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go/scanner: removed scanner/internal-only uses of token.Position

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First step towards a more light-weight implementation of token.Position:
- only use token.Position for reporting token and error position
- use offsets only for scanner control
- no interface changes yet

R=rsc
CC=golang-dev
https://golang.org/cl/2825041
This commit is contained in:
Robert Griesemer 2010-11-02 10:38:07 -07:00
parent 0808b199e0
commit 396228a652
2 changed files with 141 additions and 104 deletions
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221
src/pkg/go/scanner/scanner.go
View File

@ -29,9 +29,13 @@ type Scanner struct {
mode uint // scanning mode
// scanning state
pos token.Position // previous reading position (position before ch)
offset int // current reading offset (position after ch)
ch int // one char look-ahead
filename string // current filename; may change via //line filename:line comment
line int // current line
column int // current column
ch int // current character
offset int // character offset
rdOffset int // reading offset (position after current character)
insertSemi bool // insert a semicolon before next newline
// public state - ok to modify
@ -43,29 +47,31 @@ type Scanner struct {
// S.ch < 0 means end-of-file.
//
func (S *Scanner) next() {
if S.offset < len(S.src) {
S.pos.Offset = S.offset
S.pos.Column++
S.column++
if S.rdOffset < len(S.src) {
S.offset = S.rdOffset
if S.ch == '\n' {
// next character starts a new line
S.pos.Line++
S.pos.Column = 1
S.line++
S.column = 1
}
r, w := int(S.src[S.offset]), 1
r, w := int(S.src[S.rdOffset]), 1
switch {
case r == 0:
S.error(S.pos, "illegal character NUL")
S.error("illegal character NUL")
case r >= 0x80:
// not ASCII
r, w = utf8.DecodeRune(S.src[S.offset:])
r, w = utf8.DecodeRune(S.src[S.rdOffset:])
if r == utf8.RuneError && w == 1 {
S.error(S.pos, "illegal UTF-8 encoding")
S.error("illegal UTF-8 encoding")
}
}
S.offset += w
S.rdOffset += w
S.ch = r
} else {
S.pos.Offset = len(S.src)
S.offset = len(S.src)
if S.ch == '\n' {
S.column = 1
}
S.ch = -1 // eof
}
}
@ -94,9 +100,17 @@ func (S *Scanner) Init(filename string, src []byte, err ErrorHandler, mode uint)
S.src = src
S.err = err
S.mode = mode
S.pos = token.Position{filename, 0, 1, 0}
S.filename = filename
S.line = 1
S.column = 0
S.ch = ' '
S.offset = 0
S.rdOffset = 0
S.insertSemi = false
S.ErrorCount = 0
S.next()
}
@ -131,7 +145,12 @@ func charString(ch int) string {
}
func (S *Scanner) error(pos token.Position, msg string) {
func (S *Scanner) error(msg string) {
S.errorAt(token.Position{S.filename, S.offset, S.line, S.column}, msg)
}
func (S *Scanner) errorAt(pos token.Position, msg string) {
if S.err != nil {
S.err.Error(pos, msg)
}
@ -139,18 +158,28 @@ func (S *Scanner) error(pos token.Position, msg string) {
}
func (S *Scanner) expect(ch int) {
if S.ch != ch {
S.error(S.pos, "expected "+charString(ch)+", found "+charString(S.ch))
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.Index(text, []byte{':'}); i > 0 {
if line, err := strconv.Atoi(string(text[i+1:])); err == nil && line > 0 {
// valid //line filename:line comment;
// update scanner position
S.filename = string(text[len(prefix):i])
S.line = line - 1 // -1 since the '\n' has not been consumed yet
}
}
}
S.next() // always make progress
