cpan/Compress-Raw-Zlib/inftrees.c | |||
---|---|---|---|

Criterion | Covered | Total | % |

statement | 75 | 86 | 87.2 |

branch | n/a | ||

condition | n/a | ||

subroutine | n/a | ||

total | 75 | 86 | 87.2 |

line | stmt | bran | cond | sub | time | code |
---|---|---|---|---|---|---|

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[] = | |||||

12 | " inflate 1.2.8 Copyright 1995-2013 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 | 36660 | int ZLIB_INTERNAL inflate_table( | ||||

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, 72, 78}; | |||||

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 | 623220 | for (len = 0; len <= MAXBITS; len++) | ||||

108 | 586560 | count[len] = 0; | ||||

109 | 3479996 | for (sym = 0; sym < codes; sym++) | ||||

110 | 3479996 | count[lens[sym]]++; | ||||

111 | ||||||

112 | /* bound code lengths, force root to be within code lengths */ | |||||

113 | 36660 | root = *bits; | ||||

114 | 436704 | for (max = MAXBITS; max >= 1; max--) | ||||

115 | 436704 | if (count[max] != 0) break; | ||||

116 | 36660 | if (root > max) root = max; | ||||

117 | 36660 | if (max == 0) { /* no symbols to code at all */ | ||||

118 | 0 | here.op = (unsigned char)64; /* invalid code marker */ | ||||

119 | 0 | here.bits = (unsigned char)1; | ||||

120 | 0 | here.val = (unsigned short)0; | ||||

121 | 0 | *(*table)++ = here; /* make a table to force an error */ | ||||

122 | 0 | *(*table)++ = here; | ||||

123 | 0 | *bits = 1; | ||||

124 | 0 | return 0; /* no symbols, but wait for decoding to report error */ | ||||

125 | } | |||||

126 | 36562 | for (min = 1; min < max; min++) | ||||

127 | 61704 | if (count[min] != 0) break; | ||||

128 | 36660 | if (root < min) root = min; | ||||

129 | ||||||

130 | /* check for an over-subscribed or incomplete set of lengths */ | |||||

131 | left = 1; | |||||

132 | 586560 | for (len = 1; len <= MAXBITS; len++) { | ||||

133 | 549900 | left <<= 1; | ||||

134 | 549900 | left -= count[len]; | ||||

135 | 549900 | if (left < 0) return -1; /* over-subscribed */ | ||||

136 | } | |||||

137 | 36660 | 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 | 36622 | offs[1] = 0; | ||||

142 | 549330 | for (len = 1; len < MAXBITS; len++) | ||||

143 | 512708 | offs[len + 1] = offs[len] + count[len]; | ||||

144 | ||||||

145 | /* sort symbols by length, by symbol order within each length */ | |||||

146 | 3479274 | for (sym = 0; sym < codes; sym++) | ||||

147 | 3479274 | 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 | 36622 | switch (type) { | ||||

182 | case CODES: | |||||

183 | base = extra = work; /* dummy value--not used */ | |||||

184 | end = 19; | |||||

185 | 12866 | 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 | 36622 | 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 | 36622 | used = 1U << root; /* use root table entries */ | ||||

