/* blast.c | |

* Copyright (C) 2003, 2012, 2013 Mark Adler | |

* For conditions of distribution and use, see copyright notice in blast.h | |

* version 1.3, 24 Aug 2013 | |

* | |

* blast.c decompresses data compressed by the PKWare Compression Library. | |

* This function provides functionality similar to the explode() function of | |

* the PKWare library, hence the name "blast". | |

* | |

* This decompressor is based on the excellent format description provided by | |

* Ben Rudiak-Gould in comp.compression on August 13, 2001. Interestingly, the | |

* example Ben provided in the post is incorrect. The distance 110001 should | |

* instead be 111000. When corrected, the example byte stream becomes: | |

* | |

* 00 04 82 24 25 8f 80 7f | |

* | |

* which decompresses to "AIAIAIAIAIAIA" (without the quotes). | |

*/ | |

/* | |

* Change history: | |

* | |

* 1.0 12 Feb 2003 - First version | |

* 1.1 16 Feb 2003 - Fixed distance check for > 4 GB uncompressed data | |

* 1.2 24 Oct 2012 - Add note about using binary mode in stdio | |

* - Fix comparisons of differently signed integers | |

* 1.3 24 Aug 2013 - Return unused input from blast() | |

* - Fix test code to correctly report unused input | |

* - Enable the provision of initial input to blast() | |

*/ | |

#include <stddef.h> /* for NULL */ | |

#include <setjmp.h> /* for setjmp(), longjmp(), and jmp_buf */ | |

#include "blast.h" /* prototype for blast() */ | |

#define local static /* for local function definitions */ | |

#define MAXBITS 13 /* maximum code length */ | |

#define MAXWIN 4096 /* maximum window size */ | |

/* input and output state */ | |

struct state { | |

/* input state */ | |

blast_in infun; /* input function provided by user */ | |

void *inhow; /* opaque information passed to infun() */ | |

unsigned char *in; /* next input location */ | |

unsigned left; /* available input at in */ | |

int bitbuf; /* bit buffer */ | |

int bitcnt; /* number of bits in bit buffer */ | |

/* input limit error return state for bits() and decode() */ | |

jmp_buf env; | |

/* output state */ | |

blast_out outfun; /* output function provided by user */ | |

void *outhow; /* opaque information passed to outfun() */ | |

unsigned next; /* index of next write location in out[] */ | |

int first; /* true to check distances (for first 4K) */ | |

unsigned char out[MAXWIN]; /* output buffer and sliding window */ | |

}; | |

/* | |

* Return need bits from the input stream. This always leaves less than | |

* eight bits in the buffer. bits() works properly for need == 0. | |

* | |

* Format notes: | |

* | |

* - Bits are stored in bytes from the least significant bit to the most | |

* significant bit. Therefore bits are dropped from the bottom of the bit | |

* buffer, using shift right, and new bytes are appended to the top of the | |

* bit buffer, using shift left. | |

*/ | |

local int bits(struct state *s, int need) | |

{ | |

int val; /* bit accumulator */ | |

/* load at least need bits into val */ | |

val = s->bitbuf; | |

while (s->bitcnt < need) { | |

if (s->left == 0) { | |

s->left = s->infun(s->inhow, &(s->in)); | |

if (s->left == 0) longjmp(s->env, 1); /* out of input */ | |

} | |

val |= (int)(*(s->in)++) << s->bitcnt; /* load eight bits */ | |

s->left--; | |

s->bitcnt += 8; | |

} | |

/* drop need bits and update buffer, always zero to seven bits left */ | |

s->bitbuf = val >> need; | |

s->bitcnt -= need; | |

/* return need bits, zeroing the bits above that */ | |

return val & ((1 << need) - 1); | |

} | |

/* | |

* Huffman code decoding tables. count[1..MAXBITS] is the number of symbols of | |

* each length, which for a canonical code are stepped through in order. | |

* symbol[] are the symbol values in canonical order, where the number of | |

* entries is the sum of the counts in count[]. The decoding process can be | |

* seen in the function decode() below. | |

*/ | |

struct huffman { | |

short *count; /* number of symbols of each length */ | |

short *symbol; /* canonically ordered symbols */ | |

}; | |

/* | |

* Decode a code from the stream s using huffman table h. Return the symbol or | |

* a negative value if there is an error. If all of the lengths are zero, i.e. | |

* an empty code, or if the code is incomplete and an invalid code is received, | |

