Minor edits to the documentation in source file contents.
diff --git a/zconf.h b/zconf.h
index 0a4828e..d09f186 100644
--- a/zconf.h
+++ b/zconf.h
@@ -251,7 +251,7 @@
Of course this will generally degrade compression (there's no free lunch).
The memory requirements for inflate are (in bytes) 1 << windowBits
- that is, 32K for windowBits=15 (default value) plus a few kilobytes
+ that is, 32K for windowBits=15 (default value) plus about 7 kilobytes
for small objects.
*/
diff --git a/zconf.h.cmakein b/zconf.h.cmakein
index 752eb88..70942e4 100644
--- a/zconf.h.cmakein
+++ b/zconf.h.cmakein
@@ -253,7 +253,7 @@
Of course this will generally degrade compression (there's no free lunch).
The memory requirements for inflate are (in bytes) 1 << windowBits
- that is, 32K for windowBits=15 (default value) plus a few kilobytes
+ that is, 32K for windowBits=15 (default value) plus about 7 kilobytes
for small objects.
*/
diff --git a/zconf.h.in b/zconf.h.in
index 0a4828e..d09f186 100644
--- a/zconf.h.in
+++ b/zconf.h.in
@@ -251,7 +251,7 @@
Of course this will generally degrade compression (there's no free lunch).
The memory requirements for inflate are (in bytes) 1 << windowBits
- that is, 32K for windowBits=15 (default value) plus a few kilobytes
+ that is, 32K for windowBits=15 (default value) plus about 7 kilobytes
for small objects.
*/
diff --git a/zlib.h b/zlib.h
index fc969af..5c99039 100644
--- a/zlib.h
+++ b/zlib.h
@@ -65,7 +65,8 @@
with "gz". The gzip format is different from the zlib format. gzip is a
gzip wrapper, documented in RFC 1952, wrapped around a deflate stream.
- This library can optionally read and write gzip streams in memory as well.
+ This library can optionally read and write gzip and raw deflate streams in
+ memory as well.
The zlib format was designed to be compact and fast for use in memory
and on communications channels. The gzip format was designed for single-
@@ -74,7 +75,7 @@
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.
+ even in the case of corrupted input.
*/
typedef voidpf (*alloc_func) OF((voidpf opaque, uInt items, uInt size));
@@ -87,7 +88,7 @@
uInt avail_in; /* number of bytes available at next_in */
uLong total_in; /* total number of input bytes read so far */
- Bytef *next_out; /* next output byte should be put there */
+ Bytef *next_out; /* next output byte will go here */
uInt avail_out; /* remaining free space at next_out */
uLong total_out; /* total number of bytes output so far */
@@ -98,8 +99,9 @@
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: binary or text */
- uLong adler; /* adler32 value of the uncompressed data */
+ int data_type; /* best guess about the data type: binary or text
+ for deflate, or the decoding state for inflate */
+ uLong adler; /* Adler-32 or CRC-32 value of the uncompressed data */
uLong reserved; /* reserved for future use */
} z_stream;
@@ -142,7 +144,9 @@
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.
+ thread safe. In that case, zlib is thread-safe. When zalloc and zfree are
+ Z_NULL on entry to the initialization function, they are set to internal
+ routines that use the standard library functions malloc() and free().
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
@@ -155,7 +159,7 @@
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
+ uncompressed data and may be saved for use by the decompressor (particularly
if the decompressor wants to decompress everything in a single step).
*/
@@ -200,7 +204,7 @@
#define Z_TEXT 1
#define Z_ASCII Z_TEXT /* for compatibility with 1.2.2 and earlier */
#define Z_UNKNOWN 2
-/* Possible values of the data_type field (though see inflate()) */
+/* Possible values of the data_type field for deflate() */
#define Z_DEFLATED 8
/* The deflate compression method (the only one supported in this version) */
@@ -258,11 +262,11 @@
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
+ - Generate 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.
+ should be set only when necessary. Some output may be provided even if
+ flush is zero.
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
@@ -271,7 +275,9 @@
output when it wants, for example when the output buffer is full (avail_out
== 0), or after each call of 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.
+ buffer because there might be more output pending. See deflatePending(),
+ which can be used if desired to determine whether or not there is more ouput
+ in that case.
Normally the parameter flush is set to Z_NO_FLUSH, which allows deflate to
decide how much data to accumulate before producing output, in order to
@@ -292,8 +298,8 @@
input data so far will be available to the decompressor, as for Z_SYNC_FLUSH.
This completes the current deflate block and follows it with an empty fixed
codes block that is 10 bits long. This assures that enough bytes are output
- in order for the decompressor to finish the block before the empty fixed code
- block.
