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1 | /* inftrees.c -- generate Huffman trees for efficient decoding |
2 | * Copyright (C) 1995-2013 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[] = |
8e074056 |
12 | " inflate 1.2.8.f-Proxmark3 Copyright 1995-2013 Mark Adler "; |
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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(codetype type, unsigned short FAR *lens, |
33 | unsigned codes, code FAR * FAR *table, |
34 | unsigned FAR *bits, unsigned short FAR *work) |
35 | { |
36 | unsigned len; /* a code's length in bits */ |
37 | unsigned sym; /* index of code symbols */ |
38 | unsigned min, max; /* minimum and maximum code lengths */ |
39 | unsigned root; /* number of index bits for root table */ |
40 | unsigned curr; /* number of index bits for current table */ |
41 | unsigned drop; /* code bits to drop for sub-table */ |
42 | int left; /* number of prefix codes available */ |
43 | unsigned used; /* code entries in table used */ |
44 | unsigned huff; /* Huffman code */ |
45 | unsigned incr; /* for incrementing code, index */ |
46 | unsigned fill; /* index for replicating entries */ |
47 | unsigned low; /* low bits for current root entry */ |
48 | unsigned mask; /* mask for low root bits */ |
49 | code here; /* table entry for duplication */ |
50 | code FAR *next; /* next available space in table */ |
51 | const unsigned short FAR *base; /* base value table to use */ |
52 | const unsigned short FAR *extra; /* extra bits table to use */ |
53 | int end; /* use base and extra for symbol > end */ |
54 | unsigned short count[MAXBITS+1]; /* number of codes of each length */ |
55 | unsigned short offs[MAXBITS+1]; /* offsets in table for each length */ |
56 | static const unsigned short lbase[31] = { /* Length codes 257..285 base */ |
57 | 3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 17, 19, 23, 27, 31, |
58 | 35, 43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227, 258, 0, 0}; |
59 | static const unsigned short lext[31] = { /* Length codes 257..285 extra */ |
60 | 16, 16, 16, 16, 16, 16, 16, 16, 17, 17, 17, 17, 18, 18, 18, 18, |
61 | 19, 19, 19, 19, 20, 20, 20, 20, 21, 21, 21, 21, 16, 72, 78}; |
62 | static const unsigned short dbase[32] = { /* Distance codes 0..29 base */ |
63 | 1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49, 65, 97, 129, 193, |
64 | 257, 385, 513, 769, 1025, 1537, 2049, 3073, 4097, 6145, |
65 | 8193, 12289, 16385, 24577, 0, 0}; |
66 | static const unsigned short dext[32] = { /* Distance codes 0..29 extra */ |
67 | 16, 16, 16, 16, 17, 17, 18, 18, 19, 19, 20, 20, 21, 21, 22, 22, |
68 | 23, 23, 24, 24, 25, 25, 26, 26, 27, 27, |
69 | 28, 28, 29, 29, 64, 64}; |
70 | |
71 | /* |
72 | Process a set of code lengths to create a canonical Huffman code. The |
73 | code lengths are lens[0..codes-1]. Each length corresponds to the |
74 | symbols 0..codes-1. The Huffman code is generated by first sorting the |
75 | symbols by length from short to long, and retaining the symbol order |
76 | for codes with equal lengths. Then the code starts with all zero bits |
77 | for the first code of the shortest length, and the codes are integer |
78 | increments for the same length, and zeros are appended as the length |
79 | increases. For the deflate format, these bits are stored backwards |
80 | from their more natural integer increment ordering, and so when the |
81 | decoding tables are built in the large loop below, the integer codes |
82 | are incremented backwards. |
83 | |
84 | This routine assumes, but does not check, that all of the entries in |
85 | lens[] are in the range 0..MAXBITS. The caller must assure this. |
86 | 1..MAXBITS is interpreted as that code length. zero means that that |
87 | symbol does not occur in this code. |
88 | |
89 | The codes are sorted by computing a count of codes for each length, |
90 | creating from that a table of starting indices for each length in the |
