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-/* blast.c
- * Copyright (C) 2003, 2012 Mark Adler
- * For conditions of distribution and use, see copyright notice in blast.h
- * version 1.2, 24 Oct 2012
- *
- * 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
- */
-
-#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 */
- 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)
-{
- 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
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