+ in order for the decompressor to finish the block before the empty fixed
+ codes block.
If flush is set to Z_BLOCK, a deflate block is completed and emitted, as
for Z_SYNC_FLUSH, but the output is not aligned on a byte boundary, and up to
@@ -319,34 +325,38 @@
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.
+ enough output space. If deflate returns with Z_OK or Z_BUF_ERROR, 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 the
- value returned by deflateBound (see below). Then deflate is guaranteed to
- return Z_STREAM_END. If not enough output space is provided, deflate will
- not return Z_STREAM_END, and it must be called again as described above.
+ Z_FINISH can be used in the first deflate call after deflateInit if all the
+ compression is to be done in a single step. In order to complete in one
+ call, avail_out must be at least the value returned by deflateBound (see
+ below). Then deflate is guaranteed to return Z_STREAM_END. If not enough
+ output space is provided, deflate will not return Z_STREAM_END, and it must
+ be called again as described above.
- deflate() sets strm->adler to the adler32 checksum of all input read
- so far (that is, total_in bytes).
+ deflate() sets strm->adler to the Adler-32 checksum of all input read
+ so far (that is, total_in bytes). If a gzip stream is being generated, then
+ strm->adler will be the CRC-32 checksum of the input read so far. (See
+ deflateInit2 below.)
deflate() may update strm->data_type if it can make a good guess about
- the input data type (Z_BINARY or Z_TEXT). In doubt, the data is considered
- binary. This field is only for information purposes and does not affect the
- compression algorithm in any manner.
+ the input data type (Z_BINARY or Z_TEXT). 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 Z_NULL), Z_BUF_ERROR if no progress is possible
- (for example avail_in or avail_out was zero). Note that Z_BUF_ERROR is not
- fatal, and deflate() can be called again with more input and more output
- space to continue compressing.
+ if next_in or next_out was Z_NULL or the state was inadvertently written over
+ by the application), or Z_BUF_ERROR if no progress is possible (for example
+ avail_in or avail_out was zero). Note that Z_BUF_ERROR is not fatal, and
+ deflate() can be called again with more input and more output space to
+ continue compressing.
*/
@@ -369,23 +379,20 @@
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 of
- inflate. If zalloc and zfree are set to Z_NULL, inflateInit updates them to
- use default allocation functions.
+ the caller. In the current version of inflate, the provide input is not
+ read or consumed. Any memory allocation will be deferred to the first call
+ of inflate. 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, Z_VERSION_ERROR if the zlib library version is incompatible with the
version assumed by the caller, or Z_STREAM_ERROR if the parameters are
invalid, such as a null pointer to the structure. msg is set to null if
- there is no error message. inflateInit does not perform any decompression
- apart from possibly reading the zlib header if present: actual decompression
- will be done by inflate(). (So next_in and avail_in may be modified, but
- next_out and avail_out are unused and unchanged.) The current implementation
- of inflateInit() does not process any header information -- that is deferred
- until inflate() is called.
+ there is no error message. inflateInit does not perform any decompression.
+ Actual decompression will be done by inflate(). So next_in, and avail_in,
+ next_out, and avail_out are unused and unchanged. The current
+ implementation of inflateInit() does not process any header information --
+ that is deferred until inflate() is called.
*/
@@ -401,17 +408,20 @@
- 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().
+ enough room in the output buffer), then next_in and avail_on are updated
+ accordingly, 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
+ - Generate 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 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
+ output, and updating the next_* and avail_* values accordingly. If the
+ caller of inflate() does not provide both available input and available
+ output space, it is possible that there will be no progress made. 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 inflate returns Z_OK and with zero avail_out, it must be
@@ -428,7 +438,7 @@
gets to the end of that block, or when it runs out of data.
The Z_BLOCK option assists in appending to or combining deflate streams.
- Also to assist in this, on return inflate() will set strm->data_type to the
+ To assist in this, on return inflate() always sets strm->data_type to the
number of unused bits in the last byte taken from strm->next_in, plus 64 if
inflate() is currently decoding the last block in the deflate stream, plus
128 if inflate() returned immediately after decoding an end-of-block code or
@@ -454,7 +464,7 @@
this case all pending input is processed and all pending output is flushed;
avail_out must be large enough to hold all of the uncompressed data for the
operation to complete. (The size of the uncompressed data may have been
- saved by the compressor for this purpose.) The use of Z_FINISH is not
+ saved by the compressor for this purpose.) The use of Z_FINISH is not
required to perform an inflation in one step. However it may be used to
inform inflate that a faster approach can be used for the single inflate()
call. Z_FINISH also informs inflate to not maintain a sliding window if the
@@ -476,32 +486,33 @@
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 adler32
+ 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() can decompress and check either zlib-wrapped or gzip-wrapped
deflate data. The header type is detected automatically, if requested when
initializing with inflateInit2(). Any information contained in the gzip
- header is not retained, so applications that need that information should
- instead use raw inflate, see inflateInit2() below, or inflateBack() and
- perform their own processing of the gzip header and trailer. When processing
+ header is not retained unless inflateGetHeader() is used. When processing
gzip-wrapped deflate data, strm->adler32 is set to the CRC-32 of the output
- produced so far. The CRC-32 is checked against the gzip trailer.
