package toml import ( "fmt" "strings" "unicode/utf8" ) type itemType int const ( itemError itemType = iota itemNIL // used in the parser to indicate no type itemEOF itemText itemString itemRawString itemMultilineString itemRawMultilineString itemBool itemInteger itemFloat itemDatetime itemArray // the start of an array itemArrayEnd itemTableStart itemTableEnd itemArrayTableStart itemArrayTableEnd itemKeyStart itemCommentStart ) const ( eof = 0 tableStart = '[' tableEnd = ']' arrayTableStart = '[' arrayTableEnd = ']' tableSep = '.' keySep = '=' arrayStart = '[' arrayEnd = ']' arrayValTerm = ',' commentStart = '#' stringStart = '"' stringEnd = '"' rawStringStart = '\'' rawStringEnd = '\'' ) type stateFn func(lx *lexer) stateFn type lexer struct { input string start int pos int width int line int state stateFn items chan item // A stack of state functions used to maintain context. // The idea is to reuse parts of the state machine in various places. // For example, values can appear at the top level or within arbitrarily // nested arrays. The last state on the stack is used after a value has // been lexed. Similarly for comments. stack []stateFn } type item struct { typ itemType val string line int } func (lx *lexer) nextItem() item { for { select { case item := <-lx.items: return item default: lx.state = lx.state(lx) } } } func lex(input string) *lexer { lx := &lexer{ input: input + "\n", state: lexTop, line: 1, items: make(chan item, 10), stack: make([]stateFn, 0, 10), } return lx } func (lx *lexer) push(state stateFn) { lx.stack = append(lx.stack, state) } func (lx *lexer) pop() stateFn { if len(lx.stack) == 0 { return lx.errorf("BUG in lexer: no states to pop.") } last := lx.stack[len(lx.stack)-1] lx.stack = lx.stack[0 : len(lx.stack)-1] return last } func (lx *lexer) current() string { return lx.input[lx.start:lx.pos] } func (lx *lexer) emit(typ itemType) { lx.items <- item{typ, lx.current(), lx.line} lx.start = lx.pos } func (lx *lexer) emitTrim(typ itemType) { lx.items <- item{typ, strings.TrimSpace(lx.current()), lx.line} lx.start = lx.pos } func (lx *lexer) next() (r rune) { if lx.pos >= len(lx.input) { lx.width = 0 return eof } if lx.input[lx.pos] == '\n' { lx.line++ } r, lx.width = utf8.DecodeRuneInString(lx.input[lx.pos:]) lx.pos += lx.width return r } // ignore skips over the pending input before this point. func (lx *lexer) ignore() { lx.start = lx.pos } // backup steps back one rune. Can be called only once per call of next. func (lx *lexer) backup() { lx.pos -= lx.width if lx.pos < len(lx.input) && lx.input[lx.pos] == '\n' { lx.line-- } } // accept consumes the next rune if it's equal to `valid`. func (lx *lexer) accept(valid rune) bool { if lx.next() == valid { return true } lx.backup() return false } // peek returns but does not consume the next rune in the input. func (lx *lexer) peek() rune { r := lx.next() lx.backup() return r } // errorf stops all lexing by emitting an error and returning `nil`. // Note that any value that is a character is escaped if it's a special // character (new lines, tabs, etc.). func (lx *lexer) errorf(format string, values ...interface{}) stateFn { lx.items <- item{ itemError, fmt.Sprintf(format, values...), lx.line, } return nil } // lexTop consumes elements at the top level of TOML data. func lexTop(lx *lexer) stateFn { r := lx.next() if isWhitespace(r) || isNL(r) { return lexSkip(lx, lexTop) } switch r { case commentStart: lx.push(lexTop) return lexCommentStart case tableStart: return lexTableStart case eof: if lx.pos > lx.start { return lx.errorf("Unexpected EOF.") } lx.emit(itemEOF) return nil } // At this point, the only valid item can be a key, so we back up // and let the key lexer do the rest. lx.backup() lx.push(lexTopEnd) return lexKeyStart } // lexTopEnd is entered whenever a top-level item has been consumed. (A