ZLIB(3) | Library Functions Manual | ZLIB(3) |
zlib
—
#include <zlib.h>
zlibVersion
(void);
int
deflateInit
(z_streamp
strm, int
level);
int
deflate
(z_streamp
strm, int
flush);
int
deflateEnd
(z_streamp
strm);
int
inflateInit
(z_streamp
strm);
int
inflate
(z_streamp
strm, int
flush);
int
inflateEnd
(z_streamp
strm);
deflateInit2
(z_streamp
strm, int level,
int method,
int windowBits,
int memLevel,
int strategy);
int
deflateSetDictionary
(z_streamp
strm, const Bytef
*dictionary, uInt
dictLength);
int
deflateCopy
(z_streamp
dest, z_streamp
source);
int
deflateReset
(z_streamp
strm);
int
deflateParams
(z_streamp
strm, int level,
int strategy);
int
inflateInit2
(z_streamp
strm, int
windowBits);
int
inflateSetDictionary
(z_streamp
strm, const Bytef
*dictionary, uInt
dictLength);
int
inflateSync
(z_streamp
strm);
int
inflateReset
(z_streamp
strm);
typedef voidp gzFile ;
int
compress
(Bytef
*dest, uLongf
*destLen, const Bytef
*source, uLong
sourceLen);
int
compress2
(Bytef
*dest, uLongf
*destLen, const Bytef
*source, uLong
sourceLen, int
level);
int
uncompress
(Bytef
*dest, uLongf
*destLen, const Bytef
*source, uLong
sourceLen);
gzFile
gzopen
(const
char *path, const char
*mode);
gzFile
gzdopen
(int
fd, const char
*mode);
int
gzsetparams
(gzFile
file, int level,
int strategy);
int
gzread
(gzFile
file, voidp buf,
unsigned len);
int
gzwrite
(gzFile
file, const voidp
buf, unsigned
len);
int
gzprintf
(gzFile
file, const char
*format, ...);
int
gzputs
(gzFile
file, const char
*s);
char *
gzgets
(gzFile
file, char *buf,
int len);
int
gzputc
(gzFile
file, int c);
int
gzgetc
(gzFile
file);
int
gzflush
(gzFile
file, int
flush);
z_off_t
gzseek
(gzFile
file, z_off_t
offset, int
whence);
int
gzrewind
(gzFile
file);
z_off_t
gztell
(gzFile
file);
int
gzeof
(gzFile
file);
int
gzclose
(gzFile
file);
const char *
gzerror
(gzFile
file, int
*errnum);
adler32
(uLong
adler, const Bytef
*buf, uInt len);
uLong
crc32
(uLong
crc, const Bytef
*buf, uInt
len);
zlib
general purpose
compression library, version 1.1.4.
The zlib
compression library provides
in-memory compression and decompression functions, including integrity
checks of the uncompressed data. This version of the library supports only
one compression method (deflation) but other algorithms will be added later
and will have the same stream interface.
Compression can be done in a single step if the buffers are large enough (for example if an input file is mmap'ed), or can be done by repeated calls of the compression function. In the latter case, the application must provide more input and/or consume the output (providing more output space) before each call.
The library also supports reading and writing files in gzip(1) (.gz) format with an interface similar to that of stdio(3).
The library does not install any signal handler. The decoder checks the consistency of the compressed data, so the library should never crash even in case of corrupted input.
The functions within the library are divided into the following sections:
zlibVersion
(void);The application can compare
zlibVersion
() and
ZLIB_VERSION
for consistency. If the first
character differs, the library code actually used is not compatible with
the <zlib.h>
header file
used by the application. This check is automatically made by
deflateInit
() and
inflateInit
().
deflateInit
(z_streamp strm,
int level);The deflateInit
() function initializes
the internal stream state for compression. The fields
zalloc, zfree, and
opaque must be initialized before by the caller.
If zalloc and zfree are set
to Z_NULL
, deflateInit
()
updates them to use default allocation functions.
The compression level must be
Z_DEFAULT_COMPRESSION
, or between 0 and 9: 1
gives best speed, 9 gives best compression, 0 gives no compression at
all (the input data is simply copied a block at a time).
