| /* blast.c |
| * Copyright (C) 2003 Mark Adler |
| * For conditions of distribution and use, see copyright notice in blast.h |
| * version 1.1, 16 Feb 2003 |
| * |
| * 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 |
| */ |
| |
| #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 th 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 */ |
| int 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) |
| { |
| struct state s; /* input/output state */ |
| int err; /* return value */ |
| |
| /* initialize input state */ |
| s.infun = infun; |
| s.inhow = inhow; |
| 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 */ |
| |
| /* 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, n; |
| |
| /* decompress to stdout */ |
| ret = blast(inf, stdin, outf, stdout); |
| if (ret != 0) fprintf(stderr, "blast error: %d\n", ret); |
| |
| /* see if there are any leftover bytes */ |
| n = 0; |
| while (getchar() != EOF) n++; |
| if (n) fprintf(stderr, "blast warning: %d unused bytes of input\n", n); |
| |
| /* return blast() error code */ |
| return ret; |
| } |
| #endif |
