mirror of https://github.com/madler/zlib.git
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
656 lines
29 KiB
656 lines
29 KiB
/* zlib.h -- interface of the 'zlib' general purpose compression library |
|
version 1.0, Jan 14th, 1996. |
|
|
|
Copyright (C) 1995-1996 Jean-loup Gailly and Mark Adler |
|
|
|
This software is provided 'as-is', without any express or implied |
|
warranty. In no event will the authors be held liable for any damages |
|
arising from the use of this software. |
|
|
|
Permission is granted to anyone to use this software for any purpose, |
|
including commercial applications, and to alter it and redistribute it |
|
freely, subject to the following restrictions: |
|
|
|
1. The origin of this software must not be misrepresented; you must not |
|
claim that you wrote the original software. If you use this software |
|
in a product, an acknowledgment in the product documentation would be |
|
appreciated but is not required. |
|
2. Altered source versions must be plainly marked as such, and must not be |
|
misrepresented as being the original software. |
|
3. This notice may not be removed or altered from any source distribution. |
|
|
|
Jean-loup Gailly Mark Adler |
|
gzip@prep.ai.mit.edu madler@alumni.caltech.edu |
|
*/ |
|
|
|
#ifndef _ZLIB_H |
|
#define _ZLIB_H |
|
|
|
#ifdef __cplusplus |
|
extern "C" { |
|
#endif |
|
|
|
#include "zconf.h" |
|
|
|
#define ZLIB_VERSION "1.0" |
|
|
|
/* |
|
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 may be added later and will have the same |
|
stream interface. |
|
|
|
For compression the application must provide the output buffer and |
|
may optionally provide the input buffer for optimization. For decompression, |
|
the application must provide the input buffer and may optionally provide |
|
the output buffer for optimization. |
|
|
|
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. |
|
*/ |
|
|
|
typedef voidpf (*alloc_func) OF((voidpf opaque, uInt items, uInt size)); |
|
typedef void (*free_func) OF((voidpf opaque, voidpf address)); |
|
|
|
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 */ |
|
|
|
Byte data_type; /* best guess about the data type: ascii or binary */ |
|
|
|
} z_stream; |
|
|
|
/* |
|
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 of 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. |
|
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). |
|
*/ |
|
|
|
/* constants */ |
|
|
|
#define Z_NO_FLUSH 0 |
|
#define Z_PARTIAL_FLUSH 1 |
|
#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_ERRNO (-1) |
|
#define Z_STREAM_ERROR (-2) |
|
#define Z_DATA_ERROR (-3) |
|
#define Z_MEM_ERROR (-4) |
|
#define Z_BUF_ERROR (-5) |
|
/* error codes for the compression/decompression functions */ |
|
|
|
#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 |
|
|
|
#define Z_BINARY 0 |
|
#define Z_ASCII 1 |
|
#define Z_UNKNOWN 2 |
|
/* Used to set 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 */ |
|
|
|
extern char *zlib_version; |
|
/* The application can compare zlib_version 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. |
|
*/ |
|
|
|
/* basic functions */ |
|
|
|
extern int deflateInit OF((z_stream *strm, int level)); |
|
/* |
|
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 success, Z_MEM_ERROR if there was not |
|
enough memory, Z_STREAM_ERROR if level is not a valid compression level. |
|
msg is set to null if there is no error message. deflateInit does not |
|
perform any compression: this will be done by deflate(). |
|
*/ |
|
|
|
|
|
extern int deflate OF((z_stream *strm, int flush)); |
|
/* |
|
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 of 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 of 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 of deflate(). |
|
|
|
If the parameter flush is set to Z_PARTIAL_FLUSH, the current compression |
|
block is terminated and flushed to the output buffer so that the |
|
decompressor can get all input data available so far. For method 9, a future |
|
variant on method 8, the current block will be flushed but not terminated. |
|
Z_SYNC_FLUSH has the same effect as partial flush except that the compressed |
|
output is byte aligned (the compressor can clear its internal bit buffer) |
|
and the current block is always terminated; this can be useful if the |
|
compressor has to be restarted from scratch after an interruption (in which |
|
case the internal state of the compressor may be lost). |
|
If flush is set to Z_FULL_FLUSH, the compression block is terminated, a |
|
special marker is output and the compression dictionary is discarded; this |
|
is useful to allow the decompressor to synchronize if one compressed block |
|
has been damaged (see inflateSync below). Flushing degrades compression and |
|
so should be used only when necessary. 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, all pending input is processed, |
|
all 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() may update data_type if it can make a good guess about |
|
