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-rw-r--r--src/go/scanner/scanner.go760
1 files changed, 760 insertions, 0 deletions
diff --git a/src/go/scanner/scanner.go b/src/go/scanner/scanner.go
new file mode 100644
index 000000000..cec82ea10
--- /dev/null
+++ b/src/go/scanner/scanner.go
@@ -0,0 +1,760 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package scanner implements a scanner for Go source text.
+// It takes a []byte as source which can then be tokenized
+// through repeated calls to the Scan method.
+//
+package scanner
+
+import (
+ "bytes"
+ "fmt"
+ "go/token"
+ "path/filepath"
+ "strconv"
+ "unicode"
+ "unicode/utf8"
+)
+
+// An ErrorHandler may be provided to Scanner.Init. If a syntax error is
+// encountered and a handler was installed, the handler is called with a
+// position and an error message. The position points to the beginning of
+// the offending token.
+//
+type ErrorHandler func(pos token.Position, msg string)
+
+// A Scanner holds the scanner's internal state while processing
+// a given text. It can be allocated as part of another data
+// structure but must be initialized via Init before use.
+//
+type Scanner struct {
+ // immutable state
+ file *token.File // source file handle
+ dir string // directory portion of file.Name()
+ src []byte // source
+ err ErrorHandler // error reporting; or nil
+ mode Mode // scanning mode
+
+ // scanning state
+ ch rune // current character
+ offset int // character offset
+ rdOffset int // reading offset (position after current character)
+ lineOffset int // current line offset
+ insertSemi bool // insert a semicolon before next newline
+
+ // public state - ok to modify
+ ErrorCount int // number of errors encountered
+}
+
+const bom = 0xFEFF // byte order mark, only permitted as very first character
+
+// Read the next Unicode char into s.ch.
+// s.ch < 0 means end-of-file.
+//
+func (s *Scanner) next() {
+ if s.rdOffset < len(s.src) {
+ s.offset = s.rdOffset
+ if s.ch == '\n' {
+ s.lineOffset = s.offset
+ s.file.AddLine(s.offset)
+ }
+ r, w := rune(s.src[s.rdOffset]), 1
+ switch {
+ case r == 0:
+ s.error(s.offset, "illegal character NUL")
+ case r >= 0x80:
+ // not ASCII
+ r, w = utf8.DecodeRune(s.src[s.rdOffset:])
+ if r == utf8.RuneError && w == 1 {
+ s.error(s.offset, "illegal UTF-8 encoding")
+ } else if r == bom && s.offset > 0 {
+ s.error(s.offset, "illegal byte order mark")
+ }
+ }
+ s.rdOffset += w
+ s.ch = r
+ } else {
+ s.offset = len(s.src)
+ if s.ch == '\n' {
+ s.lineOffset = s.offset
+ s.file.AddLine(s.offset)
+ }
+ s.ch = -1 // eof
+ }
+}
+
+// A mode value is a set of flags (or 0).
+// They control scanner behavior.
+//
+type Mode uint
+
+const (
+ ScanComments Mode = 1 << iota // return comments as COMMENT tokens
+ dontInsertSemis // do not automatically insert semicolons - for testing only
+)
+
+// Init prepares the scanner s to tokenize the text src by setting the
+// scanner at the beginning of src. The scanner uses the file set file
+// for position information and it adds line information for each line.
+// It is ok to re-use the same file when re-scanning the same file as
+// line information which is already present is ignored. Init causes a
+// panic if the file size does not match the src size.
+//
+// Calls to Scan will invoke the error handler err if they encounter a
+// syntax error and err is not nil. Also, for each error encountered,
+// the Scanner field ErrorCount is incremented by one. The mode parameter
+// determines how comments are handled.
+//
+// Note that Init may call err if there is an error in the first character
+// of the file.
+//
+func (s *Scanner) Init(file *token.File, src []byte, err ErrorHandler, mode Mode) {
+ // Explicitly initialize all fields since a scanner may be reused.
