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zlib/contrib/blast/blast.c view on Meta::CPAN
* - The first code for the shortest length is all ones. Subsequent codes of
* the same length are simply integer decrements of the previous code. When
* moving up a length, a one bit is appended to the code. For a complete
* code, the last code of the longest length will be all zeros. To support
* this ordering, the bits pulled during decoding are inverted to apply the
* more "natural" ordering starting with all zeros and incrementing.
*/
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;
zlib/contrib/blast/blast.c view on Meta::CPAN
* allowed and common. For example, a distance of one and a length of 518
* simply copies the last byte 518 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.
*/
local int decomp(struct state *s)
{
int lit; /* true if literals are coded */
int dict; /* log2(dictionary size) - 6 */
int symbol; /* decoded symbol, extra bits for distance */
int len; /* length for copy */
unsigned dist; /* distance for copy */
int copy; /* copy counter */
unsigned char *from, *to; /* copy pointers */
static int virgin = 1; /* build tables once */
static short litcnt[MAXBITS+1], litsym[256]; /* litcode memory */
static short lencnt[MAXBITS+1], lensym[16]; /* lencode memory */
static short distcnt[MAXBITS+1], distsym[64]; /* distcode memory */
static struct huffman litcode = {litcnt, litsym}; /* length code */
static struct huffman lencode = {lencnt, lensym}; /* length code */
zlib/contrib/puff/puff.c view on Meta::CPAN
* moving up a length, a zero bit is appended to the code. For a complete
* code, the last code of the longest length will be all ones.
*
* - Incomplete codes are handled by this decoder, since they are permitted
* in the deflate format. See the format notes for fixed() and dynamic().
*/
#ifdef SLOW
local int decode(struct state *s, const struct huffman *h)
{
int len; /* current number of bits in code */
int code; /* len bits being decoded */
int first; /* first code of length len */
int count; /* number of codes of length len */
int index; /* index of first code of length len in symbol table */
code = first = index = 0;
for (len = 1; len <= MAXBITS; len++) {
code |= bits(s, 1); /* get next bit */
count = h->count[len];
if (code - count < first) /* if length len, return symbol */
return h->symbol[index + (code - first)];
zlib/contrib/puff/puff.c view on Meta::CPAN
/*
* A faster version of decode() for real applications of this code. It's not
* as readable, but it makes puff() twice as fast. And it only makes the code
* a few percent larger.
*/
#else /* !SLOW */
local int decode(struct state *s, const struct huffman *h)
{
int len; /* current number of bits in code */
int code; /* len bits being decoded */
int first; /* first code of length len */
int count; /* number of codes of length len */
int index; /* index of first code of length len in symbol table */
int bitbuf; /* bits from stream */
int left; /* bits left in next or left to process */
short *next; /* next number of codes */
bitbuf = s->bitbuf;
left = s->bitcnt;
code = first = index = 0;
zlib/contrib/puff/puff.c view on Meta::CPAN
* 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
zlib/contrib/puff/puff.c view on Meta::CPAN
* ignoring whether the length is greater than the distance or not implements
* this correctly. You should not use memcpy() since its behavior is not
* defined for overlapped arrays. You should not use memmove() or bcopy()
* since though their behavior -is- defined for overlapping arrays, it is
* defined to do the wrong thing in this case.
