NAME

zip_set_file_compression — set compression method for file in zip

LIBRARY

libzip (-lzip)

SYNOPSIS

#include <zip.h>

int
zip_set_file_compression(zip_t *archive, zip_uint64_t index, zip_int32_t comp, zip_uint32_t comp_flags);

DESCRIPTION

The zip_set_file_compression() function sets the compression method for the file at position index in the zip archive to comp with the compression method specific comp_flags. The comp is the same as returned by zip_stat(3). For the comp argument, currently only the following values are supported:

ZIP_CM_DEFAULT

default compression; currently the same as ZIP_CM_DEFLATE, but flags are ignored.

ZIP_CM_STORE

Store the file uncompressed.

ZIP_CM_BZIP2

Compress the file using the bzip2(1) algorithm.

ZIP_CM_DEFLATE

Deflate the file with the zlib(3) algorithm and default options.

ZIP_CM_XZ

Use the xz(1) algorithm for compression

ZIP_CM_ZSTD

Use the zstd(1) algorithm for compression

NOTE: Only the deflate and store methods can be assumed to be universally supported.

The 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 ZIP_CM_BZIP, ZIP_CM_DEFLATE, and ZIP_CM_XZ 1 is the fastest compression and 9 the best, 0 chooses the default. For ZIP_CM_ZSTD possible values are ZSTD_minCLevel(3) to ZSTD_maxCLevel(3); negative values must be cast to zip_uint32_t.

Further compression method specific flags might be added over time.

The current compression method for a file in a zip archive can be determined using zip_stat(3).

RETURN VALUES

Upon successful completion 0 is returned. Otherwise, -1 is returned and the error information in archive is set to indicate the error.

ERRORS

zip_set_file_compression() fails if:

[ZIP_ER_COMPNOTSUPP]

Unsupported compression method requested.

[ZIP_ER_INVAL]

index is not a valid file index in archive, or the argument combination is invalid.

[ZIP_ER_RDONLY]

Read-only zip file, no changes allowed.

SEE ALSO

libzip(3), zip_compression_method_supported(3), zip_stat(3)

HISTORY

zip_set_file_compression() was added in libzip 0.11.

AUTHORS

Dieter Baron <dillo@nih.at> and Thomas Klausner <wiz@gatalith.at>