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Diffstat (limited to 'zlib/contrib/puff/puff.c')
| -rw-r--r-- | zlib/contrib/puff/puff.c | 840 |
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diff --git a/zlib/contrib/puff/puff.c b/zlib/contrib/puff/puff.c new file mode 100644 index 0000000..c6c90d7 --- /dev/null +++ b/zlib/contrib/puff/puff.c @@ -0,0 +1,840 @@ +/* + * puff.c + * Copyright (C) 2002-2013 Mark Adler + * For conditions of distribution and use, see copyright notice in puff.h + * version 2.3, 21 Jan 2013 + * + * puff.c is a simple inflate written to be an unambiguous way to specify the + * deflate format. It is not written for speed but rather simplicity. As a + * side benefit, this code might actually be useful when small code is more + * important than speed, such as bootstrap applications. For typical deflate + * data, zlib's inflate() is about four times as fast as puff(). zlib's + * inflate compiles to around 20K on my machine, whereas puff.c compiles to + * around 4K on my machine (a PowerPC using GNU cc). If the faster decode() + * function here is used, then puff() is only twice as slow as zlib's + * inflate(). + * + * All dynamically allocated memory comes from the stack. The stack required + * is less than 2K bytes. This code is compatible with 16-bit int's and + * assumes that long's are at least 32 bits. puff.c uses the short data type, + * assumed to be 16 bits, for arrays in order to conserve memory. The code + * works whether integers are stored big endian or little endian. + * + * In the comments below are "Format notes" that describe the inflate process + * and document some of the less obvious aspects of the format. This source + * code is meant to supplement RFC 1951, which formally describes the deflate + * format: + * + * http://www.zlib.org/rfc-deflate.html + */ + +/* + * Change history: + * + * 1.0 10 Feb 2002 - First version + * 1.1 17 Feb 2002 - Clarifications of some comments and notes + * - Update puff() dest and source pointers on negative + * errors to facilitate debugging deflators + * - Remove longest from struct huffman -- not needed + * - Simplify offs[] index in construct() + * - Add input size and checking, using longjmp() to + * maintain easy readability + * - Use short data type for large arrays + * - Use pointers instead of long to specify source and + * destination sizes to avoid arbitrary 4 GB limits + * 1.2 17 Mar 2002 - Add faster version of decode(), doubles speed (!), + * but leave simple version for readabilty + * - Make sure invalid distances detected if pointers + * are 16 bits + * - Fix fixed codes table error + * - Provide a scanning mode for determining size of + * uncompressed data + * 1.3 20 Mar 2002 - Go back to lengths for puff() parameters [Gailly] + * - Add a puff.h file for the interface + * - Add braces in puff() for else do [Gailly] + * - Use indexes instead of pointers for readability + * 1.4 31 Mar 2002 - Simplify construct() code set check + * - Fix some comments + * - Add FIXLCODES #define + * 1.5 6 Apr 2002 - Minor comment fixes + * 1.6 7 Aug 2002 - Minor format changes + * 1.7 3 Mar 2003 - Added test code for distribution + * - Added zlib-like license + * 1.8 9 Jan 2004 - Added some comments on no distance codes case + * 1.9 21 Feb 2008 - Fix bug on 16-bit integer architectures [Pohland] + * - Catch missing end-of-block symbol error + * 2.0 25 Jul 2008 - Add #define to permit distance too far back + * - Add option in TEST code for puff to write the data + * - Add option in TEST code to skip input bytes + * - Allow TEST code to read from piped stdin + * 2.1 4 Apr 2010 - Avoid variable initialization for happier compilers + * - Avoid unsigned comparisons for even happier compilers + * 2.2 25 Apr 2010 - Fix bug in variable initializations [Oberhumer] + * - Add const where appropriate [Oberhumer] + * - Split if's and ?'s for coverage testing + * - Break out test code to separate file + * - Move NIL to puff.h + * - Allow incomplete code only if single code length is 1 + * - Add full code coverage test to Makefile + * 2.3 21 Jan 2013 - Check for invalid code length codes in dynamic blocks + */ + +#include <setjmp.h> /* for setjmp(), longjmp(), and jmp_buf */ +#include "puff.h" /* prototype for puff() */ + +#define local static /* for local function definitions */ + +/* + * Maximums for allocations and loops. It is not useful to change these -- + * they are fixed by the deflate format. + */ +#define MAXBITS 15 /* maximum bits in a code */ +#define MAXLCODES 286 /* maximum number of literal/length codes */ +#define MAXDCODES 30 /* maximum number of distance codes */ +#define MAXCODES (MAXLCODES+MAXDCODES) /* maximum codes lengths to read */ +#define FIXLCODES 288 /* number of fixed literal/length codes */ + +/* input and output state */ +struct state { + /* output state */ + unsigned char *out; /* output buffer */ + unsigned long outlen; /* available space at out */ + unsigned long outcnt; /* bytes written to out so far */ + + /* input state */ + const unsigned char *in; /* input buffer */ + unsigned long inlen; /* available input at in */ + unsigned long incnt; /* bytes read so far */ + int bitbuf; /* bit buffer */ + int bitcnt; /* number of bits in bit buffer */ + + /* input limit error return state for bits() and decode() */ + jmp_buf env; +}; + +/* + * 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) +{ + long val; /* bit accumulator (can use up to 20 bits) */ + + /* load at least need bits into val */ + val = s->bitbuf; + while (s->bitcnt < need) { + if (s->incnt == s->inlen) + longjmp(s->env, 1); /* out of input */ + val |= (long)(s->in[s->incnt++]) << s->bitcnt; /* load eight bits */ + s->bitcnt += 8; + } + + /* drop need bits and update buffer, always zero to seven bits left */ + s->bitbuf = (int)(val >> need); + s->bitcnt -= need; + + /* return need bits, zeroing the bits above that */ + return (int)(val & ((1L << need) - 1)); +} + +/* + * Process a stored block. + * + * Format notes: + * + * - After the two-bit stored block type (00), the stored block length and + * stored bytes are byte-aligned for fast copying. Therefore any leftover + * bits in the byte that has the last bit of the type, as many as seven, are + * discarded. The value of the discarded bits are not defined and should not + * be checked against any expectation. + * + * - The second inverted copy of the stored block length does not have to be + * checked, but it's probably a good idea to do so anyway. + * + * - A stored block can have zero length. This is sometimes used to byte-align + * subsets of the compressed data for random access or partial recovery. + */ +local int stored(struct state *s) +{ + unsigned len; /* length of stored block */ + + /* discard leftover bits from current byte (assumes s->bitcnt < 8) */ + s->bitbuf = 0; + s->bitcnt = 0; + + /* get length and check against its one's complement */ + if (s->incnt + 4 > s->inlen) + return 2; /* not enough input */ + len = s->in[s->incnt++]; + len |= s->in[s->incnt++] << 8; + if (s->in[s->incnt++] != (~len & 0xff) || + s->in[s->incnt++] != ((~len >> 8) & 0xff)) + return -2; /* didn't match complement! */ + + /* copy len bytes from in to out */ + if (s->incnt + len > s->inlen) + return 2; /* not enough input */ + if (s->out != NIL) { + if (s->outcnt + len > s->outlen) + return 1; /* not enough output space */ + while (len--) + s->out[s->outcnt++] = s->in[s->incnt++]; + } + else { /* just scanning */ + s->outcnt += len; + s->incnt += len; + } + + /* done with a valid stored block */ + return 0; +} + +/* + * 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 -10 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. A table-based decoding + * scheme (as used in zlib) does not need to do this reversal. + * + * - The first code for the shortest length is all zeros. Subsequent codes of + * the same length are simply integer increments of the previous code. When + * moving up a length, a zero bit is appended to the code. For a complete + * code, the last code of the longest length will be all ones. + * + * - Incomplete codes are handled by this decoder, since they are permitted + * in the deflate format. See the format notes for fixed() and dynamic(). + */ +#ifdef SLOW +local int decode(struct state *s, const 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 */ + + code = first = index = 0; + for (len = 1; len <= MAXBITS; len++) { + code |= bits(s, 1); /* get next bit */ + count = h->count[len]; + if (code - count < first) /* if length len, return symbol */ + return h->symbol[index + (code - first)]; + index += count; /* else update for next length */ + first += count; + first <<= 1; + code <<= 1; + } + return -10; /* ran out of codes */ +} + +/* + * A faster version of decode() for real applications of this code. It's not + * as readable, but it makes puff() twice as fast. And it only makes the code + * a few percent larger. + */ +#else /* !SLOW */ +local int decode(struct state *s, const 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; + bitbuf >>= 1; + count = *next++; + if (code - count < first) { /* 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->incnt == s->inlen) + longjmp(s->env, 1); /* out of input */ + bitbuf = s->in[s->incnt++]; + if (left > 8) + left = 8; + } + return -10; /* ran out of codes */ +} +#endif /* SLOW */ + +/* + * 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. + * + * Not used by decode(), but used for error checking, h->count[0] is the number + * of the n symbols not in the code. So n - h->count[0] is the number of + * codes. This is useful for checking for incomplete codes that have more