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/* |
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* puff.c |
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* Copyright (C) 2002-2013 Mark Adler |
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* For conditions of distribution and use, see copyright notice in puff.h |
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* version 2.3, 21 Jan 2013 |
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* |
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* puff.c is a simple inflate written to be an unambiguous way to specify the |
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* deflate format. It is not written for speed but rather simplicity. As a |
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* side benefit, this code might actually be useful when small code is more |
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* important than speed, such as bootstrap applications. For typical deflate |
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* data, zlib's inflate() is about four times as fast as puff(). zlib's |
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* inflate compiles to around 20K on my machine, whereas puff.c compiles to |
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* around 4K on my machine (a PowerPC using GNU cc). If the faster decode() |
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* function here is used, then puff() is only twice as slow as zlib's |
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* inflate(). |
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* |
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* All dynamically allocated memory comes from the stack. The stack required |
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* is less than 2K bytes. This code is compatible with 16-bit int's and |
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* assumes that long's are at least 32 bits. puff.c uses the short data type, |
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* assumed to be 16 bits, for arrays in order to conserve memory. The code |
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* works whether integers are stored big endian or little endian. |
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* |
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* In the comments below are "Format notes" that describe the inflate process |
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* and document some of the less obvious aspects of the format. This source |
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* code is meant to supplement RFC 1951, which formally describes the deflate |
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* format: |
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* |
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* https://datatracker.ietf.org/doc/html/rfc1951 |
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*/ |
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/* |
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* Change history: |
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* |
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* 1.0 10 Feb 2002 - First version |
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* 1.1 17 Feb 2002 - Clarifications of some comments and notes |
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* - Update puff() dest and source pointers on negative |
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* errors to facilitate debugging deflators |
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* - Remove longest from struct huffman -- not needed |
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* - Simplify offs[] index in construct() |
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* - Add input size and checking, using longjmp() to |
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* maintain easy readability |
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* - Use short data type for large arrays |
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* - Use pointers instead of long to specify source and |
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* destination sizes to avoid arbitrary 4 GB limits |
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* 1.2 17 Mar 2002 - Add faster version of decode(), doubles speed (!), |
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* but leave simple version for readability |
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* - Make sure invalid distances detected if pointers |
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* are 16 bits |
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* - Fix fixed codes table error |
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* - Provide a scanning mode for determining size of |
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* uncompressed data |
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* 1.3 20 Mar 2002 - Go back to lengths for puff() parameters [Gailly] |
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* - Add a puff.h file for the interface |
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* - Add braces in puff() for else do [Gailly] |
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* - Use indexes instead of pointers for readability |
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* 1.4 31 Mar 2002 - Simplify construct() code set check |
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* - Fix some comments |
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* - Add FIXLCODES #define |
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* 1.5 6 Apr 2002 - Minor comment fixes |
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* 1.6 7 Aug 2002 - Minor format changes |
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* 1.7 3 Mar 2003 - Added test code for distribution |
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* - Added zlib-like license |
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* 1.8 9 Jan 2004 - Added some comments on no distance codes case |
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* 1.9 21 Feb 2008 - Fix bug on 16-bit integer architectures [Pohland] |
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* - Catch missing end-of-block symbol error |
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* 2.0 25 Jul 2008 - Add #define to permit distance too far back |
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* - Add option in TEST code for puff to write the data |
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* - Add option in TEST code to skip input bytes |
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* - Allow TEST code to read from piped stdin |
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* 2.1 4 Apr 2010 - Avoid variable initialization for happier compilers |
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* - Avoid unsigned comparisons for even happier compilers |
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* 2.2 25 Apr 2010 - Fix bug in variable initializations [Oberhumer] |
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* - Add const where appropriate [Oberhumer] |
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* - Split if's and ?'s for coverage testing |
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* - Break out test code to separate file |
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* - Move NIL to puff.h |
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* - Allow incomplete code only if single code length is 1 |