+ produced so far. The CRC-32 is checked against the gzip trailer, as is the
+ uncompressed length, modulo 2^32.
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 check
- value), Z_STREAM_ERROR if the stream structure was inconsistent (for example
- next_in or next_out was Z_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. Note that Z_BUF_ERROR is not fatal, and
+ value, in which case strm->msg points to a string with a more specific
+ error), Z_STREAM_ERROR if the stream structure was inconsistent (for example
+ next_in or next_out was Z_NULL, or the state was inadvertently written over
+ by the application), Z_MEM_ERROR if there was not enough memory, Z_BUF_ERROR
+ if no progress was possible or if there was not enough room in the output
+ buffer when Z_FINISH is used. Note that Z_BUF_ERROR is not fatal, and
inflate() can be called again with more input and more output space to
continue decompressing. If Z_DATA_ERROR is returned, the application may
then call inflateSync() to look for a good compression block if a partial
- recovery of the data is desired.
+ recovery of the data is to be attempted.
*/
@@ -511,9 +522,8 @@
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).
+ inflateEnd returns Z_OK if success, or Z_STREAM_ERROR if the stream state
+ was inconsistent.
*/
@@ -554,14 +564,15 @@
windowBits can also be -8..-15 for raw deflate. In this case, -windowBits
determines the window size. deflate() will then generate raw deflate data
- with no zlib header or trailer, and will not compute an adler32 check value.
+ with no zlib header or trailer, and will not compute a check value.
windowBits can also be greater than 15 for optional gzip encoding. Add
16 to windowBits to write a simple gzip header and trailer around the
compressed data instead of a zlib wrapper. The gzip header will have no
file name, no extra data, no comment, no modification time (set to zero), no
- header crc, and the operating system will be set to 255 (unknown). If a
- gzip stream is being written, strm->adler is a crc32 instead of an adler32.
+ header crc, and the operating system will be set to the appropriate value,
+ if the operating system was determined at compile time. If a gzip stream is
+ being written, strm->adler is a CRC-32 instead of an Adler-32.
For raw deflate or gzip encoding, a request for a 256-byte window is
rejected as invalid, since only the zlib header provides a means of
@@ -626,12 +637,12 @@
addition, the current implementation of deflate will use at most the window
size minus 262 bytes of the provided dictionary.
- Upon return of this function, strm->adler is set to the adler32 value
+ 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 adler32 value
+ 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.) If a raw deflate was requested, then the
- adler32 value is not computed and strm->adler is not set.
+ Adler-32 value is not computed and strm->adler is not set.
deflateSetDictionary returns Z_OK if success, or Z_STREAM_ERROR if a
parameter is invalid (e.g. dictionary being Z_NULL) or the stream state is
@@ -819,7 +830,7 @@
is for use with other formats that use the deflate compressed data format
such as zip. Those formats provide their own check values. If a custom
format is developed using the raw deflate format for compressed data, it is
- recommended that a check value such as an adler32 or a crc32 be applied to
+ recommended that a check value such as an Adler-32 or a CRC-32 be applied to
the uncompressed data as is done in the zlib, gzip, and zip formats. For
most applications, the zlib format should be used as is. Note that comments
above on the use in deflateInit2() applies to the magnitude of windowBits.
@@ -828,7 +839,10 @@
32 to windowBits to enable zlib and gzip decoding with automatic header
detection, or add 16 to decode only the gzip format (the zlib format will
return a Z_DATA_ERROR). If a gzip stream is being decoded, strm->adler is a
- crc32 instead of an adler32.
+ CRC-32 instead of an Adler-32. Unlike the gunzip utility and gzread() (see
+ below), inflate() will not automatically decode concatenated gzip streams.