Z_DEFAULT_COMPRESSION
requests a
default compromise between speed and compression (currently equivalent
to level 6).
deflateInit
() returns
Z_OK
if successful,
Z_MEM_ERROR
if there was not enough memory,
Z_STREAM_ERROR
if level is not a valid
compression level, Z_VERSION_ERROR
if the
zlib
library version (zlib_version) is
incompatible with the version assumed by the caller (ZLIB_VERSION).
msg is set to null if there is no error message.
deflateInit
() does not perform any compression:
this will be done by deflate
().
deflate
(z_streamp strm,
int flush);deflate
() compresses as much data as
possible, and stops when the input buffer becomes empty or the output
buffer becomes full. It may introduce some output latency (reading input
without producing any output) except when forced to flush.
The detailed semantics are as follows.
deflate
() performs one or both of the following
actions:
Compress more input starting at next_in
and update next_in and
avail_in accordingly. If not all input can be
processed (because there is not enough room in the output buffer),
next_in and avail_in are
updated and processing will resume at this point for the next call to
deflate
().
Provide more output starting at next_out and update next_out and avail_out accordingly. This action is forced if the parameter flush is non-zero. Forcing flush frequently degrades the compression ratio, so this parameter should be set only when necessary (in interactive applications). Some output may be provided even if flush is not set.
Before the call to deflate
(), the
application should ensure that at least one of the actions is possible,
by providing more input and/or consuming more output, and updating
avail_in or avail_out
accordingly; avail_out should never be zero before
the call. The application can consume the compressed output when it
wants, for example when the output buffer is full (avail_out == 0), or
after each call to deflate
(). If
deflate
() returns Z_OK
and with zero avail_out, it must be called again
after making room in the output buffer because there might be more
output pending.
If the parameter flush is set to
Z_SYNC_FLUSH
, all pending output is flushed to
the output buffer and the output is aligned on a byte boundary, so that
the decompressor can get all input data available so far. (In
particular, avail_in is zero after the call if
enough output space has been provided before the call.) Flushing may
degrade compression for some compression algorithms and so it should be
used only when necessary.
If flush is set to
Z_FULL_FLUSH
, all output is flushed as with
Z_SYNC_FLUSH
, and the compression state is reset
so that decompression can restart from this point if previous compressed
data has been damaged or if random access is desired. Using
Z_FULL_FLUSH
too often can seriously degrade the
compression.
If deflate
() returns with avail_out ==
0, this function must be called again with the same value of the flush
parameter and more output space (updated
avail_out), until the flush is complete
(deflate
() returns with non-zero
avail_out).
If the parameter flush is set to
Z_FINISH
, pending input is processed, pending
output is flushed and deflate
() returns with
Z_STREAM_END
if there was enough output space;
if deflate
() returns with
Z_OK
, this function must be called again with
Z_FINISH
and more output space (updated
avail_out but no more input data, until it returns
with Z_STREAM_END
or an error. After
deflate
() has returned
Z_STREAM_END
, the only possible operations on
the stream are deflateReset
() or
deflateEnd
().
Z_FINISH
can be used immediately after
deflateInit
() if all the compression is to be
done in a single step. In this case, avail_out
must be at least 0.1% larger than avail_in plus 12
bytes. If deflate
() does not return
Z_STREAM_END
, then it must be called again as
described above.
deflate
() sets strm->adler to the
Adler-32 checksum of all input read so far (that is,
total_in bytes).
deflate
() may update
data_type if it can make a good guess about the
input data type (Z_ASCII or Z_BINARY). If in doubt, the data is
considered binary. This field is only for information purposes and does
not affect the compression algorithm in any manner.
deflate
() returns
Z_OK
if some progress has been made (more input
processed or more output produced), Z_STREAM_END
if all input has been consumed and all output has been produced (only
when flush is set to
Z_FINISH
),
Z_STREAM_ERROR
if the stream state was
inconsistent (for example, if next_in or
next_out was NULL
),
Z_BUF_ERROR
if no progress is possible (for
example, avail_in or
avail_out was zero).
deflateEnd
(z_streamp
strm);All dynamically allocated data structures for this stream are freed. This function discards any unprocessed input and does not flush any pending output.
deflateEnd
() returns
Z_OK
if successful,
Z_STREAM_ERROR
if the stream state was
inconsistent, Z_DATA_ERROR
if the stream was
freed prematurely (some input or output was discarded). In the error
case, msg may be set but then points to a static
string (which must not be deallocated).
