| 1 |
/* blast.c |
| 2 |
* Copyright (C) 2003, 2012 Mark Adler |
| 3 |
* For conditions of distribution and use, see copyright notice in blast.h |
| 4 |
* version 1.2, 24 Oct 2012 |
| 5 |
* |
| 6 |
* blast.c decompresses data compressed by the PKWare Compression Library. |
| 7 |
* This function provides functionality similar to the explode() function of |
| 8 |
* the PKWare library, hence the name "blast". |
| 9 |
* |
| 10 |
* 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: |
| 14 |
* |
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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). |
| 18 |
*/ |
| 19 |
|
| 20 |
/* |
| 21 |
* Change history: |
| 22 |
* |
| 23 |
* 1.0 12 Feb 2003 - First version |
| 24 |
* 1.1 16 Feb 2003 - Fixed distance check for > 4 GB uncompressed data |
| 25 |
* 1.2 24 Oct 2012 - Add note about using binary mode in stdio |
| 26 |
* - Fix comparisons of differently signed integers |
| 27 |
*/ |
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|
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#include <setjmp.h> /* for setjmp(), longjmp(), and jmp_buf */ |
| 30 |
#include "blast.h" /* prototype for blast() */ |
| 31 |
|
| 32 |
#define local static /* for local function definitions */ |
| 33 |
#define MAXBITS 13 /* maximum code length */ |
| 34 |
#define MAXWIN 4096 /* maximum window size */ |
| 35 |
|
| 36 |
/* input and output state */ |
| 37 |
struct state { |
| 38 |
/* input state */ |
| 39 |
blast_in infun; /* input function provided by user */ |
| 40 |
void *inhow; /* opaque information passed to infun() */ |
| 41 |
unsigned char *in; /* next input location */ |
| 42 |
unsigned left; /* available input at in */ |
| 43 |
int bitbuf; /* bit buffer */ |
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int bitcnt; /* number of bits in bit buffer */ |
| 45 |
|
| 46 |
/* input limit error return state for bits() and decode() */ |
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jmp_buf env; |
| 48 |
|
| 49 |
/* output state */ |
| 50 |
blast_out outfun; /* output function provided by user */ |
| 51 |
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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}; |
| 56 |
|
| 57 |
/* |
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* Return need bits from the input stream. This always leaves less than |
| 59 |
* eight bits in the buffer. bits() works properly for need == 0. |
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* |
| 61 |
* Format notes: |
| 62 |
* |
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* - Bits are stored in bytes from the least significant bit to the most |
| 64 |
* significant bit. Therefore bits are dropped from the bottom of the bit |
| 65 |
* buffer, using shift right, and new bytes are appended to the top of the |
| 66 |
* bit buffer, using shift left. |
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*/ |
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local int bits(struct state *s, int need) |
| 69 |
{ |
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int val; /* bit accumulator */ |
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|
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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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|
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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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|
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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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|
| 92 |
/* |
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* Huffman code decoding tables. count[1..MAXBITS] is the number of symbols of |
| 94 |
* each length, which for a canonical code are stepped through in order. |
| 95 |
* 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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/* |
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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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|
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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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/* |
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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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|
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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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|
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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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|
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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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left -= h->count[len]; /* deduct count from possible codes */ |
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if (left < 0) return left; /* over-subscribed--return negative */ |
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} /* left > 0 means incomplete */ |
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|
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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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offs[len + 1] = offs[len] + h->count[len]; |
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|
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/* |
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* put symbols in table sorted by length, by symbol order within each |
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* length |
