'\"
'\" Copyright (c) 2008 Donal K. Fellows
'\"
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\" 
'\" RCS: @(#) $Id: TclZlib.3,v 1.4 2008/12/27 00:04:17 dkf Exp $
'\" 
.so man.macros
.TH TclZlib 3 8.6 Tcl "Tcl Library Procedures"
.BS
'\" Note:  do not modify the .SH NAME line immediately below!
.SH NAME
Tcl_ZlibAdler32, Tcl_ZlibCRC32, Tcl_ZlibDeflate, Tcl_ZlibInflate, Tcl_ZlibStreamChecksum, Tcl_ZlibStreamClose, Tcl_ZlibStreamEof, Tcl_ZlibStreamGet, Tcl_ZlibStreamGetCommandName, Tcl_ZlibStreamInit, Tcl_ZlibStreamPut \- compression and decompression functions
.SH SYNOPSIS
.nf
#include <tcl.h>
.sp
Tcl_Obj *
\fBTcl_ZlibDeflate\fR(\fIinterp, format, dataObj, level, dictObj\fR)
.sp
Tcl_Obj *
\fBTcl_ZlibInflate\fR(\fIinterp, format, dataObj, dictObj\fR)
.sp
unsigned int
\fBTcl_ZlibCRC32\fR(\fIinitValue, bytes, length\fR)
.sp
unsigned int
\fBTcl_ZlibAdler32\fR(\fIinitValue, bytes, length\fR)
.sp
int
\fBTcl_ZlibStreamInit\fR(\fIinterp, mode, format, level, dictObj, zshandlePtr\fR)
.sp
Tcl_Obj *
\fBTcl_ZlibStreamGetCommandName\fR(\fIzshandle\fR)
.sp
int
\fBTcl_ZlibStreamEof\fR(\fIzshandle\fR)
.sp
int
\fBTcl_ZlibStreamClose\fR(\fIzshandle\fR)
.sp
int
\fBTcl_ZlibStreamChecksum\fR(\fIzshandle\fR)
.sp
int
\fBTcl_ZlibStreamPut\fR(\fIzshandle, dataObj, flush\fR)
.sp
int
\fBTcl_ZlibStreamGet\fR(\fIzshandle, dataObj, count\fR)
.fi
.SH ARGUMENTS
.AS Tcl_ZlibStream *zshandlePtr out
.AP Tcl_Interp *interp in
The interpreter to store resulting compressed or uncompressed data in. Also
where any error messages are written. For \fBTcl_ZlibStreamInit\fR, this can
be NULL to create a stream that is not bound to a command.
.AP int format in
What format of compressed data to work with. Must be one of
\fBTCL_ZLIB_FORMAT_ZLIB\fR for zlib-format data, \fBTCL_ZLIB_FORMAT_GZIP\fR
for gzip-format data, or \fBTCL_ZLIB_FORMAT_RAW\fR for raw compressed data. In
addition, for decompression only, \fBTCL_ZLIB_FORMAT_AUTO\fR may also be
chosen which can automatically detect whether the compressed data was in zlib
or gzip format.
.AP Tcl_Obj *dataObj in/out
A byte-array object containing the data to be compressed or decompressed, or
to which the data extracted from the stream is appended when passed to
\fBTcl_ZlibStreamGet\fR.
.AP int level in
What level of compression to use. Should be a number from 0 to 9 or one of the
following: \fBTCL_ZLIB_COMPRESS_NONE\fR for no compression,
\fBTCL_ZLIB_COMPRESS_FAST\fR for fast but inefficient compression,
\fBTCL_ZLIB_COMPRESS_BEST\fR for slow but maximal compression, or
\fBTCL_ZLIB_COMPRESS_DEFAULT\fR for the level recommended by the zlib library.
.AP Tcl_Obj *dictObj in/out
A dictionary that contains, or which will be updated to contain, a description
of the gzip header associated with the compressed data. Only useful when the
\fIformat\fR is \fBTCL_ZLIB_FORMAT_GZIP\fR or \fBTCL_ZLIB_FORMAT_AUTO\fR. If
a NULL is passed, a default header will be used on compression and the header
will be ignored (apart from integrity checks) on decompression.
