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Diffstat (limited to 'apps/plugins/imageviewer/png/inftrees.c')
-rw-r--r-- | apps/plugins/imageviewer/png/inftrees.c | 329 |
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diff --git a/apps/plugins/imageviewer/png/inftrees.c b/apps/plugins/imageviewer/png/inftrees.c new file mode 100644 index 0000000000..8a9c13ff03 --- /dev/null +++ b/apps/plugins/imageviewer/png/inftrees.c | |||
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1 | /* inftrees.c -- generate Huffman trees for efficient decoding | ||
2 | * Copyright (C) 1995-2005 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 1.2.3 Copyright 1995-2005 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 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 this; /* 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, 201, 196}; | ||
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 | this.op = (unsigned char)64; /* invalid code marker */ | ||
119 | this.bits = (unsigned char)1; | ||
120 | this.val = (unsigned short)0; | ||
121 | *(*table)++ = this; /* make a table to force an error */ | ||
122 | *(*table)++ = this; | ||
123 | *bits = 1; | ||
124 | return 0; /* no symbols, but wait for decoding to report error */ | ||
125 | } | ||
126 | for (min = 1; min <= MAXBITS; 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 when a LENS table is being made | ||
170 | against the space in *table, ENOUGH, minus the maximum space needed by | ||
171 | the worst case distance code, MAXD. This should never happen, but the | ||
172 | sufficiency of ENOUGH has not been proven exhaustively, hence the check. | ||
173 | This assumes that when type == LENS, bits == 9. | ||
174 | |||
175 | sym increments through all symbols, and the loop terminates when | ||
176 | all codes of length max, i.e. all codes, have been processed. This | ||
177 | routine permits incomplete codes, so another loop after this one fills | ||
178 | in the rest of the decoding tables with invalid code markers. | ||
179 | */ | ||
180 | |||
181 | /* set up for code type */ | ||
182 | switch (type) { | ||
183 | case CODES: | ||
184 | base = extra = work; /* dummy value--not used */ | ||
185 | end = 19; | ||
186 | break; | ||
187 | case LENS: | ||
188 | base = lbase; | ||
189 | base -= 257; | ||
190 | extra = lext; | ||
191 | extra -= 257; | ||
192 | end = 256; | ||
193 | break; | ||
194 | default: /* DISTS */ | ||
195 | base = dbase; | ||
196 | extra = dext; | ||
197 | end = -1; | ||
198 | } | ||
199 | |||
200 | /* initialize state for loop */ | ||
201 | huff = 0; /* starting code */ | ||
202 | sym = 0; /* starting code symbol */ | ||
203 | len = min; /* starting code length */ | ||
204 | next = *table; /* current table to fill in */ | ||
205 | curr = root; /* current table index bits */ | ||
206 | drop = 0; /* current bits to drop from code for index */ | ||
207 | low = (unsigned)(-1); /* trigger new sub-table when len > root */ | ||
208 | used = 1U << root; /* use root table entries */ | ||
209 | mask = used - 1; /* mask for comparing low */ | ||
210 | |||
211 | /* check available table space */ | ||
212 | if (type == LENS && used >= ENOUGH - MAXD) | ||
213 | return 1; | ||
214 | |||
215 | /* process all codes and make table entries */ | ||
216 | for (;;) { | ||
217 | /* create table entry */ | ||
218 | this.bits = (unsigned char)(len - drop); | ||
219 | if ((int)(work[sym]) < end) { | ||
220 | this.op = (unsigned char)0; | ||
221 | this.val = work[sym]; | ||
222 | } | ||
223 | else if ((int)(work[sym]) > end) { | ||
224 | this.op = (unsigned char)(extra[work[sym]]); | ||
225 | this.val = base[work[sym]]; | ||
226 | } | ||
227 | else { | ||
228 | this.op = (unsigned char)(32 + 64); /* end of block */ | ||
229 | this.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] = this; | ||
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 - MAXD) | ||
281 | return 1; | ||
282 | |||
283 | /* point entry in root table to sub-table */ | ||
284 | low = huff & mask; | ||
285 | (*table)[low].op = (unsigned char)curr; | ||
286 | (*table)[low].bits = (unsigned char)root; | ||
287 | (*table)[low].val = (unsigned short)(next - *table); | ||
288 | } | ||
289 | } | ||
290 | |||
291 | /* | ||
292 | Fill in rest of table for incomplete codes. This loop is similar to the | ||
293 | loop above in incrementing huff for table indices. It is assumed that | ||
294 | len is equal to curr + drop, so there is no loop needed to increment | ||
295 | through high index bits. When the current sub-table is filled, the loop | ||
296 | drops back to the root table to fill in any remaining entries there. | ||
297 | */ | ||
298 | this.op = (unsigned char)64; /* invalid code marker */ | ||
299 | this.bits = (unsigned char)(len - drop); | ||
300 | this.val = (unsigned short)0; | ||
301 | while (huff != 0) { | ||
302 | /* when done with sub-table, drop back to root table */ | ||
303 | if (drop != 0 && (huff & mask) != low) { | ||
304 | drop = 0; | ||
305 | len = root; | ||
306 | next = *table; | ||
307 | this.bits = (unsigned char)len; | ||
308 | } | ||
309 | |||
310 | /* put invalid code marker in table */ | ||
311 | next[huff >> drop] = this; | ||
312 | |||
313 | /* backwards increment the len-bit code huff */ | ||
314 | incr = 1U << (len - 1); | ||
315 | while (huff & incr) | ||
316 | incr >>= 1; | ||
317 | if (incr != 0) { | ||
318 | huff &= incr - 1; | ||
319 | huff += incr; | ||
320 | } | ||
321 | else | ||
322 | huff = 0; | ||
323 | } | ||
324 | |||
325 | /* set return parameters */ | ||
326 | *table += used; | ||
327 | *bits = root; | ||
328 | return 0; | ||
329 | } | ||