208 | 36622 | mask = used - 1; /* mask for comparing low */ | ||||

209 | ||||||

210 | /* check available table space */ | |||||

211 | 73244 | if ((type == LENS && used > ENOUGH_LENS) || | ||||

212 | 36622 | (type == DISTS && used > ENOUGH_DISTS)) | ||||

213 | return 1; | |||||

214 | ||||||

215 | /* process all codes and make table entries */ | |||||

216 | for (;;) { | |||||

217 | /* create table entry */ | |||||

218 | 405650 | here.bits = (unsigned char)(len - drop); | ||||

219 | 405650 | if ((int)(work[sym]) < end) { | ||||

220 | 339052 | here.op = (unsigned char)0; | ||||

221 | 339052 | here.val = work[sym]; | ||||

222 | } | |||||

223 | 66598 | else if ((int)(work[sym]) > end) { | ||||

224 | 54720 | here.op = (unsigned char)(extra[work[sym]]); | ||||

225 | 54720 | here.val = base[work[sym]]; | ||||

226 | } | |||||

227 | else { | |||||

228 | 11878 | here.op = (unsigned char)(32 + 64); /* end of block */ | ||||

229 | 11878 | here.val = 0; | ||||

230 | } | |||||

231 | ||||||

232 | /* replicate for those indices with low len bits equal to huff */ | |||||

233 | 405650 | incr = 1U << (len - drop); | ||||

234 | 405650 | fill = 1U << curr; | ||||

235 | min = fill; /* save offset to next table */ | |||||

236 | do { | |||||

237 | 1270086 | fill -= incr; | ||||

238 | 1270086 | next[(huff >> drop) + fill] = here; | ||||

239 | 1270086 | } while (fill != 0); | ||||

240 | ||||||

241 | /* backwards increment the len-bit code huff */ | |||||

242 | 405650 | incr = 1U << (len - 1); | ||||

243 | 1180328 | while (huff & incr) | ||||

244 | 369028 | incr >>= 1; | ||||

245 | 405650 | if (incr != 0) { | ||||

246 | 369028 | huff &= incr - 1; | ||||

247 | 369028 | huff += incr; | ||||

248 | } | |||||

249 | else | |||||

250 | huff = 0; | |||||

251 | ||||||

252 | /* go to next symbol, update count, len */ | |||||

253 | 405650 | sym++; | ||||

254 | 405650 | if (--(count[len]) == 0) { | ||||

255 | 112564 | if (len == max) break; | ||||

256 | 75942 | len = lens[work[sym]]; | ||||

257 | } | |||||

258 | ||||||

259 | /* create new sub-table if needed */ | |||||

260 | 369028 | if (len > root && (huff & mask) != low) { | ||||

261 | /* if first time, transition to sub-tables */ | |||||

262 | 1830 | if (drop == 0) | ||||

263 | drop = root; | |||||

264 | ||||||

265 | /* increment past last table */ | |||||

266 | 1830 | next += min; /* here min is 1 << curr */ | ||||

267 | ||||||

268 | /* determine length of next table */ | |||||

269 | 1830 | curr = len - drop; | ||||

270 | 1830 | left = (int)(1 << curr); | ||||

271 | 4352 | while (curr + drop < max) { | ||||

272 | 2272 | left -= count[curr + drop]; | ||||

273 | 2272 | if (left <= 0) break; | ||||

274 | 692 | curr++; | ||||

275 | 692 | left <<= 1; | ||||

276 | } | |||||

277 | ||||||

278 | /* check for enough space */ | |||||

279 | 1830 | used += 1U << curr; | ||||

280 | 3660 | if ((type == LENS && used > ENOUGH_LENS) || | ||||

281 | 1830 | (type == DISTS && used > ENOUGH_DISTS)) | ||||

282 | return 1; | |||||

283 | ||||||

284 | /* point entry in root table to sub-table */ | |||||

285 | 1830 | low = huff & mask; | ||||

286 | 1830 | (*table)[low].op = (unsigned char)curr; | ||||

287 | 1830 | (*table)[low].bits = (unsigned char)root; | ||||

288 | 1830 | (*table)[low].val = (unsigned short)(next - *table); | ||||

289 | } | |||||

290 | } | |||||

291 | ||||||

292 | /* fill in remaining table entry if code is incomplete (guaranteed to have | |||||

293 | at most one remaining entry, since if the code is incomplete, the | |||||

294 | maximum code length that was allowed to get this far is one bit) */ | |||||

295 | 36622 | if (huff != 0) { | ||||

296 | 0 | here.op = (unsigned char)64; /* invalid code marker */ | ||||

297 | 0 | here.bits = (unsigned char)(len - drop); | ||||

298 | 0 | here.val = (unsigned short)0; | ||||

299 | 0 | next[huff] = here; | ||||

300 | } | |||||

301 | ||||||

302 | /* set return parameters */ | |||||

303 | 36622 | *table += used; | ||||

304 | 36622 | *bits = root; | ||||

305 | 36622 | return 0; | ||||

306 | } |