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* - Add full code coverage test to Makefile |
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* 2.3 21 Jan 2013 - Check for invalid code length codes in dynamic blocks |
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*/ |
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#include <setjmp.h> /* for setjmp(), longjmp(), and jmp_buf */ |
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#include "puff.h" /* prototype for puff() */ |
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#define local static /* for local function definitions */ |
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/* |
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* Maximums for allocations and loops. It is not useful to change these -- |
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* they are fixed by the deflate format. |
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*/ |
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#define MAXBITS 15 /* maximum bits in a code */ |
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#define MAXLCODES 286 /* maximum number of literal/length codes */ |
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#define MAXDCODES 30 /* maximum number of distance codes */ |
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#define MAXCODES (MAXLCODES+MAXDCODES) /* maximum codes lengths to read */ |
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#define FIXLCODES 288 /* number of fixed literal/length codes */ |
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/* input and output state */ |
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struct state { |
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/* output state */ |
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unsigned char *out; /* output buffer */ |
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unsigned long outlen; /* available space at out */ |
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unsigned long outcnt; /* bytes written to out so far */ |
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/* input state */ |
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const unsigned char *in; /* input buffer */ |
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unsigned long inlen; /* available input at in */ |
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unsigned long incnt; /* bytes read so far */ |
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int bitbuf; /* bit buffer */ |
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int bitcnt; /* number of bits in bit buffer */ |
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/* input limit error return state for bits() and decode() */ |
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jmp_buf env; |
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}; |
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/* |
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* Return need bits from the input stream. This always leaves less than |
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* eight bits in the buffer. bits() works properly for need == 0. |
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* |
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* Format notes: |
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* |
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* - Bits are stored in bytes from the least significant bit to the most |
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* significant bit. Therefore bits are dropped from the bottom of the bit |
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* buffer, using shift right, and new bytes are appended to the top of the |
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* bit buffer, using shift left. |
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*/ |
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local int bits(struct state *s, int need) |
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{ |
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long val; /* bit accumulator (can use up to 20 bits) */ |
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/* load at least need bits into val */ |
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val = s->bitbuf; |
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while (s->bitcnt < need) { |
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if (s->incnt == s->inlen) |
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longjmp(s->env, 1); /* out of input */ |
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val |= (long)(s->in[s->incnt++]) << s->bitcnt; /* load eight bits */ |
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s->bitcnt += 8; |
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} |
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/* drop need bits and update buffer, always zero to seven bits left */ |
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s->bitbuf = (int)(val >> need); |
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s->bitcnt -= need; |
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/* return need bits, zeroing the bits above that */ |
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return (int)(val & ((1L << need) - 1)); |
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} |
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/* |
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* Process a stored block. |
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* |
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* Format notes: |
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* |
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* - After the two-bit stored block type (00), the stored block length and |
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* stored bytes are byte-aligned for fast copying. Therefore any leftover |
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* bits in the byte that has the last bit of the type, as many as seven, are |
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* discarded. The value of the discarded bits are not defined and should not |
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* be checked against any expectation. |
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* |
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* - The second inverted copy of the stored block length does not have to be |
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* checked, but it's probably a good idea to do so anyway. |
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* |
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* - A stored block can have zero length. This is sometimes used to byte-align |
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* subsets of the compressed data for random access or partial recovery. |
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*/ |
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local int stored(struct state *s) |
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{ |
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unsigned len; /* length of stored block */ |
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/* discard leftover bits from current byte (assumes s->bitcnt < 8) */ |
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s->bitbuf = 0; |
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s->bitcnt = 0; |
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/* get length and check against its one's complement */ |
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if (s->incnt + 4 > s->inlen) |