value // or a table.) It must see only whitespace, and will turn back to lexTop // upon a new line. If it sees EOF, it will quit the lexer successfully. func lexTopEnd(lx *lexer) stateFn { r := lx.next() switch { case r == commentStart: // a comment will read to a new line for us. lx.push(lexTop) return lexCommentStart case isWhitespace(r): return lexTopEnd case isNL(r): lx.ignore() return lexTop case r == eof: lx.ignore() return lexTop } return lx.errorf("Expected a top-level item to end with a new line, "+ "comment or EOF, but got %q instead.", r) } // lexTable lexes the beginning of a table. Namely, it makes sure that // it starts with a character other than '.' and ']'. // It assumes that '[' has already been consumed. // It also handles the case that this is an item in an array of tables. // e.g., '[[name]]'. func lexTableStart(lx *lexer) stateFn { if lx.peek() == arrayTableStart { lx.next() lx.emit(itemArrayTableStart) lx.push(lexArrayTableEnd) } else { lx.emit(itemTableStart) lx.push(lexTableEnd) } return lexTableNameStart } func lexTableEnd(lx *lexer) stateFn { lx.emit(itemTableEnd) return lexTopEnd } func lexArrayTableEnd(lx *lexer) stateFn { if r := lx.next(); r != arrayTableEnd { return lx.errorf("Expected end of table array name delimiter %q, "+ "but got %q instead.", arrayTableEnd, r) } lx.emit(itemArrayTableEnd) return lexTopEnd } func lexTableNameStart(lx *lexer) stateFn { switch r := lx.peek(); { case r == tableEnd || r == eof: return lx.errorf("Unexpected end of table name. (Table names cannot " + "be empty.)") case r == tableSep: return lx.errorf("Unexpected table separator. (Table names cannot " + "be empty.)") case r == stringStart || r == rawStringStart: lx.ignore() lx.push(lexTableNameEnd) return lexValue // reuse string lexing default: return lexBareTableName } } // lexTableName lexes the name of a table. It assumes that at least one // valid character for the table has already been read. func lexBareTableName(lx *lexer) stateFn { switch r := lx.next(); { case isBareKeyChar(r): return lexBareTableName case r == tableSep || r == tableEnd: lx.backup() lx.emitTrim(itemText) return lexTableNameEnd default: return lx.errorf("Bare keys cannot contain %q.", r) } } // lexTableNameEnd reads the end of a piece of a table name, optionally // consuming whitespace. func lexTableNameEnd(lx *lexer) stateFn { switch r := lx.next(); { case isWhitespace(r): return lexTableNameEnd case r == tableSep: lx.ignore() return lexTableNameStart case r == tableEnd: return lx.pop() default: return lx.errorf("Expected '.' or ']' to end table name, but got %q "+ "instead.", r) } } // lexKeyStart consumes a key name up until the first non-whitespace character. // lexKeyStart will ignore whitespace. func lexKeyStart(lx *lexer) stateFn { r := lx.peek() switch { case r == keySep: return lx.errorf("Unexpected key separator %q.", keySep) case isWhitespace(r) || isNL(r): lx.next() return lexSkip(lx, lexKeyStart) case r == stringStart || r == rawStringStart: lx.ignore() lx.emit(itemKeyStart) lx.push(lexKeyEnd) return lexValue // reuse string lexing default: lx.ignore() lx.emit(itemKeyStart) return lexBareKey } } // lexBareKey consumes the text of a bare key. Assumes that the first character // (which is not whitespace) has not yet been consumed. func lexBareKey(lx *lexer) stateFn { switch r := lx.next(); { case isBareKeyChar(r): return lexBareKey case isWhitespace(r): lx.emitTrim(itemText) return lexKeyEnd case r == keySep: lx.backup() lx.emitTrim(itemText) return lexKeyEnd default: return lx.errorf("Bare keys cannot contain %q.", r) } } // lexKeyEnd consumes the end of a key and trims whitespace (up to the key // separator). func lexKeyEnd(lx *lexer) stateFn { switch r := lx.next(); { case r == keySep: return lexSkip(lx, lexValue) case isWhitespace(r): return lexSkip(lx, lexKeyEnd) default: return lx.errorf("Expected key separator %q, but got %q instead.", keySep, r) } } // lexValue starts the consumption of a value anywhere a value is expected. // lexValue will ignore whitespace. // After a value is lexed, the last state on the next is popped and returned. func lexValue(lx *lexer) stateFn { // We allow whitespace to precede a value, but NOT new lines. // In array syntax, the array states are responsible for ignoring new // lines. r := lx.next() if isWhitespace(r) { return lexSkip(lx, lexValue) } switch { case r == arrayStart: lx.ignore() lx.emit(itemArray) return lexArrayValue case r == stringStart: if lx.accept(stringStart) { if lx.accept(stringStart) { lx.ignore() // Ignore """ return lexMultilineString } lx.backup() } lx.ignore() // ignore the '"' return lexString case r == rawStringStart: if lx.accept(rawStringStart) { if lx.accept(rawStringStart) { lx.ignore() // Ignore """ return lexMultilineRawString } lx.backup() } lx.ignore() // ignore the "'" return lexRawString case r == 't': return lexTrue case r == 'f': return lexFalse case r == '-': return lexNumberStart case isDigit(r): lx.backup() // avoid an extra state and use the same as above return lexNumberOrDateStart case r == '.': // special error case, be kind to users return lx.errorf("Floats must start with a digit, not '.'.") } return lx.errorf("Expected value but found %q instead.", r) } // lexArrayValue consumes one value in an array. It assumes that '[' or ',' // have already been consumed. All whitespace and new lines are ignored. func lexArrayValue(lx *lexer) stateFn { r := lx.next() switch { case isWhitespace(r) || isNL(r): return lexSkip(lx, lexArrayValue) case r == commentStart: lx.push(lexArrayValue) return lexCommentStart case r == arrayValTerm: return lx.errorf("Unexpected array value terminator %q.", arrayValTerm) case r == arrayEnd: return lexArrayEnd } lx.backup() lx.push(lexArrayValueEnd) return lexValue } // lexArrayValueEnd consumes the cruft between values of an array. Namely, // it ignores whitespace and expects either a ',' or a ']'. func lexArrayValueEnd(lx *lexer) stateFn { r := lx.next() switch { case isWhitespace(r) || isNL(r): return lexSkip(lx, lexArrayValueEnd) case r == commentStart: lx.push(lexArrayValueEnd) return lexCommentStart case r == arrayValTerm: lx.ignore() return lexArrayValue // move on to the next value case r == arrayEnd: return lexArrayEnd } return lx.errorf("Expected an array value terminator %q or an array "+ "terminator %q, but got %q instead.", arrayValTerm, arrayEnd, r) } // lexArrayEnd finishes the lexing of an array. It assumes that a ']' has // just been consumed. func lexArrayEnd(lx *lexer) stateFn { lx.ignore() lx.emit(itemArrayEnd) return lx.pop() } // lexString consumes the inner contents of a string. It assumes that the // beginning '"' has already been consumed and ignored. func lexString(lx *lexer) stateFn { r := lx.next() switch { case isNL(r): return lx.errorf("Strings cannot contain new lines.") case r == '\\': lx.push(lexString) return lexStringEscape case r == stringEnd: lx.backup() lx.emit(itemString) lx.next() lx.ignore() return lx.pop() } return lexString } // lexMultilineString consumes the inner contents of a string. It assumes that // the beginning '"""' has already been consumed and ignored. func lexMultilineString(lx *lexer) stateFn { r := lx.next() switch { case r == '\\': return lexMultilineStringEscape case r == stringEnd: if lx.accept(stringEnd) { if lx.accept(stringEnd) { lx.backup() lx.backup() lx.backup() lx.emit(itemMultilineString) lx.next() lx.next() lx.next() lx.ignore() return lx.pop() } lx.backup() } } return lexMultilineString } // lexRawString consumes a raw string. Nothing can be escaped in such a string. // It assumes that the beginning "'" has already been consumed and ignored. func