Class Gz.deflate

Description: This class interfaces with the compression routines in the libz library.
Note: This class is only available if libz was available and found when Pike was compiled.
See also: Gz.inflate(), Gz.compress(), Gz.uncompress()

Method create

Gz.deflate Gz.deflate(int(-9..9)|void level, int|void strategy, int(8..15)|void window_size)
Gz.deflate Gz.deflate(mapping options)

Description

This function can also be used to re-initialize a Gz.deflate object so it can be re-used.

If a mapping is passed as the only argument, it will accept the parameters described below as indices, and additionally it accepts a string as dictionary.

Parameter level

Indicates the level of effort spent to make the data compress well. Zero means no packing, 2-3 is considered 'fast', 6 is default and higher is considered 'slow' but gives better packing.

If the argument is negative, no headers will be emitted. This is needed to produce ZIP-files, as an example. The negative value is then negated, and handled as a positive value.

Parameter strategy

The strategy to be used when compressing the data. One of the following.

`DEFAULT_STRATEGY`	The default strategy as selected in the zlib library.
`FILTERED`	This strategy is intented for data created by a filter or predictor and will put more emphasis on huffman encoding and less on LZ string matching. This is between DEFAULT_STRATEGY and HUFFMAN_ONLY.
`RLE`	This strategy is even closer to the HUFFMAN_ONLY in that it only looks at the latest byte in the window, i.e. a window size of 1 byte is sufficient for decompression. This mode is not available in all zlib versions.
`HUFFMAN_ONLY`	This strategy will turn of string matching completely, only doing huffman encoding. Window size doesn't matter in this mode and the data can be decompressed with a zero size window.
`FIXED`	In this mode dynamic huffman codes are disabled, allowing for a simpler decoder for special applications. This mode is not available in all zlib versions.

Parameter window_size

Defines the size of the LZ77 window from 256 bytes to 32768 bytes, expressed as 2^x.