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return 2; /* not enough input */ |
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len = s->in[s->incnt++]; |
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len |= s->in[s->incnt++] << 8; |
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if (s->in[s->incnt++] != (~len & 0xff) || |
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s->in[s->incnt++] != ((~len >> 8) & 0xff)) |
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return -2; /* didn't match complement! */ |
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/* copy len bytes from in to out */ |
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if (s->incnt + len > s->inlen) |
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return 2; /* not enough input */ |
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if (s->out != NIL) { |
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if (s->outcnt + len > s->outlen) |
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return 1; /* not enough output space */ |
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while (len--) |
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s->out[s->outcnt++] = s->in[s->incnt++]; |
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} |
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else { /* just scanning */ |
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s->outcnt += len; |
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s->incnt += len; |
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} |
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/* done with a valid stored block */ |
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return 0; |
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} |
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/* |
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* Huffman code decoding tables. count[1..MAXBITS] is the number of symbols of |
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* each length, which for a canonical code are stepped through in order. |
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* symbol[] are the symbol values in canonical order, where the number of |
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* entries is the sum of the counts in count[]. The decoding process can be |
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* seen in the function decode() below. |
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*/ |
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struct huffman { |
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short *count; /* number of symbols of each length */ |
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short *symbol; /* canonically ordered symbols */ |
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}; |
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/* |
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* Decode a code from the stream s using huffman table h. Return the symbol or |
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* a negative value if there is an error. If all of the lengths are zero, i.e. |
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* an empty code, or if the code is incomplete and an invalid code is received, |
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* then -10 is returned after reading MAXBITS bits. |
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* |
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* Format notes: |
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* |
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* - The codes as stored in the compressed data are bit-reversed relative to |
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* a simple integer ordering of codes of the same lengths. Hence below the |
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* bits are pulled from the compressed data one at a time and used to |
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* build the code value reversed from what is in the stream in order to |
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* permit simple integer comparisons for decoding. A table-based decoding |
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* scheme (as used in zlib) does not need to do this reversal. |
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* |
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* - The first code for the shortest length is all zeros. Subsequent codes of |
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* the same length are simply integer increments of the previous code. When |
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* moving up a length, a zero bit is appended to the code. For a complete |
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* code, the last code of the longest length will be all ones. |
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* |
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* - Incomplete codes are handled by this decoder, since they are permitted |
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* in the deflate format. See the format notes for fixed() and dynamic(). |
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*/ |
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#ifdef SLOW |
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local int decode(struct state *s, const struct huffman *h) |
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{ |
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int len; /* current number of bits in code */ |
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int code; /* len bits being decoded */ |
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int first; /* first code of length len */ |
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int count; /* number of codes of length len */ |
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int index; /* index of first code of length len in symbol table */ |
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code = first = index = 0; |
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for (len = 1; len <= MAXBITS; len++) { |
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code |= bits(s, 1); /* get next bit */ |
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count = h->count[len]; |
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if (code - count < first) /* if length len, return symbol */ |
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return h->symbol[index + (code - first)]; |
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index += count; /* else update for next length */ |
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first += count; |
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first <<= 1; |
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code <<= 1; |
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} |
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return -10; /* ran out of codes */ |
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} |
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/* |
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258
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* A faster version of decode() for real applications of this code. It's not |
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* as readable, but it makes puff() twice as fast. And it only makes the code |
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* a few percent larger. |
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*/ |
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#else /* !SLOW */ |
