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/* blast.c |
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* Copyright (C) 2003, 2012, 2013 Mark Adler |
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* For conditions of distribution and use, see copyright notice in blast.h |
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* version 1.3, 24 Aug 2013 |
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* |
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* blast.c decompresses data compressed by the PKWare Compression Library. |
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* This function provides functionality similar to the explode() function of |
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* the PKWare library, hence the name "blast". |
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* |
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* This decompressor is based on the excellent format description provided by |
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* Ben Rudiak-Gould in comp.compression on August 13, 2001. Interestingly, the |
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* example Ben provided in the post is incorrect. The distance 110001 should |
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* instead be 111000. When corrected, the example byte stream becomes: |
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* |
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* 00 04 82 24 25 8f 80 7f |
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* |
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* which decompresses to "AIAIAIAIAIAIA" (without the quotes). |
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*/ |
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/* |
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* Change history: |
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* |
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* 1.0 12 Feb 2003 - First version |
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* 1.1 16 Feb 2003 - Fixed distance check for > 4 GB uncompressed data |
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* 1.2 24 Oct 2012 - Add note about using binary mode in stdio |
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* - Fix comparisons of differently signed integers |
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* 1.3 24 Aug 2013 - Return unused input from blast() |
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* - Fix test code to correctly report unused input |
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* - Enable the provision of initial input to blast() |
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*/ |
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#include <stddef.h> /* for NULL */ |
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#include <setjmp.h> /* for setjmp(), longjmp(), and jmp_buf */ |
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#include "blast.h" /* prototype for blast() */ |
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#define MAXBITS 13 /* maximum code length */ |
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#define MAXWIN 4096 /* maximum window size */ |
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/* input and output state */ |
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struct state { |
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/* input state */ |
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blast_in infun; /* input function provided by user */ |
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void *inhow; /* opaque information passed to infun() */ |
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unsigned char *in; /* next input location */ |
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unsigned left; /* available input at in */ |
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int bitbuf; /* bit buffer */ |
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int bitcnt; /* number of bits in bit buffer */ |
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/* input limit error return state for bits() and decode() */ |
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jmp_buf env; |
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/* output state */ |
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blast_out outfun; /* output function provided by user */ |
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void *outhow; /* opaque information passed to outfun() */ |
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unsigned next; /* index of next write location in out[] */ |
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int first; /* true to check distances (for first 4K) */ |
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unsigned char out[MAXWIN]; /* output buffer and sliding window */ |
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}; |
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/* |
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* Return need bits from the input stream. This always leaves less than |
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* eight bits in the buffer. bits() works properly for need == 0. |
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* |
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* Format notes: |
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* |
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* - Bits are stored in bytes from the least significant bit to the most |
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* significant bit. Therefore bits are dropped from the bottom of the bit |
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* buffer, using shift right, and new bytes are appended to the top of the |
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* bit buffer, using shift left. |
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*/ |
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local int bits(struct state *s, int need) |
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{ |
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int val; /* bit accumulator */ |
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/* load at least need bits into val */ |
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val = s->bitbuf; |
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while (s->bitcnt < need) { |
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if (s->left == 0) { |
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s->left = s->infun(s->inhow, &(s->in)); |
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if (s->left == 0) longjmp(s->env, 1); /* out of input */ |
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} |
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val |= (int)(*(s->in)++) << s->bitcnt; /* load eight bits */ |
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s->left--; |
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s->bitcnt += 8; |
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} |
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/* drop need bits and update buffer, always zero to seven bits left */ |
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s->bitbuf = val >> need; |
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s->bitcnt -= need; |
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/* return need bits, zeroing the bits above that */ |
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return val & ((1 << need) - 1); |
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} |
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/* |
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* Huffman code decoding tables. count[1..MAXBITS] is the number of symbols of |
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* each length, which for a canonical code are stepped through in order. |
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* symbol[] are the symbol values in canonical order, where the number of |
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* entries is the sum of the counts in count[]. The decoding process can be |
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* seen in the function decode() below. |
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*/ |
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struct huffman { |
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short *count; /* number of symbols of each length */ |
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short *symbol; /* canonically ordered symbols */ |
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}; |
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/* |
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* Decode a code from the stream s using huffman table h. Return the symbol or |
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* a negative value if there is an error. If all of the lengths are zero, i.e. |
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* an empty code, or if the code is incomplete and an invalid code is received, |
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* then -9 is returned after reading MAXBITS bits. |
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* |
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* Format notes: |
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* |
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* - The codes as stored in the compressed data are bit-reversed relative to |
