.Dd January 15, 2017
.Dt DEFLATEINIT 3
.Os
.
.Sh NAME
.Nm deflateInit
.Nd initialize deflate stream
.
.Sh LIBRARY
.Lb libz
.
.Sh SYNOPSIS
.In zlib.h
.
.Ft typedef voidpf
.Fo (*alloc_func)
.Fa "voidpf opaque"
.Fa "uInt items"
.Fa "uInt size"
.Fc
.
.Ft typedef void
.Fo (*free_func)
.Fa "voidpf opaque"
.Fa "voidpf address"
.Fc
.
.Bd -literal
typedef struct z_stream_s {
	z_const Bytef *next_in;
	uInt     avail_in;
	uLong    total_in;

	Bytef    *next_out;
	uInt     avail_out;
	uLong    total_out;

	z_const char *msg;
	struct internal_state FAR *state;

	alloc_func zalloc;
	free_func  zfree;
	voidpf     opaque;

	int     data_type;
	uLong   adler;
	uLong   reserved;
} z_stream;
.Ed
.
.Pp
.Vt typedef z_stream FAR *z_streamp;
.
.Ft int
.Fn deflateInit "z_streamp strm" "int level"
.
.Sh DESCRIPTION
Initializes the internal stream state for compression.
The fields
.Fa zalloc ,
.Fa zfree
and
.Fa opaque
must be initialized before by the caller.
If
.Fa zalloc
and
.Fa zfree
are set to
.Dv Z_NULL ,
.Fn deflateInit
updates them to use default allocation functions.
.Fn deflateInit
does not perform any compression:
this will be done by
.Xr deflate 3 .
.
.Pp
The compression
.Fa level
must be
.Dv 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).
.Dv Z_DEFAULT_COMPRESSION
requests a default compromise between speed and compression
(currently equivalent to level 6).
.
.Pp
The fields of
.Vt z_stream
are as follows:
.
.Bl -tag -width "data_type"
.It Fa next_in
next input byte
.It Fa avail_in
number of bytes available at
.Fa next_in
.It Fa total_in
total number of input bytes read so far
.It Fa next_out
next output byte will go here
.It Fa avail_out
remaining free space at
.Fa next_out
.It Fa total_out
total number of bytes output so far
.It Fa msg
last error message,
.Dv NULL
if no error
.It Fa state
not visible by applications
.It Fa zalloc
used to allocate the internal state
.It Fa zfree
used to free the internal state
.It Fa opaque
private data object passed to
.Fa zalloc
and
.Fa zfree
.It data_type
best guess about the data type:
binary or text for
.Xr deflate 3 ,
or the decoding state for
.Xr inflate 3
.It adler
Adler-32 or CRC-32 value of the uncompressed data
.It reserved
reserved for future use
.El
.
.Sh RETURN VALUES
.Fn deflateInit
returns
.Dv Z_OK
if success,
.Dv Z_MEM_ERROR
if there was not enough memory,
.Dv Z_STREAM_ERROR
if
.Fa level
is not a valid compression level,
or
.Dv Z_VERSION_ERROR
if the zlib library version
.Pq Xr zlibVersion 3
is incompatible with the version assumed by the caller
.Pq Dv ZLIB_VERSION .
.Fa msg
is set to null
if there is no error message.
.
.Sh SEE ALSO
.Xr deflate 3 ,
.Xr deflateCopy 3 ,
.Xr deflateEnd 3 ,
.Xr deflateInit2 3 ,
.Xr deflatePrime 3 ,
.Xr deflateReset 3 ,
.Xr deflateSetDictionary 3 ,
.Xr deflateTune 3
.
.Sh HISTORY
This manual page was converted from
.In zlib.h
to mdoc format by
.An C. McEnroe Aq Mt june@causal.agency .
.
.Sh AUTHORS
.An Jean-loup Gailly Aq Mt jloup@gzip.org
.An Mark Adler Aq Mt madler@alumni.caltech.edu