inflateInit
(z_streamp
strm);inflateInit
() function initializes the
internal stream state for decompression. The fields
next_in, avail_in,
zalloc, zfree, and
opaque must be initialized before by the caller. If
next_in is not Z_NULL
and
avail_in is large enough (the exact value depends on
the compression method), inflateInit
() determines
the compression method from the zlib
header and
allocates all data structures accordingly; otherwise the allocation will
be deferred to the first call to inflate
(). If
zalloc and zfree are set to
Z_NULL
, inflateInit
()
updates them to use default allocation functions.
inflateInit
() returns
Z_OK
if successful,
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. msg is set to null
if there is no error message. inflateInit
() does
not perform any decompression apart from reading the
zlib
header if present: this will be done by
inflate
(). (So next_in and
avail_in may be modified, but
next_out and avail_out are
unchanged.)
inflate
(z_streamp strm,
int flush);inflate
() decompresses as much data as possible,
and stops when the input buffer becomes empty or the output buffer becomes
full. It may introduce some output latency (reading input without
producing any output) except when forced to flush.
The detailed semantics are as follows.
inflate
() performs one or both of the following
actions:
Decompress more input starting at
next_in and update next_in
and avail_in accordingly. If not all input can be
processed (because there is not enough room in the output buffer),
next_in is updated and processing will resume at
this point for the next call to inflate
().
Provide more output starting at next_out
and update next_out and
avail_out accordingly.
inflate
() provides as much output as possible,
until there is no more input data or no more space in the output buffer
(see below about the flush parameter).
Before the call to inflate
(), the
application should ensure that at least one of the actions is possible,
by providing more input and/or consuming more output, and updating the
next_* and avail_* values accordingly. The application can consume the
uncompressed output when it wants, for example when the output buffer is
full (avail_out == 0), or after each call to
inflate
(). If inflate
()
returns Z_OK
and with zero
avail_out, it must be called again after making
room in the output buffer because there might be more output
pending.
If the parameter flush is set to
Z_SYNC_FLUSH
, inflate
()
flushes as much output as possible to the output buffer. The flushing
behavior of inflate
() is not specified for
values of the flush parameter other than
Z_SYNC_FLUSH
and
Z_FINISH
, but the current implementation
actually flushes as much output as possible anyway.
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 to 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 the
uncompressed data. (The size of the uncompressed data may have been
saved by the compressor for this purpose.) The next operation on this
stream must be inflateEnd
() to deallocate the
decompression state. The use of Z_FINISH
is
never required, but can be used to inform
inflate
() that a faster routine may be used for
the single inflate
() call.
If a preset dictionary is needed at this point (see
inflateSetDictionary
() below),
inflate
() sets strm->adler to the Adler-32
checksum of the dictionary chosen by the compressor and returns
Z_NEED_DICT
; otherwise it sets strm->adler to
the Adler-32 checksum of all output produced so far (that is,
total_out bytes) and returns
Z_OK
, Z_STREAM_END
, or
an error code as described below. At the end of the stream,
inflate
() checks that its computed Adler-32
checksum is equal to that saved by the compressor and returns
Z_STREAM_END
only if the checksum is
correct.
inflate
() returns
Z_OK
if some progress has been made (more input
processed or more output produced), Z_STREAM_END
if the end of the compressed data has been reached and all uncompressed
output has been produced, Z_NEED_DICT
if a
preset dictionary is needed at this point,
Z_DATA_ERROR
if the input data was corrupted
(input stream not conforming to the zlib
format
or incorrect Adler-32 checksum), Z_STREAM_ERROR
if the stream structure was inconsistent (for example, if
next_in or next_out was
NULL
), Z_MEM_ERROR
if
there was not enough memory, Z_BUF_ERROR
if no
progress is possible or if there was not enough room in the output
buffer when Z_FINISH
is used. In the
Z_DATA_ERROR
case, the application may then call
inflateSync
() to look for a good compression
block.
inflateEnd
(z_streamp
strm);inflateEnd
() returns
Z_OK
if successful, or
Z_STREAM_ERROR
if the stream state was
inconsistent. In the error case, msg may be set
but then points to a static string (which must not be deallocated).
deflateInit2
(z_streamp strm,
int level, int method,
int windowBits, int memLevel,
int strategy);This is another version of
deflateInit
() with more compression options. The
fields next_in, zalloc,
zfree, and opaque must be
initialized before by the caller.
