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  1. class MyJSONError < StandardError; end
  2.  
  3. # - - - - - - - - - - -
  4.  
  5. def is_space_char(text, ptr = 0)
  6.     !!(text[ptr]=~/^\s/)
  7. end
  8.  
  9. def is_digit_char(text, ptr = 0)
  10.     !!(text[ptr]=~/^[0-9]/)
  11. end
  12.  
  13. # - - - - - - - - - - -
  14.  
  15. def json_parse_true(text, ptr = 0)
  16.     if text[ptr..(ptr+3)] == 'true'
  17.         return [true, ptr+4]
  18.     else
  19.         raise MyJSONError.new("invalid keyword at #{ptr}")
  20.     end
  21. end
  22.  
  23. def json_parse_false(text, ptr = 0)
  24.     if text[ptr..(ptr+4)] == 'false'
  25.         return [false, ptr+5]
  26.     else
  27.         raise MyJSONError.new("invalid keyword at #{ptr}")
  28.     end
  29. end
  30.  
  31. def json_parse_null(text, ptr = 0)
  32.     if text[ptr..(ptr+3)] == 'null'
  33.         return [nil, ptr+4]
  34.     else
  35.         raise MyJSONError.new("invalid keyword at #{ptr}")
  36.     end
  37. end
  38.  
  39. def json_parse_string(text, ptr = 0)
  40.     abort "json_parse_string" if text[ptr] != '"'
  41.     ptr += 1
  42.     state = :string
  43.     str = ""
  44.     hex4 = ""
  45.     while text[ptr]
  46.         if state == :string
  47.             if text[ptr] == '"'
  48.                 return [str, ptr+1]
  49.             elsif text[ptr] == "\\" 
  50.                 state = :escape
  51.                 ptr += 1
  52.             else
  53.                 str << text[ptr]
  54.                 ptr += 1
  55.             end
  56.         elsif state == :escape
  57.             if text[ptr] == '"'
  58.                 str << '"'; state = :string; ptr += 1
  59.             elsif text[ptr] == "\\"
  60.                 str << "\\"; state = :string; ptr += 1
  61.             elsif text[ptr] == "/"
  62.                 str << "/"; state = :string; ptr += 1
  63.             elsif text[ptr] == "b"
  64.                 str << "\b"; state = :string; ptr += 1
  65.             elsif text[ptr] == "f"
  66.                 str << "\f"; state = :string; ptr += 1
  67.             elsif text[ptr] == "n"
  68.                 str << "\n"; state = :string; ptr += 1
  69.             elsif text[ptr] == "r"
  70.                 str << "\r"; state = :string; ptr += 1
  71.             elsif text[ptr] == "t"
  72.                 str << "\t"; state = :string; ptr += 1
  73.             elsif text[ptr] == "u"
  74.                 hex4 = ""; state = :hexadec; ptr += 1
  75.             end
  76.         elsif state == :hexadec
  77.             hex4 << text[ptr]
  78.             if hex4.size == 4
  79.                 str << [hex4.to_i(16)].pack("U")
  80.                 state = :string
  81.             end
  82.             ptr += 1
  83.         end
  84.     end
  85.     raise MyJSONError.new("invalid 4 hexadecimal digits at #{ptr}") if state == :hexadec
  86.     raise MyJSONError.new("not found '\"' at #{ptr}")
  87.     # メモ：シングルクオートはエスケープしないが，
  88.     #       エディタがエスケープするので'\'ではなく"\\"に...
  89. end
  90.  
  91. def json_parse_number(text, ptr = 0)
  92.     sgn = 1
  93.     val = 0
  94.     if text[ptr] == '-'
  95.         sgn = -1
  96.         ptr += 1
  97.     end
  98.     while is_digit_char(text, ptr)
  99.         val = val*10 + text[ptr].to_i
  100.         ptr += 1
  101.     end
  102.     return [sgn*val, ptr]
  103. end
  104.  
  105. def json_parse_array(text, ptr = 0)
  106.     abort "json_parse_array" if text[ptr] != '['
  107.     ptr += 1
  108.     arr = []
  109.     state = :initial
  110.     while text[ptr]
  111.         if is_space_char(text, ptr)
  112.             ptr += 1
  113.         elsif text[ptr] == ']'
  114.             raise MyJSONError.new("invalid ',' at #{ptr}") if state != :initial && state != :value
  115.             return [arr, ptr+1]
  116.         elsif text[ptr] == ','
  117.             raise MyJSONError.new("invalid ',' at #{ptr}") if state != :value
  118.             state = :comma
  119.             ptr += 1
  120.         else
  121.             v, ptr = json_parse(text, ptr)
  122.             arr << v
  123.             state = :value
  124.         end
  125.     end
  126.     raise MyJSONError.new("not found ']' at #{ptr}")
  127. end
  128.  