lexRawString(lx *lexer) stateFn { r := lx.next() switch { case isNL(r): return lx.errorf("Strings cannot contain new lines.") case r == rawStringEnd: lx.backup() lx.emit(itemRawString) lx.next() lx.ignore() return lx.pop() } return lexRawString } // lexMultilineRawString consumes a raw string. Nothing can be escaped in such // a string. It assumes that the beginning "'" has already been consumed and // ignored. func lexMultilineRawString(lx *lexer) stateFn { r := lx.next() switch { case r == rawStringEnd: if lx.accept(rawStringEnd) { if lx.accept(rawStringEnd) { lx.backup() lx.backup() lx.backup() lx.emit(itemRawMultilineString) lx.next() lx.next() lx.next() lx.ignore() return lx.pop() } lx.backup() } } return lexMultilineRawString } // lexMultilineStringEscape consumes an escaped character. It assumes that the // preceding '\\' has already been consumed. func lexMultilineStringEscape(lx *lexer) stateFn { // Handle the special case first: if isNL(lx.next()) { return lexMultilineString } else { lx.backup() lx.push(lexMultilineString) return lexStringEscape(lx) } } func lexStringEscape(lx *lexer) stateFn { r := lx.next() switch r { case 'b': fallthrough case 't': fallthrough case 'n': fallthrough case 'f': fallthrough case 'r': fallthrough case '"': fallthrough case '\\': return lx.pop() case 'u': return lexShortUnicodeEscape case 'U': return lexLongUnicodeEscape } return lx.errorf("Invalid escape character %q. Only the following "+ "escape characters are allowed: "+ "\\b, \\t, \\n, \\f, \\r, \\\", \\/, \\\\, "+ "\\uXXXX and \\UXXXXXXXX.", r) } func lexShortUnicodeEscape(lx *lexer) stateFn { var r rune for i := 0; i < 4; i++ { r = lx.next() if !isHexadecimal(r) { return lx.errorf("Expected four hexadecimal digits after '\\u', "+ "but got '%s' instead.", lx.current()) } } return lx.pop() } func lexLongUnicodeEscape(lx *lexer) stateFn { var r rune for i := 0; i < 8; i++ { r = lx.next() if !isHexadecimal(r) { return lx.errorf("Expected eight hexadecimal digits after '\\U', "+ "but got '%s' instead.", lx.current()) } } return lx.pop() } // lexNumberOrDateStart consumes either a (positive) integer, float or // datetime. It assumes that NO negative sign has been consumed. func lexNumberOrDateStart(lx *lexer) stateFn { r := lx.next() if !isDigit(r) { if r == '.' { return lx.errorf("Floats must start with a digit, not '.'.") } else { return lx.errorf("Expected a digit but got %q.", r) } } return lexNumberOrDate } // lexNumberOrDate consumes either a (positive) integer, float or datetime. func lexNumberOrDate(lx *lexer) stateFn { r := lx.next() switch { case r == '-': if lx.pos-lx.start != 5 { return lx.errorf("All ISO8601 dates must be in full Zulu form.") } return lexDateAfterYear case isDigit(r): return lexNumberOrDate case r == '.': return lexFloatStart } lx.backup() lx.emit(itemInteger) return lx.pop() } // lexDateAfterYear consumes a full Zulu Datetime in ISO8601 format. // It assumes that "YYYY-" has already been consumed. func lexDateAfterYear(lx *lexer) stateFn { formats := []rune{ // digits are '0'. // everything else is direct equality. '0', '0', '-', '0', '0', 'T', '0', '0', ':', '0', '0', ':', '0', '0', 'Z', } for _, f := range formats { r := lx.next() if f == '0' { if !isDigit(r) { return lx.errorf("Expected digit in ISO8601 datetime, "+ "but found %q instead.", r) } } else if f != r { return lx.errorf("Expected %q in ISO8601 datetime, "+ "but found %q instead.", f, r) } } lx.emit(itemDatetime) return lx.pop() } // lexNumberStart consumes either an integer or a float. It assumes that // a negative sign has already been read, but that *no* digits have been // consumed. lexNumberStart will move to the appropriate integer or float // states. func lexNumberStart(lx *lexer) stateFn { // we MUST see a digit. Even floats have to start with a digit. r := lx.next() if !isDigit(r) { if r == '.' { return lx.errorf("Floats must start with a digit, not '.'