*/
local int codes(struct state *s,
const struct huffman *lencode,
const struct huffman *distcode)
{
int symbol; /* decoded symbol */
int len; /* length for copy */
unsigned dist; /* distance for copy */
static const short lens[29] = { /* Size base for length codes 257..285 */
3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 17, 19, 23, 27, 31,
35, 43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227, 258};
static const short lext[29] = { /* Extra bits for length codes 257..285 */
0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2,
3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 0};
static const short dists[30] = { /* Offset base for distance codes 0..29 */
1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49, 65, 97, 129, 193,
zlib/contrib/puff/puff.c view on Meta::CPAN
lengths[order[index]] = 0;
/* build huffman table for code lengths codes (use lencode temporarily) */
err = construct(&lencode, lengths, 19);
if (err != 0) /* require complete code set here */
return -4;
/* read length/literal and distance code length tables */
index = 0;
while (index < nlen + ndist) {
int symbol; /* decoded value */
int len; /* last length to repeat */
symbol = decode(s, &lencode);
if (symbol < 0)
return symbol; /* invalid symbol */
if (symbol < 16) /* length in 0..15 */
lengths[index++] = symbol;
else { /* repeat instruction */
len = 0; /* assume repeating zeros */
if (symbol == 16) { /* repeat last length 3..6 times */
zlib/contrib/puff/puff.c view on Meta::CPAN
* -6: dynamic block code description: repeat more than specified lengths
* -7: dynamic block code description: invalid literal/length code lengths
* -8: dynamic block code description: invalid distance code lengths
* -9: dynamic block code description: missing end-of-block code
* -10: invalid literal/length or distance code in fixed or dynamic block
* -11: distance is too far back in fixed or dynamic block
*
* Format notes:
*
* - Three bits are read for each block to determine the kind of block and
* whether or not it is the last block. Then the block is decoded and the
* process repeated if it was not the last block.
*
* - The leftover bits in the last byte of the deflate data after the last
* block (if it was a fixed or dynamic block) are undefined and have no
* expected values to check.
*/
int puff(unsigned char *dest, /* pointer to destination pointer */
unsigned long *destlen, /* amount of output space */
const unsigned char *source, /* pointer to source data pointer */
unsigned long *sourcelen) /* amount of input available */
zlib/doc/algorithm.txt view on Meta::CPAN
other extreme, you could make a new table for every bit in the code. In fact,
that's essentially a Huffman tree. But then you spend too much time
traversing the tree while decoding, even for short symbols.
So the number of bits for the first lookup table is a trade of the time to
fill out the table vs. the time spent looking at the second level and above of
the table.
Here is an example, scaled down:
The code being decoded, with 10 symbols, from 1 to 6 bits long:
A: 0
B: 10
C: 1100
D: 11010
E: 11011
F: 11100
G: 11101
H: 11110
I: 111110
zlib/doc/rfc1951.txt view on Meta::CPAN
Deutsch Informational [Page 10]
RFC 1951 DEFLATE Compressed Data Format Specification May 1996
preset dictionary might discard part of the output stream; a
distance can refer to that part of the output stream anyway)
Note also that the referenced string may overlap the current
position; for example, if the last 2 bytes decoded have values
X and Y, a string reference with <length = 5, distance = 2>
adds X,Y,X,Y,X to the output stream.
We now specify each compression method in turn.
3.2.4. Non-compressed blocks (BTYPE=00)
Any bits of input up to the next byte boundary are ignored.
The rest of the block consists of the following information:
zlib/examples/zran.c view on Meta::CPAN
/* Version History:
1.0 29 May 2005 First version
1.1 29 Sep 2012 Fix memory reallocation error
1.2 14 Oct 2018 Handle gzip streams with multiple members
Add a header file to facilitate usage in applications
*/
/* Illustrate the use of Z_BLOCK, inflatePrime(), and inflateSetDictionary()
for random access of a compressed file. A file containing a zlib or gzip
stream is provided on the command line. The compressed stream is decoded in
its entirety, and an index built with access points about every SPAN bytes
in the uncompressed output. The compressed file is left open, and can then
be read randomly, having to decompress on the average SPAN/2 uncompressed
bytes before getting to the desired block of data.