The method parameter is the compression
method. It must be Z_DEFLATED
in this version of
the library.
The windowBits parameter is the base two
logarithm of the window size (the size of the history buffer). It should
be in the range 8..15 for this version of the library. Larger values of
this parameter result in better compression at the expense of memory
usage. The default value is 15 if deflateInit
()
is used instead.
The memLevel parameter specifies how
much memory should be allocated for the internal compression state.
memLevel=1 uses minimum memory but is slow and reduces compression
ratio; memLevel=9 uses maximum memory for optimal speed. The default
value is 8. See
<zconf.h>
for total
memory usage as a function of windowBits and
memLevel.
The strategy parameter is used to tune
the compression algorithm. Use the value
Z_DEFAULT_STRATEGY
for normal data;
Z_FILTERED
for data produced by a filter (or
predictor); or Z_HUFFMAN_ONLY
to force Huffman
encoding only (no string match). Filtered data consists mostly of small
values with a somewhat random distribution. In this case, the
compression algorithm is tuned to compress them better. The effect of
Z_FILTERED
is to force more Huffman coding and
less string matching; it is somewhat intermediate between
Z_DEFAULT
and
Z_HUFFMAN_ONLY
. The
strategy parameter only affects the compression
ratio but not the correctness of the compressed output, even if it is
not set appropriately.
deflateInit2
() returns
Z_OK
if successful,
Z_MEM_ERROR
if there was not enough memory,
Z_STREAM_ERROR
if a parameter is invalid (such
as an invalid method). msg is set to null if there
is no error message. deflateInit2
() does not
perform any compression: this will be done by
deflate
().
deflateSetDictionary
(z_streamp
strm, const Bytef *dictionary,
uInt dictLength);Initializes the compression dictionary from the given byte
sequence without producing any compressed output. This function must be
called immediately after deflateInit
(),
deflateInit2
(), or
deflateReset
(), before any call to
deflate
(). The compressor and decompressor must
use exactly the same dictionary (see
inflateSetDictionary
()).
The dictionary should consist of strings (byte sequences) that are likely to be encountered later in the data to be compressed, with the most commonly used strings preferably put towards the end of the dictionary. Using a dictionary is most useful when the data to be compressed is short and can be predicted with good accuracy; the data can then be compressed better than with the default empty dictionary.
Depending on the size of the compression data structures
selected by deflateInit
() or
deflateInit2
(), a part of the dictionary may in
effect be discarded, for example if the dictionary is larger than the
window size in deflate
() or
deflate2
(). Thus the strings most likely to be
useful should be put at the end of the dictionary, not at the front.
Upon return of this function, strm->adler is set to the Adler-32 value of the dictionary; the decompressor may later use this value to determine which dictionary has been used by the compressor. (The Adler-32 value applies to the whole dictionary even if only a subset of the dictionary is actually used by the compressor.)
deflateSetDictionary
() returns
Z_OK
if successful, or
Z_STREAM_ERROR
if a parameter is invalid (such
as NULL dictionary) or the stream state is inconsistent (for example if
deflate
() has already been called for this
stream or if the compression method is bsort).
deflateSetDictionary
() does not perform any
compression: this will be done by deflate
().
deflateCopy
(z_streamp dest,
z_streamp source);The deflateCopy
() function sets the
destination stream as a complete copy of the source stream.
This function can be useful when several compression
strategies will be tried, for example when there are several ways of
pre-processing the input data with a filter. The streams that will be
discarded should then be freed by calling
deflateEnd
(). Note that
deflateCopy
() duplicates the internal
compression state which can be quite large, so this strategy is slow and
can consume lots of memory.
deflateCopy
() returns
Z_OK
if successful,
Z_MEM_ERROR
if there was not enough memory,
Z_STREAM_ERROR
if the source stream state was
inconsistent (such as zalloc being NULL).
msg is left unchanged in both source and
destination.
deflateReset
(z_streamp
strm);This function is equivalent to
deflateEnd
() followed by
deflateInit
(), but does not free and reallocate
all the internal compression state. The stream will keep the same
compression level and any other attributes that may have been set by
deflateInit2
().
deflateReset
() returns
Z_OK
if successful, or
Z_STREAM_ERROR
if the source stream state was
inconsistent (such as zalloc or
state being NULL).
deflateParams
(z_streamp strm,
int level, int strategy);The deflateParams
() function
dynamically updates the compression level and compression strategy. The
interpretation of level and strategy is as in
deflateInit2
(). This can be used to switch
between compression and straight copy of the input data, or to switch to
a different kind of input data requiring a different strategy. If the
compression level is changed, the input available so far is compressed
with the old level (and may be flushed); the new level will take effect
only at the next call to deflate
().
