ |
95 | sorted table, and then entering the symbols in order in the sorted␊ |
96 | table. The sorted table is work[], with that space being provided by␊ |
97 | the caller.␊ |
98 | ␊ |
99 | The length counts are used for other purposes as well, i.e. finding␊ |
100 | the minimum and maximum length codes, determining if there are any␊ |
101 | codes at all, checking for a valid set of lengths, and looking ahead␊ |
102 | at length counts to determine sub-table sizes when building the␊ |
103 | decoding tables.␊ |
104 | */␊ |
105 | ␊ |
106 | /* accumulate lengths for codes (assumes lens[] all in 0..MAXBITS) */␊ |
107 | for (len = 0; len <= MAXBITS; len++)␊ |
108 | count[len] = 0;␊ |
109 | for (sym = 0; sym < codes; sym++)␊ |
110 | count[lens[sym]]++;␊ |
111 | ␊ |
112 | /* bound code lengths, force root to be within code lengths */␊ |
113 | root = *bits;␊ |
114 | for (max = MAXBITS; max >= 1; max--)␊ |
115 | if (count[max] != 0) break;␊ |
116 | if (root > max) root = max;␊ |
117 | if (max == 0) { /* no symbols to code at all */␊ |
118 | here.op = (unsigned char)64; /* invalid code marker */␊ |
119 | here.bits = (unsigned char)1;␊ |
120 | here.val = (unsigned short)0;␊ |
121 | *(*table)++ = here; /* make a table to force an error */␊ |
122 | *(*table)++ = here;␊ |
123 | *bits = 1;␊ |
124 | return 0; /* no symbols, but wait for decoding to report error */␊ |
125 | }␊ |
126 | for (min = 1; min < max; min++)␊ |
127 | if (count[min] != 0) break;␊ |
128 | if (root < min) root = min;␊ |
129 | ␊ |
130 | /* check for an over-subscribed or incomplete set of lengths */␊ |
131 | left = 1;␊ |
132 | for (len = 1; len <= MAXBITS; len++) {␊ |
133 | left <<= 1;␊ |
134 | left -= count[len];␊ |
135 | if (left < 0) return -1; /* over-subscribed */␊ |
136 | }␊ |
137 | if (left > 0 && (type == CODES || max != 1))␊ |
138 | return -1; /* incomplete set */␊ |
139 | ␊ |
140 | /* generate offsets into symbol table for each length for sorting */␊ |
141 | offs[1] = 0;␊ |
142 | for (len = 1; len < MAXBITS; len++)␊ |
143 | offs[len + 1] = offs[len] + count[len];␊ |
144 | ␊ |
145 | /* sort symbols by length, by symbol order within each length */␊ |
146 | for (sym = 0; sym < codes; sym++)␊ |
147 | if (lens[sym] != 0) work[offs[lens[sym]]++] = (unsigned short)sym;␊ |
148 | ␊ |
149 | /*␊ |
150 | Create and fill in decoding tables. In this loop, the table being␊ |
151 | filled is at next and has curr index bits. The code being used is huff␊ |
152 | with length len. That code is converted to an index by dropping drop␊ |
153 | bits off of the bottom. For codes where len is less than drop + curr,␊ |
154 | those top drop + curr - len bits are incremented through all values to␊ |
155 | fill the table with replicated entries.␊ |
156 | ␊ |
157 | root is the number of index bits for the root table. When len exceeds␊ |
158 | root, sub-tables are created pointed to by the root entry with an index␊ |
159 | of the low root bits of huff. This is saved in low to check for when a␊ |
160 | new sub-table should be started. drop is zero when the root table is␊ |
161 | being filled, and drop is root when sub-tables are being filled.␊ |
162 | ␊ |
163 | When a new sub-table is needed, it is necessary to look ahead in the␊ |
164 | code lengths to determine what size sub-table is needed. The length␊ |
165 | counts are used for this, and so count[] is decremented as codes are␊ |
166 | entered in the tables.␊ |
167 | ␊ |
168 | used keeps track of how many table entries have been allocated from the␊ |
169 | provided *table space. It is checked for LENS and DIST tables against␊ |
170 | the constants ENOUGH_LENS and ENOUGH_DISTS to guard against changes in␊ |
171 | the initial root table size constants. See the comments in inftrees.h␊ |
172 | for more information.␊ |
173 | ␊ |
174 | sym increments through all symbols, and the loop terminates when␊ |
175 | all codes of length max, i.e. all codes, have been processed. This␊ |
176 | routine permits incomplete codes, so another loop after this one fills␊ |
177 | in the rest of the decoding tables with invalid code markers.␊ |
178 | */␊ |
179 | ␊ |
180 | /* set up for code type */␊ |
181 | switch (type) {␊ |
182 | case CODES:␊ |
183 | base = extra = work; /* dummy value--not used */␊ |
184 | end = 19;␊ |
185 | break;␊ |
186 | case LENS:␊ |
187 | base = lbase;␊ |
188 | base -= 257;␊ |
189 | extra = lext;␊ |
190 | extra -= 257;␊ |
191 | end = 256;␊ |
192 | break;␊ |
193 | default: /* DISTS */␊ |
194 | base = dbase;␊ |
195 | extra = dext;␊ |
