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zlib bindings for Chicken Scheme

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zlib bindings for Chicken Scheme

zlib is a popular data compression library that uses the DEFLATE algorithm internally. It is defined in RFC 1950.


These bindings provide two procedures:

(open-zlib-compressed-input-port [INPUT-PORT])
(open-zlib-compressed-output-port [OUTPUT-PORT])

The first is for inflating an existing zlib stream and the second for deflating data into a new stream.


Inflating a stream:

(with-input-from-port (open-zlib-compressed-input-port)

Deflating a stream:

(with-output-to-port (open-zlib-compressed-output-port)
  (lambda ()
    (write-string (read-string))
    (close-output-port (current-output-port))))  


  • This is expecting the zlib format, not raw DEFLATE or the gzip format, which are defined in RFCs 1951 and 1952 respectively.
  • When finished deflating, it is important to always close the zlib output-port. This will ensure that the zlib trailing data is written along with any data still buffered. The destination port will remain open after the zlib port is closed.


expose compression level settings (currently uses level 6, the default)

test on low memory environment (currently uses a hard-coded chunk size of 32k)

improve general efficiency of memory usage

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