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Copy pathlexer.go
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221 lines (196 loc) · 3.36 KB
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package pattern
import (
"fmt"
"go/token"
"unicode"
"unicode/utf8"
)
type lexer struct {
f *token.File
input string
start int
pos int
width int
items chan item
}
type itemType int
const eof = -1
const (
itemError itemType = iota
itemLeftParen
itemRightParen
itemLeftBracket
itemRightBracket
itemTypeName
itemVariable
itemAt
itemColon
itemBlank
itemString
itemEOF
)
func (typ itemType) String() string {
switch typ {
case itemError:
return "ERROR"
case itemLeftParen:
return "("
case itemRightParen:
return ")"
case itemLeftBracket:
return "["
case itemRightBracket:
return "]"
case itemTypeName:
return "TYPE"
case itemVariable:
return "VAR"
case itemAt:
return "@"
case itemColon:
return ":"
case itemBlank:
return "_"
case itemString:
return "STRING"
case itemEOF:
return "EOF"
default:
return fmt.Sprintf("itemType(%d)", typ)
}
}
type item struct {
typ itemType
val string
pos int
}
type stateFn func(*lexer) stateFn
func (l *lexer) run() {
for state := lexStart; state != nil; {
state = state(l)
}
close(l.items)
}
func (l *lexer) emitValue(t itemType, value string) {
l.items <- item{t, value, l.start}
l.start = l.pos
}
func (l *lexer) emit(t itemType) {
l.items <- item{t, l.input[l.start:l.pos], l.start}
l.start = l.pos
}
func lexStart(l *lexer) stateFn {
switch r := l.next(); {
case r == eof:
l.emit(itemEOF)
return nil
case unicode.IsSpace(r):
l.ignore()
case r == '(':
l.emit(itemLeftParen)
case r == ')':
l.emit(itemRightParen)
case r == '[':
l.emit(itemLeftBracket)
case r == ']':
l.emit(itemRightBracket)
case r == '@':
l.emit(itemAt)
case r == ':':
l.emit(itemColon)
case r == '_':
l.emit(itemBlank)
case r == '"':
l.backup()
return lexString
case unicode.IsUpper(r):
l.backup()
return lexType
case unicode.IsLower(r):
l.backup()
return lexVariable
default:
return l.errorf("unexpected character %c", r)
}
return lexStart
}
func (l *lexer) next() (r rune) {
if l.pos >= len(l.input) {
l.width = 0
return eof
}
r, l.width = utf8.DecodeRuneInString(l.input[l.pos:])
if r == '\n' {
l.f.AddLine(l.pos)
}
l.pos += l.width
return r
}
func (l *lexer) ignore() {
l.start = l.pos
}
func (l *lexer) backup() {
l.pos -= l.width
}
func (l *lexer) errorf(format string, args ...interface{}) stateFn {
// TODO(dh): emit position information in errors
l.items <- item{
itemError,
fmt.Sprintf(format, args...),
l.start,
}
return nil
}
func isAlphaNumeric(r rune) bool {
return r >= '0' && r <= '9' ||
r >= 'a' && r <= 'z' ||
r >= 'A' && r <= 'Z'
}
func lexString(l *lexer) stateFn {
l.next() // skip quote
escape := false
var runes []rune
for {
switch r := l.next(); r {
case eof:
return l.errorf("unterminated string")
case '"':
if !escape {
l.emitValue(itemString, string(runes))
return lexStart
} else {
runes = append(runes, '"')
escape = false
}
case '\\':
if escape {
runes = append(runes, '\\')
escape = false
} else {
escape = true
}
default:
runes = append(runes, r)
}
}
}
func lexType(l *lexer) stateFn {
l.next()
for {
if !isAlphaNumeric(l.next()) {
l.backup()
l.emit(itemTypeName)
return lexStart
}
}
}
func lexVariable(l *lexer) stateFn {
l.next()
for {
if !isAlphaNumeric(l.next()) {
l.backup()
l.emit(itemVariable)
return lexStart
}
}
}