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Article contents:== [[http://www.zstd.net/|zstd]] bindings for [[http://call-cc.org|Chicken Scheme]] [[toc:]] === Requirements * [[http://www.zstd.net/|zstd]] version 1.4.0+. === Source Code Hosted [[https://github.com/kristianlm/chicken-zstd|here]]. === API <procedure>(zstd-compress src #!key (level 3))</procedure> Compress the string or blob {{src}}, returning the entire compressed frame as a string. This is faster than using ports but may not be suitable for large inputs. If {{level}} is supplied, it sets the compression level as documented by {{man zstd}}, and should be an integer in the range [1-19]. <procedure>(zstd-decompress trg)</procedure> Decompress the string or blob {{trg}}, which must be a valid zstd frame. Returns the uncompressed data as a string. Note that {{zstd-decompress}} cannot decompress data from the port-based API, because the frame sizes are unknown ahead of time. It is therefore safest to always decompress using the port-based API. <procedure>(zstd-frame-content-size frame)</procedure> Return the size of the uncompressed data stored in {{frame}} in number of bytes, or {{#f}} if the frame size is unknown. The port-based API will produce frames of unknown sizes. {{frame}} can only be decompressed using {{zstd-decompress}} if this function returns non-{{#f}}. <procedure>(compressing-output-port output-port #!key (level 3)) => output-port</procedure> Returns an output-port to which uncompressed data can be written, and its compressed form will be written to {{output-port}}. It is important to close this port in order to flush internal zstd buffers. Closing this output-port does not close {{output-port}}. If {{level}} is supplied, it sets the compression level as documented by {{man zstd}}, and should be an integer in the range [1-19]. <procedure>(decompressing-input-port input-port) => input-port</procedure> Returns an input-port from which uncompressed data can be read. Compressed data read, from {{input-port}}, will be read in the process. Closing this input-port does not close {{input-port}}. === Examples Some very basic usage for illustration. <enscript highlight="scheme"> (import zstd chicken.process chicken.io chicken.port) (with-input-from-pipe ;; => "hello hello hello\n" "echo hello hello hello | zstd" (lambda () (with-input-from-port (decompressing-input-port) read-string))) (with-output-to-pipe ;; prints "hello world" to stdout "zstd -d" (lambda () (current-output-port (compressing-output-port)) (print "hello world") (close-output-port (current-output-port)))) </enscript> === Example code for benchmarking and testing The code under {{./examples}} may be useful to try things out and compare against the {{zstd}} command-line-tool. <enscript highlight="sh"> > cd examples > make csc hello.scm csc zstd.scm csc unzstd.scm > ./hello | pv -cNu | sha1sum u: 18.0MiB 0:00:00 [47.2MiB/s] 7c363606a232e640bb0f9dce8b0023a78f7059ba - > ./hello | pv -cNu | ./zstd -1 | pv -cNz | ./unzstd | sha1sum u: 18.0MiB 0:00:00 [46.2MiB/s] z: 343KiB 0:00:00 [ 879KiB/s] 7c363606a232e640bb0f9dce8b0023a78f7059ba - > ./hello | pv -cNu | ./zstd -22 | pv -cNz | ./unzstd | sha1sum u: 18.0MiB 0:00:22 [ 828KiB/s] z: 115KiB 0:00:22 [5.15KiB/s] 7c363606a232e640bb0f9dce8b0023a78f7059ba - > ./hello | pv -cNu | zstd -1 | pv -cNz | unzstd | sha1sum u: 18.0MiB 0:00:00 [46.5MiB/s] z: 486KiB 0:00:00 [1.22MiB/s] 7c363606a232e640bb0f9dce8b0023a78f7059ba - </enscript> === Development status * This egg does not support the dictionary features of the zstd C API. * This egg does not support re-using {{z-stream}} contexts.Description of your changes:

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