mirror of
https://github.com/go-gitea/gitea.git
synced 2024-12-04 14:46:57 -05:00
343 lines
7.9 KiB
Go
343 lines
7.9 KiB
Go
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// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package scanner implements a scanner for gcfg configuration text.
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// It takes a []byte as source which can then be tokenized
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// through repeated calls to the Scan method.
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//
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// Note that the API for the scanner package may change to accommodate new
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// features or implementation changes in gcfg.
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//
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package scanner
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import (
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"fmt"
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"path/filepath"
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"unicode"
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"unicode/utf8"
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)
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import (
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"github.com/src-d/gcfg/token"
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)
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// An ErrorHandler may be provided to Scanner.Init. If a syntax error is
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// encountered and a handler was installed, the handler is called with a
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// position and an error message. The position points to the beginning of
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// the offending token.
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//
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type ErrorHandler func(pos token.Position, msg string)
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// A Scanner holds the scanner's internal state while processing
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// a given text. It can be allocated as part of another data
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// structure but must be initialized via Init before use.
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//
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type Scanner struct {
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// immutable state
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file *token.File // source file handle
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dir string // directory portion of file.Name()
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src []byte // source
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err ErrorHandler // error reporting; or nil
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mode Mode // scanning mode
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// scanning state
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ch rune // current character
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offset int // character offset
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rdOffset int // reading offset (position after current character)
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lineOffset int // current line offset
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nextVal bool // next token is expected to be a value
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// public state - ok to modify
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ErrorCount int // number of errors encountered
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}
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// Read the next Unicode char into s.ch.
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// s.ch < 0 means end-of-file.
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//
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func (s *Scanner) next() {
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if s.rdOffset < len(s.src) {
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s.offset = s.rdOffset
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if s.ch == '\n' {
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s.lineOffset = s.offset
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s.file.AddLine(s.offset)
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}
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r, w := rune(s.src[s.rdOffset]), 1
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switch {
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case r == 0:
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s.error(s.offset, "illegal character NUL")
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case r >= 0x80:
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// not ASCII
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r, w = utf8.DecodeRune(s.src[s.rdOffset:])
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if r == utf8.RuneError && w == 1 {
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s.error(s.offset, "illegal UTF-8 encoding")
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}
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}
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s.rdOffset += w
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s.ch = r
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} else {
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s.offset = len(s.src)
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if s.ch == '\n' {
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s.lineOffset = s.offset
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s.file.AddLine(s.offset)
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}
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s.ch = -1 // eof
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}
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}
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// A mode value is a set of flags (or 0).
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// They control scanner behavior.
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//
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type Mode uint
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const (
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ScanComments Mode = 1 << iota // return comments as COMMENT tokens
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)
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// Init prepares the scanner s to tokenize the text src by setting the
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// scanner at the beginning of src. The scanner uses the file set file
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// for position information and it adds line information for each line.
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// It is ok to re-use the same file when re-scanning the same file as
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// line information which is already present is ignored. Init causes a
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// panic if the file size does not match the src size.
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//
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// Calls to Scan will invoke the error handler err if they encounter a
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// syntax error and err is not nil. Also, for each error encountered,
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// the Scanner field ErrorCount is incremented by one. The mode parameter
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// determines how comments are handled.
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//
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// Note that Init may call err if there is an error in the first character
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// of the file.
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//
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func (s *Scanner) Init(file *token.File, src []byte, err ErrorHandler, mode Mode) {
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// Explicitly initialize all fields since a scanner may be reused.
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if file.Size() != len(src) {
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panic(fmt.Sprintf("file size (%d) does not match src len (%d)", file.Size(), len(src)))
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}
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s.file = file
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s.dir, _ = filepath.Split(file.Name())
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s.src = src
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s.err = err
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s.mode = mode
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s.ch = ' '
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s.offset = 0
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s.rdOffset = 0
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s.lineOffset = 0
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s.ErrorCount = 0
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s.nextVal = false
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s.next()
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}
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func (s *Scanner) error(offs int, msg string) {
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if s.err != nil {
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s.err(s.file.Position(s.file.Pos(offs)), msg)
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}
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s.ErrorCount++
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}
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func (s *Scanner) scanComment() string {
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// initial [;#] already consumed
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offs := s.offset - 1 // position of initial [;#]
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for s.ch != '\n' && s.ch >= 0 {
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s.next()
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}
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return string(s.src[offs:s.offset])
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}
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func isLetter(ch rune) bool {
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return 'a' <= ch && ch <= 'z' || 'A' <= ch && ch <= 'Z' || ch >= 0x80 && unicode.IsLetter(ch)
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}
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func isDigit(ch rune) bool {
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return '0' <= ch && ch <= '9' || ch >= 0x80 && unicode.IsDigit(ch)
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}
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func (s *Scanner) scanIdentifier() string {
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offs := s.offset
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for isLetter(s.ch) || isDigit(s.ch) || s.ch == '-' {
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s.next()
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}
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return string(s.src[offs:s.offset])
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}
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func (s *Scanner) scanEscape(val bool) {
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offs := s.offset
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ch := s.ch
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s.next() // always make progress
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switch ch {
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case '\\', '"':
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// ok
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case 'n', 't', 'b':
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if val {
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break // ok
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}
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fallthrough
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default:
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s.error(offs, "unknown escape sequence")
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}
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}
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func (s *Scanner) scanString() string {
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// '"' opening already consumed
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offs := s.offset - 1
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for s.ch != '"' {
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ch := s.ch
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s.next()
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if ch == '\n' || ch < 0 {
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s.error(offs, "string not terminated")
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break
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}
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if ch == '\\' {
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s.scanEscape(false)
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}
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}
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s.next()
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return string(s.src[offs:s.offset])
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}
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func stripCR(b []byte) []byte {
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c := make([]byte, len(b))
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i := 0
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for _, ch := range b {
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if ch != '\r' {
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c[i] = ch
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i++
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}
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}
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return c[:i]
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}
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func (s *Scanner) scanValString() string {
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offs := s.offset
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hasCR := false
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end := offs
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inQuote := false
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loop:
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for inQuote || s.ch >= 0 && s.ch != '\n' && s.ch != ';' && s.ch != '#' {
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ch := s.ch
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s.next()
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switch {
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case inQuote && ch == '\\':
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s.scanEscape(true)
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case !inQuote && ch == '\\':
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if s.ch == '\r' {
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hasCR = true
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s.next()
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}
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if s.ch != '\n' {
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s.scanEscape(true)
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} else {
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s.next()
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}
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case ch == '"':
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inQuote = !inQuote
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case ch == '\r':
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hasCR = true
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case ch < 0 || inQuote && ch == '\n':
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s.error(offs, "string not terminated")
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break loop
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}
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if inQuote || !isWhiteSpace(ch) {
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end = s.offset
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}
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}
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lit := s.src[offs:end]
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if hasCR {
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lit = stripCR(lit)
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}
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return string(lit)
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}
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func isWhiteSpace(ch rune) bool {
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return ch == ' ' || ch == '\t' || ch == '\r'
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}
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func (s *Scanner) skipWhitespace() {
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for isWhiteSpace(s.ch) {
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s.next()
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}
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}
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// Scan scans the next token and returns the token position, the token,
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// and its literal string if applicable. The source end is indicated by
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// token.EOF.
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//
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// If the returned token is a literal (token.IDENT, token.STRING) or
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// token.COMMENT, the literal string has the corresponding value.
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//
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// If the returned token is token.ILLEGAL, the literal string is the
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// offending character.
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//
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// In all other cases, Scan returns an empty literal string.
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//
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// For more tolerant parsing, Scan will return a valid token if
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// possible even if a syntax error was encountered. Thus, even
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// if the resulting token sequence contains no illegal tokens,
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// a client may not assume that no error occurred. Instead it
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// must check the scanner's ErrorCount or the number of calls
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// of the error handler, if there was one installed.
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//
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// Scan adds line information to the file added to the file
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// set with Init. Token positions are relative to that file
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// and thus relative to the file set.
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//
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func (s *Scanner) Scan() (pos token.Pos, tok token.Token, lit string) {
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scanAgain:
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s.skipWhitespace()
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// current token start
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pos = s.file.Pos(s.offset)
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// determine token value
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switch ch := s.ch; {
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case s.nextVal:
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lit = s.scanValString()
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tok = token.STRING
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s.nextVal = false
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case isLetter(ch):
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lit = s.scanIdentifier()
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tok = token.IDENT
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default:
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s.next() // always make progress
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switch ch {
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case -1:
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tok = token.EOF
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case '\n':
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tok = token.EOL
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case '"':
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tok = token.STRING
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lit = s.scanString()
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case '[':
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tok = token.LBRACK
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case ']':
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tok = token.RBRACK
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case ';', '#':
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// comment
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lit = s.scanComment()
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if s.mode&ScanComments == 0 {
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// skip comment
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goto scanAgain
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}
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tok = token.COMMENT
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case '=':
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tok = token.ASSIGN
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s.nextVal = true
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default:
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s.error(s.file.Offset(pos), fmt.Sprintf("illegal character %#U", ch))
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tok = token.ILLEGAL
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lit = string(ch)
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}
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}
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return
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}
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