}
var prefix = []byte("line ")
func (S *Scanner) scanComment(pos token.Position) {
// first '/' already consumed
func (S *Scanner) scanComment() {
// initial '/' already consumed; S.ch == '/' || S.ch == '*'
offs := S.offset - 1 // position of initial '/'
col := S.column - 1
pos := token.Position{S.filename, S.offset - 1, S.line, S.column - 1}
if S.ch == '/' {
//-style comment
@ -159,21 +188,9 @@ func (S *Scanner) scanComment(pos token.Position) {
if S.ch == '\n' {
// '\n' is not part of the comment for purposes of scanning
// (the comment ends on the same line where it started)
if pos.Column == 1 {
text := S.src[pos.Offset+2 : S.pos.Offset]
if bytes.HasPrefix(text, prefix) {
// comment starts at beginning of line with "//line ";
// get filename and line number, if any
i := bytes.Index(text, []byte{':'})
if i >= 0 {
if line, err := strconv.Atoi(string(text[i+1:])); err == nil && line > 0 {
// valid //line filename:line comment;
// update scanner position
S.pos.Filename = string(text[len(prefix):i])
S.pos.Line = line - 1 // -1 since the '\n' has not been consumed yet
}
}
}
if col == 1 {
// comment starts at the beginning of the current line
S.interpretLineComment(S.src[offs:S.offset])
}
return
}
@ -181,7 +198,7 @@ func (S *Scanner) scanComment(pos token.Position) {
} else {
/*-style comment */
S.expect('*')
S.next()
for S.ch >= 0 {
ch := S.ch
S.next()
@ -192,47 +209,56 @@ func (S *Scanner) scanComment(pos token.Position) {
}
}
S.error(pos, "comment not terminated")
S.errorAt(pos, "comment not terminated")
}
func (S *Scanner) findLineEnd(pos token.Position) bool {
// initial '/' already consumed; pos is position of '/'
func (S *Scanner) findLineEnd() bool {
// initial '/' already consumed
defer func(line, col, offs int) {
// reset scanner state to where it was upon calling findLineEnd
// (we don't scan //line comments and ignore errors thus
// S.filename and S.ErrorCount don't change)
S.line = line
S.column = col
S.ch = '/'
S.offset = offs
S.rdOffset = offs + 1
S.next() // consume initial '/' again
}(S.line, S.column-1, S.offset-1)
// read ahead until a newline, EOF, or non-comment token is found
lineend := false
for pos1 := pos; S.ch == '/' || S.ch == '*'; {
for S.ch == '/' || S.ch == '*' {
if S.ch == '/' {
//-style comment always contains a newline
lineend = true
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.scanComment(pos1)
if pos1.Line < S.pos.Line {
/*-style comment contained a newline */
lineend = true
break
}
S.skipWhitespace() // S.insertSemi is set
if S.ch < 0 || S.ch == '\n' {
// line end
lineend = true
break
return true
}
if S.ch != '/' {
// non-comment token
break
return false
}
pos1 = S.pos
S.next() // consume '/'
}
// reset position to where it was upon calling findLineEnd
S.pos = pos
S.offset = pos.Offset + 1
S.next() // consume initial '/' again
return lineend
return false
}
@ -247,11 +273,11 @@ func isDigit(ch int) bool {
func (S *Scanner) scanIdentifier() token.Token {
pos := S.pos.Offset
offs := S.offset
for isLetter(S.ch) || isDigit(S.ch) {
S.next()
}
return token.Lookup(S.src[pos:S.pos.Offset])
return token.Lookup(S.src[offs:S.offset])
}
@ -275,7 +301,7 @@ func (S *Scanner) scanMantissa(base int) {
}
func (S *Scanner) scanNumber(pos token.Position, seenDecimalPoint bool) token.Token {
func (S *Scanner) scanNumber(seenDecimalPoint bool) token.Token {
// digitVal(S.ch) < 10
tok := token.INT