+ if file.Size() != len(src) {
+ panic(fmt.Sprintf("file size (%d) does not match src len (%d)", file.Size(), len(src)))
+ }
+ s.file = file
+ s.dir, _ = filepath.Split(file.Name())
+ s.src = src
+ s.err = err
+ s.mode = mode
+
+ s.ch = ' '
+ s.offset = 0
+ s.rdOffset = 0
+ s.lineOffset = 0
+ s.insertSemi = false
+ s.ErrorCount = 0
+
+ s.next()
+ if s.ch == bom {
+ s.next() // ignore BOM at file beginning
+ }
+}
+
+func (s *Scanner) error(offs int, msg string) {
+ if s.err != nil {
+ s.err(s.file.Position(s.file.Pos(offs)), msg)
+ }
+ s.ErrorCount++
+}
+
+var prefix = []byte("//line ")
+
+func (s *Scanner) interpretLineComment(text []byte) {
+ if bytes.HasPrefix(text, prefix) {
+ // get filename and line number, if any
+ if i := bytes.LastIndex(text, []byte{':'}); i > 0 {
+ if line, err := strconv.Atoi(string(text[i+1:])); err == nil && line > 0 {
+ // valid //line filename:line comment
+ filename := string(bytes.TrimSpace(text[len(prefix):i]))
+ if filename != "" {
+ filename = filepath.Clean(filename)
+ if !filepath.IsAbs(filename) {
+ // make filename relative to current directory
+ filename = filepath.Join(s.dir, filename)
+ }
+ }
+ // update scanner position
+ s.file.AddLineInfo(s.lineOffset+len(text)+1, filename, line) // +len(text)+1 since comment applies to next line
+ }
+ }
+ }
+}
+
+func (s *Scanner) scanComment() string {
+ // initial '/' already consumed; s.ch == '/' || s.ch == '*'
+ offs := s.offset - 1 // position of initial '/'
+ hasCR := false
+
+ if s.ch == '/' {
+ //-style comment
+ s.next()
+ for s.ch != '\n' && s.ch >= 0 {
+ if s.ch == '\r' {
+ hasCR = true
+ }
+ s.next()
+ }
+ if offs == s.lineOffset {
+ // comment starts at the beginning of the current line
+ s.interpretLineComment(s.src[offs:s.offset])
+ }
+ goto exit
+ }
+
+ /*-style comment */
+ s.next()
+ for s.ch >= 0 {
+ ch := s.ch
+ if ch == '\r' {
+ hasCR = true
+ }
+ s.next()
+ if ch == '*' && s.ch == '/' {
+ s.next()
+ goto exit
+ }
+ }
+
+ s.error(offs, "comment not terminated")
+
+exit:
+ lit := s.src[offs:s.offset]
+ if hasCR {
+ lit = stripCR(lit)
+ }
+
+ return string(lit)
+}
+
+func (s *Scanner) findLineEnd() bool {
+ // initial '/' already consumed
+
+ defer func(offs int) {
+ // reset scanner state to where it was upon calling findLineEnd
+ s.ch = '/'
+ s.offset = offs
+ s.rdOffset = offs + 1
+ s.next() // consume initial '/' again
+ }(s.offset - 1)
+
+ // read ahead until a newline, EOF, or non-comment token is found
+ for s.ch == '/' || s.ch == '*' {
+ if s.ch == '/' {
+ //-style comment always contains a newline
+ return true
+ }
+ /*-style comment: look for newline */
+ s.next()
+ for s.ch >= 0 {
+ ch := s.ch
+ if ch == '\n' {
+ return true
+ }
+ s.next()
+ if ch == '*' && s.ch == '/' {
+ s.next()
+ break
+ }
+ }
+ s.skipWhitespace() // s.insertSemi is set
+ if s.ch < 0 || s.ch == '\n' {
+ return true
+ }
+ if s.ch != '/' {
+ // non-comment token
+ return false
+ }
+ s.next() // consume '/'
+ }
+
+ return false
+}
+
+func isLetter(ch rune) bool {
+ return 'a' <= ch && ch <= 'z' || 'A' <= ch && ch <= 'Z' || ch == '_' || ch >= 0x80 && unicode.IsLetter(ch)
+}
+
+func isDigit(ch rune) bool {
+ return '0' <= ch && ch <= '9' || ch >= 0x80 && unicode.IsDigit(ch)
+}
+
+func (s *Scanner) scanIdentifier() string {
+ offs := s.offset
+ for isLetter(s.ch) || isDigit(s.ch) {
+ s.next()
+ }
+ return string(s.src[offs:s.offset])
+}
+
+func digitVal(ch rune) int {
+ switch {
+ case '0' <= ch && ch <= '9':
+ return int(ch - '0')
+ case 'a' <= ch && ch <= 'f':
+ return int(ch - 'a' + 10)
+ case 'A' <= ch && ch <= 'F':
+ return int(ch - 'A' + 10)
+ }
+ return 16 // larger than any legal digit val
+}
+
+func (s *Scanner) scanMantissa(base int) {
+ for digitVal(s.ch) < base {
+ s.next()
+ }
+}
+
+func (s *Scanner) scanNumber(seenDecimalPoint bool) (token.Token, string) {
+ // digitVal(s.ch) < 10
+ offs := s.offset
+ tok := token.INT
+
+ if seenDecimalPoint {
+ offs--
+ tok = token.FLOAT
+ s.scanMantissa(10)
+ goto exponent
+ }
+
+ if s.ch == '0' {
