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regexp: bug fix: need to track whether match begins with fixed prefix.

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Fixes #872.

R=rsc
CC=golang-dev
https://golang.org/cl/1731043
This commit is contained in:
Rob Pike 2010-06-22 16:02:14 -07:00
parent 537e5f4b7e
commit a8cd6c2012
2 changed files with 20 additions and 17 deletions
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3
src/pkg/regexp/all_test.go
View File

@ -100,7 +100,8 @@ var matches = []tester{
// fixed bugs
tester{`ab$`, "cab", vec{1, 3}},
tester{`axxb$`, "axxcb", vec{}},
tester{`data`, "daXY data", vec{5, 9}},
tester{`da(.)a$`, "daXY data", vec{5, 9, 7, 8}},
// can backslash-escape any punctuation
tester{`\!\"\#\$\%\&\'\(\)\*\+\,\-\.\/\:\;\<\=\>\?\@\[\\\]\^\_\{\|\}\~`,

34
src/pkg/regexp/regexp.go
View File

@ -727,34 +727,35 @@ func (a *matchArena) noMatch() *matchVec {
}
type state struct {
inst instr // next instruction to execute
match *matchVec
inst instr // next instruction to execute
prefixed bool // this match began with a fixed prefix
match *matchVec
}
// Append new state to to-do list. Leftmost-longest wins so avoid
// adding a state that's already active. The matchVec will be inc-ref'ed
// if it is assigned to a state.
func (a *matchArena) addState(s []state, inst instr, match *matchVec, pos, end int) []state {
func (a *matchArena) addState(s []state, inst instr, prefixed bool, match *matchVec, pos, end int) []state {
switch inst.kind() {
case _BOT:
if pos == 0 {
s = a.addState(s, inst.next(), match, pos, end)
s = a.addState(s, inst.next(), prefixed, match, pos, end)
}
return s
case _EOT:
if pos == end {
s = a.addState(s, inst.next(), match, pos, end)
s = a.addState(s, inst.next(), prefixed, match, pos, end)
}
return s
case _BRA:
n := inst.(*_Bra).n
match.m[2*n] = pos
s = a.addState(s, inst.next(), match, pos, end)
s = a.addState(s, inst.next(), prefixed, match, pos, end)
return s
case _EBRA:
n := inst.(*_Ebra).n
match.m[2*n+1] = pos
s = a.addState(s, inst.next(), match, pos, end)
s = a.addState(s, inst.next(), prefixed, match, pos, end)
return s
}
index := inst.index()
@ -773,12 +774,13 @@ func (a *matchArena) addState(s []state, inst instr, match *matchVec, pos, end i
}
s = s[0 : l+1]
s[l].inst = inst
s[l].prefixed = prefixed
s[l].match = match
match.ref++
if inst.kind() == _ALT {
s = a.addState(s, inst.(*_Alt).left, a.copy(match), pos, end)
s = a.addState(s, inst.(*_Alt).left, prefixed, a.copy(match), pos, end)
// give other branch a copy of this match vector
s = a.addState(s, inst.next(), a.copy(match), pos, end)
s = a.addState(s, inst.next(), prefixed, a.copy(match), pos, end)
}
return s
}
@ -818,10 +820,10 @@ func (re *Regexp) doExecute(str string, bytestr []byte, pos int) []int {
match := arena.noMatch()
match.m[0] = pos
if prefixed {
s[out] = arena.addState(s[out], re.prefixStart, match, pos, end)
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(), 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
}
@ -852,19 +854,19 @@ func (re *Regexp) doExecute(str string, bytestr []byte, pos int) []int {
case _EOT:
case _CHAR:
if c == st.inst.(*_Char).char {
s[out] = arena.addState(s[out], st.inst.next(), st.match, pos, end)
s[out] = arena.addState(s[out], st.inst.next(), st.prefixed, st.match, pos, end)
}
case _CHARCLASS:
if st.inst.(*_CharClass).matches(c) {
s[out] = arena.addState(s[out], st.inst.next(), st.match, pos, end)
s[out] = arena.addState(s[out], st.inst.next(), st.prefixed, st.match, pos, end)
}
case _ANY:
if c != endOfFile {
s[out] = arena.addState(s[out], st.inst.next(), st.match, pos, end)
s[out] = arena.addState(s[out], st.inst.next(), st.prefixed, st.match, pos, end)
}
case _NOTNL:
if c != endOfFile && c != '\n' {
s[out] = arena.addState(s[out], st.inst.next(), st.match, pos, end)
s[out] = arena.addState(s[out], st.inst.next(), st.prefixed, st.match, pos, end)
}
case _BRA:
case _EBRA:
@ -892,7 +894,7 @@ func (re *Regexp) doExecute(str string, bytestr []byte, pos int) []int {
return nil
}
// if match found, back up start of match by width of prefix.
if re.prefix != "" && len(final.match.m) > 0 {
if final.prefixed && len(final.match.m) > 0 {
final.match.m[0] -= len(re.prefix)
}
return final.match.m