- zopen(+Stream, -ZStream, +Options)
- Creates ZStream, providing compressed access to Stream.
If an input stream is wrapped, it recognises a gzip or deflate header.
If an output stream is wrapped, Options define the desired
wrapper and compression level. The new ZStream inherits its
encoding from Stream. In other words, if Stream
is a text-stream, so is ZStream. The original Stream
is switched to binary mode while it is wrapped. The original encoding of
Stream is restored if ZStream is closed. Note that zopen/3
does not actually process any data and therefore succeeds on input
streams that do not contain valid data. Errors may be generated by read
operations performed on the stream.
Defined options on output streams are:
deflateenvelope is simple and short and is typically used for compressed (network) communication. The
raw_deflatedoes not include an envelope and is often used as a step in crypographic encodings. The
gzipenvelope is compatible to the gzip program and intended to read/write compressed files.
- Number between 0 and 9, specifying the compression level, Higher levels use more resources. Default is 6, generally believed to be a good compromise between speed, memory requirement and compression.
true, restart reading if the input is not at end-of-file. The default is
truefor gzip streams.
Generic options are:
true(default), closing the compressed stream also closes (and thus invalidates) the wrapped stream. If
false, the wrapped stream is not closed. This can be used to read/write a compressed data block as partial input/output on a stream.
- gzopen(+File, +Mode, -Stream)
- Same as
gzopen(File, Mode, Stream,).
- gzopen(+File, +Mode, -Stream, +Options)
- Open gzip compatible File for reading or writing. If a
file is opened in =append= mode, a new gzip image will be added to the
end of the file. The gzip standard defines that a file can hold multiple
gzip images and inflating the file results in a concatenated stream of
all inflated images. Options are passed to open/4
Default format is