than + * one symbol, which is an error in a dynamic block. + * + * Assumption: for all i in 0..n-1, 0 <= length[i] <= MAXBITS + * This is assured by the construction of the length arrays in dynamic() and + * fixed() and is not verified by construct(). + * + * Format notes: + * + * - Permitted and expected examples of incomplete codes are one of the fixed + * codes and any code with a single symbol which in deflate is coded as one + * bit instead of zero bits. See the format notes for fixed() and dynamic(). + * + * - Within a given code length, the symbols are kept in ascending order for + * the code bits definition. + */ +local int construct(struct huffman *h, const short *length, 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 */ + + /* 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 literal/length and distance codes until an end-of-block code. + * + * Format notes: + * + * - Compressed data that is after the block type if fixed or after the code + * description if dynamic is a combination of literals and length/distance + * pairs terminated by and end-of-block code. Literals are simply Huffman + * coded 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. + * + * - Literals, lengths, and the end-of-block code are combined into a single + * code of up to 286 symbols. They are 256 literals (0..255), 29 length + * symbols (257..285), and the end-of-block symbol (256). + * + * - There are 256 possible lengths (3..258), and so 29 symbols are not enough + * to represent all of those. Lengths 3..10 and 258 are in fact represented + * by just a length symbol. Lengths 11..257 are represented as a symbol and + * some number of extra bits that are added as an integer to the base length + * of the length symbol. The number of extra bits is determined by the base + * length symbol. These are in the static arrays below, lens[] for the base + * lengths and lext[] for the corresponding number of extra bits. + * + * - The reason that 258 gets its own symbol is that the longest length is used + * often in highly redundant files. Note that 258 can also be coded as the + * base value 227 plus the maximum extra value of 31. While a good deflate + * should never do this, it is not an error, and should be decoded properly. + * + * - If a length is decoded, including its extra bits if any, then it is + * followed a distance code. There are up to 30 distance symbols. Again + * there are many more possible distances (1..32768), so extra bits are added + * to a base value represented by the symbol. The distances 1..4 get their + * own symbol, but the rest require extra bits. The base distances and + * corresponding number of extra bits are below in the static arrays dist[] + * and dext[]. + * + * - 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 258 + * simply copies the last byte 258 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. You should not use memcpy() since its behavior is not + * defined for overlapped arrays. You should not use memmove() or bcopy() + * since though their behavior -is- defined for overlapping arrays, it is + * defined to do the wrong thing in this case. + */ +local int codes(struct state *s, + const struct huffman *lencode, + const struct huffman *distcode) +{ + int symbol; /* decoded symbol */ + int len; /* length for copy */ + unsigned dist; /* distance for copy */ + static const short lens[29] = { /* Size base for length codes 257..285 */ + 3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 17, 19, 23, 27, 31, + 35, 43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227, 258}; + static const short lext[29] = { /* Extra bits for length codes 257..285 */ + 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2, + 3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 0}; + static const short dists[30] = { /* Offset base for distance codes 0..29 */ + 1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49, 65, 97, 129, 193, + 257, 385, 513, 769, 1025, 1537, 2049, 3073, 4097, 6145, + 8193, 12289, 16385, 24577}; + static const short dext[30] = { /* Extra bits for distance codes 0..29 */ + 0, 0, 0, 0, 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6, + 7, 7, 8, 8, 9, 9, 10, 10, 11, 11, + 12, 12, 13, 13}; + + /* decode literals and length/distance pairs */ + do { + symbol = decode(s, lencode); + if (symbol < 0) + return symbol; /* invalid symbol */ + if (symbol < 256) { /* literal: symbol is the byte */ + /* write out the literal */ + if (s->out != NIL) { + if (s->outcnt == s->outlen) + return 1; + s->out[s->outcnt] = symbol; + } + s->outcnt++; + } + else if (symbol > 256) { /* length */ + /* get and compute length */ + symbol -= 257; + if (symbol >= 29) + return -10; /* invalid fixed code */ + len = lens[symbol] + bits(s, lext[symbol]); + + /* get and check distance */ + symbol = decode(s, distcode); + if (symbol < 0) + return symbol; /* invalid symbol */ + dist = dists[symbol] + bits(s, dext[symbol]); +#ifndef INFLATE_ALLOW_INVALID_DISTANCE_TOOFAR_ARRR + if (dist > s->outcnt) + return -11; /* distance too far back */ +#endif + + /* copy length bytes from distance bytes back */ + if (s->out != NIL) { + if (s->outcnt + len > s->outlen) + return 1; + while (len--) { + s->out[s->outcnt] = +#ifdef INFLATE_ALLOW_INVALID_DISTANCE_TOOFAR_ARRR + dist > s->outcnt ? + 0 : +#endif + s->out[s->outcnt - dist]; + s->outcnt++; + } + } + else + s->outcnt += len; + } + } while (symbol != 256); /* end of block symbol */ + + /* done with a valid fixed or dynamic block */ + return 0; +} + +/* + * Process a fixed codes block. + * + * Format notes: + * + * - This block type can be useful for compressing small amounts of data for + * which the size of the code descriptions in a dynamic block exceeds the + * benefit of custom codes for that block. For fixed codes, no bits are + * spent on code descriptions. Instead the code lengths for literal/length + * codes and distance codes are fixed. The specific lengths for each symbol + * can be seen in the "for" loops below. + * + * - The literal/length code is complete, but has two symbols that are invalid + * and should result in an error if received. This cannot be implemented + * simply as an incomplete code since those two symbols are in the "middle" + * of the code. They are eight bits long and the longest literal/length\ + * code is nine bits. Therefore the code must be constructed with those + * symbols, and the invalid symbols must be detected after decoding. + * + * - The fixed distance codes also have two invalid symbols that should result + * in an error if received. Since all of the distance codes are the same + * length, this can be implemented as an incomplete code. Then the invalid + * codes are detected while decoding. + */ +local int fixed(struct state *s) +{ + static int virgin = 1; + static short lencnt[MAXBITS+1], lensym[FIXLCODES]; + static short distcnt[MAXBITS+1], distsym[MAXDCODES]; + static struct huffman lencode, distcode; + + /* build fixed huffman tables if first call (may not be thread safe) */ + if (virgin) { + int symbol; + short lengths[FIXLCODES]; + + /* construct lencode and distcode */ + lencode.count = lencnt; + lencode.symbol = lensym; + distcode.count = distcnt; + distcode.symbol = distsym; + + /* literal/length table */ + for (symbol = 0; symbol < 144; symbol++) + lengths[symbol] = 8; + for (; symbol < 256; symbol++) + lengths[symbol] = 9; + for (; symbol < 280; symbol++) + lengths[symbol] = 7; + for (; symbol < FIXLCODES; symbol++) + lengths[symbol] = 8; + construct(&lencode, lengths, FIXLCODES); + + /* distance table */ + for (symbol = 0; symbol < MAXDCODES; symbol++) + lengths[symbol] = 5; + construct(&distcode, lengths, MAXDCODES); + + /* do this just once */ + virgin = 0; + } + + /* decode data until end-of-block code */ + return codes(s, &lencode, &distcode); +} + +/* + * Process a dynamic codes block. + * + * Format notes: + * + * - A dynamic block starts with a description of the literal/length and + * distance codes for that block. New dynamic blocks allow the compressor to + * rapidly adapt to changing data with new codes optimized for that data. + * + * - The codes used by the deflate format are "canonical", which means that + * the actual bits of the codes are generated in an unambiguous way simply + * from the number of bits in each code. Therefore the code descriptions + * are simply a list of code lengths for each symbol. + * + * - The code lengths are stored in order for the symbols, so lengths are + * provided for each of the literal/length symbols, and for each of the + * distance symbols. + * + * - If a symbol is not used in the block, this is represented by a zero as + * as the code length. This does not mean a zero-length code, but rather + * that no code should be created for this symbol. There is no way in the + * deflate format to represent a zero-length code. + * + * - The maximum number of bits in a code is 15, so the possible lengths for + * any code are 1..15. + * + * - The fact that a length of zero is not permitted for a code has an + * interesting consequence. Normally if only one symbol is used for a given + * code, then in fact that code could be represented with zero bits. However + * in deflate, that code has to be at least one bit. So for example, if + * only a single distance base symbol appears in a block, then it will be + * represented by a single code of length one, in particular one 0 bit. This + * is an incomplete code, since if a 1 bit is received, it has no meaning, + * and should result in an error. So incomplete distance codes of one symbol + * should be permitted, and the receipt of invalid codes should be