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Diffstat (limited to 'lib/json/pure/parser.rb')
| -rw-r--r-- | lib/json/pure/parser.rb | 241 |
1 files changed, 241 insertions, 0 deletions
diff --git a/lib/json/pure/parser.rb b/lib/json/pure/parser.rb new file mode 100644 index 0000000000..6118fe489e --- /dev/null +++ b/lib/json/pure/parser.rb @@ -0,0 +1,241 @@ +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 |