196 | end = -1;␊ |
197 | }␊ |
198 | ␊ |
199 | /* initialize state for loop */␊ |
200 | huff = 0; /* starting code */␊ |
201 | sym = 0; /* starting code symbol */␊ |
202 | len = min; /* starting code length */␊ |
203 | next = *table; /* current table to fill in */␊ |
204 | curr = root; /* current table index bits */␊ |
205 | drop = 0; /* current bits to drop from code for index */␊ |
206 | low = (unsigned)(-1); /* trigger new sub-table when len > root */␊ |
207 | used = 1U << root; /* use root table entries */␊ |
208 | mask = used - 1; /* mask for comparing low */␊ |
209 | ␊ |
210 | /* check available table space */␊ |
211 | if ((type == LENS && used >= ENOUGH_LENS) ||␊ |
212 | (type == DISTS && used >= ENOUGH_DISTS))␊ |
213 | return 1;␊ |
214 | ␊ |
215 | /* process all codes and make table entries */␊ |
216 | for (;;) {␊ |
217 | /* create table entry */␊ |
218 | here.bits = (unsigned char)(len - drop);␊ |
219 | if ((int)(work[sym]) < end) {␊ |
220 | here.op = (unsigned char)0;␊ |
221 | here.val = work[sym];␊ |
222 | }␊ |
223 | else if ((int)(work[sym]) > end) {␊ |
224 | here.op = (unsigned char)(extra[work[sym]]);␊ |
225 | here.val = base[work[sym]];␊ |
226 | }␊ |
227 | else {␊ |
228 | here.op = (unsigned char)(32 + 64); /* end of block */␊ |
229 | here.val = 0;␊ |
230 | }␊ |
231 | ␊ |
232 | /* replicate for those indices with low len bits equal to huff */␊ |
233 | incr = 1U << (len - drop);␊ |
234 | fill = 1U << curr;␊ |
235 | min = fill; /* save offset to next table */␊ |
236 | do {␊ |
237 | fill -= incr;␊ |
238 | next[(huff >> drop) + fill] = here;␊ |
239 | } while (fill != 0);␊ |
240 | ␊ |
241 | /* backwards increment the len-bit code huff */␊ |
242 | incr = 1U << (len - 1);␊ |
243 | while (huff & incr)␊ |
244 | incr >>= 1;␊ |
245 | if (incr != 0) {␊ |
246 | huff &= incr - 1;␊ |
247 | huff += incr;␊ |
248 | }␊ |
249 | else␊ |
250 | huff = 0;␊ |
251 | ␊ |
252 | /* go to next symbol, update count, len */␊ |
253 | sym++;␊ |
254 | if (--(count[len]) == 0) {␊ |
255 | if (len == max) break;␊ |
256 | len = lens[work[sym]];␊ |
257 | }␊ |
258 | ␊ |
259 | /* create new sub-table if needed */␊ |
260 | if (len > root && (huff & mask) != low) {␊ |
261 | /* if first time, transition to sub-tables */␊ |
262 | if (drop == 0)␊ |
263 | drop = root;␊ |
264 | ␊ |
265 | /* increment past last table */␊ |
266 | next += min; /* here min is 1 << curr */␊ |
267 | ␊ |
268 | /* determine length of next table */␊ |
269 | curr = len - drop;␊ |
270 | left = (int)(1 << curr);␊ |
271 | while (curr + drop < max) {␊ |
272 | left -= count[curr + drop];␊ |
273 | if (left <= 0) break;␊ |
274 | curr++;␊ |
275 | left <<= 1;␊ |
276 | }␊ |
277 | ␊ |
278 | /* check for enough space */␊ |
279 | used += 1U << curr;␊ |
280 | if ((type == LENS && used >= ENOUGH_LENS) ||␊ |
281 | (type == DISTS && used >= ENOUGH_DISTS))␊ |
282 | return 1;␊ |
283 | ␊ |
284 | /* point entry in root table to sub-table */␊ |
285 | low = huff & mask;␊ |
286 | (*table)[low].op = (unsigned char)curr;␊ |
287 | (*table)[low].bits = (unsigned char)root;␊ |
288 | (*table)[low].val = (unsigned short)(next - *table);␊ |
289 | }␊ |
290 | }␊ |
291 | ␊ |
292 | /*␊ |
293 | Fill in rest of table for incomplete codes. This loop is similar to the␊ |
294 | loop above in incrementing huff for table indices. It is assumed that␊ |
295 | len is equal to curr + drop, so there is no loop needed to increment␊ |
296 | through high index bits. When the current sub-table is filled, the loop␊ |
297 | drops back to the root table to fill in any remaining entries there.␊ |
298 | */␊ |
299 | here.op = (unsigned char)64; /* invalid code marker */␊ |
300 | here.bits = (unsigned char)(len - drop);␊ |
301 | here.val = (unsigned short)0;␊ |
302 | while (huff != 0) {␊ |
303 | /* when done with sub-table, drop back to root table */␊ |
304 | if (drop != 0 && (huff & mask) != low) {␊ |
305 | drop = 0;␊ |
306 | len = root;␊ |
307 | next = *table;␊ |
308 | here.bits = (unsigned char)len;␊ |
309 | }␊ |
310 | ␊ |
311 | /* put invalid code marker in table */␊ |
312 | next[huff >> drop] = here;␊ |
313 | ␊ |
314 | /* backwards increment the len-bit code huff */␊ |
315 | incr = 1U << (len - 1);␊ |
316 | while (huff & incr)␊ |
317 | incr >>= 1;␊ |
318 | if (incr != 0) {␊ |
319 | huff &= incr - 1;␊ |
320 | huff += incr;␊ |
321 | }␊ |
322 | else␊ |
323 | huff = 0;␊ |
324 | }␊ |
325 | ␊ |
326 | /* set return parameters */␊ |
327 | *table += used;␊ |
328 | *bits = root;␊ |
329 | return 0;␊ |
330 | }␊ |
331 |