const
char
*
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
)
int
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
)
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
)
uLong
adler32(
uLong adler
, const Bytef *buf
, uInt len
)
uLong
crc32(
uLong crc
, const Bytef *buf
, uInt len
)
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:
const
char
*
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(
).
int
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(
).
int
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).
int
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).
int
inflateInit(
z_streamp strm
);
The
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.)
int
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.
int
inflateEnd(
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.
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).
int
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(
).
int
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(
).
int
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.
int
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).
int
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.
int
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.)
int
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(
).
int
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.
int
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).
int
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.
int
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.
int
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.
gzFile
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
).
gzFile
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.
int
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.
int
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).
int
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).
int
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).
int
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.
char
*
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.
int
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.
int
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.
int
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.
z_off_t
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.
int
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).
z_off_t
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).
int
gzeof(
gzFile file
);
The
gzeof()
function returns 1 when
EOF
has previously been detected reading the given input stream, otherwise zero.
int
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).
const
char
*
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.
uLong
adler32(
uLong adler
, const Bytef *buf
, uInt len
);
The
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();
uLong
crc32(
uLong crc
, const Bytef *buf
, uInt len
);
The
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 */
z_stream
.
int
deflateInit_(
z_stream strm
, int level
, const char *version
, int stream_size
);
int
inflateInit_(
z_stream strm
, const char *version
, int stream_size
);
int
deflateInit2_(
z_stream strm
int level
int method
int windowBits
int memLevel
int strategy
const char *version
int stream_size
)
int
inflateInit2_(
z_stream strm
, int windowBits
, const char *version
, int stream_size
);
const
char
*
zError(
int err
);
int
inflateSyncPoint(
z_streamp z
);
const
uLongf
*
get_crc_table(
void
);
http://www.gzip.org/zlib/
zlib.h
>
converted by
piaip <piaip@csie.ntu.edu.tw>