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*/ |
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for (symbol = 0; symbol < n; symbol++) |
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if (length[symbol] != 0) |
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h->symbol[offs[length[symbol]]++] = symbol; |
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|
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/* return zero for complete set, positive for incomplete set */ |
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return left; |
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} |
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|
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/* |
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* Decode PKWare Compression Library stream. |
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* |
| 243 |
* Format notes: |
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* |
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* - First byte is 0 if literals are uncoded or 1 if they are coded. Second |
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* byte is 4, 5, or 6 for the number of extra bits in the distance code. |
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* This is the base-2 logarithm of the dictionary size minus six. |
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* |
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* - Compressed data is a combination of literals and length/distance pairs |
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* terminated by an end code. Literals are either Huffman coded or |
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* uncoded bytes. A length/distance pair is a coded length followed by a |
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* coded distance to represent a string that occurs earlier in the |
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* uncompressed data that occurs again at the current location. |
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* |
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* - A bit preceding a literal or length/distance pair indicates which comes |
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* next, 0 for literals, 1 for length/distance. |
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* |
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* - If literals are uncoded, then the next eight bits are the literal, in the |
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* normal bit order in th stream, i.e. no bit-reversal is needed. Similarly, |
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* no bit reversal is needed for either the length extra bits or the distance |
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* extra bits. |
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* |
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* - Literal bytes are simply written to the output. A length/distance pair is |
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* an instruction to copy previously uncompressed bytes to the output. The |
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* copy is from distance bytes back in the output stream, copying for length |
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* bytes. |
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* |
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* - Distances pointing before the beginning of the output data are not |
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* permitted. |
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* |
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* - Overlapped copies, where the length is greater than the distance, are |
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* allowed and common. For example, a distance of one and a length of 518 |
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* simply copies the last byte 518 times. A distance of four and a length of |
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* twelve copies the last four bytes three times. A simple forward copy |
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* ignoring whether the length is greater than the distance or not implements |
| 276 |
* this correctly. |
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*/ |
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local int decomp(struct state *s) |
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{ |
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int lit; /* true if literals are coded */ |
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int dict; /* log2(dictionary size) - 6 */ |
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int symbol; /* decoded symbol, extra bits for distance */ |
| 283 |
int len; /* length for copy */ |
| 284 |
unsigned dist; /* distance for copy */ |
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int copy; /* copy counter */ |
| 286 |
unsigned char *from, *to; /* copy pointers */ |
| 287 |
static int virgin = 1; /* build tables once */ |
| 288 |
static short litcnt[MAXBITS+1], litsym[256]; /* litcode memory */ |
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static short lencnt[MAXBITS+1], lensym[16]; /* lencode memory */ |
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static short distcnt[MAXBITS+1], distsym[64]; /* distcode memory */ |
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static struct huffman litcode = {litcnt, litsym}; /* length code */ |
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static struct huffman lencode = {lencnt, lensym}; /* length code */ |