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local int decode(struct state *s, const struct huffman *h) |
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{ |
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int len; /* current number of bits in code */ |
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int code; /* len bits being decoded */ |
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int first; /* first code of length len */ |
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int count; /* number of codes of length len */ |
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int index; /* index of first code of length len in symbol table */ |
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int bitbuf; /* bits from stream */ |
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int left; /* bits left in next or left to process */ |
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short *next; /* next number of codes */ |
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274
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bitbuf = s->bitbuf; |
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left = s->bitcnt; |
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code = first = index = 0; |
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len = 1; |
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next = h->count + 1; |
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while (1) { |
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while (left--) { |
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281
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code |= bitbuf & 1; |
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bitbuf >>= 1; |
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count = *next++; |
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if (code - count < first) { /* if length len, return symbol */ |
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s->bitbuf = bitbuf; |
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s->bitcnt = (s->bitcnt - len) & 7; |
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return h->symbol[index + (code - first)]; |
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} |
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index += count; /* else update for next length */ |
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first += count; |
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first <<= 1; |
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code <<= 1; |
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len++; |
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} |
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left = (MAXBITS+1) - len; |
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if (left == 0) |
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break; |
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if (s->incnt == s->inlen) |
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longjmp(s->env, 1); /* out of input */ |
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300
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bitbuf = s->in[s->incnt++]; |
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301
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if (left > 8) |
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302
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left = 8; |
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303
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} |
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304
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return -10; /* ran out of codes */ |
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305
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} |
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306
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#endif /* SLOW */ |
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307
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308
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/* |
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309
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* Given the list of code lengths length[0..n-1] representing a canonical |
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310
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* Huffman code for n symbols, construct the tables required to decode those |
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311
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* codes. Those tables are the number of codes of each length, and the symbols |
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312
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* sorted by length, retaining their original order within each length. The |
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313
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* return value is zero for a complete code set, negative for an over- |
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314
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* subscribed code set, and positive for an incomplete code set. The tables |
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315
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* can be used if the return value is zero or positive, but they cannot be used |
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316
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* if the return value is negative. If the return value is zero, it is not |
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317
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* possible for decode() using that table to return an error--any stream of |
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318
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* enough bits will resolve to a symbol. If the return value is positive, then |
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319
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* it is possible for decode() using that table to return an error for received |
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320
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* codes past the end of the incomplete lengths. |
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321
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* |
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322
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* Not used by decode(), but used for error checking, h->count[0] is the number |
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323
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* of the n symbols not in the code. So n - h->count[0] is the number of |
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324
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* codes. This is useful for checking for incomplete codes that have more than |
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325
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* one symbol, which is an error in a dynamic block. |
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326
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* |
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327
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* Assumption: for all i in 0..n-1, 0 <= length[i] <= MAXBITS |
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328
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* This is assured by the construction of the length arrays in dynamic() and |