the input data type (Z_ASCII or Z_BINARY). 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. |
|
*/ |
|
|
|
|
|
extern int deflateEnd OF((z_stream *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 success, 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). |
|
*/ |
|
|
|
|
|
extern int inflateInit OF((z_stream *strm)); |
|
/* |
|
Initializes the internal stream state for decompression. The fields |
|
zalloc, zfree and opaque must be initialized before by the caller. If |
|
zalloc and zfree are set to Z_NULL, inflateInit updates them to use default |
|
allocation functions. |
|
|
|
inflateInit returns Z_OK if success, Z_MEM_ERROR if there was not |
|
enough memory. msg is set to null if there is no error message. |
|
inflateInit does not perform any decompression: this will be done by |
|
inflate(). |
|
*/ |
|
|
|
|
|
extern int inflate OF((z_stream *strm, int flush)); |
|
/* |
|
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 of inflate(). |
|
|
|
- Provide more output starting at next_out and update next_out and avail_out |
|
accordingly. inflate() always provides as much output as possible |
|
(until there is no more input data or no more space in the output buffer). |
|
|
|
Before the call of 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 of inflate(). |
|
|
|
If the parameter flush is set to Z_PARTIAL_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_PARTIAL_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 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 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. |
|
|
|
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_DATA_ERROR if the input data was corrupted, 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. |
|
*/ |
|
|
|
|
|
extern int inflateEnd OF((z_stream *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 success, 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). |
|
*/ |
|
|
|
/* advanced functions */ |
|
|
|
/* |
|
The following functions are needed only in some special applications. |
|
*/ |
|
|
|
extern int deflateInit2 OF((z_stream *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. (Method 9 will allow a 64K history buffer and |
|
partial block flushes.) |
|
|
|
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 (the value 16 will be allowed for method 9). 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 strategy |
|
parameter only affects the compression ratio but not the correctness of |
|
the compressed output even if it is not set appropriately. |
|
|
|
If next_in is not null, the library will use this buffer to hold also |
|
some history information; the buffer must either hold the entire input |
|
data, or have at least 1<<(windowBits+1) bytes and be writable. If next_in |
|
is null, the library will allocate its own history buffer (and leave next_in |
|
null). next_out need not be provided here but must be provided by the |
|
application for the next call of deflate(). |
|
|
|
If the history buffer is provided by the application, next_in must |
|
must never be changed by the application since the compressor maintains |
|
information inside this buffer from call to call; the application |
|
must provide more input only by increasing avail_in. next_in is always |
|
reset by the library in this case. |
|
|
|
deflateInit2 returns Z_OK if success, 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(). |
|
*/ |
|
|
|
extern int deflateCopy OF((z_stream *dest, |
|
z_stream *source)); |
|
/* |
|
Sets the destination stream as a complete copy of the source stream. If |
|
the source stream is using an application-supplied history buffer, a new |
|
buffer is allocated for the destination stream. The compressed output |
|
buffer is always application-supplied. It's the responsibility of the |
|
application to provide the correct values of next_out and avail_out for the |
|
next call of deflate. |
|
|
|
This function is 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 success, 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. |
|
*/ |
|
|
|
extern int deflateReset OF((z_stream *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 success, or Z_STREAM_ERROR if the source |
|
stream state was inconsistent (such as zalloc or state being NULL). |
|
*/ |
|
|
|
extern int deflateParams OF((z_stream *strm, int level, int strategy)); |
|
/* |
|
Dynamically update the compression level and compression strategy. |
|
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 of deflate(). |
|
|
|
deflateParams returns Z_OK if success, Z_STREAM_ERROR if the source |
|
stream state was inconsistent or if a parameter was invalid. |
|
*/ |
|
|
|
extern int inflateInit2 OF((z_stream *strm, |
|
int windowBits)); |
|
/* |
|
This is another version of inflateInit with more compression options. The |
|
fields next_out, 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 value 16 will be allowed soon). 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. |
|
|
|
If next_out is not null, the library will use this buffer for the history |
|