91 | sorted table, and then entering the symbols in order in the sorted |
92 | table. The sorted table is work[], with that space being provided by |
93 | the caller. |
94 | |
95 | The length counts are used for other purposes as well, i.e. finding |
96 | the minimum and maximum length codes, determining if there are any |
97 | codes at all, checking for a valid set of lengths, and looking ahead |
98 | at length counts to determine sub-table sizes when building the |
99 | decoding tables. |
100 | */ |
101 | |
102 | /* accumulate lengths for codes (assumes lens[] all in 0..MAXBITS) */ |
103 | for (len = 0; len <= MAXBITS; len++) |
104 | count[len] = 0; |
105 | for (sym = 0; sym < codes; sym++) |
106 | count[lens[sym]]++; |
107 | |
108 | /* bound code lengths, force root to be within code lengths */ |
109 | root = *bits; |
110 | for (max = MAXBITS; max >= 1; max--) |
111 | if (count[max] != 0) break; |
112 | if (root > max) root = max; |
113 | if (max == 0) { /* no symbols to code at all */ |
114 | here.op = (unsigned char)64; /* invalid code marker */ |
115 | here.bits = (unsigned char)1; |
116 | here.val = (unsigned short)0; |
117 | *(*table)++ = here; /* make a table to force an error */ |
118 | *(*table)++ = here; |
119 | *bits = 1; |
120 | return 0; /* no symbols, but wait for decoding to report error */ |
121 | } |
122 | for (min = 1; min < max; min++) |
123 | if (count[min] != 0) break; |
124 | if (root < min) root = min; |
125 | |
126 | /* check for an over-subscribed or incomplete set of lengths */ |
127 | left = 1; |
128 | for (len = 1; len <= MAXBITS; len++) { |
129 | left <<= 1; |
130 | left -= count[len]; |
131 | if (left < 0) return -1; /* over-subscribed */ |
132 | } |
133 | if (left > 0 && (type == CODES || max != 1)) |
134 | return -1; /* incomplete set */ |
135 | |
136 | /* generate offsets into symbol table for each length for sorting */ |
137 | offs[1] = 0; |
138 | for (len = 1; len < MAXBITS; len++) |
139 | offs[len + 1] = offs[len] + count[len]; |
140 | |
141 | /* sort symbols by length, by symbol order within each length */ |
142 | for (sym = 0; sym < codes; sym++) |
143 | if (lens[sym] != 0) work[offs[lens[sym]]++] = (unsigned short)sym; |
144 | |
145 | /* |
146 | Create and fill in decoding tables. In this loop, the table being |
147 | filled is at next and has curr index bits. The code being used is huff |
148 | with length len. That code is converted to an index by dropping drop |
149 | bits off of the bottom. For codes where len is less than drop + curr, |
150 | those top drop + curr - len bits are incremented through all values to |
151 | fill the table with replicated entries. |
152 | |
153 | root is the number of index bits for the root table. When len exceeds |
154 | root, sub-tables are created pointed to by the root entry with an index |
155 | of the low root bits of huff. This is saved in low to check for when a |
156 | new sub-table should be started. drop is zero when the root table is |
157 | being filled, and drop is root when sub-tables are being filled. |
158 | |
159 | When a new sub-table is needed, it is necessary to look ahead in the |
160 | code lengths to determine what size sub-table is needed. The length |
161 | counts are used for this, and so count[] is decremented as codes are |
162 | entered in the tables. |
163 | |
164 | used keeps track of how many table entries have been allocated from the |
165 | provided *table space. It is checked for LENS and DIST tables against |
166 | the constants ENOUGH_LENS and ENOUGH_DISTS to guard against changes in |
167 | the initial root table size constants. See the comments in inftrees.h |
168 | for more information. |
169 | |
170 | sym increments through all symbols, and the loop terminates when |
171 | all codes of length max, i.e. all codes, have been processed. This |
172 | routine permits incomplete codes, so another loop after this one fills |
173 | in the rest of the decoding tables with invalid code markers. |
174 | */ |
175 | |