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329
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* fixed() and is not verified by construct(). |
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330
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* |
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331
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* Format notes: |
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332
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* |
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333
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* - Permitted and expected examples of incomplete codes are one of the fixed |
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334
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* codes and any code with a single symbol which in deflate is coded as one |
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335
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* bit instead of zero bits. See the format notes for fixed() and dynamic(). |
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336
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* |
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337
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* - Within a given code length, the symbols are kept in ascending order for |
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338
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* the code bits definition. |
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339
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*/ |
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340
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local int construct(struct huffman *h, const short *length, int n) |
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341
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{ |
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342
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int symbol; /* current symbol when stepping through length[] */ |
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343
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int len; /* current length when stepping through h->count[] */ |
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344
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int left; /* number of possible codes left of current length */ |
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345
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short offs[MAXBITS+1]; /* offsets in symbol table for each length */ |
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346
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347
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/* count number of codes of each length */ |
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348
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for (len = 0; len <= MAXBITS; len++) |
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349
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h->count[len] = 0; |
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350
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for (symbol = 0; symbol < n; symbol++) |
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351
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(h->count[length[symbol]])++; /* assumes lengths are within bounds */ |
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352
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if (h->count[0] == n) /* no codes! */ |
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353
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return 0; /* complete, but decode() will fail */ |
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354
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|
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355
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/* check for an over-subscribed or incomplete set of lengths */ |
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356
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left = 1; /* one possible code of zero length */ |
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357
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for (len = 1; len <= MAXBITS; len++) { |
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358
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left <<= 1; /* one more bit, double codes left */ |
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359
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left -= h->count[len]; /* deduct count from possible codes */ |
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360
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if (left < 0) |
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361
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return left; /* over-subscribed--return negative */ |
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362
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} /* left > 0 means incomplete */ |
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363
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|
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364
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/* generate offsets into symbol table for each length for sorting */ |
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365
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offs[1] = 0; |
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366
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for (len = 1; len < MAXBITS; len++) |
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367
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offs[len + 1] = offs[len] + h->count[len]; |
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368
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|
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369
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/* |
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370
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* put symbols in table sorted by length, by symbol order within each |
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371
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* length |
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372
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*/ |
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373
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for (symbol = 0; symbol < n; symbol++) |
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374
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if (length[symbol] != 0) |
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375
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h->symbol[offs[length[symbol]]++] = symbol; |
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376
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|
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377
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/* return zero for complete set, positive for incomplete set */ |
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378
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return left; |
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379
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} |
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380
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|
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381
