JSON Parser

(import (macduffie json))

(macduffie json) is just a simple JSON parser. This library is now based on the SchemeSpheres JSON parser, and no longer has any code from Dominique Boucher. With this change, the license is now Expat (MIT). Furthermore, the parser looks close to standards compliant, but there remains a problem with Unicode surrogate pairs.

This library depends on (srfi 69) to represent JSON objects. Otherwise, only scheme-small libraries are used.

This library is regularly tested in Chibi, Kawa, and Gauche (in R7RS-strict mode).

Library Procedures

• (json-read [port]) Reads a JSON file from port and converts it to Scheme data. port defaults to (current-input-port).
• (json-write value [port]) Converts value to a JSON file and writes it to port. port defaults to (current-output-port).
• (json-read-string str) Reads a JSON string str and returns the corresponding Scheme data.
• (json-read-file filepath) Reads a JSON file at filepath and returns the corresponding Scheme data.
• (json-write-string value [prettify] [space-char space-count]) Writes value to a new JSON string which is returned. prettify writes the JSON in pretty-printed form, and defaults to #f. space-char and space-count specify the indentation for pretty-printing, and default to #\tab and 1.
• (json-write-file value filepath [prettify] [space-char space-count]) Writes value to a JSON file at filepath. The optional arguments are the same as json-write-string and have the same defaults.
• (json-null) Returns a record of the type json-null, for which (eq? (json-null) (json-null)) always returns #t.
• (json-null? v) Returns #t if v is a record of the type json-null.

To do:

• Correctly write Unicode surrogate pairs

Performance

This library will not work well for very large files. According to my tests, here are the relative performance of Chibi, Kawa, and Gauche:

• Kawa was ok with a 1,000-line JSON file. Performance was unacceptable for a 5,000-line JSON file.
• Chibi was ok with a 5,000-line JSON file. Performance was unacceptable for a 10,000-line JSON file.
• Gauche was ok with a 100,000-line JSON file. Performance was unacceptable for a 500,000-line JSON file.

Data types

Note that keys are internally represented as symbols.