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regexp: fix prefix bug.

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After a prefix match, the old code advanced the length of the
prefix.  This is incorrect since the full match might begin
in the middle of the prefix. (Consider "aaaab+" matching
"aaaaaab").

Fixes #1373

R=rsc
CC=golang-dev
https://golang.org/cl/3795044
This commit is contained in:
Rob Pike 2011-01-03 11:35:34 -08:00
parent c0d0d4ef05
commit 15cb7ed34f
2 changed files with 3 additions and 9 deletions
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1
src/pkg/regexp/find_test.go
View File

@ -78,6 +78,7 @@ var findTests = []FindTest{
{`axxb$`, "axxcb", nil},
{`data`, "daXY data", build(1, 5, 9)},
{`da(.)a$`, "daXY data", build(1, 5, 9, 7, 8)},
{`zx+`, "zzx", build(1, 1, 3)},
// can backslash-escape any punctuation
{`\!\"\#\$\%\&\'\(\)\*\+\,\-\.\/\:\;\<\=\>\?\@\[\\\]\^\_\{\|\}\~`,

11
src/pkg/regexp/regexp.go
View File

@ -758,7 +758,6 @@ func (re *Regexp) doExecute(str string, bytestr []byte, pos int) []int {
return nil
}
// fast check for initial plain substring
prefixed := false // has this iteration begun by skipping a prefix?
if re.prefix != "" {
advance := 0
if anchored {
@ -781,8 +780,7 @@ func (re *Regexp) doExecute(str string, bytestr []byte, pos int) []int {
if advance == -1 {
return nil
}
pos += advance + len(re.prefix)
prefixed = true
pos += advance
}
arena := &matchArena{nil, 2 * (re.nbra + 1)}
for pos <= end {
@ -790,12 +788,7 @@ func (re *Regexp) doExecute(str string, bytestr []byte, pos int) []int {
// prime the pump if we haven't seen a match yet
match := arena.noMatch()
match.m[0] = pos
if prefixed {
s[out] = arena.addState(s[out], re.prefixStart, true, match, pos, end)
prefixed = false // next iteration should start at beginning of machine.
} else {
s[out] = arena.addState(s[out], re.start.next, false, match, pos, end)
}
s[out] = arena.addState(s[out], re.start.next, false, match, pos, end)
arena.free(match) // if addState saved it, ref was incremented
}
in, out = out, in // old out state is new in state