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/* |
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382
|
* Decode literal/length and distance codes until an end-of-block code. |
|
383
|
* |
|
384
|
* Format notes: |
|
385
|
* |
|
386
|
* - Compressed data that is after the block type if fixed or after the code |
|
387
|
* description if dynamic is a combination of literals and length/distance |
|
388
|
* pairs terminated by and end-of-block code. Literals are simply Huffman |
|
389
|
* coded bytes. A length/distance pair is a coded length followed by a |
|
390
|
* coded distance to represent a string that occurs earlier in the |
|
391
|
* uncompressed data that occurs again at the current location. |
|
392
|
* |
|
393
|
* - Literals, lengths, and the end-of-block code are combined into a single |
|
394
|
* code of up to 286 symbols. They are 256 literals (0..255), 29 length |
|
395
|
* symbols (257..285), and the end-of-block symbol (256). |
|
396
|
* |
|
397
|
* - There are 256 possible lengths (3..258), and so 29 symbols are not enough |
|
398
|
* to represent all of those. Lengths 3..10 and 258 are in fact represented |
|
399
|
* by just a length symbol. Lengths 11..257 are represented as a symbol and |
|
400
|
* some number of extra bits that are added as an integer to the base length |
|
401
|
* of the length symbol. The number of extra bits is determined by the base |
|
402
|
* length symbol. These are in the static arrays below, lens[] for the base |
|
403
|
* lengths and lext[] for the corresponding number of extra bits. |
|
404
|
* |
|
405
|
* - The reason that 258 gets its own symbol is that the longest length is used |
|
406
|
* often in highly redundant files. Note that 258 can also be coded as the |
|
407
|
* base value 227 plus the maximum extra value of 31. While a good deflate |
|
408
|
* should never do this, it is not an error, and should be decoded properly. |
|
409
|
* |
|
410
|
* - If a length is decoded, including its extra bits if any, then it is |
|
411
|
* followed a distance code. There are up to 30 distance symbols. Again |
|
412
|
* there are many more possible distances (1..32768), so extra bits are added |
|
413
|
* to a base value represented by the symbol. The distances 1..4 get their |
|
414
|
* own symbol, but the rest require extra bits. The base distances and |
|
415
|
* corresponding number of extra bits are below in the static arrays dist[] |
|
416
|
* and dext[]. |
|
417
|
* |
|
418
|
* - Literal bytes are simply written to the output. A length/distance pair is |
|
419
|
* an instruction to copy previously uncompressed bytes to the output. The |
|
420
|
* copy is from distance bytes back in the output stream, copying for length |
|
421
|
* bytes. |
|
422
|
* |
|
423
|
* - Distances pointing before the beginning of the output data are not |
|
424
|
* permitted. |
|
425
|
* |
|
426
|
* - Overlapped copies, where the length is greater than the distance, are |
|
427
|
* allowed and common. For example, a distance of one and a length of 258 |
|
428
|
* simply copies the last byte 258 times. A distance of four and a length of |
|
429
|
* twelve copies the last four bytes three times. A simple forward copy |
|
430
|
* ignoring whether the length is greater than the distance or not implements |
|
431
|
* this correctly. You should not use memcpy() since its behavior is not |
|
432
|
* defined for overlapped arrays. You should not use memmove() or bcopy() |
|
433
|
* since though their behavior -is- defined for overlapping arrays, it is |
|
434
|
* defined to do the wrong thing in this case. |
|
435
|
*/ |
|
436
|
local int codes(struct state *s, |
|
437
|
const struct huffman *lencode, |
|
438
|
const struct huffman *distcode) |
|
439
|
{ |
|
440
|
int symbol; /* decoded symbol */ |
|
441
|
int len; /* length for copy */ |
|
442
|
unsigned dist; /* distance for copy */ |
|
443
|
static const short lens[29] = { /* Size base for length codes 257..285 */ |
|
444
|
3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 17, 19, 23, 27, 31, |
|
445
|
35, 43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227, 258}; |
|
446
|
static const short lext[29] = { /* Extra bits for length codes 257..285 */ |
|
447
|
0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2, |
|
448
|
3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 0}; |
|
449
|
static const short dists[30] = { /* Offset base for distance codes 0..29 */ |
|
450
|
1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49, 65, 97, 129, 193, |
|
451
|
257, 385, 513, 769, 1025, 1537, 2049, 3073, 4097, 6145, |
|
452
|
8193, 12289, 16385, 24577}; |
|
453
|
static const short dext[30] = { /* Extra bits for distance codes 0..29 */ |
|
454
|
0, 0, 0, 0, 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6, |
|
455
|
7, 7, 8, 8, 9, 9, 10, 10, 11, 11, |
|
456
|
12, 12, 13, 13}; |
|
457
|
|
|
458
|
/* decode literals and length/distance pairs */ |
|
459
|
do { |
|
460
|
symbol = decode(s, lencode); |
|
461
|
if (symbol < 0) |
|
462
|
return symbol; /* invalid symbol */ |
|
463
|
if (symbol < 256) { /* literal: symbol is the byte */ |
|
464
|
/* write out the literal */ |
|
465
|
if (s->out != NIL) { |
|
466
|
if (s->outcnt == s->outlen) |
|
467
|
return 1; |
|
468
|
s->out[s->outcnt] = symbol; |
|
469
|
} |
|
470
|
s->outcnt++; |
|
471
|
} |
|
472
|
else if (symbol > 256) { /* length */ |
|
473
|
/* get and compute length */ |
|
474
|
symbol -= 257; |
|
475
|
if (symbol >= 29) |
|
476
|
return -10; /* invalid fixed code */ |
|
477
|
len = lens[symbol] + bits(s, lext[symbol]); |
|
478
|
|
|
479
|
/* get and check distance */ |
|
480
|
symbol = decode(s, distcode); |
|
481
|
if (symbol < 0) |
|
482
|
return symbol; /* invalid symbol */ |
|
483
|
dist = dists[symbol] + bits(s, dext[symbol]); |
|
484
|
#ifndef INFLATE_ALLOW_INVALID_DISTANCE_TOOFAR_ARRR |
|
485
|
if (dist > s->outcnt) |
|
486
|
return -11; /* distance too far back */ |
|
487
|
#endif |
|
488
|
|
|
489
|
/* copy length bytes from distance bytes back */ |
|
490
|
if (s->out != NIL) { |
|
491
|
if (s->outcnt + len > s->outlen) |
|
492
|
return 1; |
|
493
|
while (len--) { |
|
494
|
s->out[s->outcnt] = |
|
495
|
#ifdef INFLATE_ALLOW_INVALID_DISTANCE_TOOFAR_ARRR |
|
496
|
dist > s->outcnt ? |
|
497
|
0 : |
|
498
|
#endif |
|
499
|
s->out[s->outcnt - dist]; |
|
500
|
s->outcnt++; |
|
501
|
} |
|
502
|
} |
|
503
|
else |
|
504
|
s->outcnt += len; |
|
505
|
} |
|
506
|
} while (symbol != 256); /* end of block symbol */ |
|
507
|
|
|
508
|
/* done with a valid fixed or dynamic block */ |
|
509
|
return 0; |
|
510
|
} |
|
511
|
|
|
512
|
/* |
|
513
|
* Process a fixed codes block. |
|
514
|
* |
|
515
|
* Format notes: |
|
516
|
* |
|
517
|
* - This block type can be useful for compressing small amounts of data for |
|
518
|
* which the size of the code descriptions in a dynamic block exceeds the |
|
519
|
* benefit of custom codes for that block. For fixed codes, no bits are |
|
520
|
* spent on code descriptions. Instead the code lengths for literal/length |
|
521
|
* codes and distance codes are fixed. The specific lengths for each symbol |
|
522
|
* can be seen in the "for" loops below. |
|
523
|
* |
|
524
|
* - The literal/length code is complete, but has two symbols that are invalid |
|
525
|
* and should result in an error if received. This cannot be implemented |
|
526
|
* simply as an incomplete code since those two symbols are in the "middle" |
|
527
|
* of the code. They are eight bits long and the longest literal/length\ |
|
528
|
* code is nine bits. Therefore the code must be constructed with those |
|
529
|
* symbols, and the invalid symbols must be detected after decoding. |
|
530
|
* |
|
531
|