* then -9 is returned after reading MAXBITS bits. | |

* | |

* Format notes: | |

* | |

* - The codes as stored in the compressed data are bit-reversed relative to | |

* a simple integer ordering of codes of the same lengths. Hence below the | |

* bits are pulled from the compressed data one at a time and used to | |

* build the code value reversed from what is in the stream in order to | |

* permit simple integer comparisons for decoding. | |

* | |

* - The first code for the shortest length is all ones. Subsequent codes of | |

* the same length are simply integer decrements of the previous code. When | |

* moving up a length, a one bit is appended to the code. For a complete | |

* code, the last code of the longest length will be all zeros. To support | |

* this ordering, the bits pulled during decoding are inverted to apply the | |

* more "natural" ordering starting with all zeros and incrementing. | |

*/ | |

local int decode(struct state *s, struct huffman *h) | |

{ | |

int len; /* current number of bits in code */ | |

int code; /* len bits being decoded */ | |

int first; /* first code of length len */ | |

int count; /* number of codes of length len */ | |

int index; /* index of first code of length len in symbol table */ | |

int bitbuf; /* bits from stream */ | |

int left; /* bits left in next or left to process */ | |

short *next; /* next number of codes */ | |

bitbuf = s->bitbuf; | |

left = s->bitcnt; | |

code = first = index = 0; | |

len = 1; | |

next = h->count + 1; | |

while (1) { | |

while (left--) { | |

code |= (bitbuf & 1) ^ 1; /* invert code */ | |

bitbuf >>= 1; | |

count = *next++; | |

if (code < first + count) { /* if length len, return symbol */ | |

s->bitbuf = bitbuf; | |

s->bitcnt = (s->bitcnt - len) & 7; | |

return h->symbol[index + (code - first)]; | |

} | |

index += count; /* else update for next length */ | |

first += count; | |

first <<= 1; | |

code <<= 1; | |

len++; | |

} | |

left = (MAXBITS+1) - len; | |

if (left == 0) break; | |

if (s->left == 0) { | |

s->left = s->infun(s->inhow, &(s->in)); | |

if (s->left == 0) longjmp(s->env, 1); /* out of input */ | |

} | |

bitbuf = *(s->in)++; | |

s->left--; | |

if (left > 8) left = 8; | |

} | |

return -9; /* ran out of codes */ | |

} | |

/* | |

* Given a list of repeated code lengths rep[0..n-1], where each byte is a | |

* count (high four bits + 1) and a code length (low four bits), generate the | |

* list of code lengths. This compaction reduces the size of the object code. | |

* Then given the list of code lengths length[0..n-1] representing a canonical | |

* Huffman code for n symbols, construct the tables required to decode those | |

* codes. Those tables are the number of codes of each length, and the symbols | |

* sorted by length, retaining their original order within each length. The | |

* return value is zero for a complete code set, negative for an over- | |

* subscribed code set, and positive for an incomplete code set. The tables | |

* can be used if the return value is zero or positive, but they cannot be used | |

* if the return value is negative. If the return value is zero, it is not | |

* possible for decode() using that table to return an error--any stream of | |

* enough bits will resolve to a symbol. If the return value is positive, then | |

* it is possible for decode() using that table to return an error for received | |

