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/*
* 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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