Before the call to deflateParams
(),
the stream state must be set as for a call to
deflate
(), since the currently available input
may have to be compressed and flushed. In particular, strm->avail_out
must be non-zero.
deflateParams
() returns
Z_OK
if successful,
Z_STREAM_ERROR
if the source stream state was
inconsistent or if a parameter was invalid, or
Z_BUF_ERROR
if strm->avail_out was zero.
inflateInit2
(z_streamp strm,
int windowBits);This is another version of
inflateInit
() with an extra parameter. The
fields next_in, avail_in,
zalloc, zfree, and
opaque must be initialized before by the
caller.
The windowBits parameter is the base two
logarithm of the maximum window size (the size of the history buffer).
It should be in the range 8..15 for this version of the library. The
default value is 15 if inflateInit
() is used
instead. If a compressed stream with a larger window size is given as
input, inflate
() will return with the error code
Z_DATA_ERROR
instead of trying to allocate a
larger window.
inflateInit2
() returns
Z_OK
if successful,
Z_MEM_ERROR
if there was not enough memory,
Z_STREAM_ERROR
if a parameter is invalid (such
as a negative memLevel). msg
is set to null if there is no error message.
inflateInit2
() does not perform any
decompression apart from reading the zlib
header
if present: this will be done by inflate
(). (So
next_in and avail_in may be
modified, but next_out and
avail_out are unchanged.)
inflateSetDictionary
(z_streamp
strm, const Bytef *dictionary,
uInt dictLength);Initializes the decompression dictionary from the given
uncompressed byte sequence. This function must be called immediately
after a call to inflate
() if this call returned
Z_NEED_DICT
. The dictionary chosen by the
compressor can be determined from the Adler-32 value returned by this
call to inflate
(). The compressor and
decompressor must use exactly the same dictionary (see
deflateSetDictionary
()).
inflateSetDictionary
() returns
Z_OK
if successful,
Z_STREAM_ERROR
if a parameter is invalid (such
as NULL dictionary) or the stream state is inconsistent,
Z_DATA_ERROR
if the given dictionary doesn't
match the expected one (incorrect Adler-32 value).
inflateSetDictionary
() does not perform any
decompression: this will be done by subsequent calls of
inflate
().
inflateSync
(z_streamp
strm);Skips invalid compressed data until a full flush point (see
above the description of deflate
() with
Z_FULL_FLUSH
) can be found, or until all
available input is skipped. No output is provided.
inflateSync
() returns
Z_OK
if a full flush point has been found,
Z_BUF_ERROR
if no more input was provided,
Z_DATA_ERROR
if no flush point has been found,
or Z_STREAM_ERROR
if the stream structure was
inconsistent. In the success case, the application may save the current
value of total_in which indicates where valid
compressed data was found. In the error case, the application may
repeatedly call inflateSync
(), providing more
input each time, until success or end of the input data.
inflateReset
(z_streamp
strm);This function is equivalent to
inflateEnd
() followed by
inflateInit
(), but does not free and reallocate
all the internal decompression state. The stream will keep attributes
that may have been set by inflateInit2
().
inflateReset
() returns
Z_OK
if successful, or
Z_STREAM_ERROR
if the source stream state was
inconsistent (such as zalloc or
state being NULL).
compress
(Bytef *dest,
uLongf *destLen, const Bytef
*source, uLong sourceLen);The compress
() function compresses the
source buffer into the destination buffer.
sourceLen is the byte length of the source buffer.