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* a simple integer ordering of codes of the same lengths. Hence below the |
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* bits are pulled from the compressed data one at a time and used to |
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* build the code value reversed from what is in the stream in order to |
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* permit simple integer comparisons for decoding. |
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* |
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* - The first code for the shortest length is all ones. Subsequent codes of |
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* the same length are simply integer decrements of the previous code. When |
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* moving up a length, a one bit is appended to the code. For a complete |
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* code, the last code of the longest length will be all zeros. To support |
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* this ordering, the bits pulled during decoding are inverted to apply the |
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* more "natural" ordering starting with all zeros and incrementing. |
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*/ |
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local int decode(struct state *s, struct huffman *h) |
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{ |
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int len; /* current number of bits in code */ |
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int code; /* len bits being decoded */ |
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int first; /* first code of length len */ |
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int count; /* number of codes of length len */ |
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int index; /* index of first code of length len in symbol table */ |
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int bitbuf; /* bits from stream */ |
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int left; /* bits left in next or left to process */ |
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short *next; /* next number of codes */ |
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bitbuf = s->bitbuf; |
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left = s->bitcnt; |
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code = first = index = 0; |
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len = 1; |
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next = h->count + 1; |
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while (1) { |
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while (left--) { |
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code |= (bitbuf & 1) ^ 1; /* invert code */ |
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bitbuf >>= 1; |
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count = *next++; |
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if (code < first + count) { /* if length len, return symbol */ |
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s->bitbuf = bitbuf; |
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s->bitcnt = (s->bitcnt - len) & 7; |
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return h->symbol[index + (code - first)]; |
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} |
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index += count; /* else update for next length */ |
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first += count; |
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first <<= 1; |
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code <<= 1; |
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len++; |
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} |
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left = (MAXBITS+1) - len; |
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if (left == 0) break; |
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if (s->left == 0) { |
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s->left = s->infun(s->inhow, &(s->in)); |
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if (s->left == 0) longjmp(s->env, 1); /* out of input */ |
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} |
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bitbuf = *(s->in)++; |
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s->left--; |
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if (left > 8) left = 8; |
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} |
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return -9; /* ran out of codes */ |
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} |
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/* |
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* Given a list of repeated code lengths rep[0..n-1], where each byte is a |
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* count (high four bits + 1) and a code length (low four bits), generate the |
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* list of code lengths. This compaction reduces the size of the object code. |
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* Then given the list of code lengths length[0..n-1] representing a canonical |
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* Huffman code for n symbols, construct the tables required to decode those |
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* codes. Those tables are the number of codes of each length, and the symbols |
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* sorted by length, retaining their original order within each length. The |
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* return value is zero for a complete code set, negative for an over- |
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* subscribed code set, and positive for an incomplete code set. The tables |
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* can be used if the return value is zero or positive, but they cannot be used |
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* if the return value is negative. If the return value is zero, it is not |
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* possible for decode() using that table to return an error--any stream of |
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* enough bits will resolve to a symbol. If the return value is positive, then |
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* it is possible for decode() using that table to return an error for received |
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* codes past the end of the incomplete lengths. |
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*/ |
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local int construct(struct huffman *h, const unsigned char *rep, int n) |
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{ |
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int symbol; /* current symbol when stepping through length[] */ |
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int len; /* current length when stepping through h->count[] */ |
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int left; /* number of possible codes left of current length */ |
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short offs[MAXBITS+1]; /* offsets in symbol table for each length */ |
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short length[256]; /* code lengths */ |
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/* convert compact repeat counts into symbol bit length list */ |
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symbol = 0; |
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do { |
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len = *rep++; |
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left = (len >> 4) + 1; |
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len &= 15; |
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do { |
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length[symbol++] = len; |
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} while (--left); |
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} while (--n); |
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n = symbol; |
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/* count number of codes of each length */ |
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for (len = 0; len <= MAXBITS; len++) |
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h->count[len] = 0; |
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for (symbol = 0; symbol < n; symbol++) |
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(h->count[length[symbol]])++; /* assumes lengths are within bounds */ |
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if (h->count[0] == n) /* no codes! */ |
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return 0; /* complete, but decode() will fail */ |
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217
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218
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/* check for an over-subscribed or incomplete set of lengths */ |
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left = 1; /* one possible code of zero length */ |
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for (len = 1; len <= MAXBITS; len++) { |
