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tokenizer.go
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tokenizer.go
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package main
import (
"bufio"
"fmt"
"io"
"unicode"
)
type Tokenizer struct {
in *bufio.Reader
Line int
}
func NewTokenizer(in io.Reader) *Tokenizer {
return &Tokenizer{
in: bufio.NewReader(in),
Line: 1,
}
}
func (t *Tokenizer) Next() (string, error) {
if err := t.eatWhitespace(); err != nil {
return "", err
}
token, err := t.nextToken()
if err != nil {
return "", err
}
if token == "<<" {
// Multiline literal
if err := t.eatWhitespace(); err != nil {
return "", err
}
delimToken, err := t.nextToken()
if err != nil {
return "", err
}
// Eat all whitespace up to a newline.
for {
r, _, err := t.in.ReadRune()
if err != nil {
return "", err
}
if r == '\n' {
t.Line++
break
}
if !unicode.IsSpace(r) {
return "", fmt.Errorf("line %d: garbage after multiline delimiter", t.Line)
}
}
// We only match the deliminator at the beginning of a line.
delim := []rune("--" + delimToken)
var literal []rune
matched := 0
for {
r, _, err := t.in.ReadRune()
if err != nil {
return "", err
}
if r == '\n' {
t.Line++
}
literal = append(literal, r)
if r == delim[matched] {
matched++
if matched == len(delim) {
return string(literal[:len(literal)-len(delim)]), nil
}
} else {
matched = 0
if r == delim[matched] {
matched++
}
}
}
}
return token, nil
}
func (t *Tokenizer) eatWhitespace() error {
var isComment bool
for {
r, _, err := t.in.ReadRune()
if err != nil {
return err
}
switch {
case r == '\n':
t.Line++
isComment = false
case isComment:
continue
case unicode.IsSpace(r):
continue
case r == '#':
isComment = true
default:
t.in.UnreadRune()
return nil
}
}
panic("unreachable")
}
func (t *Tokenizer) nextToken() (string, error) {
var token []rune
var firstIsSpecial, isQuote bool
for {
r, _, err := t.in.ReadRune()
if err == io.EOF && len(token) != 0 {
if isQuote {
return "", fmt.Errorf("line %d: hit EOF in quoted string", t.Line)
}
return string(token), nil
}
if err != nil {
return "", err
}
isSpecial := !unicode.IsDigit(r) && !unicode.IsLetter(r)
isWhitespace := unicode.IsSpace(r)
if len(token) == 0 {
if isWhitespace && !isQuote {
panic("impossible")
}
firstIsSpecial = isSpecial
if r == '"' {
if isQuote {
// Empty quotes
return "", nil
}
isQuote = true
continue
}
}
if isQuote {
if r == '"' {
return string(token), nil
}
if r == '\n' {
return "", fmt.Errorf("line %d: new line in quoted string", t.Line)
}
if r == '\\' {
r, _, err = t.in.ReadRune()
if err != nil {
return "", err
}
}
} else if isWhitespace || firstIsSpecial != isSpecial {
t.in.UnreadRune()
return string(token), nil
}
token = append(token, r)
}
panic("unreachable")
}