set compression method for file in zip

libzip (-lzip)

#include <zip.h>

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

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:
default compression; currently the same as ZIP_CM_DEFLATE, but flags are ignored.
Store the file uncompressed.
Compress the file using the bzip2(1) algorithm.
Deflate the file with the zlib(3) algorithm and default options.

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

The comp_flags argument defines the compression level, 1 being fastest compression and 9 highest. Allowed values are 0 (which uses the default compression for the algorithm) and 1-9, other values are undefined. 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).

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

zip_set_file_compression() fails if:
Unsupported compression method requested.
index is not a valid file index in archive, or the argument combination is invalid.
Read-only zip file, no changes allowed.

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

zip_set_file_compression() was added in libzip 0.11.

Dieter Baron <> and Thomas Klausner <>