Upon entry, destLen is the total size of the
destination buffer, which must be at least 0.1% larger than
sourceLen plus 12 bytes. Upon exit,
destLen is the actual size of the compressed
buffer. This function can be used to compress a whole file at once if
the input file is mmap'ed.
compress
() returns
Z_OK
if successful,
Z_MEM_ERROR
if there was not enough memory, or
Z_BUF_ERROR
if there was not enough room in the
output buffer.
compress2
(Bytef *dest,
uLongf *destLen, const Bytef
*source, uLong sourceLen, int
level);The compress2
() function compresses
the source buffer into the destination buffer. The
level parameter has the same meaning as in
deflateInit
(). sourceLen
is the byte length of the source buffer. Upon entry,
destLen is the total size of the destination
buffer, which must be at least 0.1% larger than
sourceLen plus 12 bytes. Upon exit,
destLen is the actual size of the compressed
buffer.
compress2
() returns
Z_OK
if successful,
Z_MEM_ERROR
if there was not enough memory,
Z_BUF_ERROR
if there was not enough room in the
output buffer, or Z_STREAM_ERROR
if the level
parameter is invalid.
uncompress
(Bytef *dest,
uLongf *destLen, const Bytef
*source, uLong sourceLen);The uncompress
() function decompresses
the source buffer into the destination buffer.
sourceLen is the byte length of the source buffer.
Upon entry, destLen is the total size of the
destination buffer, which must be large enough to hold the entire
uncompressed data. (The size of the uncompressed data must have been
saved previously by the compressor and transmitted to the decompressor
by some mechanism outside the scope of this compression library.) Upon
exit, destLen is the actual size of the compressed
buffer. This function can be used to decompress a whole file at once if
the input file is mmap'ed.
uncompress
() returns
Z_OK
if successful,
Z_MEM_ERROR
if there was not enough memory,
Z_BUF_ERROR
if there was not enough room in the
output buffer, or Z_DATA_ERROR
if the input data
was corrupted.
gzopen
(const char *path,
const char *mode);The gzopen
() function opens a gzip
(.gz) file for reading or writing. The mode parameter is as in
fopen(3)
(“rb” or “wb”) but can also include a
compression level (“wb9”) or a strategy: ‘f’
for filtered data, as in “wb6f”; ‘h’ for
Huffman only compression, as in “wb1h”. (See the
description of deflateInit2
() for more
information about the strategy parameter.)
gzopen
() can be used to read a file
which is not in gzip format; in this case
gzread
() will directly read from the file
without decompression.
gzopen
() returns
NULL
if the file could not be opened or if there
was insufficient memory to allocate the (de)compression state; errno can
be checked to distinguish the two cases (if errno is zero, the
zlib
error is
Z_MEM_ERROR
).
gzdopen
(int fd,
const char *mode);The gzdopen
() function associates a
gzFile with the file descriptor fd. File
descriptors are obtained from calls like
open(2),
dup(2),
creat(3),
pipe(2), or
fileno(3) (if the file has
been previously opened with
fopen(3)). The
mode parameter is as in
gzopen
().
The next call to gzclose
() on the
returned gzFile will also close the file descriptor fd, just like
fclose(fdopen(fd), mode) closes the file descriptor fd. If you want to
keep fd open, use gzdopen(dup(fd), mode).
gzdopen
() returns
NULL
if there was insufficient memory to
allocate the (de)compression state.
gzsetparams
(gzFile file,
int level, int strategy);The gzsetparams
() function dynamically
updates the compression level or strategy. See the description of
deflateInit2
() for the meaning of these
parameters.
gzsetparams
() returns
Z_OK
if successful, or
Z_STREAM_ERROR
if the file was not opened for
writing.
gzread
(gzFile file,
voidp buf, unsigned len);The gzread
() function reads the given
number of uncompressed bytes from the compressed file. If the input file
was not in gzip format, gzread
() copies the
given number of bytes into the buffer.
gzread
() returns the number of
uncompressed bytes actually read (0 for end of file, -1 for error).
gzwrite
(gzFile file,
const voidp buf, unsigned
len);The gzwrite
() function writes the
given number of uncompressed bytes into the compressed file.
gzwrite
() returns the number of uncompressed
bytes actually written (0 in case of error).
gzprintf
(gzFile file,
const char *format, ...);The gzprintf
() function converts,
formats, and writes the args to the compressed file under control of the
format string, as in
fprintf(3).
gzprintf
() returns the number of uncompressed
bytes actually written (0 in case of error).
