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require 'strscan'
module JSON
module Pure
# This class implements the JSON parser that is used to parse a JSON string
# into a Ruby data structure.
class Parser < StringScanner
STRING = /" ((?:[^\x0-\x1f"\\] |
\\["\\\/bfnrt] |
\\u[0-9a-fA-F]{4} |
\\[\x20-\xff])*)
"/nx
INTEGER = /(-?0|-?[1-9]\d*)/
FLOAT = /(-?
(?:0|[1-9]\d*)
(?:
\.\d+(?i:e[+-]?\d+) |
\.\d+ |
(?i:e[+-]?\d+)
)
)/x
OBJECT_OPEN = /\{/
OBJECT_CLOSE = /\}/
ARRAY_OPEN = /\[/
ARRAY_CLOSE = /\]/
PAIR_DELIMITER = /:/
COLLECTION_DELIMITER = /,/
TRUE = /true/
FALSE = /false/
NULL = /null/
IGNORE = %r(
(?:
//[^\n\r]*[\n\r]| # line comments
/\* # c-style comments
(?:
[^*/]| # normal chars
/[^*]| # slashes that do not start a nested comment
\*[^/]| # asterisks that do not end this comment
/(?=\*/) # single slash before this comment's end
)*
\*/ # the End of this comment
|[ \t\r\n]+ # whitespaces: space, horicontal tab, lf, cr
)+
)mx
UNPARSED = Object.new
# Creates a new JSON::Pure::Parser instance for the string _source_.
#
# It will be configured by the _opts_ hash. _opts_ can have the following
# keys:
# * *max_nesting*: The maximum depth of nesting allowed in the parsed data
# structures. Disable depth checking with :max_nesting => false.
def initialize(source, opts = {})
super
if !opts.key?(:max_nesting) # defaults to 19
@max_nesting = 19
elsif opts[:max_nesting]
@max_nesting = opts[:max_nesting]
else
@max_nesting = 0
end
@create_id = JSON.create_id
end
alias source string
# Parses the current JSON string _source_ and returns the complete data
# structure as a result.
def parse
reset
obj = nil
until eos?
case
when scan(OBJECT_OPEN)
obj and raise ParserError, "source '#{peek(20)}' not in JSON!"
@current_nesting = 1
obj = parse_object
when scan(ARRAY_OPEN)
obj and raise ParserError, "source '#{peek(20)}' not in JSON!"
@current_nesting = 1
obj = parse_array
when skip(IGNORE)
;
else
raise ParserError, "source '#{peek(20)}' not in JSON!"
end
end
obj or raise ParserError, "source did not contain any JSON!"
obj
end
private
# Unescape characters in strings.
UNESCAPE_MAP = Hash.new { |h, k| h[k] = k.chr }
UNESCAPE_MAP.update({
?" => '"',
?\\ => '\\',
?/ => '/',
?b => "\b",
?f => "\f",
?n => "\n",
?r => "\r",
?t => "\t",
?u => nil,
})
def parse_string
if scan(STRING)
return '' if self[1].empty?
self[1].gsub(%r((?:\\[\\bfnrt"/]|(?:\\u(?:[A-Fa-f\d]{4}))+|\\[\x20-\xff]))n) do |c|
if u = UNESCAPE_MAP[c[1]]
u
else # \uXXXX
bytes = ''
i = 0
while c[6 * i] == ?\\ && c[6 * i + 1] == ?u
bytes << c[6 * i + 2, 2].to_i(16) << c[6 * i + 4, 2].to_i(16)
i += 1
end
JSON::UTF16toUTF8.iconv(bytes)
end
end
else
UNPARSED
end
rescue Iconv::Failure => e
raise GeneratorError, "Caught #{e.class}: #{e}"
end
def parse_value
case
when scan(FLOAT)
Float(self[1])
when scan(INTEGER)
Integer(self[1])
when scan(TRUE)
true
when scan(FALSE)
false
when scan(NULL)
nil
when (string = parse_string) != UNPARSED
string
when scan(ARRAY_OPEN)
@current_nesting += 1
ary = parse_array
@current_nesting -= 1
ary
when scan(OBJECT_OPEN)
@current_nesting += 1
obj = parse_object
@current_nesting -= 1
obj
else
UNPARSED
end
end
def parse_array
raise NestingError, "nesting of #@current_nesting is to deep" if
@max_nesting.nonzero? && @current_nesting > @max_nesting
result = []
delim = false
until eos?
case
when (value = parse_value) != UNPARSED
delim = false
result << value
skip(IGNORE)
if scan(COLLECTION_DELIMITER)
delim = true
elsif match?(ARRAY_CLOSE)
;
else
raise ParserError, "expected ',' or ']' in array at '#{peek(20)}'!"
end
when scan(ARRAY_CLOSE)
if delim
raise ParserError, "expected next element in array at '#{peek(20)}'!"
end
break
when skip(IGNORE)
;
else
raise ParserError, "unexpected token in array at '#{peek(20)}'!"
end
end
result
end
def parse_object
raise NestingError, "nesting of #@current_nesting is to deep" if
@max_nesting.nonzero? && @current_nesting > @max_nesting
result = {}
delim = false
until eos?
case
when (string = parse_string) != UNPARSED
skip(IGNORE)
unless scan(PAIR_DELIMITER)
raise ParserError, "expected ':' in object at '#{peek(20)}'!"
end
skip(IGNORE)
unless (value = parse_value).equal? UNPARSED
result[string] = value
delim = false
skip(IGNORE)
if scan(COLLECTION_DELIMITER)
delim = true
elsif match?(OBJECT_CLOSE)
;
else
raise ParserError, "expected ',' or '}' in object at '#{peek(20)}'!"
end
else
raise ParserError, "expected value in object at '#{peek(20)}'!"
end
when scan(OBJECT_CLOSE)
if delim
raise ParserError, "expected next name, value pair in object at '#{peek(20)}'!"
end
if klassname = result[@create_id]
klass = JSON.deep_const_get klassname
break unless klass and klass.json_creatable?
result = klass.json_create(result)
result
end
break
when skip(IGNORE)
;
else
raise ParserError, "unexpected token in object at '#{peek(20)}'!"
end
end
result
end
end
end
end
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