  129. def json_parse_object(text, ptr = 0)
  130.     abort "json_parse_object" if text[ptr] != '{'
  131.     ptr += 1
  132.     hash = {}
  133.     key = nil
  134.     state = :initial
  135.     while text[ptr]
  136.         if is_space_char(text, ptr)
  137.             ptr += 1
  138.         elsif text[ptr] == '}'
  139.             raise MyJSONError.new("invalid ',' at #{ptr}") if state != :initial && state != :value
  140.             return [hash, ptr+1]
  141.         elsif text[ptr] == ','
  142.             raise MyJSONError.new("invalid ',' at #{ptr}") if state != :value
  143.             state = :comma
  144.             ptr += 1
  145.         elsif text[ptr] == ':'
  146.             raise MyJSONError.new("invalid ':' at #{ptr}") if state != :key
  147.             state = :colon
  148.             ptr += 1
  149.         elsif text[ptr] == '"' && (state == :comma || state == :initial)
  150.             key, ptr = json_parse(text, ptr)
  151.             state = :key
  152.         else
  153.             val, ptr = json_parse(text, ptr)
  154.             hash[key] = val
  155.             state = :value
  156.         end
  157.     end
  158.     raise MyJSONError.new("not found '}' at #{ptr}")
  159. end
  160.  
  161. def json_parse(text, ptr = 0)
  162.     while text[ptr]
  163.         if is_space_char(text, ptr)
  164.             ptr += 1
  165.         elsif text[ptr] == 't'
  166.             return json_parse_true(text, ptr)
  167.         elsif text[ptr] == 'f'
  168.             return json_parse_false(text, ptr)
  169.         elsif text[ptr] == 'n'
  170.             return json_parse_null(text, ptr)
  171.         elsif text[ptr] == '"'
  172.             return json_parse_string(text, ptr)
  173.         elsif text[ptr] == '-'
  174.             return json_parse_number(text, ptr)
  175.         elsif is_digit_char(text, ptr)
  176.             return json_parse_number(text, ptr)
  177.         elsif text[ptr] == '['
  178.             return json_parse_array(text, ptr)
  179.         elsif text[ptr] == '{'
  180.             return json_parse_object(text, ptr)
  181.         else
  182.             raise MyJSONError.new("invalid at #{ptr}")
  183.         end
  184.     end
  185. end
  186.  
  187.  
  188.  
  189. # - - - - - - - - - - -
  190.  
  191. def test_sub
  192.     abort "is_space_char" unless is_space_char(" ") == true
  193.     abort "is_space_char" unless is_space_char("t") == false
  194. end
  195. test_sub
  196.  
  197. def test_main
  198.     abort "failed: true" unless json_parse('true')[0] == true
  199.     abort "failed: false" unless json_parse('false')[0] == false
  200.     abort "failed: null" unless json_parse('null')[0] == nil
  201.     abort "failed: string" unless json_parse('"str"')[0] == 'str'
  202.     abort "failed: escape" unless json_parse('"foo\nbar"')[0] == "foo\nbar"
  203.     abort "failed: hexadecimal" unless json_parse('"\u7D05\u7389"')[0] == "紅玉"
  204.     abort "failed: number" unless json_parse('1234567890')[0] == 1234567890
  205.     abort "failed: negative number" unless json_parse('-1')[0] == -1
  206.     abort "failed: array 1" unless json_parse('[1,2,3]')[0] == [1,2,3]
  207.     abort "failed: array 2" unless json_parse('[1,"foo",null]')[0] == [1,'foo',nil]
  208.     abort "failed: matrix" unless json_parse('[[1,2],[3,4],[5,6]]')[0] == [[1,2],[3,4],[5,6]]
  209.     abort "failed: russian array" unless json_parse('[0,[1,[2,[3,[4]]]]]')[0] == [0,[1,[2,[3,[4]]]]]
  210.     abort "failed: object 1" unless json_parse('{"key":"val"}')[0] == {"key"=>"val"}
  211.     abort "failed: object 2" unless json_parse('{"a":null,"b":[1,2],"c":true,"d":{"x":"\t"}}')[0] == {"a"=>nil,"b"=>[1,2],"c"=>true,"d"=>{"x"=>"\t"}}
  212. end
  213. test_main
Success #stdin #stdout 0.01s 5936KB
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https://ideone.com/q9bdiG
language:
Ruby (ruby 2.5.5)
created:
5 years ago
visibility:
public

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