* codes past the end of the incomplete lengths. | |

*/ | |

local int construct(struct huffman *h, const unsigned char *rep, int n) | |

{ | |

int symbol; /* current symbol when stepping through length[] */ | |

int len; /* current length when stepping through h->count[] */ | |

int left; /* number of possible codes left of current length */ | |

short offs[MAXBITS+1]; /* offsets in symbol table for each length */ | |

short length[256]; /* code lengths */ | |

/* convert compact repeat counts into symbol bit length list */ | |

symbol = 0; | |

do { | |

len = *rep++; | |

left = (len >> 4) + 1; | |

len &= 15; | |

do { | |

length[symbol++] = len; | |

} while (--left); | |

} while (--n); | |

n = symbol; | |

/* count number of codes of each length */ | |

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

h->count[len] = 0; | |

for (symbol = 0; symbol < n; symbol++) | |

(h->count[length[symbol]])++; /* assumes lengths are within bounds */ | |

if (h->count[0] == n) /* no codes! */ | |

return 0; /* complete, but decode() will fail */ | |

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

left = 1; /* one possible code of zero length */ | |

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

left <<= 1; /* one more bit, double codes left */ | |

left -= h->count[len]; /* deduct count from possible codes */ | |

if (left < 0) return left; /* over-subscribed--return negative */ | |

} /* left > 0 means incomplete */ | |

/* generate offsets into symbol table for each length for sorting */ | |

offs[1] = 0; | |

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

offs[len + 1] = offs[len] + h->count[len]; | |

/* | |

* put symbols in table sorted by length, by symbol order within each | |

* length | |

*/ | |

for (symbol = 0; symbol < n; symbol++) | |

if (length[symbol] != 0) | |

h->symbol[offs[length[symbol]]++] = symbol; | |

/* return zero for complete set, positive for incomplete set */ | |

return left; | |

} | |

/* | |

* Decode PKWare Compression Library stream. | |

* | |

* Format notes: | |

* | |

* - First byte is 0 if literals are uncoded or 1 if they are coded. Second | |

* byte is 4, 5, or 6 for the number of extra bits in the distance code. | |

* This is the base-2 logarithm of the dictionary size minus six. | |

* | |

* - Compressed data is a combination of literals and length/distance pairs | |

* terminated by an end code. Literals are either Huffman coded or | |

* uncoded bytes. A length/distance pair is a coded length followed by a | |

* coded distance to represent a string that occurs earlier in the | |

* uncompressed data that occurs again at the current location. | |

* | |

* - A bit preceding a literal or length/distance pair indicates which comes | |

* next, 0 for literals, 1 for length/distance. | |

* | |

* - If literals are uncoded, then the next eight bits are the literal, in the | |

* normal bit order in the stream, i.e. no bit-reversal is needed. Similarly, | |

* no bit reversal is needed for either the length extra bits or the distance | |

* extra bits. | |

* | |

* - Literal bytes are simply written to the output. A length/distance pair is | |