gzputs
(gzFile file,
const char *s);The gzputs
() function writes the given
null-terminated string to the compressed file, excluding the terminating
null character.
gzputs
() returns the number of
characters written, or -1 in case of error.
gzgets
(gzFile file,
char *buf, int len);The gzgets
() function reads bytes from
the compressed file until len-1 characters are read, or a newline
character is read and transferred to buf, or an
end-of-file condition is encountered. The string is then terminated with
a null character.
gzgets
() returns
buf, or Z_NULL
in case of
error.
gzputc
(gzFile file,
int c);The gzputc
() function writes
c, converted to an unsigned char, into the
compressed file. gzputc
() returns the value that
was written, or -1 in case of error.
gzgetc
(gzFile file);The gzgetc
() function reads one byte
from the compressed file. gzgetc
() returns this
byte or -1 in case of end of file or error.
gzflush
(gzFile file,
int flush);The gzflush
() function flushes all
pending output into the compressed file. The parameter
flush is as in the
deflate
() function. The return value is the
zlib
error number (see function
gzerror
() below).
gzflush
() returns Z_OK
if the flush parameter is Z_FINISH
and all
output could be flushed.
gzflush
() should be called only when
strictly necessary because it can degrade compression.
gzseek
(gzFile file,
z_off_t offset, int
whence);Sets the starting position for the next
gzread
() or gzwrite
() on
the given compressed file. The offset represents a number of bytes in
the uncompressed data stream. The whence parameter is defined as in
lseek(2); the value
SEEK_END
is not supported.
If the file is opened for reading, this function is emulated
but can be extremely slow. If the file is opened for writing, only
forward seeks are supported; gzseek
() then
compresses a sequence of zeroes up to the new starting position.
gzseek
() returns the resulting offset
location as measured in bytes from the beginning of the uncompressed
stream, or -1 in case of error, in particular if the file is opened for
writing and the new starting position would be before the current
position.
gzrewind
(gzFile file);The gzrewind
() function rewinds the
given file. This function is supported only for
reading.
gzrewind(file) is equivalent to (int)gzseek(file, 0L, SEEK_SET).
gztell
(gzFile file);The gztell
() function returns the
starting position for the next gzread
() or
gzwrite
() on the given compressed file. This
position represents a number of bytes in the uncompressed data
stream.
gztell(file) is equivalent to gzseek(file, 0L, SEEK_CUR).
gzeof
(gzFile file);The gzeof
() function returns 1 when
EOF
has previously been detected reading the
given input stream, otherwise zero.
gzclose
(gzFile file);The gzclose
() function flushes all
pending output if necessary, closes the compressed file and deallocates
all the (de)compression state. The return value is the
zlib
error number (see function
gzerror
() below).
gzerror
(gzFile file,
int *errnum);The gzerror
() function returns the
error message for the last error which occurred on the given compressed
file. errnum is set to the
zlib
error number. If an error occurred in the
file system and not in the compression library,
errnum is set to Z_ERRNO
and the application may consult errno to get the exact error code.
adler32
(uLong adler,
const Bytef *buf, uInt
len);adler32
() function updates a running Adler-32
checksum with the bytes buf[0..len-1] and returns the updated checksum. If
buf is NULL
, this function
returns the required initial value for the checksum.
An Adler-32 checksum is almost as reliable as a CRC32 but can be computed much faster. Usage example:
uLong adler = adler32(0L, Z_NULL, 0); while (read_buffer(buffer, length) != EOF) { adler = adler32(adler, buffer, length); } if (adler != original_adler) error();
crc32
(uLong crc,
const Bytef *buf, uInt
len);crc32
() function updates a running CRC with
the bytes buf[0..len-1] and returns the updated CRC. If
buf is NULL
, this function
returns the required initial value for the CRC. Pre- and post-conditioning
(one's complement) is performed within this function so it shouldn't be
done by the application. Usage example:
uLong crc = crc32(0L, Z_NULL, 0); while (read_buffer(buffer, length) != EOF) { crc = crc32(crc, buffer, length); } if (crc != original_crc) error();
struct internal_state; typedef struct z_stream_s { Bytef *next_in; /* next input byte */ uInt avail_in; /* number of bytes available at next_in */ uLong total_in; /* total nb of input bytes read so far */ Bytef *next_out; /* next output byte should be put there */ uInt avail_out; /* remaining free space at next_out */ uLong total_out; /* total nb of bytes output so far */ char *msg; /* last error message, NULL if no error */ struct internal_state FAR *state; /* not visible by applications */ alloc_func zalloc; /* used to allocate the internal state */ free_func zfree; /* used to free the internal state */ voidpf opaque; /* private data object passed to zalloc and zfree*/ int data_type; /*best guess about the data type: ascii or binary*/ uLong adler; /* Adler-32 value of the uncompressed data */ uLong reserved; /* reserved for future use */ } z_stream; typedef z_stream FAR * z_streamp;
The application must update next_in and avail_in when avail_in has dropped to zero. It must update next_out and avail_out when avail_out has dropped to zero. The application must initialize zalloc, zfree, and opaque before calling the init function. All other fields are set by the compression library and must not be updated by the application.
