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fix bug in prefix code: must stop one character before any potential match of an empty string

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Fixes #308.

R=rsc
CC=golang-dev
https://golang.org/cl/157142
This commit is contained in:
Rob Pike 2009-11-23 14:06:21 -08:00
parent b050a1b223
commit 3b7f552fbb
2 changed files with 8 additions and 3 deletions
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9
src/pkg/regexp/regexp.go
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@ -633,15 +633,18 @@ func (re *Regexp) setPrefix() {
var utf = make([]byte, utf8.UTFMax);
// First instruction is start; skip that.
i := re.inst.At(0).(instr).next().index();
Loop:
for i < re.inst.Len() {
inst := re.inst.At(i).(instr);
// stop if this is not a char
if inst.kind() != _CHAR {
break
}
// stop if this char starts a closure; liberal but easy test: is an ALT next?
if re.inst.At(inst.next().index()).(instr).kind() == _ALT {
break
// stop if this char can be followed by a match for an empty string,
// which includes closures, ^, and $.
switch re.inst.At(inst.next().index()).(instr).kind() {
case _BOT, _EOT, _ALT:
break Loop
}
n := utf8.EncodeRune(inst.(*_Char).char, utf);
b = bytes.Add(b, utf[0:n]);