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left <<= 1; /* one more bit, double codes left */ |
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222
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left -= h->count[len]; /* deduct count from possible codes */ |
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223
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if (left < 0) return left; /* over-subscribed--return negative */ |
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224
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} /* left > 0 means incomplete */ |
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225
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226
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/* generate offsets into symbol table for each length for sorting */ |
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offs[1] = 0; |
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for (len = 1; len < MAXBITS; len++) |
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229
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offs[len + 1] = offs[len] + h->count[len]; |
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230
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231
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/* |
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232
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* put symbols in table sorted by length, by symbol order within each |
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233
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* length |
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234
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*/ |
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235
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for (symbol = 0; symbol < n; symbol++) |
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236
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if (length[symbol] != 0) |
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237
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h->symbol[offs[length[symbol]]++] = symbol; |
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238
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239
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/* return zero for complete set, positive for incomplete set */ |
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240
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return left; |
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241
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} |
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242
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243
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/* |
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244
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* Decode PKWare Compression Library stream. |
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245
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* |
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246
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* Format notes: |
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247
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* |
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248
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* - First byte is 0 if literals are uncoded or 1 if they are coded. Second |
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249
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* byte is 4, 5, or 6 for the number of extra bits in the distance code. |
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250
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* This is the base-2 logarithm of the dictionary size minus six. |
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251
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* |
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252
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* - Compressed data is a combination of literals and length/distance pairs |
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253
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* terminated by an end code. Literals are either Huffman coded or |
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254
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* uncoded bytes. A length/distance pair is a coded length followed by a |
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255
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* coded distance to represent a string that occurs earlier in the |
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256
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* uncompressed data that occurs again at the current location. |
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257
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* |
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258
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* - A bit preceding a literal or length/distance pair indicates which comes |
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259
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* next, 0 for literals, 1 for length/distance. |
|
260
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* |
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261
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* - If literals are uncoded, then the next eight bits are the literal, in the |
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262
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* normal bit order in the stream, i.e. no bit-reversal is needed. Similarly, |
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263
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* no bit reversal is needed for either the length extra bits or the distance |
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264
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* extra bits. |
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265
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* |
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266
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* - Literal bytes are simply written to the output. A length/distance pair is |
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267
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* an instruction to copy previously uncompressed bytes to the output. The |
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268
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* copy is from distance bytes back in the output stream, copying for length |
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269
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* bytes. |
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270
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* |
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271
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* - Distances pointing before the beginning of the output data are not |
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272
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* permitted. |
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273
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* |
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274
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* - Overlapped copies, where the length is greater than the distance, are |
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275
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* allowed and common. For example, a distance of one and a length of 518 |
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276
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* simply copies the last byte 518 times. A distance of four and a length of |
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277
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* twelve copies the last four bytes three times. A simple forward copy |
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278
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* ignoring whether the length is greater than the distance or not implements |
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279
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* this correctly. |
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280
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*/ |
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281
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local int decomp(struct state *s) |
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282
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{ |
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283
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int lit; /* true if literals are coded */ |
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284
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int dict; /* log2(dictionary size) - 6 */ |
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285
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int symbol; /* decoded symbol, extra bits for distance */ |
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286
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int len; /* length for copy */ |
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287
