zip_set_file_compression3

Usage

Library

libzip (-lzip)

Overview

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.