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Diffstat (limited to 'Userland/Libraries/LibCore/puff.cpp')
| -rw-r--r-- | Userland/Libraries/LibCore/puff.cpp | 832 |
1 files changed, 0 insertions, 832 deletions
diff --git a/Userland/Libraries/LibCore/puff.cpp b/Userland/Libraries/LibCore/puff.cpp deleted file mode 100644 index b17f26a00e..0000000000 --- a/Userland/Libraries/LibCore/puff.cpp +++ /dev/null @@ -1,832 +0,0 @@ -/* - * 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 "puff.h" /* prototype for puff() */ -#include <setjmp.h> /* for setjmp(), longjmp(), and jmp_buf */ - -#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; -} |