buffer; the buffer must either be large enough to hold the entire output |
|
data, or have at least 1<<windowBits bytes. If next_out is null, the |
|
library will allocate its own buffer (and leave next_out null). next_in |
|
need not be provided here but must be provided by the application for the |
|
next call of inflate(). |
|
|
|
If the history buffer is provided by the application, next_out must |
|
never be changed by the application since the decompressor maintains |
|
history information inside this buffer from call to call; the application |
|
can only reset next_out to the beginning of the history buffer when |
|
avail_out is zero and all output has been consumed. |
|
|
|
inflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was |
|
not enough memory, Z_STREAM_ERROR if a parameter is invalid (such as |
|
windowBits < 8). msg is set to null if there is no error message. |
|
inflateInit2 does not perform any decompression: this will be done by |
|
inflate(). |
|
*/ |
|
|
|
extern int inflateSync OF((z_stream *strm)); |
|
/* |
|
Skips invalid compressed data until the special marker (see deflate() |
|
above) can be found, or until all available input is skipped. No output |
|
is provided. |
|
|
|
inflateSync returns Z_OK if the special marker has been found, Z_BUF_ERROR |
|
if no more input was provided, Z_DATA_ERROR if no marker has been found, |
|
or Z_STREAM_ERROR if the stream structure was inconsistent. In the success |
|
case, the application may save the current 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. |
|
*/ |
|
|
|
extern int inflateReset OF((z_stream *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 success, or Z_STREAM_ERROR if the source |
|
stream state was inconsistent (such as zalloc or state being NULL). |
|
*/ |
|
|
|
|
|
/* utility functions */ |
|
|
|
/* |
|
The following utility functions are implemented on top of the |
|
basic stream-oriented functions. To simplify the interface, some |
|
default options are assumed (compression level, window size, |
|
standard memory allocation functions). The source code of these |
|
utility functions can easily be modified if you need special options. |
|
*/ |
|
|
|
extern int compress OF((Bytef *dest, uLongf *destLen, |
|
Bytef *source, uLong sourceLen)); |
|
/* |
|
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 success, Z_MEM_ERROR if there was not |
|
enough memory, Z_BUF_ERROR if there was not enough room in the output |
|
buffer. |
|
*/ |
|
|
|
extern int uncompress OF((Bytef *dest, uLongf *destLen, |
|
Bytef *source, uLong sourceLen)); |
|
/* |
|
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 success, 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. |
|
*/ |
|
|
|
|
|
typedef voidp gzFile; |
|
|
|
extern gzFile gzopen OF((char *path, char *mode)); |
|
/* |
|
Opens a gzip (.gz) file for reading or writing. The mode parameter |
|
is as in fopen ("rb" or "wb") but can also include a compression level |
|
("wb9"). 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). |
|
*/ |
|
|
|
extern gzFile gzdopen OF((int fd, char *mode)); |
|
/* |
|
gzdopen() associates a gzFile with the file descriptor fd. File |
|
descriptors are obtained from calls like open, dup, creat, pipe or |
|
fileno (in the file has been previously opened with fopen). |
|
The mode parameter is as in fopen ("rb" or "wb"). |
|
gzdopen returns NULL if there was insufficient memory to allocate |
|
the (de)compression state. |
|
*/ |
|
|
|
extern int gzread OF((gzFile file, voidp buf, unsigned len)); |
|
/* |
|
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). */ |
|
|
|
extern int gzwrite OF((gzFile file, voidp buf, unsigned len)); |
|
/* |
|
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). |
|
*/ |
|
|
|
extern int gzflush OF((gzFile file, int flush)); |
|
/* |
|
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. |
|
*/ |
|
|
|
extern int gzclose OF((gzFile file)); |
|
/* |
|
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). |
|
*/ |
|
|
|
extern char* gzerror OF((gzFile file, int *errnum)); |
|
/* |
|
Returns the error message for the last error which occurred on the |
|
given compressed file. errnum is set to 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. |
|
*/ |
|
|
|
/* checksum functions */ |
|
|
|
/* |
|
These functions are not related to compression but are exported |
|
anyway because they might be useful in applications using the |
|
compression library. |
|
*/ |
|
|
|
extern uLong adler32 OF((uLong adler, Bytef *buf, uInt len)); |
|
|
|
/* |
|
Update a running Adler-32 checksum with the bytes buf[0..len-1] and |
|
return 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(); |
|
*/ |
|
|
|
extern uLong crc32 OF((uLong crc, Bytef *buf, uInt len)); |
|
/* |
|
Update a running crc with the bytes buf[0..len-1] and return 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(); |
|
*/ |
|
|
|
#ifndef _Z_UTIL_H |
|
struct internal_state {int dummy;}; /* hack for buggy compilers */ |
|
#endif |
|
|
|
#ifdef __cplusplus |
|
} |
|
#endif |
|
|
|
#endif /* _ZLIB_H */
|
|
|