+ inflate() will return Z_STREAM_END at the end of the gzip stream. The state
+ would need to be reset to continue decoding a subsequent gzip stream.
inflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was not enough
memory, Z_VERSION_ERROR if the zlib library version is incompatible with the
@@ -849,7 +863,7 @@
Initializes the decompression dictionary from the given uncompressed byte
sequence. This function must be called immediately after a call of inflate,
if that call returned Z_NEED_DICT. The dictionary chosen by the compressor
- can be determined from the adler32 value returned by that call of inflate.
+ can be determined from the Adler-32 value returned by that call of inflate.
The compressor and decompressor must use exactly the same dictionary (see
deflateSetDictionary). For raw inflate, this function can be called at any
time to set the dictionary. If the provided dictionary is smaller than the
@@ -860,7 +874,7 @@
inflateSetDictionary returns Z_OK if success, Z_STREAM_ERROR if a
parameter is invalid (e.g. dictionary being Z_NULL) or the stream state is
inconsistent, Z_DATA_ERROR if the given dictionary doesn't match the
- expected one (incorrect adler32 value). inflateSetDictionary does not
+ expected one (incorrect Adler-32 value). inflateSetDictionary does not
perform any decompression: this will be done by subsequent calls of
inflate().
*/
@@ -918,7 +932,7 @@
ZEXTERN int ZEXPORT inflateReset OF((z_streamp strm));
/*
This function is equivalent to inflateEnd followed by inflateInit,
- but does not free and reallocate all the internal decompression state. The
+ but does not free and reallocate 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
@@ -930,7 +944,9 @@
/*
This function is the same as inflateReset, but it also permits changing
the wrap and window size requests. The windowBits parameter is interpreted
- the same as it is for inflateInit2.
+ the same as it is for inflateInit2. If the window size is changed, then the
+ memory allocated for the window is freed, and the window will be reallocated
+ by inflate() if needed.
inflateReset2 returns Z_OK if success, or Z_STREAM_ERROR if the source
stream state was inconsistent (such as zalloc or state being Z_NULL), or if
@@ -982,7 +998,7 @@
location in the input stream can be determined from avail_in and data_type
as noted in the description for the Z_BLOCK flush parameter for inflate.
- inflateMark returns the value noted above or -65536 if the provided
+ inflateMark returns the value noted above, or -65536 if the provided
source stream state was inconsistent.
*/
@@ -1074,9 +1090,9 @@
This routine would normally be used in a utility that reads zip or gzip
files and writes out uncompressed files. The utility would decode the
header and process the trailer on its own, hence this routine expects only
- the raw deflate stream to decompress. This is different from the normal
- behavior of inflate(), which expects either a zlib or gzip header and
- trailer around the deflate stream.
+ the raw deflate stream to decompress. This is different from the default
+ behavior of inflate(), which expects a zlib header and trailer around the
+ deflate stream.
inflateBack() uses two subroutines supplied by the caller that are then
called by inflateBack() for input and output. inflateBack() calls those
@@ -1085,12 +1101,12 @@
parameters and return types are defined above in the in_func and out_func
typedefs. inflateBack() will call in(in_desc, &buf) which should return the
number of bytes of provided input, and a pointer to that input in buf. If
- there is no input available, in() must return zero--buf is ignored in that
- case--and inflateBack() will return a buffer error. inflateBack() will call
- out(out_desc, buf, len) to write the uncompressed data buf[0..len-1]. out()
- should return zero on success, or non-zero on failure. If out() returns
- non-zero, inflateBack() will return with an error. Neither in() nor out()
- are permitted to change the contents of the window provided to
+ there is no input available, in() must return zero -- buf is ignored in that
+ case -- and inflateBack() will return a buffer error. inflateBack() will
+ call out(out_desc, buf, len) to write the uncompressed data buf[0..len-1].
+ out() should return zero on success, or non-zero on failure. If out()
+ returns non-zero, inflateBack() will return with an error. Neither in() nor
+ out() are permitted to change the contents of the window provided to
inflateBackInit(), which is also the buffer that out() uses to write from.
The length written by out() will be at most the window size. Any non-zero
amount of input may be provided by in().
@@ -1118,7 +1134,7 @@
using strm->next_in which will be Z_NULL only if in() returned an error. If
strm->next_in is not Z_NULL, then the Z_BUF_ERROR was due to out() returning
non-zero. (in() will always be called before out(), so strm->next_in is
- assured to be defined if out() returns non-zero.) Note that inflateBack()
+ assured to be defined if out() returns non-zero.) Note that inflateBack()
cannot return Z_OK.
*/
@@ -1598,7 +1614,7 @@
return the updated checksum. If buf is Z_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
+ An Adler-32 checksum is almost as reliable as a CRC-32 but can be computed
much faster.
Usage example:
