457 lines
10 KiB
Go
457 lines
10 KiB
Go
/*
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Copyright 2012 Google Inc. All Rights Reserved.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package shlex
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/*
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Package shlex implements a simple lexer which splits input in to tokens using
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shell-style rules for quoting and commenting.
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*/
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import (
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"bufio"
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"errors"
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"fmt"
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"io"
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"strings"
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)
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/*
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A TokenType is a top-level token; a word, space, comment, unknown.
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*/
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type TokenType int
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/*
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A RuneTokenType is the type of a UTF-8 character; a character, quote, space, escape.
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*/
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type RuneTokenType int
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type lexerState int
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type Token struct {
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tokenType TokenType
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value string
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}
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/*
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Two tokens are equal if both their types and values are equal. A nil token can
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never equal another token.
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*/
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func (a *Token) Equal(b *Token) bool {
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if a == nil || b == nil {
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return false
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}
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if a.tokenType != b.tokenType {
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return false
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}
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return a.value == b.value
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}
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const (
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RUNE_CHAR string = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789._-,/@$*()+=><:;&^%~|!?[]{}"
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RUNE_SPACE string = " \t\r\n"
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RUNE_ESCAPING_QUOTE string = "\""
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RUNE_NONESCAPING_QUOTE string = "'"
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RUNE_ESCAPE = "\\"
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RUNE_COMMENT = "#"
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RUNETOKEN_UNKNOWN RuneTokenType = 0
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RUNETOKEN_CHAR RuneTokenType = 1
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RUNETOKEN_SPACE RuneTokenType = 2
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RUNETOKEN_ESCAPING_QUOTE RuneTokenType = 3
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RUNETOKEN_NONESCAPING_QUOTE RuneTokenType = 4
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RUNETOKEN_ESCAPE RuneTokenType = 5
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RUNETOKEN_COMMENT RuneTokenType = 6
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RUNETOKEN_EOF RuneTokenType = 7
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TOKEN_UNKNOWN TokenType = 0
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TOKEN_WORD TokenType = 1
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TOKEN_SPACE TokenType = 2
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TOKEN_COMMENT TokenType = 3
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STATE_START lexerState = 0
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STATE_INWORD lexerState = 1
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STATE_ESCAPING lexerState = 2
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STATE_ESCAPING_QUOTED lexerState = 3
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STATE_QUOTED_ESCAPING lexerState = 4
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STATE_QUOTED lexerState = 5
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STATE_COMMENT lexerState = 6
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INITIAL_TOKEN_CAPACITY int = 100
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)
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/*
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A type for classifying characters. This allows for different sorts of
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classifiers - those accepting extended non-ascii chars, or strict posix
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compatibility, for example.
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*/
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type TokenClassifier struct {
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typeMap map[int32]RuneTokenType
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}
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func addRuneClass(typeMap *map[int32]RuneTokenType, runes string, tokenType RuneTokenType) {
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for _, rune := range runes {
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(*typeMap)[int32(rune)] = tokenType
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}
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}
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/*
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Create a new classifier for basic ASCII characters.
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*/
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func NewDefaultClassifier() *TokenClassifier {
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typeMap := map[int32]RuneTokenType{}
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addRuneClass(&typeMap, RUNE_CHAR, RUNETOKEN_CHAR)
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addRuneClass(&typeMap, RUNE_SPACE, RUNETOKEN_SPACE)
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addRuneClass(&typeMap, RUNE_ESCAPING_QUOTE, RUNETOKEN_ESCAPING_QUOTE)
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addRuneClass(&typeMap, RUNE_NONESCAPING_QUOTE, RUNETOKEN_NONESCAPING_QUOTE)
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addRuneClass(&typeMap, RUNE_ESCAPE, RUNETOKEN_ESCAPE)
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addRuneClass(&typeMap, RUNE_COMMENT, RUNETOKEN_COMMENT)
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return &TokenClassifier{
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typeMap: typeMap}
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}
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func (classifier *TokenClassifier) ClassifyRune(rune int32) RuneTokenType {
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return classifier.typeMap[rune]
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}
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/*
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A type for turning an input stream in to a sequence of strings. Whitespace and
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comments are skipped.
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*/
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type Lexer struct {
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tokenizer *Tokenizer
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}
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/*
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Create a new lexer.
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*/
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func NewLexer(r io.Reader) (*Lexer, error) {
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tokenizer, err := NewTokenizer(r)
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if err != nil {
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return nil, err
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}
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lexer := &Lexer{tokenizer: tokenizer}
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return lexer, nil
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}
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/*
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Return the next word, and an error value. If there are no more words, the error
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will be io.EOF.
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*/
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func (l *Lexer) NextWord() (string, error) {
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var token *Token
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var err error
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for {
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token, err = l.tokenizer.NextToken()
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if err != nil {
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return "", err
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}
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switch token.tokenType {
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case TOKEN_WORD:
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{
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return token.value, nil
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}
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case TOKEN_COMMENT:
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{
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// skip comments
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}
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default:
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{
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panic(fmt.Sprintf("Unknown token type: %v", token.tokenType))
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}
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}
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}
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return "", io.EOF
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}
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/*
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A type for turning an input stream in to a sequence of typed tokens.
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*/
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type Tokenizer struct {
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input *bufio.Reader
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classifier *TokenClassifier
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}
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/*
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Create a new tokenizer.
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*/
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func NewTokenizer(r io.Reader) (*Tokenizer, error) {
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input := bufio.NewReader(r)
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classifier := NewDefaultClassifier()
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tokenizer := &Tokenizer{
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input: input,
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classifier: classifier}
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return tokenizer, nil
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}
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/*
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Scan the stream for the next token.
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This uses an internal state machine. It will panic if it encounters a character
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which it does not know how to handle.
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*/
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func (t *Tokenizer) scanStream() (*Token, error) {
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state := STATE_START
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var tokenType TokenType
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value := make([]int32, 0, INITIAL_TOKEN_CAPACITY)
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var (
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nextRune int32
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nextRuneType RuneTokenType
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err error
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)
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SCAN:
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for {
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nextRune, _, err = t.input.ReadRune()
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nextRuneType = t.classifier.ClassifyRune(nextRune)
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if err != nil {
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if err == io.EOF {
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nextRuneType = RUNETOKEN_EOF
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err = nil
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} else {
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return nil, err
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}
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}
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switch state {
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case STATE_START: // no runes read yet
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{
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switch nextRuneType {
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case RUNETOKEN_EOF:
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{
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return nil, io.EOF
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}
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case RUNETOKEN_CHAR:
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{
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tokenType = TOKEN_WORD
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value = append(value, nextRune)
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state = STATE_INWORD
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}
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case RUNETOKEN_SPACE:
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{
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}
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case RUNETOKEN_ESCAPING_QUOTE:
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{
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tokenType = TOKEN_WORD
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state = STATE_QUOTED_ESCAPING
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}
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case RUNETOKEN_NONESCAPING_QUOTE:
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{
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tokenType = TOKEN_WORD
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state = STATE_QUOTED
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}
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case RUNETOKEN_ESCAPE:
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{
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tokenType = TOKEN_WORD
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state = STATE_ESCAPING
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}
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case RUNETOKEN_COMMENT:
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{
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tokenType = TOKEN_COMMENT
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state = STATE_COMMENT
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}
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default:
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{
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return nil, errors.New(fmt.Sprintf("Unknown rune: %v", nextRune))
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}
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}
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}
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case STATE_INWORD: // in a regular word
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{
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switch nextRuneType {
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case RUNETOKEN_EOF:
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{
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break SCAN
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}
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case RUNETOKEN_CHAR, RUNETOKEN_COMMENT:
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{
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value = append(value, nextRune)
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}
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case RUNETOKEN_SPACE:
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{
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t.input.UnreadRune()
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break SCAN
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}
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case RUNETOKEN_ESCAPING_QUOTE:
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{
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state = STATE_QUOTED_ESCAPING
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}
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case RUNETOKEN_NONESCAPING_QUOTE:
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{
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state = STATE_QUOTED
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}
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case RUNETOKEN_ESCAPE:
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{
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state = STATE_ESCAPING
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}
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default:
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{
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return nil, errors.New(fmt.Sprintf("Uknown rune: %v", nextRune))
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}
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}
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}
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case STATE_ESCAPING: // the next rune after an escape character
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{
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switch nextRuneType {
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case RUNETOKEN_EOF:
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{
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err = errors.New("EOF found after escape character")
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break SCAN
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}
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case RUNETOKEN_CHAR, RUNETOKEN_SPACE, RUNETOKEN_ESCAPING_QUOTE, RUNETOKEN_NONESCAPING_QUOTE, RUNETOKEN_ESCAPE, RUNETOKEN_COMMENT:
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{
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state = STATE_INWORD
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value = append(value, nextRune)
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}
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default:
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{
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return nil, errors.New(fmt.Sprintf("Uknown rune: %v", nextRune))
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}
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}
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}
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case STATE_ESCAPING_QUOTED: // the next rune after an escape character, in double quotes
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{
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switch nextRuneType {
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case RUNETOKEN_EOF:
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{
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err = errors.New("EOF found after escape character")
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break SCAN
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}
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case RUNETOKEN_CHAR, RUNETOKEN_SPACE, RUNETOKEN_ESCAPING_QUOTE, RUNETOKEN_NONESCAPING_QUOTE, RUNETOKEN_ESCAPE, RUNETOKEN_COMMENT:
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{
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state = STATE_QUOTED_ESCAPING
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value = append(value, nextRune)
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}
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default:
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{
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return nil, errors.New(fmt.Sprintf("Uknown rune: %v", nextRune))
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}
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}
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}
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case STATE_QUOTED_ESCAPING: // in escaping double quotes
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{
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switch nextRuneType {
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case RUNETOKEN_EOF:
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{
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err = errors.New("EOF found when expecting closing quote.")
