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
HISTORY
zip_set_file_compression() was added in libzip 0.11.
AUTHORS
Dieter Baron ⟨[email protected]⟩ and Thomas Klausner ⟨[email protected]⟩