+ // int or float
+ offs := s.offset
+ s.next()
+ if s.ch == 'x' || s.ch == 'X' {
+ // hexadecimal int
+ s.next()
+ s.scanMantissa(16)
+ if s.offset-offs <= 2 {
+ // only scanned "0x" or "0X"
+ s.error(offs, "illegal hexadecimal number")
+ }
+ } else {
+ // octal int or float
+ seenDecimalDigit := false
+ s.scanMantissa(8)
+ if s.ch == '8' || s.ch == '9' {
+ // illegal octal int or float
+ seenDecimalDigit = true
+ s.scanMantissa(10)
+ }
+ if s.ch == '.' || s.ch == 'e' || s.ch == 'E' || s.ch == 'i' {
+ goto fraction
+ }
+ // octal int
+ if seenDecimalDigit {
+ s.error(offs, "illegal octal number")
+ }
+ }
+ goto exit
+ }
+
+ // decimal int or float
+ s.scanMantissa(10)
+
+fraction:
+ if s.ch == '.' {
+ tok = token.FLOAT
+ s.next()
+ s.scanMantissa(10)
+ }
+
+exponent:
+ if s.ch == 'e' || s.ch == 'E' {
+ tok = token.FLOAT
+ s.next()
+ if s.ch == '-' || s.ch == '+' {
+ s.next()
+ }
+ s.scanMantissa(10)
+ }
+
+ if s.ch == 'i' {
+ tok = token.IMAG
+ s.next()
+ }
+
+exit:
+ return tok, string(s.src[offs:s.offset])
+}
+
+// scanEscape parses an escape sequence where rune is the accepted
+// escaped quote. In case of a syntax error, it stops at the offending
+// character (without consuming it) and returns false. Otherwise
+// it returns true.
+func (s *Scanner) scanEscape(quote rune) bool {
+ offs := s.offset
+
+ var n int
+ var base, max uint32
+ switch s.ch {
+ case 'a', 'b', 'f', 'n', 'r', 't', 'v', '\\', quote:
+ s.next()
+ return true
+ case '0', '1', '2', '3', '4', '5', '6', '7':
+ n, base, max = 3, 8, 255
+ case 'x':
+ s.next()
+ n, base, max = 2, 16, 255
+ case 'u':
+ s.next()
+ n, base, max = 4, 16, unicode.MaxRune
+ case 'U':
+ s.next()
+ n, base, max = 8, 16, unicode.MaxRune
+ default:
+ msg := "unknown escape sequence"
+ if s.ch < 0 {
+ msg = "escape sequence not terminated"
+ }
+ s.error(offs, msg)
+ return false
+ }
+
+ var x uint32
+ for n > 0 {
+ d := uint32(digitVal(s.ch))
+ if d >= base {
+ msg := fmt.Sprintf("illegal character %#U in escape sequence", s.ch)
+ if s.ch < 0 {
+ msg = "escape sequence not terminated"
+ }
+ s.error(s.offset, msg)
+ return false
+ }
+ x = x*base + d
+ s.next()
+ n--
+ }
+
+ if x > max || 0xD800 <= x && x < 0xE000 {
+ s.error(offs, "escape sequence is invalid Unicode code point")
+ return false
+ }
+
+ return true
+}
+
+func (s *Scanner) scanRune() string {
+ // '\'' opening already consumed
+ offs := s.offset - 1
+
+ valid := true
+ n := 0
+ for {
+ ch := s.ch
+ if ch == '\n' || ch < 0 {
+ // only report error if we don't have one already
+ if valid {
+ s.error(offs, "rune literal not terminated")
+ valid = false
+ }
+ break
+ }
+ s.next()
+ if ch == '\'' {
+ break
+ }
+ n++
+ if ch == '\\' {
+ if !s.scanEscape('\'') {
+ valid = false
+ }
+ // continue to read to closing quote
+ }
+ }
+
+ if valid && n != 1 {
+ s.error(offs, "illegal rune literal")
+ }
+
+ return string(s.src[offs:s.offset])
+}
+
+func (s *Scanner) scanString() string {
+ // '"' opening already consumed
+ offs := s.offset - 1
+
+ for {
+ ch := s.ch
+ if ch == '\n' || ch < 0 {
+ s.error(offs, "string literal not terminated")
+ break
+ }
+ s.next()
+ if ch == '"' {
+ break
+ }
+ if ch == '\\' {
+ s.scanEscape('"')
+ }
+ }
+
+ return string(s.src[offs:s.offset])
+}
+
+func stripCR(b []byte) []byte {
+ c := make([]byte, len(b))
+ i := 0
+ for _, ch := range b {
+ if ch != '\r' {
+ c[i] = ch
+ i++
+ }
+ }
+ return c[:i]
+}
+
+func (s *Scanner) scanRawString() string {
+ // '`' opening already consumed
+ offs := s.offset - 1
+
+ hasCR := false
+ for {
+ ch := s.ch
+ if ch < 0 {
+ s.error(offs, "raw string literal not terminated")
+ break
+ }
+ s.next()
+ if ch == '`' {
+ break
+ }
+ if ch == '\r' {
+ hasCR = true
+ }
+ }
+
+ lit := s.src[offs:s.offset]
+ if hasCR {
+ lit = stripCR(lit)
+ }
+
+ return string(lit)
+}
+
+func (s *Scanner) skipWhitespace() {
+ for s.ch == ' ' || s.ch == '\t' || s.ch == '\n' && !s.insertSemi || s.ch == '\r' {
+ s.next()
+ }
+}
+
+// Helper functions for scanning multi-byte tokens such as >> += >>= .