@ -287,6 +313,7 @@ func (S *Scanner) scanNumber(pos token.Position, seenDecimalPoint bool) token.To
if S.ch == '0' {
// int or float
pos := token.Position{S.filename, S.offset, S.line, S.column}
S.next()
if S.ch == 'x' || S.ch == 'X' {
// hexadecimal int
@ -306,7 +333,7 @@ func (S *Scanner) scanNumber(pos token.Position, seenDecimalPoint bool) token.To
}
// octal int
if seenDecimalDigit {
S.error(pos, "illegal octal number")
S.errorAt(pos, "illegal octal number")
}
}
goto exit
@ -343,7 +370,7 @@ exit:
func (S *Scanner) scanEscape(quote int) {
pos := S.pos
pos := token.Position{S.filename, S.offset, S.line, S.column}
var i, base, max uint32
switch S.ch {
@ -363,7 +390,7 @@ func (S *Scanner) scanEscape(quote int) {
i, base, max = 8, 16, unicode.MaxRune
default:
S.next() // always make progress
S.error(pos, "unknown escape sequence")
S.errorAt(pos, "unknown escape sequence")
return
}
@ -371,7 +398,7 @@ func (S *Scanner) scanEscape(quote int) {
for ; i > 0 && S.ch != quote && S.ch >= 0; i-- {
d := uint32(digitVal(S.ch))
if d >= base {
S.error(S.pos, "illegal character in escape sequence")
S.error("illegal character in escape sequence")
break
}
x = x*base + d
@ -382,13 +409,14 @@ func (S *Scanner) scanEscape(quote int) {
S.next()
}
if x > max || 0xd800 <= x && x < 0xe000 {
S.error(pos, "escape sequence is invalid Unicode code point")
S.errorAt(pos, "escape sequence is invalid Unicode code point")
}
}
func (S *Scanner) scanChar(pos token.Position) {
// '\'' already consumed
func (S *Scanner) scanChar() {
// '\'' opening already consumed
pos := token.Position{S.filename, S.offset - 1, S.line, S.column - 1}
n := 0
for S.ch != '\'' {
@ -396,7 +424,7 @@ func (S *Scanner) scanChar(pos token.Position) {
n++
S.next()
if ch == '\n' || ch < 0 {
S.error(pos, "character literal not terminated")
S.errorAt(pos, "character literal not terminated")
n = 1
break
}
@ -408,19 +436,20 @@ func (S *Scanner) scanChar(pos token.Position) {
S.next()
if n != 1 {
S.error(pos, "illegal character literal")
S.errorAt(pos, "illegal character literal")
}
}
func (S *Scanner) scanString(pos token.Position) {
// '"' already consumed
func (S *Scanner) scanString() {
// '"' opening already consumed
pos := token.Position{S.filename, S.offset - 1, S.line, S.column - 1}
for S.ch != '"' {
ch := S.ch
S.next()
if ch == '\n' || ch < 0 {
S.error(pos, "string not terminated")
S.errorAt(pos, "string not terminated")
break
}
if ch == '\\' {
@ -432,14 +461,15 @@ func (S *Scanner) scanString(pos token.Position) {
}
func (S *Scanner) scanRawString(pos token.Position) {
// '`' already consumed
func (S *Scanner) scanRawString() {
// '`' opening already consumed
pos := token.Position{S.filename, S.offset - 1, S.line, S.column - 1}
for S.ch != '`' {
ch := S.ch
S.next()
if ch < 0 {
S.error(pos, "string not terminated")
S.errorAt(pos, "string not terminated")
break
}
}
@ -524,7 +554,8 @@ scanAgain:
// current token start
insertSemi := false
pos, tok = S.pos, token.ILLEGAL
pos, tok = token.Position{S.filename, S.offset, S.line, S.column}, token.ILLEGAL
offs := S.offset
// determine token value
switch ch := S.ch; {
@ -536,7 +567,7 @@ scanAgain:
}
case digitVal(ch) < 10:
insertSemi = true
tok = S.scanNumber(pos, false)
tok = S.scanNumber(false)
default:
S.next() // always make progress
switch ch {
@ -555,21 +586,21 @@ scanAgain:
case '"':
insertSemi = true
tok = token.STRING