handled. + * + * - It is also possible to have a single literal/length code, but that code + * must be the end-of-block code, since every dynamic block has one. This + * is not the most efficient way to create an empty block (an empty fixed + * block is fewer bits), but it is allowed by the format. So incomplete + * literal/length codes of one symbol should also be permitted. + * + * - If there are only literal codes and no lengths, then there are no distance + * codes. This is represented by one distance code with zero bits. + * + * - The list of up to 286 length/literal lengths and up to 30 distance lengths + * are themselves compressed using Huffman codes and run-length encoding. In + * the list of code lengths, a 0 symbol means no code, a 1..15 symbol means + * that length, and the symbols 16, 17, and 18 are run-length instructions. + * Each of 16, 17, and 18 are follwed by extra bits to define the length of + * the run. 16 copies the last length 3 to 6 times. 17 represents 3 to 10 + * zero lengths, and 18 represents 11 to 138 zero lengths. Unused symbols + * are common, hence the special coding for zero lengths. + * + * - The symbols for 0..18 are Huffman coded, and so that code must be + * described first. This is simply a sequence of up to 19 three-bit values + * representing no code (0) or the code length for that symbol (1..7). + * + * - A dynamic block starts with three fixed-size counts from which is computed + * the number of literal/length code lengths, the number of distance code + * lengths, and the number of code length code lengths (ok, you come up with + * a better name!) in the code descriptions. For the literal/length and + * distance codes, lengths after those provided are considered zero, i.e. no + * code. The code length code lengths are received in a permuted order (see + * the order[] array below) to make a short code length code length list more + * likely. As it turns out, very short and very long codes are less likely + * to be seen in a dynamic code description, hence what may appear initially + * to be a peculiar ordering. + * + * - Given the number of literal/length code lengths (nlen) and distance code + * lengths (ndist), then they are treated as one long list of nlen + ndist + * code lengths. Therefore run-length coding can and often does cross the + * boundary between the two sets of lengths. + * + * - So to summarize, the code description at the start of a dynamic block is + * three counts for the number of code lengths for the literal/length codes, + * the distance codes, and the code length codes. This is followed by the + * code length code lengths, three bits each. This is used to construct the + * code length code which is used to read the remainder of the lengths. Then + * the literal/length code lengths and distance lengths are read as a single + * set of lengths using the code length codes. Codes are constructed from + * the resulting two sets of lengths, and then finally you can start + * decoding actual compressed data in the block. + * + * - For reference, a "typical" size for the code description in a dynamic + * block is around 80 bytes. + */ +local int dynamic(struct state *s) +{ + int nlen, ndist, ncode; /* number of lengths in descriptor */ + int index; /* index of lengths[] */ + int err; /* construct() return value */ + short lengths[MAXCODES]; /* descriptor code lengths */ + short lencnt[MAXBITS+1], lensym[MAXLCODES]; /* lencode memory */ + short distcnt[MAXBITS+1], distsym[MAXDCODES]; /* distcode memory */ + struct huffman lencode, distcode; /* length and distance codes */ + static const short order[19] = /* permutation of code length codes */ + {16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15}; + + /* construct lencode and distcode */ + lencode.count = lencnt; + lencode.symbol = lensym; + distcode.count = distcnt; + distcode.symbol = distsym; + + /* get number of lengths in each table, check lengths */ + nlen = bits(s, 5) + 257; + ndist = bits(s, 5) + 1; + ncode = bits(s, 4) + 4; + if (nlen > MAXLCODES || ndist > MAXDCODES) + return -3; /* bad counts */ + + /* read code length code lengths (really), missing lengths are zero */ + for (index = 0; index < ncode; index++) + lengths[order[index]] = bits(s, 3); + for (; index < 19; index++) + lengths[order[index]] = 0; + + /* build huffman table for code lengths codes (use lencode temporarily) */ + err = construct(&lencode, lengths, 19); + if (err != 0) /* require complete code set here */ + return -4; + + /* read length/literal and distance code length tables */ + index = 0; + while (index < nlen + ndist) { + int symbol; /* decoded value */ + int len; /* last length to repeat */ + + symbol = decode(s, &lencode); + if (symbol < 0) + return symbol; /* invalid symbol */ + if (symbol < 16) /* length in 0..15 */ + lengths[index++] = symbol; + else { /* repeat instruction */ + len = 0; /* assume repeating zeros */ + if (symbol == 16) { /* repeat last length 3..6 times */ + if (index == 0) + return -5; /* no last length! */ + len = lengths[index - 1]; /* last length */ + symbol = 3 + bits(s, 2); + } + else if (symbol == 17) /* repeat zero 3..10 times */ + symbol = 3 + bits(s, 3); + else /* == 18, repeat zero 11..138 times */ + symbol = 11 + bits(s, 7); + if (index + symbol > nlen + ndist) + return -6; /* too many lengths! */ + while (symbol--) /* repeat last or zero symbol times */ + lengths[index++] = len; + } + } + + /* check for end-of-block code -- there better be one! */ + if (lengths[256] == 0) + return -9; + + /* build huffman table for literal/length codes */ + err = construct(&lencode, lengths, nlen); + if (err && (err < 0 || nlen != lencode.count[0] + lencode.count[1])) + return -7; /* incomplete code ok only for single length 1 code */ + + /* build huffman table for distance codes */ + err = construct(&distcode, lengths + nlen, ndist); + if (err && (err < 0 || ndist != distcode.count[0] + distcode.count[1])) + return -8; /* incomplete code ok only for single length 1 code */ + + /* decode data until end-of-block code */ + return codes(s, &lencode, &distcode); +} + +/* + * Inflate source to dest. On return, destlen and sourcelen are updated to the + * size of the uncompressed data and the size of the deflate data respectively. + * On success, the return value of puff() is zero. If there is an error in the + * source data, i.e. it is not in the deflate format, then a negative value is + * returned. If there is not enough input available or there is not enough + * output space, then a positive error is returned. In that case, destlen and + * sourcelen are not updated to facilitate retrying from the beginning with the + * provision of more input data or more output space. In the case of invalid + * inflate data (a negative error), the dest and source pointers are updated to + * facilitate the debugging of deflators. + * + * puff() also has a mode to determine the size of the uncompressed output with + * no output written. For this dest must be (unsigned char *)0. In this case, + * the input value of *destlen is ignored, and on return *destlen is set to the + * size of the uncompressed output. + * + * The return codes are: + * + * 2: available inflate data did not terminate + * 1: output space exhausted before completing inflate + * 0: successful inflate + * -1: invalid block type (type == 3) + * -2: stored block length did not match one's complement + * -3: dynamic block code description: too many length or distance codes + * -4: dynamic block code description: code lengths codes incomplete + * -5: dynamic block code description: repeat lengths with no first length + * -6: dynamic block code description: repeat more than specified lengths + * -7: dynamic block code description: invalid literal/length code lengths + * -8: dynamic block code description: invalid distance code lengths + * -9: dynamic block code description: missing end-of-block code + * -10: invalid literal/length or distance code in fixed or dynamic block + * -11: distance is too far back in fixed or dynamic block + * + * Format notes: + * + * - Three bits are read for each block to determine the kind of block and + * whether or not it is the last block. Then the block is decoded and the + * process repeated if it was not the last block. + * + * - The leftover bits in the last byte of the deflate data after the last + * block (if it was a fixed or dynamic block) are undefined and have no + * expected values to check. + */ +int puff(unsigned char *dest, /* pointer to destination pointer */ + unsigned long *destlen, /* amount of output space */ + const unsigned char *source, /* pointer to source data pointer */ + unsigned long *sourcelen) /* amount of input available */ +{ + struct state s; /* input/output state */ + int last, type; /* block information */ + int err; /* return value */ + + /* initialize output state */ + s.out = dest; + s.outlen = *destlen; /* ignored if dest is NIL */ + s.outcnt = 0; + + /* initialize input state */ + s.in = source; + s.inlen = *sourcelen; + s.incnt = 0; + s.bitbuf = 0; + s.bitcnt = 0; + + /* 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 do-loop, return error */ + else { + /* process blocks until last block or error */ + do { + last = bits(&s, 1); /* one if last block */ + type = bits(&s, 2); /* block type 0..3 */ + err = type == 0 ? + stored(&s) : + (type == 1 ? + fixed(&s) : + (type == 2 ? + dynamic(&s) : + -1)); /* type == 3, invalid */ + if (err != 0) + break; /* return with error */ + } while (!last); + } + + /* update the lengths and return */ + if (err <= 0) { + *destlen = s.outcnt; + *sourcelen = s.incnt; + } + return err; +} |