Skip to content

regexp: speed up onepass prefix check #48892

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
wants to merge 2 commits into
base: master
Choose a base branch
from
+21 −22
Open

regexp: speed up onepass prefix check #48892

Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
8574350
regexp: speed up onepass prefix check
bboreham Oct 9, 2021
d63b833
Neaten up
bboreham Oct 11, 2021
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
43 changes: 21 additions & 22 deletions src/regexp/exec.go
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -401,46 +401,45 @@ func (re *Regexp) doOnePass(ir io.RuneReader, ib []byte, is string, pos, ncap in
}

m := newOnePassMachine()
matched := false
i, _ := m.inputs.init(ir, ib, is)

r, r1 := endOfText, endOfText
width, width1 := 0, 0
var flag lazyFlag
var pc int
var inst onePassInst

// If there is a simple literal prefix, skip over it.
if pos == 0 && len(re.prefix) > 0 && i.canCheckPrefix() {
// Match requires literal prefix; fast search for it.
if !i.hasPrefix(re) {
goto Return
}
pos += len(re.prefix)
pc = int(re.prefixEnd)
} else {
pc = re.onepass.Start
}

if cap(m.matchcap) < ncap {
m.matchcap = make([]int, ncap)
} else {
m.matchcap = m.matchcap[:ncap]
}

matched := false
for i := range m.matchcap {
m.matchcap[i] = -1
}

i, _ := m.inputs.init(ir, ib, is)

r, r1 := endOfText, endOfText
width, width1 := 0, 0
r, width = i.step(pos)
if r != endOfText {
r1, width1 = i.step(pos + width)
}
var flag lazyFlag
if pos == 0 {
flag = newLazyFlag(-1, r)
} else {
flag = i.context(pos)
}
pc := re.onepass.Start
inst := re.onepass.Inst[pc]
// If there is a simple literal prefix, skip over it.
if pos == 0 && flag.match(syntax.EmptyOp(inst.Arg)) &&
len(re.prefix) > 0 && i.canCheckPrefix() {
// Match requires literal prefix; fast search for it.
if !i.hasPrefix(re) {
goto Return
}
pos += len(re.prefix)
r, width = i.step(pos)
r1, width1 = i.step(pos + width)
flag = i.context(pos)
pc = int(re.prefixEnd)
}
for {
inst = re.onepass.Inst[pc]
pc = int(inst.Out)
Expand Down