Class: JSON5::Parser

Inherits:
Object
  • Object
show all
Defined in:
lib/json5/parser.rb

Constant Summary collapse

ESCAPEE = 
{
  "'" =>  "'",
  '"' =>  '"',
  '\\' => '\\',
  '/' =>  '/',
  "\n" => '',       # Replace escaped newlines in strings w/ empty string
  'b' => '\b',
  'f' => '\f',
  'n' => "\n",
  'r' => '\r',
  't' => '\t',
}

Instance Method Summary collapse

Constructor Details

#initialize(source, reviver = nil) ⇒ Parser

Returns a new instance of Parser.



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# File 'lib/json5/parser.rb', line 421

def initialize source, reviver = nil
  @text    = source
  @at      = 0
  @ch      = ' '
  @reviver = reviver
end

Instance Method Details

#array ⇒ Object 



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# File 'lib/json5/parser.rb', line 325

def array
  # Parse an array value.

  array = []

  if (@ch == '[')
    get_next('[')
    white
    while (@ch) do
      if (@ch == ']')
        get_next(']')
          return array;   # Potentially empty array
        end
      # ES5 allows omitting elements in arrays, e.g. [,] and
      # [,null]. We don't allow this in JSON5.
      if (@ch == ',')
        error("Missing array element")
      else
        array.push(value)
      end
      white
      # If there's no comma after this value, this needs t
      # be the end of the array.
      if (@ch != ',')
        get_next(']')
        return array
      end
      get_next(',')
      white
    end
  end
  error("Bad array")
end

#blockComment ⇒ Object 



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# File 'lib/json5/parser.rb', line 222

def blockComment

  # Skip a block comment, assuming this is one. The current @character should be
  # the * @character in the /* pair that begins this block comment.
  # To finish the block comment, we look for an ending */ pair of @characters,
  # but we also wat@ch for the end of text before the comment is terminated.

  if (@ch != '*')
    error("Not a block comment")
  end

  begin
    get_next
    while (@ch == '*') do
      get_next('*')
      if (@ch == '/')
        get_next('/')
        return
      end
    end
  end while (@ch)

  error("Unterminated block comment")
end

#comment ⇒ Object 



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# File 'lib/json5/parser.rb', line 247

def comment
  # Skip a comment, whether inline or block-level, assuming this is one.
  # Comments always begin with a / @character.

  if (@ch != '/')
    error("Not a comment")
  end

  get_next('/')

  if (@ch == '/')
    inlineComment
  elsif (@ch == '*')
    blockComment
  else
    error("Unrecognized comment")
  end
end

#error(m) ⇒ Object 



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# File 'lib/json5/parser.rb', line 3

def error(m)
  error = SyntaxError.new("#{m} at #{@at}: #{@text}")
  raise error
end

#get_next(c = nil) ⇒ Object 



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# File 'lib/json5/parser.rb', line 8

def get_next c = nil
  if (c && c != @ch)
    error("Expected '" + c + "' instead of '" + @ch + "'")
  end

  # Get the next character. When there are no more characters,
  # return the empty string.

  # ch = text.charAt(at)
  @ch = @text[@at]
  @at += 1
  return @ch
end

#identifier ⇒ Object 



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# File 'lib/json5/parser.rb', line 36

def identifier
  # Parse an identifier. Normally, reserved words are disallowed here, but we
  # only use this for unquoted object keys, where reserved words are allowed,
  # so we don't check for those here. References:
  # - http://es5.github.com/#x7.6
  # - https://developer.mozilla.org/en/Core_JavaScript_1.5_Guide/Core_Language_Features#Variables
  # - http://docstore.mik.ua/orelly/webprog/jscript/ch02_07.htm
  # TODO Identifiers can have Unicode "letters" in them; add support for those.

  key = @ch

  # Identifiers must start with a letter, _ or $.
  if ((@ch != '_' && @ch != '$') && (@ch < 'a' || @ch > 'z') && (@ch < 'A' || @ch > 'Z'))
    error("Bad identifier")
  end

  # Subsequent characters can contain digits.
  while (get_next && (
    @ch == '_' || @ch == '$' ||
    (@ch >= 'a' && @ch <= 'z') ||
    (@ch >= 'A' && @ch <= 'Z') ||
    (@ch >= '0' && @ch <= '9'))) do
    key += @ch
  end

  return key
end

#inlineComment ⇒ Object 



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# File 'lib/json5/parser.rb', line 204

def inlineComment
  # Skip an inline comment, assuming this is one. The current character should
  # be the second / character in the # pair that begins this inline comment.
  # To finish the inline comment, we look for a newline or the end of the text.

  if (@ch != '/')
    error("Not an inline comment")
  end

  begin
    get_next
    if (@ch == "\n")
      get_next("\n")
      return
    end
  end while (@ch)
end

#number ⇒ Object 



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# File 'lib/json5/parser.rb', line 64

def number
  # Parse a number value.
  number = nil
  sign   = ''
  string = ''
  base   = 10

  if (@ch == '-' || @ch == '+')
    sign = string = @ch
    get_next(@ch)
  end

  # support for Infinity (could tweak to allow other words):
  if (@ch == 'I')
    number = word
    if (number.is_a?(Integer))
      error('Unexpected word for number')
    end
    return (sign == '-') ? -number : number
  end

  # support for NaN
  if (@ch == 'N' )
    number = word
    if (!isNaN(number))
      error('expected word to be NaN')
    end
    # ignore sign as -NaN also is NaN
    return number
  end

  if (@ch == '0')
    string += @ch
    get_next
    if (@ch == 'x' || @ch == 'X')
      string += @ch
      get_next
      base = 16
    elsif (@ch >= '0' && @ch <= '9')
      error('Octal literal')
    end
  end