.") } else { return lx.errorf("Expected a digit but got %q.", r) } } return lexNumber } // lexNumber consumes an integer or a float after seeing the first digit. func lexNumber(lx *lexer) stateFn { r := lx.next() switch { case isDigit(r): return lexNumber case r == '.': return lexFloatStart } lx.backup() lx.emit(itemInteger) return lx.pop() } // lexFloatStart starts the consumption of digits of a float after a '.'. // Namely, at least one digit is required. func lexFloatStart(lx *lexer) stateFn { r := lx.next() if !isDigit(r) { return lx.errorf("Floats must have a digit after the '.', but got "+ "%q instead.", r) } return lexFloat } // lexFloat consumes the digits of a float after a '.'. // Assumes that one digit has been consumed after a '.' already. func lexFloat(lx *lexer) stateFn { r := lx.next() if isDigit(r) { return lexFloat } lx.backup() lx.emit(itemFloat) return lx.pop() } // lexConst consumes the s[1:] in s. It assumes that s[0] has already been // consumed. func lexConst(lx *lexer, s string) stateFn { for i := range s[1:] { if r := lx.next(); r != rune(s[i+1]) { return lx.errorf("Expected %q, but found %q instead.", s[:i+1], s[:i]+string(r)) } } return nil } // lexTrue consumes the "rue" in "true". It assumes that 't' has already // been consumed. func lexTrue(lx *lexer) stateFn { if fn := lexConst(lx, "true"); fn != nil { return fn } lx.emit(itemBool) return lx.pop() } // lexFalse consumes the "alse" in "false". It assumes that 'f' has already // been consumed. func lexFalse(lx *lexer) stateFn { if fn := lexConst(lx, "false"); fn != nil { return fn } lx.emit(itemBool) return lx.pop() } // lexCommentStart begins the lexing of a comment. It will emit // itemCommentStart and consume no characters, passing control to lexComment. func lexCommentStart(lx *lexer) stateFn { lx.ignore() lx.emit(itemCommentStart) return lexComment } // lexComment lexes an entire comment. It assumes that '#' has been consumed. // It will consume *up to* the first new line character, and pass control // back to the last state on the stack. func lexComment(lx *lexer) stateFn { r := lx.peek() if isNL(r) || r == eof { lx.emit(itemText) return lx.pop() } lx.next() return lexComment } // lexSkip ignores all slurped input and moves on to the next state. func lexSkip(lx *lexer, nextState stateFn) stateFn { return func(lx *lexer) stateFn { lx.ignore() return nextState } } // isWhitespace returns true if `r` is a whitespace character according // to the spec. func isWhitespace(r rune) bool { return r == '\t' || r == ' ' } func isNL(r rune) bool { return r == '\n' || r == '\r' } func isDigit(r rune) bool { return r >= '0' && r <= '9' } func isHexadecimal(r rune) bool { return (r >= '0' && r <= '9') || (r >= 'a' && r <= 'f') || (r >= 'A' && r <= 'F') } func isBareKeyChar(r rune) bool { return (r >= 'A' && r <= 'Z') || (r >= 'a' && r <= 'z') || (r >= '0' && r <= '9') || r == '_' || r == '-' } func (itype itemType) String() string { switch itype { case itemError: return "Error" case itemNIL: return "NIL" case itemEOF: return "EOF" case itemText: return "Text" case itemString: return "String" case itemRawString: return "String" case itemMultilineString: return "String" case itemRawMultilineString: return "String" case itemBool: return "Bool" case itemInteger: return "Integer" case itemFloat: return "Float" case itemDatetime: return "DateTime" case itemTableStart: return "TableStart" case itemTableEnd: return "TableEnd" case itemKeyStart: return "KeyStart" case itemArray: return "Array" case itemArrayEnd: return "ArrayEnd" case itemCommentStart: return "CommentStart" } panic(fmt.Sprintf("BUG: Unknown type '%d'.", int(itype))) } func (item item) String() string { return fmt.Sprintf("(%s, %s)", item.typ.String(), item.val) }