.AP "unsigned int" initValue in
The initial value for the checksum algorithm.
.AP "unsigned char" *bytes in
An array of bytes to run the checksum algorithm over, or NULL to get the
recommended initial value for the checksum algorithm.
.AP int length in
The number of bytes in the array.
.AP int mode in
What mode to operate the stream in. Should be either
\fBTCL_ZLIB_STREAM_DEFLATE\fR for a compressing stream or
\fBTCL_ZLIB_STREAM_INFLATE\fR for a decompressing stream.
.AP Tcl_ZlibStream *zshandlePtr out
A pointer to a variable in which to write the abstract token for the stream
upon successful creation.
.AP Tcl_ZlibStream zshandle in
The abstract token for the stream to operate on.
.AP int flush in
Whether and how to flush the stream after writing the data to it. Must be one
of: \fBTCL_ZLIB_NO_FLUSH\fR if no flushing is to be done, \fBTCL_ZLIB_FLUSH\fR
if the currently compressed data must be made available for access using
\fBTcl_ZlibStreamGet\fR, \fBTCL_ZLIB_FULLFLUSH\fR if the stream must be put
into a state where the decompressor can recover from on corruption, or
\fBTCL_ZLIB_FINALIZE\fR to ensure that the stream is finished and that any
trailer demanded by the format is written.
.AP int count in
The maximum number of bytes to get from the stream, or -1 to get all remaining
bytes from the stream's buffers.
.BE
.SH DESCRIPTION
These functions form the interface from the Tcl library to the Zlib
library by Jean-loup Gailly and Mark Adler.
.PP
\fBTcl_ZlibDeflate\fR and \fBTcl_ZlibInflate\fR compress and decompress data
respectively. Upon success, they leave the resulting compressed or
decompressed data in a byte-array object that is the Tcl interpreter's
result. Note that the \fIdictObj\fR parameter is only used when the
\fIformat\fR parameter is \fBTCL_ZLIB_FORMAT_GZIP\fR or
\fBTCL_ZLIB_FORMAT_AUTO\fR.
.PP
\fBTcl_ZlibAdler32\fR and \fBTcl_ZlibCRC32\fR compute checksums on arrays of
bytes. Typical usage is:
.PP
.CS
checksum = \fBTcl_ZlibCRC32\fR(\fBTcl_ZlibCRC32\fR(0,NULL,0), data, length);
.CE
.SS "ZLIB STREAMS"
.PP
\fBTcl_ZlibStreamInit\fR creates a compressing or decompressing stream that is
linked to a Tcl command, according to its arguments, and provides an abstract
token for the stream and returns a normal Tcl result code;
\fBTcl_ZlibStreamGetCommandName\fR returns the name of that command given the
stream token, or NULL if the stream has no command.
.PP
Once a stream has been constructed, \fBTcl_ZlibStreamPut\fR is used to add
data to the stream and \fBTcl_ZlibStreamGet\fR is used to retrieve data from
the stream after processing. Both return normal Tcl result codes. With
\fBTcl_ZlibStreamPut\fR, the data buffer object passed to it should not be
modified afterwards. With \fBTcl_ZlibStreamGet\fR, the data buffer object
passed to it will have the data bytes appended to it.
.PP
\fBTcl_ZlibStreamChecksum\fR returns the checksum computed over the
uncompressed data according to the format, and \fBTcl_ZlibStreamEof\fR returns
whether the end of the uncompressed data has been reached.
.PP
Finally, \fBTcl_ZlibStreamClose\fR will clean up the stream and delete the
associated command: using \fBTcl_DeleteCommand\fR on the stream's command is
equivalent.
.SH "PORTABILITY NOTES"
These functions will fail gracefully if Tcl is not linked with the zlib
library.
.SH "SEE ALSO"
Tcl_NewByteArrayObj(3), zlib(n)
'\"Tcl_StackChannel(3)
.SH "KEYWORDS"
compress, decompress, deflate, gzip, inflate
'\" Local Variables:
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