An access point can be created at the start of any deflate block, by saving
the starting file offset and bit of that block, and the 32K bytes of
uncompressed data that precede that block. Also the uncompressed offset of
that block is saved to provide a reference for locating a desired starting
point in the uncompressed stream. deflate_index_build() works by
zlib/test/infcover.c view on Meta::CPAN
do {
if (*hex >= '0' && *hex <= '9')
val = (val << 4) + *hex - '0';
else if (*hex >= 'A' && *hex <= 'F')
val = (val << 4) + *hex - 'A' + 10;
else if (*hex >= 'a' && *hex <= 'f')
val = (val << 4) + *hex - 'a' + 10;
else if (val != 1 && val < 32) /* one digit followed by delimiter */
val += 240; /* make it look like two digits */
if (val > 255) { /* have two digits */
in[next++] = val & 0xff; /* save the decoded byte */
val = 1; /* start over */
}
} while (*hex++); /* go through the loop with the terminating null */
if (len != NULL)
*len = next;
re = realloc(in, next);
return re == NULL ? in : re;
}
/* generic inflate() run, where hex is the hexadecimal input data, what is the
zlib/zlib.h view on Meta::CPAN
stream. The end-of-block will not be indicated until all of the uncompressed
data from that block has been written to strm->next_out. The number of
unused bits may in general be greater than seven, except when bit 7 of
data_type is set, in which case the number of unused bits will be less than
eight. data_type is set as noted here every time inflate() returns for all
flush options, and so can be used to determine the amount of currently
consumed input in bits.
The Z_TREES option behaves as Z_BLOCK does, but it also returns when the
end of each deflate block header is reached, before any actual data in that
block is decoded. This allows the caller to determine the length of the
deflate block header for later use in random access within a deflate block.
256 is added to the value of strm->data_type when inflate() returns
immediately after reaching the end of the deflate block header.
inflate() should normally be called until it returns Z_STREAM_END or an
error. However if all decompression is to be performed in a single step (a
single call of inflate), the parameter flush should be set to Z_FINISH. In
this case all pending input is processed and all pending output is flushed;
avail_out must be large enough to hold all of the uncompressed data for the
operation to complete. (The size of the uncompressed data may have been
zlib/zlib.h view on Meta::CPAN
such as zip. Those formats provide their own check values. If a custom
format is developed using the raw deflate format for compressed data, it is
recommended that a check value such as an Adler-32 or a CRC-32 be applied to
the uncompressed data as is done in the zlib, gzip, and zip formats. For
most applications, the zlib format should be used as is. Note that comments
above on the use in deflateInit2() applies to the magnitude of windowBits.
windowBits can also be greater than 15 for optional gzip decoding. Add
32 to windowBits to enable zlib and gzip decoding with automatic header
detection, or add 16 to decode only the gzip format (the zlib format will
return a Z_DATA_ERROR). If a gzip stream is being decoded, strm->adler is a
CRC-32 instead of an Adler-32. Unlike the gunzip utility and gzread() (see
below), inflate() will *not* automatically decode concatenated gzip members.
inflate() will return Z_STREAM_END at the end of the gzip member. The state
would need to be reset to continue decoding a subsequent gzip member. This
*must* be done if there is more data after a gzip member, in order for the
decompression to be compliant with the gzip standard (RFC 1952).
inflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was not enough
memory, Z_VERSION_ERROR if the zlib library version is incompatible with the
version assumed by the caller, or Z_STREAM_ERROR if the parameters are
zlib/zlib.h view on Meta::CPAN
*/
ZEXTERN int ZEXPORT inflateGetHeader OF((z_streamp strm,
gz_headerp head));
/*
inflateGetHeader() requests that gzip header information be stored in the
provided gz_header structure. inflateGetHeader() may be called after
inflateInit2() or inflateReset(), and before the first call of inflate().
As inflate() processes the gzip stream, head->done is zero until the header
is completed, at which time head->done is set to one. If a zlib stream is
being decoded, then head->done is set to -1 to indicate that there will be
no gzip header information forthcoming. Note that Z_BLOCK or Z_TREES can be
used to force inflate() to return immediately after header processing is
complete and before any actual data is decompressed.
The text, time, xflags, and os fields are filled in with the gzip header
contents. hcrc is set to true if there is a header CRC. (The header CRC
was valid if done is set to one.) If extra is not Z_NULL, then extra_max
contains the maximum number of bytes to write to extra. Once done is true,
extra_len contains the actual extra field length, and extra contains the
extra field, or that field truncated if extra_max is less than extra_len.
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