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static struct huffman distcode = {distcnt, distsym};/* distance code */ |
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/* bit lengths of literal codes */ |
| 295 |
static const unsigned char litlen[] = { |
| 296 |
11, 124, 8, 7, 28, 7, 188, 13, 76, 4, 10, 8, 12, 10, 12, 10, 8, 23, 8, |
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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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7, 24, 6, 11, 9, 6, 7, 22, 7, 11, 38, 7, 9, 8, 25, 11, 8, 11, 9, 12, |
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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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44, 253, 253, 253, 252, 252, 252, 13, 12, 45, 12, 45, 12, 61, 12, 45, |
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44, 173}; |
| 302 |
/* bit lengths of length codes 0..15 */ |
| 303 |
static const unsigned char lenlen[] = {2, 35, 36, 53, 38, 23}; |
| 304 |
/* bit lengths of distance codes 0..63 */ |
| 305 |
static const unsigned char distlen[] = {2, 20, 53, 230, 247, 151, 248}; |
| 306 |
static const short base[16] = { /* base for length codes */ |
| 307 |
3, 2, 4, 5, 6, 7, 8, 9, 10, 12, 16, 24, 40, 72, 136, 264}; |
| 308 |
static const char extra[16] = { /* extra bits for length codes */ |
| 309 |
0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 3, 4, 5, 6, 7, 8}; |
| 310 |
|
| 311 |
/* set up decoding tables (once--might not be thread-safe) */ |
| 312 |
if (virgin) { |
| 313 |
construct(&litcode, litlen, sizeof(litlen)); |
| 314 |
construct(&lencode, lenlen, sizeof(lenlen)); |
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construct(&distcode, distlen, sizeof(distlen)); |
| 316 |
virgin = 0; |
| 317 |
} |
| 318 |
|
| 319 |
/* read header */ |
| 320 |
lit = bits(s, 8); |
| 321 |
if (lit > 1) return -1; |
| 322 |
dict = bits(s, 8); |
| 323 |
if (dict < 4 || dict > 6) return -2; |
| 324 |
|
| 325 |
/* decode literals and length/distance pairs */ |
| 326 |
do { |
| 327 |
if (bits(s, 1)) { |
| 328 |
/* get length */ |
| 329 |
symbol = decode(s, &lencode); |
| 330 |
len = base[symbol] + bits(s, extra[symbol]); |
| 331 |
if (len == 519) break; /* end code */ |
| 332 |
|
| 333 |
/* get distance */ |
| 334 |
symbol = len == 2 ? 2 : dict; |
| 335 |
dist = decode(s, &distcode) << symbol; |
| 336 |
dist += bits(s, symbol); |
| 337 |
dist++; |
| 338 |
if (s->first && dist > s->next) |
| 339 |
return -3; /* distance too far back */ |
| 340 |
|
| 341 |
/* copy length bytes from distance bytes back */ |
| 342 |
do { |
| 343 |
to = s->out + s->next; |
| 344 |
from = to - dist; |
| 345 |
copy = MAXWIN; |
| 346 |
if (s->next < dist) { |
| 347 |
from += copy; |
| 348 |
copy = dist; |
| 349 |
} |
| 350 |
copy -= s->next; |
| 351 |
if (copy > len) copy = len; |
| 352 |
len -= copy; |
| 353 |
s->next += copy; |
| 354 |
do { |
| 355 |
*to++ = *from++; |
| 356 |
} while (--copy); |
| 357 |
if (s->next == MAXWIN) { |
| 358 |
if (s->outfun(s->outhow, s->out, s->next)) return 1; |
| 359 |
s->next = 0; |
| 360 |
s->first = 0; |
| 361 |
} |
| 362 |
} while (len != 0); |
| 363 |
} |
| 364 |
else { |
| 365 |
/* get literal and write it */ |
| 366 |
symbol = lit ? decode(s, &litcode) : bits(s, 8); |
| 367 |
s->out[s->next++] = symbol; |
| 368 |
if (s->next == MAXWIN) { |
| 369 |
if (s->outfun(s->outhow, s->out, s->next)) return 1; |
| 370 |
s->next = 0; |
| 371 |
s->first = 0; |
| 372 |
} |
| 373 |
} |
| 374 |
} while (1); |
| 375 |
return 0; |
| 376 |
} |
| 377 |
|
| 378 |
/* See comments in blast.h */ |
| 379 |
int blast(blast_in infun, void *inhow, blast_out outfun, void *outhow) |
| 380 |
{ |
| 381 |
struct state s; /* input/output state */ |
| 382 |
int err; /* return value */ |
| 383 |
|
| 384 |
/* initialize input state */ |
| 385 |
s.infun = infun; |
| 386 |
s.inhow = inhow; |
| 387 |
s.left = 0; |
| 388 |
s.bitbuf = 0; |
| 389 |
s.bitcnt = 0; |
| 390 |
|
| 391 |
/* initialize output state */ |
| 392 |
s.outfun = outfun; |
| 393 |
s.outhow = outhow; |
| 394 |
s.next = 0; |
| 395 |
s.first = 1; |
| 396 |
|
| 397 |
/* return if bits() or decode() tries to read past available input */ |
| 398 |
if (setjmp(s.env) != 0) /* if came back here via longjmp(), */ |
| 399 |
err = 2; /* then skip decomp(), return error */ |
| 400 |
else |
| 401 |
err = decomp(&s); /* decompress */ |
| 402 |
|
| 403 |
/* write any leftover output and update the error code if needed */ |
| 404 |
if (err != 1 && s.next && s.outfun(s.outhow, s.out, s.next) && err == 0) |
| 405 |
err = 1; |
| 406 |
return err; |
| 407 |
} |
| 408 |
|
| 409 |
#ifdef TEST |
| 410 |
/* Example of how to use blast() */ |
| 411 |
#include <stdio.h> |
| 412 |
#include <stdlib.h> |
| 413 |
|
| 414 |
#define CHUNK 16384 |
| 415 |
|
| 416 |
local unsigned inf(void *how, unsigned char **buf) |
| 417 |
{ |
| 418 |
static unsigned char hold[CHUNK]; |
| 419 |
|
| 420 |
*buf = hold; |
| 421 |
return fread(hold, 1, CHUNK, (FILE *)how); |
| 422 |
} |
| 423 |
|
| 424 |
local int outf(void *how, unsigned char *buf, unsigned len) |
| 425 |
{ |
| 426 |
return fwrite(buf, 1, len, (FILE *)how) != len; |
| 427 |
} |
| 428 |
|
| 429 |
/* Decompress a PKWare Compression Library stream from stdin to stdout */ |
| 430 |
int main(void) |
| 431 |
{ |
| 432 |
int ret, n; |
| 433 |
|
| 434 |
/* decompress to stdout */ |
| 435 |
ret = blast(inf, stdin, outf, stdout); |
| 436 |
if (ret != 0) fprintf(stderr, "blast error: %d\n", ret); |
| 437 |
|
| 438 |
/* see if there are any leftover bytes */ |
| 439 |
n = 0; |
| 440 |
while (getchar() != EOF) n++; |
| 441 |
if (n) fprintf(stderr, "blast warning: %d unused bytes of input\n", n); |
| 442 |
|
| 443 |
/* return blast() error code */ |
| 444 |
return ret; |
| 445 |
} |
| 446 |
#endif |
