parsejson

This module implements a json parser. It is used and exported by the json standard library module, but can also be used in its own right.

Imports

strutils, lexbase, streams, unicode

Types

JsonEventKind = enum
  jsonError,                ## an error occurred during parsing
  jsonEof,                  ## end of file reached
  jsonString,               ## a string literal
  jsonInt,                  ## an integer literal
  jsonFloat,                ## a float literal
  jsonTrue,                 ## the value ``true``
  jsonFalse,                ## the value ``false``
  jsonNull,                 ## the value ``null``
  jsonObjectStart,          ## start of an object: the ``{`` token
  jsonObjectEnd,            ## end of an object: the ``}`` token
  jsonArrayStart,           ## start of an array: the ``[`` token
  jsonArrayEnd               ## end of an array: the ``]`` token

enumeration of all events that may occur when parsing Source Edit

TokKind = enum
  tkError, tkEof, tkString, tkInt, tkFloat, tkTrue, tkFalse, tkNull, tkCurlyLe,
  tkCurlyRi, tkBracketLe, tkBracketRi, tkColon, tkComma

Source Edit

JsonError = enum
  errNone,                  ## no error
  errInvalidToken,          ## invalid token
  errStringExpected,        ## string expected
  errColonExpected,         ## ``:`` expected
  errCommaExpected,         ## ``,`` expected
  errBracketRiExpected,     ## ``]`` expected
  errCurlyRiExpected,       ## ``}`` expected
  errQuoteExpected,         ## ``"`` or ``'`` expected
  errEOC_Expected,          ## ``*/`` expected
  errEofExpected,           ## EOF expected
  errExprExpected            ## expr expected

enumeration that lists all errors that can occur Source Edit

JsonParser = object of BaseLexer
  a*: string
  tok*: TokKind
  kind: JsonEventKind
  err: JsonError
  state: seq[ParserState]
  filename: string
  rawStringLiterals: bool

the parser object. Source Edit

JsonKindError = object of ValueError

raised by the to macro if the JSON kind is incorrect. Source Edit

JsonParsingError = object of ValueError

is raised for a JSON error Source Edit

Consts

errorMessages: array[JsonError, string] = ["no error", "invalid token",
    "string expected", "\':\' expected", "\',\' expected", "\']\' expected",
    "\'}\' expected", "\'\"\' or \"\'\" expected", "\'*/\' expected",
    "EOF expected", "expression expected"]

Source Edit

Procs

proc open(my: var JsonParser; input: Stream; filename: string;
          rawStringLiterals = false) {...}{.raises: [IOError, OSError],
                                       tags: [ReadIOEffect].}

initializes the parser with an input stream. Filename is only used for nice error messages. If rawStringLiterals is true, string literals are kept with their surrounding quotes and escape sequences in them are left untouched too. Source Edit

proc close(my: var JsonParser) {...}{.inline, raises: [Exception, IOError, OSError],
                                 tags: [WriteIOEffect].}

closes the parser my and its associated input stream. Source Edit

proc str(my: JsonParser): string {...}{.inline, raises: [], tags: [].}

returns the character data for the events: jsonInt, jsonFloat, jsonString Source Edit

proc getInt(my: JsonParser): BiggestInt {...}{.inline, raises: [ValueError], tags: [].}

returns the number for the event: jsonInt Source Edit

proc getFloat(my: JsonParser): float {...}{.inline, raises: [ValueError], tags: [].}

returns the number for the event: jsonFloat Source Edit

proc kind(my: JsonParser): JsonEventKind {...}{.inline, raises: [], tags: [].}

returns the current event type for the JSON parser Source Edit

proc getColumn(my: JsonParser): int {...}{.inline, raises: [], tags: [].}

get the current column the parser has arrived at. Source Edit

proc getLine(my: JsonParser): int {...}{.inline, raises: [], tags: [].}

get the current line the parser has arrived at. Source Edit

proc getFilename(my: JsonParser): string {...}{.inline, raises: [], tags: [].}

get the filename of the file that the parser processes. Source Edit

proc errorMsg(my: JsonParser): string {...}{.raises: [ValueError], tags: [].}

returns a helpful error message for the event jsonError Source Edit

proc errorMsgExpected(my: JsonParser; e: string): string {...}{.raises: [ValueError],
    tags: [].}

returns an error message "e expected" in the same format as the other error messages Source Edit

proc parseEscapedUTF16(buf: cstring; pos: var int): int {...}{.raises: [], tags: [].}

Source Edit

proc getTok(my: var JsonParser): TokKind {...}{.raises: [IOError, OSError],
    tags: [ReadIOEffect].}

Source Edit

proc next(my: var JsonParser) {...}{.raises: [IOError, OSError], tags: [ReadIOEffect].}

retrieves the first/next event. This controls the parser. Source Edit

proc raiseParseErr(p: JsonParser; msg: string) {...}{.noinline, noreturn,
    raises: [JsonParsingError, ValueError], tags: [].}

raises an EJsonParsingError exception. Source Edit

proc eat(p: var JsonParser; tok: TokKind) {...}{.
    raises: [IOError, OSError, JsonParsingError, ValueError],
    tags: [ReadIOEffect].}

Source Edit