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# SSON - S-Expression Standard Object Notation
# a faithful embedding of JSON (RFC 8259) into a S-Expression syntax
#
# value = "#n" / "#t" / "#f" /
# "(" value* ")" / "#(" (string value)* ")" /
# json-number / string
# string = json-string / literal
# literal = [^0-9#;()" \t\r\n+-][^#;()" \t\r\n]*
# ";" starts a comment until end of line, it is treated as whitespace
#
# To the extent possible under law, Leah Neukirchen <leah@vuxu.org>
# has waived all copyright and related or neighboring rights to this work.
# http://creativecommons.org/publicdomain/zero/1.0/
require 'json'
require 'prettyprint'
require 'strscan'
module SSON
VERSION = "0.1"
class SSONError < StandardError; end
class GeneratorError < SSONError; end
class ParserError < SSONError; end
end
class << SSON
SCANIDENT = /[^0-9#;()" \t\r\n+-][^#;()" \t\r\n]*/
IDENT = /\A#{SCANIDENT}\z/
def generate(o)
case o
when Hash
r = "#("
o.each { |k, v|
r << " " if r.size > 2
r << generate(k.to_s) << " " << generate(v)
}
r << ")"
r
when Array
r = "("
o.each { |e|
r << " " if r.size > 1
r << generate(e)
}
r << ")"
r
when true
"#t"
when false
"#f"
when nil
"#n"
when Integer
o.to_s
when Float
if o.nan?
raise GeneratorError, "NaN not allowed in SSON"
elsif o.infinite?
raise GeneratorError, "Infinity not allowed in SSON"
end
o.to_s
when String
if o =~ IDENT
o
else
JSON.generate(o)
end
else
# like JSON.generate
generate(o.to_s)
end
end
def pretty_generate(obj)
return PrettyPrint.format('', 80) { |q|
inner = lambda { |o|
case o
when Array
q.group(1) {
q.text "("
b = false
o.each { |e|
q.breakable " " if b
b = true
inner[e]
}
q.text ")"
}
when Hash
q.group(2) {
q.text "#("
b = false
o.each { |k, v|
q.breakable " " if b
b = true
q.group {
inner[k]
q.text " "
inner[v]
}
}
q.text ")"
}
when true; q.text "#t"
when false; q.text "#f"
when nil; q.text "#n"
when Integer
q.text o.to_s
when Float
if o.nan?
raise GeneratorError, "NaN not allowed in SSON"
elsif o.infinite?
raise GeneratorError, "Infinity not allowed in SSON"
end
q.text o.to_s
when String
if o =~ IDENT
q.text o # ES5 identifier
else
q.text JSON.generate(o)
end
end
}
inner[obj]
}
end
def parse(str)
e = SSON.enum_for(:tok, str)
r = parse_form e
begin
e.next
rescue StopIteration
r
else
raise SSON::ParserError, "trailing garbage"
end
end
private
def tok(str)
ss = StringScanner.new(str)
until ss.eos?
if ss.scan(/\A[ \t\r\n]+/) || ss.scan(/;[^\n]*$/)
# ignore
elsif ss.scan(/\(/); yield :OPEN
elsif ss.scan(/\)/); yield :CLOSE
elsif ss.scan(/#\(/); yield :HASH
elsif ss.scan(/#n/); yield :NULL
elsif ss.scan(/#t/); yield :TRUE
elsif ss.scan(/#f/); yield :FALSE
elsif s = ss.scan(/"(\\"|[^"])*"/)
yield JSON.parse(s)
elsif s = ss.scan(SCANIDENT)
yield s
elsif s = ss.scan(/[-+]?(?:\d*\.?\d+|\d+\.?\d*)(?:[eE][-+]?\d+)?/)
yield Float(s)
else
raise SSON::ParserError, "invalid SSON: " + ss.peek(20).dump
end
end
end
def parse_form(e)
case t = e.next
when :OPEN
r = []
while e.peek != :CLOSE
r << parse_form(e)
end
e.next
r
when :HASH
r = {}
while e.peek != :CLOSE
k = e.next
raise "non string key" unless k.kind_of?(String)
v = parse_form(e)
r[k] = v
end
e.next
r
when :CLOSE; raise SSON::ParserError, "invalid SSON, toplevel )"
when :NULL; nil
when :TRUE; true
when :FALSE; false
when String; t
when Float; t
end
rescue StopIteration
raise ParserError, "early EOF"
end
end
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