* an instruction to copy previously uncompressed bytes to the output. The | |

* copy is from distance bytes back in the output stream, copying for length | |

* bytes. | |

* | |

* - Distances pointing before the beginning of the output data are not | |

* permitted. | |

* | |

* - Overlapped copies, where the length is greater than the distance, are | |

* allowed and common. For example, a distance of one and a length of 518 | |

* simply copies the last byte 518 times. A distance of four and a length of | |

* twelve copies the last four bytes three times. A simple forward copy | |

* ignoring whether the length is greater than the distance or not implements | |

* this correctly. | |

*/ | |

local int decomp(struct state *s) | |

{ | |

int lit; /* true if literals are coded */ | |

int dict; /* log2(dictionary size) - 6 */ | |

int symbol; /* decoded symbol, extra bits for distance */ | |

int len; /* length for copy */ | |

unsigned dist; /* distance for copy */ | |

int copy; /* copy counter */ | |

unsigned char *from, *to; /* copy pointers */ | |

static int virgin = 1; /* build tables once */ | |

static short litcnt[MAXBITS+1], litsym[256]; /* litcode memory */ | |

static short lencnt[MAXBITS+1], lensym[16]; /* lencode memory */ | |

static short distcnt[MAXBITS+1], distsym[64]; /* distcode memory */ | |

static struct huffman litcode = {litcnt, litsym}; /* length code */ | |

static struct huffman lencode = {lencnt, lensym}; /* length code */ | |

static struct huffman distcode = {distcnt, distsym};/* distance code */ | |

/* bit lengths of literal codes */ | |

static const unsigned char litlen[] = { | |

11, 124, 8, 7, 28, 7, 188, 13, 76, 4, 10, 8, 12, 10, 12, 10, 8, 23, 8, | |

9, 7, 6, 7, 8, 7, 6, 55, 8, 23, 24, 12, 11, 7, 9, 11, 12, 6, 7, 22, 5, | |

7, 24, 6, 11, 9, 6, 7, 22, 7, 11, 38, 7, 9, 8, 25, 11, 8, 11, 9, 12, | |

8, 12, 5, 38, 5, 38, 5, 11, 7, 5, 6, 21, 6, 10, 53, 8, 7, 24, 10, 27, | |

44, 253, 253, 253, 252, 252, 252, 13, 12, 45, 12, 45, 12, 61, 12, 45, | |

44, 173}; | |

/* bit lengths of length codes 0..15 */ | |

static const unsigned char lenlen[] = {2, 35, 36, 53, 38, 23}; | |

/* bit lengths of distance codes 0..63 */ | |

static const unsigned char distlen[] = {2, 20, 53, 230, 247, 151, 248}; | |

static const short base[16] = { /* base for length codes */ | |

3, 2, 4, 5, 6, 7, 8, 9, 10, 12, 16, 24, 40, 72, 136, 264}; | |

static const char extra[16] = { /* extra bits for length codes */ | |

0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 3, 4, 5, 6, 7, 8}; | |

/* set up decoding tables (once--might not be thread-safe) */ | |

if (virgin) { | |

construct(&litcode, litlen, sizeof(litlen)); | |

construct(&lencode, lenlen, sizeof(lenlen)); | |

construct(&distcode, distlen, sizeof(distlen)); | |

virgin = 0; | |

} | |

/* read header */ | |

lit = bits(s, 8); | |

if (lit > 1) return -1; | |

dict = bits(s, 8); | |

if (dict < 4 || dict > 6) return -2; | |

/* decode literals and length/distance pairs */ | |

do { | |

if (bits(s, 1)) { | |

/* get length */ | |

symbol = decode(s, &lencode); | |

len = base[symbol] + bits(s, extra[symbol]); | |

if (len == 519) break; /* end code */ | |

/* get distance */ | |

symbol = len == 2 ? 2 : dict; | |

dist = decode(s, &distcode) << symbol; | |

dist += bits(s, symbol); | |

dist++; | |

if (s->first && dist > s->next) | |

return -3; /* distance too far back */ | |

/* copy length bytes from distance bytes back */ | |

do { | |

to = s->out + s->next; | |

from = to - dist; | |

copy = MAXWIN; | |

if (s->next < dist) { | |

from += copy; | |

copy = dist; | |

} | |

copy -= s->next; | |

if (copy > len) copy = len; | |

len -= copy; | |

s->next += copy; | |

do { | |

*to++ = *from++; | |

} while (--copy); | |

if (s->next == MAXWIN) { | |

if (s->outfun(s->outhow, s->out, s->next)) return 1; | |

s->next = 0; | |

s->first = 0; | |

} | |

} while (len != 0); | |

} | |

else { | |

/* get literal and write it */ | |

symbol = lit ? decode(s, &litcode) : bits(s, 8); | |

s->out[s->next++] = symbol; | |

if (s->next == MAXWIN) { | |

if (s->outfun(s->outhow, s->out, s->next)) return 1; | |

s->next = 0; | |

s->first = 0; | |

} | |

} | |

} while (1); | |

return 0; | |

} | |

/* See comments in blast.h */ | |

int blast(blast_in infun, void *inhow, blast_out outfun, void *outhow, | |

unsigned *left, unsigned char **in) | |

{ | |

struct state s; /* input/output state */ | |

int err; /* return value */ | |

/* initialize input state */ | |

s.infun = infun; | |

s.inhow = inhow; | |

if (left != NULL && *left) { | |

s.left = *left; | |

s.in = *in; | |

} | |

else | |

s.left = 0; | |

s.bitbuf = 0; | |

s.bitcnt = 0; | |

/* initialize output state */ | |

s.outfun = outfun; | |

s.outhow = outhow; | |

s.next = 0; | |

s.first = 1; | |

/* return if bits() or decode() tries to read past available input */ | |

if (setjmp(s.env) != 0) /* if came back here via longjmp(), */ | |

err = 2; /* then skip decomp(), return error */ | |

else | |

err = decomp(&s); /* decompress */ | |

/* return unused input */ | |

if (left != NULL) | |

*left = s.left; | |

if (in != NULL) | |

*in = s.left ? s.in : NULL; | |

/* write any leftover output and update the error code if needed */ | |

if (err != 1 && s.next && s.outfun(s.outhow, s.out, s.next) && err == 0) | |

err = 1; | |

return err; | |

} | |

#ifdef TEST | |

/* Example of how to use blast() */ | |

#include <stdio.h> | |

#include <stdlib.h> | |

#define CHUNK 16384 | |

local unsigned inf(void *how, unsigned char **buf) | |

{ | |

static unsigned char hold[CHUNK]; | |

*buf = hold; | |

return fread(hold, 1, CHUNK, (FILE *)how); | |

} | |

local int outf(void *how, unsigned char *buf, unsigned len) | |

{ | |

return fwrite(buf, 1, len, (FILE *)how) != len; | |

} | |

/* Decompress a PKWare Compression Library stream from stdin to stdout */ | |

int main(void) | |

{ | |

int ret; | |

unsigned left; | |

/* decompress to stdout */ | |

left = 0; | |

ret = blast(inf, stdin, outf, stdout, &left, NULL); | |

if (ret != 0) | |

fprintf(stderr, "blast error: %d\n", ret); | |

/* count any leftover bytes */ | |

while (getchar() != EOF) | |

left++; | |

if (left) | |

fprintf(stderr, "blast warning: %u unused bytes of input\n", left); | |

/* return blast() error code */ | |

return ret; | |

} | |

#endif |