* - The fixed distance codes also have two invalid symbols that should result |
|
532
|
* in an error if received. Since all of the distance codes are the same |
|
533
|
* length, this can be implemented as an incomplete code. Then the invalid |
|
534
|
* codes are detected while decoding. |
|
535
|
*/ |
|
536
|
local int fixed(struct state *s) |
|
537
|
{ |
|
538
|
static int virgin = 1; |
|
539
|
static short lencnt[MAXBITS+1], lensym[FIXLCODES]; |
|
540
|
static short distcnt[MAXBITS+1], distsym[MAXDCODES]; |
|
541
|
static struct huffman lencode, distcode; |
|
542
|
|
|
543
|
/* build fixed huffman tables if first call (may not be thread safe) */ |
|
544
|
if (virgin) { |
|
545
|
int symbol; |
|
546
|
short lengths[FIXLCODES]; |
|
547
|
|
|
548
|
/* construct lencode and distcode */ |
|
549
|
lencode.count = lencnt; |
|
550
|
lencode.symbol = lensym; |
|
551
|
distcode.count = distcnt; |
|
552
|
distcode.symbol = distsym; |
|
553
|
|
|
554
|
/* literal/length table */ |
|
555
|
for (symbol = 0; symbol < 144; symbol++) |
|
556
|
lengths[symbol] = 8; |
|
557
|
for (; symbol < 256; symbol++) |
|
558
|
lengths[symbol] = 9; |
|
559
|
for (; symbol < 280; symbol++) |
|
560
|
lengths[symbol] = 7; |
|
561
|
for (; symbol < FIXLCODES; symbol++) |
|
562
|
lengths[symbol] = 8; |
|
563
|
construct(&lencode, lengths, FIXLCODES); |
|
564
|
|
|
565
|
/* distance table */ |
|
566
|
for (symbol = 0; symbol < MAXDCODES; symbol++) |
|
567
|
lengths[symbol] = 5; |
|
568
|
construct(&distcode, lengths, MAXDCODES); |
|
569
|
|
|
570
|
/* do this just once */ |
|
571
|
virgin = 0; |
|
572
|
} |
|
573
|
|
|
574
|
/* decode data until end-of-block code */ |
|
575
|
return codes(s, &lencode, &distcode); |
|
576
|
} |
|
577
|
|
|
578
|
/* |
|
579
|
* Process a dynamic codes block. |
|
580
|
* |
|
581
|
* Format notes: |
|
582
|
* |
|
583
|
* - A dynamic block starts with a description of the literal/length and |
|
584
|
* distance codes for that block. New dynamic blocks allow the compressor to |
|
585
|
* rapidly adapt to changing data with new codes optimized for that data. |
|
586
|
* |
|
587
|
* - The codes used by the deflate format are "canonical", which means that |
|
588
|
* the actual bits of the codes are generated in an unambiguous way simply |
|
589
|
* from the number of bits in each code. Therefore the code descriptions |
|
590
|
* are simply a list of code lengths for each symbol. |
|
591
|
* |
|
592
|
* - The code lengths are stored in order for the symbols, so lengths are |
|
593
|
* provided for each of the literal/length symbols, and for each of the |
|
594
|
* distance symbols. |
|
595
|
* |
|
596
|
* - If a symbol is not used in the block, this is represented by a zero as the |
|
597
|
* code length. This does not mean a zero-length code, but rather that no |
|
598
|
* code should be created for this symbol. There is no way in the deflate |
|
599
|
* format to represent a zero-length code. |
|
600
|
* |
|
601
|
* - The maximum number of bits in a code is 15, so the possible lengths for |
|
602
|
* any code are 1..15. |
|
603
|
* |
|
604
|
* - The fact that a length of zero is not permitted for a code has an |
|
605
|
* interesting consequence. Normally if only one symbol is used for a given |
|
606
|
* code, then in fact that code could be represented with zero bits. However |
|
607
|
* in deflate, that code has to be at least one bit. So for example, if |
|
608
|
* only a single distance base symbol appears in a block, then it will be |
|
609
|
* represented by a single code of length one, in particular one 0 bit. This |
|
610
|
* is an incomplete code, since if a 1 bit is received, it has no meaning, |
|
611
|
* and should result in an error. So incomplete distance codes of one symbol |
|
612
|
* should be permitted, and the receipt of invalid codes should be handled. |
|
613
|
* |
|
614
|
* - It is also possible to have a single literal/length code, but that code |
|
615
|
* must be the end-of-block code, since every dynamic block has one. This |
|
616
|
* is not the most efficient way to create an empty block (an empty fixed |
|
617
|
* block is fewer bits), but it is allowed by the format. So incomplete |
|
618
|
* literal/length codes of one symbol should also be permitted. |
|
619
|
* |
|
620
|
* - If there are only literal codes and no lengths, then there are no distance |
|
621
|
* codes. This is represented by one distance code with zero bits. |
|
622
|
* |
|
623
|
* - The list of up to 286 length/literal lengths and up to 30 distance lengths |
|
624
|
* are themselves compressed using Huffman codes and run-length encoding. In |
|
625
|
* the list of code lengths, a 0 symbol means no code, a 1..15 symbol means |
|
626
|
* that length, and the symbols 16, 17, and 18 are run-length instructions. |
|
627
|
* Each of 16, 17, and 18 are followed by extra bits to define the length of |
|
628
|
* the run. 16 copies the last length 3 to 6 times. 17 represents 3 to 10 |
|
629
|
* zero lengths, and 18 represents 11 to 138 zero lengths. Unused symbols |
|
630
|
* are common, hence the special coding for zero lengths. |
|
631
|
* |
|
632
|
* - The symbols for 0..18 are Huffman coded, and so that code must be |
|
633
|
* described first. This is simply a sequence of up to 19 three-bit values |
|
634
|
* representing no code (0) or the code length for that symbol (1..7). |
|
635
|
* |
|
636
|
* - A dynamic block starts with three fixed-size counts from which is computed |
|
637
|
* the number of literal/length code lengths, the number of distance code |
|
638
|
* lengths, and the number of code length code lengths (ok, you come up with |
|
639
|
* a better name!) in the code descriptions. For the literal/length and |
|
640
|
* distance codes, lengths after those provided are considered zero, i.e. no |
|
641
|
* code. The code length code lengths are received in a permuted order (see |
|
642
|
* the order[] array below) to make a short code length code length list more |
|
643
|
* likely. As it turns out, very short and very long codes are less likely |
|
644
|
* to be seen in a dynamic code description, hence what may appear initially |
|
645
|
* to be a peculiar ordering. |
|
646
|
* |
|
647
|
* - Given the number of literal/length code lengths (nlen) and distance code |
|
648
|
* lengths (ndist), then they are treated as one long list of nlen + ndist |
|
649
|
* code lengths. Therefore run-length coding can and often does cross the |
|
650
|
* boundary between the two sets of lengths. |
|
651
|
* |
|
652
|
* - So to summarize, the code description at the start of a dynamic block is |
|
653
|
* three counts for the number of code lengths for the literal/length codes, |
|
654
|
* the distance codes, and the code length codes. This is followed by the |
|
655
|
* code length code lengths, three bits each. This is used to construct the |
|
656
|
* code length code which is used to read the remainder of the lengths. Then |
|
657
|
* the literal/length code lengths and distance lengths are read as a single |
|
658
|
* set of lengths using the code length codes. Codes are constructed from |
|
659
|
* the resulting two sets of lengths, and then finally you can start |
|
660
|
* decoding actual compressed data in the block. |
|
661
|
* |
|
662
|
* - For reference, a "typical" size for the code description in a dynamic |
|
663
|
* block is around 80 bytes. |
|
664
|
*/ |
|
665
|
local int dynamic(struct state *s) |
|
666
|
{ |
|
667
|
int nlen, ndist, ncode; /* number of lengths in descriptor */ |
|
668
|
int index; /* index of lengths[] */ |
|
669
|
int err; /* construct() return value */ |
|
670
|
short lengths[MAXCODES]; /* descriptor code lengths */ |
|
671
|
