deflate_init

Initialize an incremental deflate context

&reftitle.description; ``DeflateContext``false```deflate_init` `int` `encoding` `array` `options`[]

Initializes an incremental deflate context using the specified `encoding`.

Note that the `window` option here only sets the window size of the algorithm, differently from the zlib filters where the same parameter also sets the encoding to use; the encoding must be set with the `encoding` parameter.

Limitation: there is currently no way to set the header information on a GZIP compressed stream, which are set as follows: GZIP signature (`\x1f\x8B`); compression method (`\x08` == DEFLATE); 6 zero bytes; the operating system set to the current system (`\x00` = Windows, `\x03` = Unix, etc.)

&reftitle.parameters;

`encoding`

- One of the `ZLIB_ENCODING_`*`` constants.

`options`

- An associative array which may contain the following elements:

  `level`

- The compression level in range -1..9; defaults to -1.

`memory`

- The compression memory level in range 1..9; defaults to 8.

`window`

- The zlib window size (logarithmic) in range `8`..`15`; defaults to `15`. zlib changes a window size of `8` to `9`, and as of zlib 1.2.8 fails with a warning, if a window size of `8` is requested for `ZLIB_ENCODING_RAW` or `ZLIB_ENCODING_GZIP`.

`strategy`

- One of `ZLIB_FILTERED`, `ZLIB_HUFFMAN_ONLY`, `ZLIB_RLE`, `ZLIB_FIXED` or `ZLIB_DEFAULT_STRATEGY` (the default).

`dictionary`

- A `string` or an `array` of `strings` of the preset dictionary (default: no preset dictionary).

&reftitle.returnvalues;

Returns a deflate context resource (`zlib.deflate`) on success, &return.falseforfailure;.

&reftitle.errors;

If an invalid option is passed to `options` or the context couldn't be created, an error of level `E_WARNING` is generated.

&reftitle.changelog;

&Version; | &Description;
8.0.0 | On success, this function returns a `DeflateContext` instance now; previously, a `resource` was returned.

&reftitle.seealso;

- `deflate_add`
- `inflate_init`