+// Different routines recognize different length tok_i based on matches
+// of ch_i. If a token ends in '=', the result is tok1 or tok3
+// respectively. Otherwise, the result is tok0 if there was no other
+// matching character, or tok2 if the matching character was ch2.
+
+func (s *Scanner) switch2(tok0, tok1 token.Token) token.Token {
+ if s.ch == '=' {
+ s.next()
+ return tok1
+ }
+ return tok0
+}
+
+func (s *Scanner) switch3(tok0, tok1 token.Token, ch2 rune, tok2 token.Token) token.Token {
+ if s.ch == '=' {
+ s.next()
+ return tok1
+ }
+ if s.ch == ch2 {
+ s.next()
+ return tok2
+ }
+ return tok0
+}
+
+func (s *Scanner) switch4(tok0, tok1 token.Token, ch2 rune, tok2, tok3 token.Token) token.Token {
+ if s.ch == '=' {
+ s.next()
+ return tok1
+ }
+ if s.ch == ch2 {
+ s.next()
+ if s.ch == '=' {
+ s.next()
+ return tok3
+ }
+ return tok2
+ }
+ return tok0
+}
+
+// Scan scans the next token and returns the token position, the token,
+// and its literal string if applicable. The source end is indicated by
+// token.EOF.
+//
+// If the returned token is a literal (token.IDENT, token.INT, token.FLOAT,
+// token.IMAG, token.CHAR, token.STRING) or token.COMMENT, the literal string
+// has the corresponding value.
+//
+// If the returned token is a keyword, the literal string is the keyword.
+//
+// If the returned token is token.SEMICOLON, the corresponding
+// literal string is ";" if the semicolon was present in the source,
+// and "\n" if the semicolon was inserted because of a newline or
+// at EOF.
+//
+// If the returned token is token.ILLEGAL, the literal string is the
+// offending character.
+//
+// In all other cases, Scan returns an empty literal string.
+//
+// For more tolerant parsing, Scan will return a valid token if
+// possible even if a syntax error was encountered. Thus, even
+// if the resulting token sequence contains no illegal tokens,
+// a client may not assume that no error occurred. Instead it
+// must check the scanner's ErrorCount or the number of calls
+// of the error handler, if there was one installed.
+//
+// Scan adds line information to the file added to the file
+// set with Init. Token positions are relative to that file
+// and thus relative to the file set.