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break SCAN
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}
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case RUNETOKEN_CHAR, RUNETOKEN_UNKNOWN, RUNETOKEN_SPACE, RUNETOKEN_NONESCAPING_QUOTE, RUNETOKEN_COMMENT:
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{
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value = append(value, nextRune)
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}
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case RUNETOKEN_ESCAPING_QUOTE:
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{
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state = STATE_INWORD
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}
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case RUNETOKEN_ESCAPE:
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{
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state = STATE_ESCAPING_QUOTED
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}
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default:
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{
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return nil, errors.New(fmt.Sprintf("Uknown rune: %v", nextRune))
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}
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}
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}
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case STATE_QUOTED: // in non-escaping single quotes
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{
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switch nextRuneType {
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case RUNETOKEN_EOF:
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{
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err = errors.New("EOF found when expecting closing quote.")
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break SCAN
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}
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case RUNETOKEN_CHAR, RUNETOKEN_UNKNOWN, RUNETOKEN_SPACE, RUNETOKEN_ESCAPING_QUOTE, RUNETOKEN_ESCAPE, RUNETOKEN_COMMENT:
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{
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value = append(value, nextRune)
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}
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case RUNETOKEN_NONESCAPING_QUOTE:
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{
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state = STATE_INWORD
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}
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default:
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{
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return nil, errors.New(fmt.Sprintf("Uknown rune: %v", nextRune))
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}
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}
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}
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case STATE_COMMENT:
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{
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switch nextRuneType {
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case RUNETOKEN_EOF:
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{
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break SCAN
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}
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case RUNETOKEN_CHAR, RUNETOKEN_UNKNOWN, RUNETOKEN_ESCAPING_QUOTE, RUNETOKEN_ESCAPE, RUNETOKEN_COMMENT, RUNETOKEN_NONESCAPING_QUOTE:
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{
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value = append(value, nextRune)
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}
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case RUNETOKEN_SPACE:
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{
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if nextRune == '\n' {
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state = STATE_START
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break SCAN
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} else {
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value = append(value, nextRune)
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}
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}
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default:
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{
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return nil, errors.New(fmt.Sprintf("Uknown rune: %v", nextRune))
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}
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}
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}
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default:
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{
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panic(fmt.Sprintf("Unexpected state: %v", state))
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}
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}
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}
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token := &Token{
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tokenType: tokenType,
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value: string(value)}
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return token, err
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}
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/*
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Return the next token in the stream, and an error value. If there are no more
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tokens available, the error value will be io.EOF.
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*/
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func (t *Tokenizer) NextToken() (*Token, error) {
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return t.scanStream()
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}
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/*
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Split a string in to a slice of strings, based upon shell-style rules for
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quoting, escaping, and spaces.
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*/
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func Split(s string) ([]string, error) {
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l, err := NewLexer(strings.NewReader(s))
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if err != nil {
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return nil, err
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}
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subStrings := []string{}
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for {
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word, err := l.NextWord()
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if err != nil {
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if err == io.EOF {
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return subStrings, nil
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}
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return subStrings, err
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}
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subStrings = append(subStrings, word)
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}
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return subStrings, nil
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}
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