short lencnt[MAXBITS+1], lensym[MAXLCODES]; /* lencode memory */ |
|
672
|
short distcnt[MAXBITS+1], distsym[MAXDCODES]; /* distcode memory */ |
|
673
|
struct huffman lencode, distcode; /* length and distance codes */ |
|
674
|
static const short order[19] = /* permutation of code length codes */ |
|
675
|
{16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15}; |
|
676
|
|
|
677
|
/* construct lencode and distcode */ |
|
678
|
lencode.count = lencnt; |
|
679
|
lencode.symbol = lensym; |
|
680
|
distcode.count = distcnt; |
|
681
|
distcode.symbol = distsym; |
|
682
|
|
|
683
|
/* get number of lengths in each table, check lengths */ |
|
684
|
nlen = bits(s, 5) + 257; |
|
685
|
ndist = bits(s, 5) + 1; |
|
686
|
ncode = bits(s, 4) + 4; |
|
687
|
if (nlen > MAXLCODES || ndist > MAXDCODES) |
|
688
|
return -3; /* bad counts */ |
|
689
|
|
|
690
|
/* read code length code lengths (really), missing lengths are zero */ |
|
691
|
for (index = 0; index < ncode; index++) |
|
692
|
lengths[order[index]] = bits(s, 3); |
|
693
|
for (; index < 19; index++) |
|
694
|
lengths[order[index]] = 0; |
|
695
|
|
|
696
|
/* build huffman table for code lengths codes (use lencode temporarily) */ |
|
697
|
err = construct(&lencode, lengths, 19); |
|
698
|
if (err != 0) /* require complete code set here */ |
|
699
|
return -4; |
|
700
|
|
|
701
|
/* read length/literal and distance code length tables */ |
|
702
|
index = 0; |
|
703
|
while (index < nlen + ndist) { |
|
704
|
int symbol; /* decoded value */ |
|
705
|
int len; /* last length to repeat */ |
|
706
|
|
|
707
|
symbol = decode(s, &lencode); |
|
708
|
if (symbol < 0) |
|
709
|
return symbol; /* invalid symbol */ |
|
710
|
if (symbol < 16) /* length in 0..15 */ |
|
711
|
lengths[index++] = symbol; |
|
712
|
else { /* repeat instruction */ |
|
713
|
len = 0; /* assume repeating zeros */ |
|
714
|
if (symbol == 16) { /* repeat last length 3..6 times */ |
|
715
|
if (index == 0) |
|
716
|
return -5; /* no last length! */ |
|
717
|
len = lengths[index - 1]; /* last length */ |
|
718
|
symbol = 3 + bits(s, 2); |
|
719
|
} |
|
720
|
else if (symbol == 17) /* repeat zero 3..10 times */ |
|
721
|
symbol = 3 + bits(s, 3); |
|
722
|
else /* == 18, repeat zero 11..138 times */ |
|
723
|
symbol = 11 + bits(s, 7); |
|
724
|
if (index + symbol > nlen + ndist) |
|
725
|
return -6; /* too many lengths! */ |
|
726
|
while (symbol--) /* repeat last or zero symbol times */ |
|
727
|
lengths[index++] = len; |
|
728
|
} |
|
729
|
} |
|
730
|
|
|
731
|
/* check for end-of-block code -- there better be one! */ |
|
732
|
if (lengths[256] == 0) |
|
733
|
return -9; |
|
734
|
|
|
735
|
/* build huffman table for literal/length codes */ |
|
736
|
err = construct(&lencode, lengths, nlen); |
|
737
|
if (err && (err < 0 || nlen != lencode.count[0] + lencode.count[1])) |
|
738
|
return -7; /* incomplete code ok only for single length 1 code */ |
|
739
|
|
|
740
|
/* build huffman table for distance codes */ |
|
741
|
err = construct(&distcode, lengths + nlen, ndist); |
|
742
|
if (err && (err < 0 || ndist != distcode.count[0] + distcode.count[1])) |
|
743
|
return -8; /* incomplete code ok only for single length 1 code */ |
|
744
|
|
|
745
|
/* decode data until end-of-block code */ |
|
746
|
return codes(s, &lencode, &distcode); |
|
747
|
} |
|
748
|
|
|
749
|
/* |
|
750
|
* Inflate source to dest. On return, destlen and sourcelen are updated to the |
|
751
|
* size of the uncompressed data and the size of the deflate data respectively. |
|
752
|
* On success, the return value of puff() is zero. If there is an error in the |
|
753
|
* source data, i.e. it is not in the deflate format, then a negative value is |
|
754
|
* returned. If there is not enough input available or there is not enough |
|
755
|
* output space, then a positive error is returned. In that case, destlen and |
|
756
|
* sourcelen are not updated to facilitate retrying from the beginning with the |
|
757
|
* provision of more input data or more output space. In the case of invalid |
|
758
|
* inflate data (a negative error), the dest and source pointers are updated to |
|
759
|
* facilitate the debugging of deflators. |
|
760
|
* |
|
761
|
* puff() also has a mode to determine the size of the uncompressed output with |
|
762
|
* no output written. For this dest must be (unsigned char *)0. In this case, |
|
763
|
* the input value of *destlen is ignored, and on return *destlen is set to the |
|
764
|
* size of the uncompressed output. |
|
765
|
* |
|
766
|
* The return codes are: |
|
767
|
* |
|
768
|
* 2: available inflate data did not terminate |
|
769
|
* 1: output space exhausted before completing inflate |
|
770
|
* 0: successful inflate |
|
771
|
* -1: invalid block type (type == 3) |
|
772
|
* -2: stored block length did not match one's complement |
|
773
|
* -3: dynamic block code description: too many length or distance codes |
|
774
|
* -4: dynamic block code description: code lengths codes incomplete |
|
775
|
* -5: dynamic block code description: repeat lengths with no first length |
|
776
|
* -6: dynamic block code description: repeat more than specified lengths |
|
777
|
* -7: dynamic block code description: invalid literal/length code lengths |
|
778
|
* -8: dynamic block code description: invalid distance code lengths |
|
779
|
* -9: dynamic block code description: missing end-of-block code |
|
780
|
* -10: invalid literal/length or distance code in fixed or dynamic block |
|
781
|
* -11: distance is too far back in fixed or dynamic block |
|
782
|
* |
|
783
|
* Format notes: |
|
784
|
* |
|
785
|
* - Three bits are read for each block to determine the kind of block and |
|
786
|
* whether or not it is the last block. Then the block is decoded and the |
|
787
|
* process repeated if it was not the last block. |
|
788
|
* |
|
789
|
* - The leftover bits in the last byte of the deflate data after the last |
|
790
|
* block (if it was a fixed or dynamic block) are undefined and have no |
|
791
|
* expected values to check. |
|
792
|
*/ |
|
793
|
int puff(unsigned char *dest, /* pointer to destination pointer */ |
|
794
|
unsigned long *destlen, /* amount of output space */ |
|
795
|
const unsigned char *source, /* pointer to source data pointer */ |
|
796
|
unsigned long *sourcelen) /* amount of input available */ |
|
797
|
{ |
|
798
|
struct state s; /* input/output state */ |
|
799
|
int last, type; /* block information */ |
|
800
|
int err; /* return value */ |
|
801
|
|
|
802
|
/* initialize output state */ |
|
803
|
s.out = dest; |
|
804
|
s.outlen = *destlen; /* ignored if dest is NIL */ |
|
805
|
s.outcnt = 0; |
|
806
|
|
|
807
|
/* initialize input state */ |
|
808
|
s.in = source; |
|
809
|
s.inlen = *sourcelen; |
|
810
|
s.incnt = 0; |
|
811
|
s.bitbuf = 0; |
|
812
|
s.bitcnt = 0; |
|
813
|
|
|
814
|
/* return if bits() or decode() tries to read past available input */ |
|
815
|
if (setjmp(s.env) != 0) /* if came back here via longjmp() */ |
|
816
|
err = 2; /* then skip do-loop, return error */ |
|
817
|
else { |
|
818
|
/* process blocks until last block or error */ |
|
819
|
do { |
|
820
|
last = bits(&s, 1); /* one if last block */ |
|
821
|
type = bits(&s, 2); /* block type 0..3 */ |
|
822
|
err = type == 0 ? |
|
823
|
stored(&s) : |
|
824
|
(type == 1 ? |
|
825
|
fixed(&s) : |
|
826
|
(type == 2 ? |
|
827
|
dynamic(&s) : |
|
828
|
-1)); /* type == 3, invalid */ |
|
829
|
if (err != 0) |
|
830
|
break; /* return with error */ |
|
831
|
} while (!last); |
|
832
|
} |
|
833
|
|
|
834
|
/* update the lengths and return */ |
|
835
|
if (err <= 0) { |
|
836
|
*destlen = s.outcnt; |
|
837
|
*sourcelen = s.incnt; |
|
838
|
} |
|
839
|
return err; |
|
840
|
} |
|
841
|
|