176 | /* set up for code type */ |
177 | switch (type) { |
178 | case CODES: |
179 | base = extra = work; /* dummy value--not used */ |
180 | end = 19; |
181 | break; |
182 | case LENS: |
183 | base = lbase; |
184 | base -= 257; |
185 | extra = lext; |
186 | extra -= 257; |
187 | end = 256; |
188 | break; |
189 | default: /* DISTS */ |
190 | base = dbase; |
191 | extra = dext; |
192 | end = -1; |
193 | } |
194 | |
195 | /* initialize state for loop */ |
196 | huff = 0; /* starting code */ |
197 | sym = 0; /* starting code symbol */ |
198 | len = min; /* starting code length */ |
199 | next = *table; /* current table to fill in */ |
200 | curr = root; /* current table index bits */ |
201 | drop = 0; /* current bits to drop from code for index */ |
202 | low = (unsigned)(-1); /* trigger new sub-table when len > root */ |
203 | used = 1U << root; /* use root table entries */ |
204 | mask = used - 1; /* mask for comparing low */ |
205 | |
206 | /* check available table space */ |
207 | if ((type == LENS && used > ENOUGH_LENS) || |
208 | (type == DISTS && used > ENOUGH_DISTS)) |
209 | return 1; |
210 | |
211 | /* process all codes and make table entries */ |
212 | for (;;) { |
213 | /* create table entry */ |
214 | here.bits = (unsigned char)(len - drop); |
215 | if ((int)(work[sym]) < end) { |
216 | here.op = (unsigned char)0; |
217 | here.val = work[sym]; |
218 | } |
219 | else if ((int)(work[sym]) > end) { |
220 | here.op = (unsigned char)(extra[work[sym]]); |
221 | here.val = base[work[sym]]; |
222 | } |
223 | else { |
224 | here.op = (unsigned char)(32 + 64); /* end of block */ |
225 | here.val = 0; |
226 | } |
227 | |
228 | /* replicate for those indices with low len bits equal to huff */ |
229 | incr = 1U << (len - drop); |
230 | fill = 1U << curr; |
231 | min = fill; /* save offset to next table */ |
232 | do { |
233 | fill -= incr; |
234 | next[(huff >> drop) + fill] = here; |
235 | } while (fill != 0); |
236 | |
237 | /* backwards increment the len-bit code huff */ |
238 | incr = 1U << (len - 1); |
239 | while (huff & incr) |
240 | incr >>= 1; |
241 | if (incr != 0) { |
242 | huff &= incr - 1; |
243 | huff += incr; |
244 | } |
245 | else |
246 | huff = 0; |
247 | |
248 | /* go to next symbol, update count, len */ |
249 | sym++; |
250 | if (--(count[len]) == 0) { |
251 | if (len == max) break; |
252 | len = lens[work[sym]]; |
253 | } |
254 | |
255 | /* create new sub-table if needed */ |
256 | if (len > root && (huff & mask) != low) { |
257 | /* if first time, transition to sub-tables */ |
258 | if (drop == 0) |
259 | drop = root; |
260 | |
261 | /* increment past last table */ |
262 | next += min; /* here min is 1 << curr */ |
263 | |
264 | /* determine length of next table */ |
265 | curr = len - drop; |
266 | left = (int)(1 << curr); |
267 | while (curr + drop < max) { |
268 | left -= count[curr + drop]; |
269 | if (left <= 0) break; |
270 | curr++; |
271 | left <<= 1; |
272 | } |
273 | |
274 | /* check for enough space */ |
275 | used += 1U << curr; |
276 | if ((type == LENS && used > ENOUGH_LENS) || |
277 | (type == DISTS && used > ENOUGH_DISTS)) |
278 | return 1; |
279 | |
280 | /* point entry in root table to sub-table */ |
281 | low = huff & mask; |
282 | (*table)[low].op = (unsigned char)curr; |
283 | (*table)[low].bits = (unsigned char)root; |
284 | (*table)[low].val = (unsigned short)(next - *table); |
285 | } |
286 | } |
287 | |
288 | /* fill in remaining table entry if code is incomplete (guaranteed to have |
289 | at most one remaining entry, since if the code is incomplete, the |
290 | maximum code length that was allowed to get this far is one bit) */ |
291 | if (huff != 0) { |
292 | here.op = (unsigned char)64; /* invalid code marker */ |
293 | here.bits = (unsigned char)(len - drop); |
294 | here.val = (unsigned short)0; |
295 | next[huff] = here; |
296 | } |
297 | |
298 | /* set return parameters */ |
299 | *table += used; |
300 | *bits = root; |
301 | return 0; |
302 | } |