gh-ost/vendor/github.com/BurntSushi/toml/lex.go

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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
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 = '"'
)
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 lx.next() {
case tableEnd, eof:
return lx.errorf("Unexpected end of table. (Tables cannot " +
"be empty.)")
case tableSep:
return lx.errorf("Unexpected table separator. (Tables cannot " +
"be empty.)")
}
return lexTableName
}
// lexTableName lexes the name of a table. It assumes that at least one
// valid character for the table has already been read.
func lexTableName(lx *lexer) stateFn {
switch lx.peek() {
case eof:
return lx.errorf("Unexpected end of table name %q.", lx.current())
case tableStart:
return lx.errorf("Table names cannot contain %q or %q.",
tableStart, tableEnd)
case tableEnd:
lx.emit(itemText)
lx.next()
return lx.pop()
case tableSep:
lx.emit(itemText)
lx.next()
lx.ignore()
return lexTableNameStart
}
lx.next()
return lexTableName
}
// 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)
}
lx.ignore()
lx.emit(itemKeyStart)
lx.next()
return lexKey
}
// lexKey consumes the text of a key. Assumes that the first character (which
// is not whitespace) has already been consumed.
func lexKey(lx *lexer) stateFn {
r := lx.peek()
// Keys cannot contain a '#' character.
if r == commentStart {
return lx.errorf("Key cannot contain a '#' character.")
}
// XXX: Possible divergence from spec?
// "Keys start with the first non-whitespace character and end with the
// last non-whitespace character before the equals sign."
// Note here that whitespace is either a tab or a space.
// But we'll call it quits if we see a new line too.
if isNL(r) {
lx.emitTrim(itemText)
return lexKeyEnd
}
// Let's also call it quits if we see an equals sign.
if r == keySep {
lx.emitTrim(itemText)
return lexKeyEnd
}
lx.next()
return lexKey
}
// lexKeyEnd consumes the end of a key (up to the key separator).
// Assumes that any whitespace after a key has been consumed.
func lexKeyEnd(lx *lexer) stateFn {
r := lx.next()
if r == keySep {
return lexSkip(lx, lexValue)
}
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:
lx.ignore() // ignore the '"'
return lexString
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 == '\\':
return lexStringEscape
case r == stringEnd:
lx.backup()
lx.emit(itemString)
lx.next()
lx.ignore()
return lx.pop()
}
return lexString
}
// lexStringEscape consumes an escaped character. It assumes that the preceding
// '\\' has already been consumed.
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 '/':
fallthrough
case '\\':
return lexString
case 'u':
return lexStringUnicode
}
return lx.errorf("Invalid escape character %q. Only the following "+
"escape characters are allowed: "+
"\\b, \\t, \\n, \\f, \\r, \\\", \\/, \\\\, and \\uXXXX.", r)
}
// lexStringBinary consumes two hexadecimal digits following '\x'. It assumes
// that the '\x' has already been consumed.
func lexStringUnicode(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 '\\x', "+
"but got '%s' instead.", lx.current())
}
}
return lexString
}
// 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 (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 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)
}