  # https://github.com/aseemk/json5/issues/36
  if (base == 16 && !sign.empty?)
    error('Signed hexadecimal literal')
  end

  case (base)
  when 10
    while (@ch >= '0' && @ch <= '9' ) do
      string += @ch
      get_next
    end
    if (@ch == '.')
      string += '.'
      while (get_next && @ch >= '0' && @ch <= '9') do
        string += @ch
      end
    end
    if (@ch == 'e' || @ch == 'E')
      string += @ch
      get_next
      if (@ch == '-' || @ch == '+')
        string += @ch
        get_next
      end
      while (@ch >= '0' && @ch <= '9') do
        string += @ch
        get_next
      end
    end
  when 16
    while (@ch >= '0' && @ch <= '9' || @ch >= 'A' && @ch <= 'F' || @ch >= 'a' && @ch <= 'f') do
      string += @ch
      get_next
    end
  end

  string.chomp!('.')
  begin
    if string.include?('.') || string.include?('e-')
      Float(string).to_f
    else
      Float(string).to_i
    end
  rescue
    error("Bad number")
  end
end

#object ⇒ Object 



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# File 'lib/json5/parser.rb', line 359

def object
  # Parse an object value.
  key = nil
  object = {}

  if (@ch == '{')
    get_next('{')
    white
    while (@ch) do
      if (@ch == '}')
        get_next('}')
        return object;   # Potentially empty object
      end

      # Keys can be unquoted. If they are, they need to b
      # valid JS identifiers.
      if (@ch == '"' || @ch == "'")
        key = string
      else
        key = identifier
      end

      white
      get_next(':')

      if (object.has_key? key)
        error('Duplicate key "' + key + '"')
      end
      object[key] = value
      white
      # If there's no comma after this pair, this needs to b
      # the end of the object.
      if (@ch != ',')
        get_next('}')
        return object
      end
      get_next(',')
      white
    end
  end
  error("Bad object")
end

#run ⇒ Object 



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# File 'lib/json5/parser.rb', line 428

def run
  result = value
  white
  if (@ch)
    error("Syntax error")
  end

  # If there is a reviver function, we recursively walk the new structure,
  # passing each name/value pair to the reviver function for possible
  # transformation, starting with a temporary root object that holds the result
  # in an empty key. If there is not a reviver function, we simply return the
  # result.

  walk = ->(holder, key) do
    k, v, value = holder[key]
    if (value)
      value.each do |k|
        if (Object.prototype.hasOwnProperty.call(value, k))
          v = walk(value, k)
          if (v != undefined)
            value[k] = v
          else
            delete value[k]
          end
        end
      end
    end
    return @reviver.call(holder, key, value)
  end

  return @reviver ? walk.call({ '' => result }, '') : result
end

#string ⇒ Object 



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# File 'lib/json5/parser.rb', line 155

def string
# Parse a string value.

hex     = nil
i       = nil
string  = ''
delim   = nil      # double quote or single quote
uffff   = nil

# When parsing for string values, we must look for ' or " and \ characters

if (@ch == '"' || @ch == "'")
  delim = @ch
  while (get_next) do
    if (@ch == delim)
      get_next
      return string
    elsif (@ch == '\\')
      get_next
      if (@ch == 'u')
        uffff = 0
            # for (i = 0; i < 4; i += 1) do
            for i in 0...4 do
              hex = parseInt(get_next, 16)
              if (!isFinite(hex))
                break
              end
              uffff = uffff * 16 + hex
            end
            string += String.fromCharCode(uffff)
          elsif ESCAPEE.has_key? @ch
            string += ESCAPEE[@ch]
          else
            break
          end
        elsif (@ch == "\n")
        # unescaped newlines are invalid; see:
        # https://github.com/aseemk/json5/issues/24
        # TODO this feels special-cased; are there other
        # invalid unescaped chars?
        break
      else
        string += @ch
      end
    end
  end
  error("Bad string")
end

#value ⇒ Object 



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# File 'lib/json5/parser.rb', line 402

def value
  # Parse a JSON value. It could be an object, an array, a string, a number,
  # or a word.

  white
  case (@ch)
  when '{'
    return object
  when '['
    return array
  when '"',  "'"
    return string
  when '-', '+', '.'
    return number
  else
    return @ch >= '0' && @ch <= '9' ? number : word
  end
end

#white ⇒ Object 



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# File 'lib/json5/parser.rb', line 266

def white
  # Skip whitespace and comments.
  # Note that we're detecting comments by only a single / @character.
  # This works since regular expressions are not valid JSON(5), but this will
  # break if there are other valid values that begin with a / @character

  while (@ch) do
    if (@ch == '/')
      comment
    elsif (@ch <= ' ')
      get_next
    else
      return
    end
  end
end

#word ⇒ Object 



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# File 'lib/json5/parser.rb', line 283

def word
  # true, false, or null.

  case (@ch)
  when 't'
    get_next('t')
    get_next('r')
    get_next('u')
    get_next('e')
    return true
  when 'f'
    get_next('f')
    get_next('a')
    get_next('l')
    get_next('s')
    get_next('e')
    return false
  when 'n'
    get_next('n')
    get_next('u')
    get_next('l')
    get_next('l')
    return nil
  when 'I'
    get_next('I')
    get_next('n')
    get_next('f')
    get_next('i')
    get_next('n')
    get_next('i')
    get_next('t')
    get_next('y')
    return Float::INFINITY
  when 'N'
    get_next( 'N' )
    get_next( 'a' )
    get_next( 'N' )
    return Float::NAN
  end
  error("Unexpected '" + @ch + "'")
end