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unsigned dist; /* distance for copy */ |
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288
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int copy; /* copy counter */ |
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289
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unsigned char *from, *to; /* copy pointers */ |
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290
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static int virgin = 1; /* build tables once */ |
|
291
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static short litcnt[MAXBITS+1], litsym[256]; /* litcode memory */ |
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292
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static short lencnt[MAXBITS+1], lensym[16]; /* lencode memory */ |
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293
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static short distcnt[MAXBITS+1], distsym[64]; /* distcode memory */ |
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294
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static struct huffman litcode = {litcnt, litsym}; /* length code */ |
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295
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static struct huffman lencode = {lencnt, lensym}; /* length code */ |
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296
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static struct huffman distcode = {distcnt, distsym};/* distance code */ |
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297
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/* bit lengths of literal codes */ |
|
298
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static const unsigned char litlen[] = { |
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299
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11, 124, 8, 7, 28, 7, 188, 13, 76, 4, 10, 8, 12, 10, 12, 10, 8, 23, 8, |
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300
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9, 7, 6, 7, 8, 7, 6, 55, 8, 23, 24, 12, 11, 7, 9, 11, 12, 6, 7, 22, 5, |
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301
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7, 24, 6, 11, 9, 6, 7, 22, 7, 11, 38, 7, 9, 8, 25, 11, 8, 11, 9, 12, |
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302
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8, 12, 5, 38, 5, 38, 5, 11, 7, 5, 6, 21, 6, 10, 53, 8, 7, 24, 10, 27, |
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303
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44, 253, 253, 253, 252, 252, 252, 13, 12, 45, 12, 45, 12, 61, 12, 45, |
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304
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44, 173}; |
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305
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/* bit lengths of length codes 0..15 */ |
|
306
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static const unsigned char lenlen[] = {2, 35, 36, 53, 38, 23}; |
|
307
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/* bit lengths of distance codes 0..63 */ |
|
308
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static const unsigned char distlen[] = {2, 20, 53, 230, 247, 151, 248}; |
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309
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static const short base[16] = { /* base for length codes */ |
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310
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3, 2, 4, 5, 6, 7, 8, 9, 10, 12, 16, 24, 40, 72, 136, 264}; |
|
311
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static const char extra[16] = { /* extra bits for length codes */ |
|
312
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0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 3, 4, 5, 6, 7, 8}; |
|
313
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|
|
314
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/* set up decoding tables (once--might not be thread-safe) */ |
|
315
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if (virgin) { |
|
316
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construct(&litcode, litlen, sizeof(litlen)); |
|
317
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construct(&lencode, lenlen, sizeof(lenlen)); |
|
318
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construct(&distcode, distlen, sizeof(distlen)); |
|
319
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virgin = 0; |
|
320
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} |
|
321
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|
|
322
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/* read header */ |
|
323
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lit = bits(s, 8); |
|
324
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if (lit > 1) return -1; |
|
325
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dict = bits(s, 8); |
|
326
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if (dict < 4 || dict > 6) return -2; |
|
327
|
|
|
328
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/* decode literals and length/distance pairs */ |
|
329
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do { |
|
330
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if (bits(s, 1)) { |
|
331
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/* get length */ |
|
332
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symbol = decode(s, &lencode); |
|
333
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len = base[symbol] + bits(s, extra[symbol]); |
|
334
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if (len == 519) break; /* end code */ |
|
335
|
|
|
336
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/* get distance */ |
|
337
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symbol = len == 2 ? 2 : dict; |
|
338
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dist = decode(s, &distcode) << symbol; |
|
339
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dist += bits(s, symbol); |
|
340
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dist++; |
|
341
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if (s->first && dist > s->next) |
|
342
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return -3; /* distance too far back */ |
|
343
|
|
|
344
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/* copy length bytes from distance bytes back */ |
|
345
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do { |
|
346
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to = s->out + s->next; |
|
347
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from = to - dist; |
|
348
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copy = MAXWIN; |
|
349
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if (s->next < dist) { |
|
350
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from += copy; |
|
351
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copy = dist; |
|
352
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} |
|
353
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copy -= s->next; |
|
354
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if (copy > len) copy = len; |
|
355
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len -= copy; |
|
356
|
s->next += copy; |
|
357
|
do { |
|
358
|
*to++ = *from++; |
|
359
|
} while (--copy); |
|
360
|
if (s->next == MAXWIN) { |
|
361
|
if (s->outfun(s->outhow, s->out, s->next)) return 1; |
|
362
|
s->next = 0; |
|
363
|
s->first = 0; |
|
364
|
} |
|
365
|
} while (len != 0); |
|
366
|
} |
|
367
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else { |
|
368
|
/* get literal and write it */ |
|
369
|
symbol = lit ? decode(s, &litcode) : bits(s, 8); |
|
370
|
s->out[s->next++] = symbol; |
|
371
|
if (s->next == MAXWIN) { |
|
372
|
if (s->outfun(s->outhow, s->out, s->next)) return 1; |
|
373
|
s->next = 0; |
|
374
|
s->first = 0; |
|
375
|
} |
|
376
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} |
|
377
|
} while (1); |
|
378
|
return 0; |
|
379
|
} |
|
380
|
|
|
381
|
/* See comments in blast.h */ |
|
382
|
int blast(blast_in infun, void *inhow, blast_out outfun, void *outhow, |
|
383
|
unsigned *left, unsigned char **in) |
|
384
|
{ |
|
385
|
struct state s; /* input/output state */ |
|
386
|
int err; /* return value */ |
|
387
|
|
|
388
|
/* initialize input state */ |
|
389
|
s.infun = infun; |
|
390
|
s.inhow = inhow; |
|
391
|
if (left != NULL && *left) { |
|
392
|
s.left = *left; |
|
393
|
s.in = *in; |
|
394
|
} |
|
395
|
else |
|
396
|
s.left = 0; |
|
397
|
s.bitbuf = 0; |
|
398
|
s.bitcnt = 0; |
|
399
|
|
|
400
|
/* initialize output state */ |
|
401
|
s.outfun = outfun; |
|
402
|
s.outhow = outhow; |
|
403
|
s.next = 0; |
|
404
|
s.first = 1; |
|
405
|
|
|
406
|
/* return if bits() or decode() tries to read past available input */ |
|
407
|
if (setjmp(s.env) != 0) /* if came back here via longjmp(), */ |
|
408
|
err = 2; /* then skip decomp(), return error */ |
|
409
|
else |
|
410
|
err = decomp(&s); /* decompress */ |
|
411
|
|
|
412
|
/* return unused input */ |
|
413
|
if (left != NULL) |
|
414
|
*left = s.left; |
|
415
|
if (in != NULL) |
|
416
|
*in = s.left ? s.in : NULL; |
|
417
|
|
|
418
|
/* write any leftover output and update the error code if needed */ |
|
419
|
if (err != 1 && s.next && s.outfun(s.outhow, s.out, s.next) && err == 0) |
|
420
|
err = 1; |
|
421
|
return err; |
|
422
|
} |
|
423
|
|