/* * puff.c * Copyright (C) 2002-2004 Mark Adler * For conditions of distribution and use, see copyright notice in puff.h * version 1.8, 9 Jan 2004 * * 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 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 [Jean-loup] * - Add a puff.h file for the interface * - Add braces in puff() for else do [Jean-loup] * - 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 */ #include <setjmp.h> /* for setjmp(), longjmp(), and jmp_buf */ #include "puff.h" /* prototype for puff() */ #define local static /* for local function definitions */ #define NIL ((unsigned char *)0) /* for no output option */ /* * 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 */ 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 -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. 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, 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 < first + count) /* 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 -9; /* 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, 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 < 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->incnt == s->inlen) longjmp(s->env, 1); /* out of input */ bitbuf = s->in[s->incnt++]; if (left > 8) left = 8; } return -9; /* 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, 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, struct huffman *lencode, 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 -9; /* 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]); if (dist > s->outcnt) return -10; /* distance too far back */ /* 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] = 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 = {lencnt, lensym}; static struct huffman distcode = {distcnt, distsym}; /* build fixed huffman tables if first call (may not be thread safe) */ if (virgin) { int symbol; short lengths[FIXLCODES]; /* 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 = {lencnt, lensym}; /* length code */ struct huffman distcode = {distcnt, distsym}; /* distance code */ 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}; /* 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) return -4; /* require complete code set here */ /* 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 < 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; } } /* build huffman table for literal/length codes */ err = construct(&lencode, lengths, nlen); if (err < 0 || (err > 0 && nlen - lencode.count[0] != 1)) return -7; /* only allow incomplete codes if just one code */ /* build huffman table for distance codes */ err = construct(&distcode, lengths + nlen, ndist); if (err < 0 || (err > 0 && ndist - distcode.count[0] != 1)) return -8; /* only allow incomplete codes if just one 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: invalid literal/length or distance code in fixed or dynamic block * -10: 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 */ 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; } #ifdef TEST /* Example of how to use puff() */ #include <stdio.h> #include <stdlib.h> #include <sys/types.h> #include <sys/stat.h> local unsigned char *yank(char *name, unsigned long *len) { unsigned long size; unsigned char *buf; FILE *in; struct stat s; *len = 0; if (stat(name, &s)) return NULL; if ((s.st_mode & S_IFMT) != S_IFREG) return NULL; size = (unsigned long)(s.st_size); if (size == 0 || (off_t)size != s.st_size) return NULL; in = fopen(name, "r"); if (in == NULL) return NULL; buf = malloc(size); if (buf != NULL && fread(buf, 1, size, in) != size) { free(buf); buf = NULL; } fclose(in); *len = size; return buf; } int main(int argc, char **argv) { int ret; unsigned char *source; unsigned long len, sourcelen, destlen; if (argc < 2) return 2; source = yank(argv[1], &len); if (source == NULL) return 2; sourcelen = len; ret = puff(NIL, &destlen, source, &sourcelen); if (ret) printf("puff() failed with return code %d\n", ret); else { printf("puff() succeeded uncompressing %lu bytes\n", destlen); if (sourcelen < len) printf("%lu compressed bytes unused\n", len - sourcelen); } free(source); return ret; } #endif

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