.\" zip_set_file_compression.mdoc -- set compression method and its flags
.\" Copyright (C) 2012-2020 Dieter Baron and Thomas Klausner
.\"
.\" This file is part of libzip, a library to manipulate ZIP files.
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.Dd March 19, 2021
.Dt ZIP_SET_FILE_COMPRESSION 3
.Os
.Sh NAME
.Nm zip_set_file_compression
.Nd set compression method for file in zip
.Sh LIBRARY
libzip (-lzip)
.Sh SYNOPSIS
.In zip.h
.Ft int
.Fn zip_set_file_compression "zip_t *archive" "zip_uint64_t index" "zip_int32_t comp" "zip_uint32_t comp_flags"
.Sh DESCRIPTION
The
.Fn zip_set_file_compression
function sets the compression method for the file at position
.Ar index
in the zip archive to
.Ar comp
with the compression method specific
.Ar comp_flags .
The
.Ar comp
is the same as returned by
.Xr zip_stat 3 .
For the
.Ar comp
argument, currently only the following values are supported:
.Bl -tag -width ZIP_CM_DEFLATE_XX
.It Dv ZIP_CM_DEFAULT
default compression; currently the same as
.Dv ZIP_CM_DEFLATE ,
but
.Ar flags
are ignored.
.It Dv ZIP_CM_STORE
Store the file uncompressed.
.It Dv ZIP_CM_BZIP2
Compress the file using the
.Xr bzip2 1
algorithm.
.It Dv ZIP_CM_DEFLATE
Deflate the file with the
.Xr zlib 3
algorithm and default options.
.It Dv ZIP_CM_XZ
Use the
.Xr xz 1
algorithm for compression
.It Dv ZIP_CM_ZSTD
Use the
.Xr zstd 1
algorithm for compression
.El
.Pp
.Em NOTE :
Only the deflate and store methods can be assumed to be universally
supported.
.Pp
The
.Ar comp_flags
argument defines the compression level.
This value is dependent on the compression algorithm.
In general, lower numbers mean faster de/compression and higher
numbers mean slower de/compression.
For
.Dv ZIP_CM_BZIP ,
.Dv ZIP_CM_DEFLATE ,
and
.Dv ZIP_CM_XZ
1 is the fastest compression and 9 the best, 0 chooses the default.
For
.Dv ZIP_CM_ZSTD
the value go from
.Xr ZSTD_minCLevel 3
to
.Xr ZSTD_maxCLevel 3 .
.Pp
Further compression method specific flags might be added over time.
.Pp
The current compression method for a file in a zip archive can be
determined using
.Xr zip_stat 3 .
.Sh RETURN VALUES
Upon successful completion 0 is returned.
Otherwise, \-1 is returned and the error information in
.Ar archive
is set to indicate the error.
.Sh ERRORS
.Fn zip_set_file_compression
fails if:
.Bl -tag -width Er
.It Bq Er ZIP_ER_COMPNOTSUPP
Unsupported compression method requested.
.It Bq Er ZIP_ER_INVAL
.Ar index
is not a valid file index in
.Ar archive ,
or the argument combination is invalid.
.It Bq Er ZIP_ER_RDONLY
Read-only zip file, no changes allowed.
.El
.Sh SEE ALSO
.Xr libzip 3 ,
.Xr zip_compression_method_supported 3 ,
.Xr zip_stat 3
.Sh HISTORY
.Fn zip_set_file_compression
was added in libzip 0.11.
.Sh AUTHORS
.An -nosplit
.An Dieter Baron Aq Mt dillo@nih.at
and
.An Thomas Klausner Aq Mt tk@giga.or.at