+//
+func (s *Scanner) Scan() (pos token.Pos, tok token.Token, lit string) {
+scanAgain:
+ s.skipWhitespace()
+
+ // current token start
+ pos = s.file.Pos(s.offset)
+
+ // determine token value
+ insertSemi := false
+ switch ch := s.ch; {
+ case isLetter(ch):
+ lit = s.scanIdentifier()
+ if len(lit) > 1 {
+ // keywords are longer than one letter - avoid lookup otherwise
+ tok = token.Lookup(lit)
+ switch tok {
+ case token.IDENT, token.BREAK, token.CONTINUE, token.FALLTHROUGH, token.RETURN:
+ insertSemi = true
+ }
+ } else {
+ insertSemi = true
+ tok = token.IDENT
+ }
+ case '0' <= ch && ch <= '9':
+ insertSemi = true
+ tok, lit = s.scanNumber(false)
+ default:
+ s.next() // always make progress
+ switch ch {
+ case -1:
+ if s.insertSemi {
+ s.insertSemi = false // EOF consumed
+ return pos, token.SEMICOLON, "\n"
+ }
+ tok = token.EOF
+ case '\n':
+ // we only reach here if s.insertSemi was
+ // set in the first place and exited early
+ // from s.skipWhitespace()
+ s.insertSemi = false // newline consumed
+ return pos, token.SEMICOLON, "\n"
+ case '"':
+ insertSemi = true
+ tok = token.STRING
+ lit = s.scanString()
+ case '\'':
+ insertSemi = true
+ tok = token.CHAR
+ lit = s.scanRune()
+ case '`':
+ insertSemi = true
+ tok = token.STRING
+ lit = s.scanRawString()
+ case ':':
+ tok = s.switch2(token.COLON, token.DEFINE)
+ case '.':
+ if '0' <= s.ch && s.ch <= '9' {
+ insertSemi = true
+ tok, lit = s.scanNumber(true)
+ } else if s.ch == '.' {
+ s.next()
+ if s.ch == '.' {
+ s.next()
+ tok = token.ELLIPSIS
+ }
+ } else {
+ tok = token.PERIOD
+ }
+ case ',':
+ tok = token.COMMA
+ case ';':
+ tok = token.SEMICOLON
+ lit = ";"
+ case '(':
+ tok = token.LPAREN
+ case ')':
+ insertSemi = true
+ tok = token.RPAREN
+ case '[':
+ tok = token.LBRACK
+ case ']':
+ insertSemi = true
+ tok = token.RBRACK
+ case '{':
+ tok = token.LBRACE
+ case '}':
+ insertSemi = true
+ tok = token.RBRACE
+ case '+':
+ tok = s.switch3(token.ADD, token.ADD_ASSIGN, '+', token.INC)
+ if tok == token.INC {
+ insertSemi = true
+ }
+ case '-':
+ tok = s.switch3(token.SUB, token.SUB_ASSIGN, '-', token.DEC)
+ if tok == token.DEC {
+ insertSemi = true
+ }
+ case '*':
+ tok = s.switch2(token.MUL, token.MUL_ASSIGN)
+ case '/':
+ if s.ch == '/' || s.ch == '*' {
+ // comment
+ if s.insertSemi && s.findLineEnd() {
+ // reset position to the beginning of the comment
+ s.ch = '/'
+ s.offset = s.file.Offset(pos)
+ s.rdOffset = s.offset + 1
+ s.insertSemi = false // newline consumed
+ return pos, token.SEMICOLON, "\n"
+ }
+ lit = s.scanComment()
+ if s.mode&ScanComments == 0 {
+ // skip comment
+ s.insertSemi = false // newline consumed
+ goto scanAgain
+ }
+ tok = token.COMMENT
+ } else {
+ tok = s.switch2(token.QUO, token.QUO_ASSIGN)
+ }
+ case '%':
+ tok = s.switch2(token.REM, token.REM_ASSIGN)
+ case '^':
+ tok = s.switch2(token.XOR, token.XOR_ASSIGN)
+ case '<':
+ if s.ch == '-' {
+ s.next()
+ tok = token.ARROW
+ } else {
+ tok = s.switch4(token.LSS, token.LEQ, '<', token.SHL, token.SHL_ASSIGN)
+ }
+ case '>':
+ tok = s.switch4(token.GTR, token.GEQ, '>', token.SHR, token.SHR_ASSIGN)
+ case '=':
+ tok = s.switch2(token.ASSIGN, token.EQL)
+ case '!':
+ tok = s.switch2(token.NOT, token.NEQ)
+ case '&':
+ if s.ch == '^' {
+ s.next()
+ tok = s.switch2(token.AND_NOT, token.AND_NOT_ASSIGN)
+ } else {
+ tok = s.switch3(token.AND, token.AND_ASSIGN, '&', token.LAND)
+ }
+ case '|':
+ tok = s.switch3(token.OR, token.OR_ASSIGN, '|', token.LOR)
+ default:
+ // next reports unexpected BOMs - don't repeat
+ if ch != bom {
+ s.error(s.file.Offset(pos), fmt.Sprintf("illegal character %#U", ch))
+ }
+ insertSemi = s.insertSemi // preserve insertSemi info
+ tok = token.ILLEGAL
+ lit = string(ch)
+ }
+ }
+ if s.mode&dontInsertSemis == 0 {
+ s.insertSemi = insertSemi
+ }
+
+ return
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-05-17 21:40:59 +0000