The opaque value provided by the application
will be passed as the first parameter for calls to
zalloc
() and zfree
(). This
can be useful for custom memory management. The compression library attaches
no meaning to the opaque value.
zalloc must return
Z_NULL
if there is not enough memory for the object.
If zlib
is used in a multi-threaded application,
zalloc and zfree must be thread
safe.
On 16-bit systems, the functions zalloc and
zfree must be able to allocate exactly 65536 bytes,
but will not be required to allocate more than this if the symbol MAXSEG_64K
is defined (see
<zconf.h>
).
WARNING: On MSDOS, pointers returned by
zalloc for objects of exactly 65536 bytes *must* have
their offset normalized to zero. The default allocation function provided by
this library ensures this (see zutil.c). To reduce
memory requirements and avoid any allocation of 64K objects, at the expense
of compression ratio, compile the library with -DMAX_WBITS=14 (see
<zconf.h>
).
The fields total_in and total_out can be used for statistics or progress reports. After compression, total_in holds the total size of the uncompressed data and may be saved for use in the decompressor (particularly if the decompressor wants to decompress everything in a single step).
#define Z_NO_FLUSH 0 #define Z_PARTIAL_FLUSH 1 /* will be removed, use Z_SYNC_FLUSH instead */ #define Z_SYNC_FLUSH 2 #define Z_FULL_FLUSH 3 #define Z_FINISH 4 /* Allowed flush values; see deflate() below for details */ #define Z_OK 0 #define Z_STREAM_END 1 #define Z_NEED_DICT 2 #define Z_ERRNO (-1) #define Z_STREAM_ERROR (-2) #define Z_DATA_ERROR (-3) #define Z_MEM_ERROR (-4) #define Z_BUF_ERROR (-5) #define Z_VERSION_ERROR (-6) /* Return codes for the compression/decompression functions. * Negative values are errors, * positive values are used for special but normal events. */ #define Z_NO_COMPRESSION 0 #define Z_BEST_SPEED 1 #define Z_BEST_COMPRESSION 9 #define Z_DEFAULT_COMPRESSION (-1) /* compression levels */ #define Z_FILTERED 1 #define Z_HUFFMAN_ONLY 2 #define Z_DEFAULT_STRATEGY 0 /* compression strategy; see deflateInit2() below for details */ #define Z_BINARY 0 #define Z_ASCII 1 #define Z_UNKNOWN 2 /* Possible values of the data_type field */ #define Z_DEFLATED 8 /* The deflate compression method * (the only one supported in this version) */ #define Z_NULL 0 /* for initializing zalloc, zfree, opaque */ #define zlib_version zlibVersion() /* for compatibility with versions < 1.0.2 */
zlib
version and the compiler's view of
z_stream.
deflateInit_
(z_stream strm,
int level, const char *version,
int stream_size);inflateInit_
(z_stream strm,
const char *version, int
stream_size);deflateInit2_
(z_stream strm,
int level, int method,
int windowBits, int memLevel,
int strategy, const char
*version, int stream_size);inflateInit2_
(z_stream strm,
int windowBits, const char
*version, int stream_size);zError
(int err);inflateSyncPoint
(z_streamp
z);get_crc_table
(void);<zlib.h>
converted by
piaip
<piaip@csie.ntu.edu.tw>
and was converted to mdoc format by the OpenBSD
project.
May 1, 2004 | NetBSD 9.0 |