S.scanString(pos)
S.scanString()
case '\'':
insertSemi = true
tok = token.CHAR
S.scanChar(pos)
S.scanChar()
case '`':
insertSemi = true
tok = token.STRING
S.scanRawString(pos)
S.scanRawString()
case ':':
tok = S.switch2(token.COLON, token.DEFINE)
case '.':
if digitVal(S.ch) < 10 {
insertSemi = true
tok = S.scanNumber(pos, true)
tok = S.scanNumber(true)
} else if S.ch == '.' {
S.next()
if S.ch == '.' {
@ -613,15 +644,19 @@ scanAgain:
case '/':
if S.ch == '/' || S.ch == '*' {
// comment
if S.insertSemi && S.findLineEnd(pos) {
line := S.line
col := S.column - 1 // beginning of comment
if S.insertSemi && S.findLineEnd() {
// reset position to the beginning of the comment
S.pos = pos
S.offset = pos.Offset + 1
S.line = line
S.column = col
S.ch = '/'
S.offset = offs
S.rdOffset = offs + 1
S.insertSemi = false // newline consumed
return pos, token.SEMICOLON, newline
}
S.scanComment(pos)
S.scanComment()
if S.mode&ScanComments == 0 {
// skip comment
S.insertSemi = false // newline consumed
@ -659,7 +694,7 @@ scanAgain:
tok = S.switch3(token.OR, token.OR_ASSIGN, '|', token.LOR)
default:
if S.mode&AllowIllegalChars == 0 {
S.error(pos, "illegal character "+charString(ch))
S.errorAt(pos, "illegal character "+charString(ch))
}
insertSemi = S.insertSemi // preserve insertSemi info
}
@ -668,7 +703,7 @@ scanAgain:
if S.mode&InsertSemis != 0 {
S.insertSemi = insertSemi
}
return pos, tok, S.src[pos.Offset:S.pos.Offset]
return pos, tok, S.src[offs:S.offset]
}

20
src/pkg/go/scanner/scanner_test.go
View File

@ -198,16 +198,16 @@ func newlineCount(s string) int {
func checkPos(t *testing.T, lit string, pos, expected token.Position) {
if pos.Filename != expected.Filename {
t.Errorf("bad filename for %s: got %s, expected %s", lit, pos.Filename, expected.Filename)
t.Errorf("bad filename for %q: got %s, expected %s", lit, pos.Filename, expected.Filename)
}
if pos.Offset != expected.Offset {
t.Errorf("bad position for %s: got %d, expected %d", lit, pos.Offset, expected.Offset)
t.Errorf("bad position for %q: got %d, expected %d", lit, pos.Offset, expected.Offset)
}
if pos.Line != expected.Line {
t.Errorf("bad line for %s: got %d, expected %d", lit, pos.Line, expected.Line)
t.Errorf("bad line for %q: got %d, expected %d", lit, pos.Line, expected.Line)
}
if pos.Column != expected.Column {
t.Errorf("bad column for %s: got %d, expected %d", lit, pos.Column, expected.Column)
t.Errorf("bad column for %q: got %d, expected %d", lit, pos.Column, expected.Column)
}
}
@ -276,15 +276,15 @@ func checkSemi(t *testing.T, line string, mode uint) {
semiLit = ";"
}
// next token must be a semicolon
offs := pos.Offset + 1
semiPos := pos
semiPos.Offset++
semiPos.Column++
pos, tok, lit = S.Scan()
if tok == token.SEMICOLON {
if pos.Offset != offs {
t.Errorf("bad offset for %q: got %d, expected %d", line, pos.Offset, offs)
}
if string(lit) != semiLit {
t.Errorf(`bad literal for %q: got %q, expected %q`, line, lit, semiLit)
}
checkPos(t, line, pos, semiPos)
} else {
t.Errorf("bad token for %q: got %s, expected ;", line, tok.String())
}
@ -399,11 +399,13 @@ var lines = []string{
"foo$/*\n*/",
"foo$/*comment*/ \n",
"foo$/*\n*/ ",
"foo $// comment\n",
"foo $/*comment*/\n",
"foo $/*\n*/",
"foo $/* */ /* \n */ bar$/**/\n",
"foo $/*0*/ /*1*/ /*2*/\n",
"foo $/*comment*/ \n",
"foo $/*0*/ /*1*/ /*2*/ \n",
"foo $/**/ /*-------------*/ /*----\n*/bar $/* \n*/baa$\n",