transform/urlreplacers: Cache the next position of `urlreplacer.prefix`

Improved performance due to `bytes.Index` repeated calls

Fixes #5942

diff --git a/transform/urlreplacers/absurlreplacer.go b/transform/urlreplacers/absurlreplacer.go
index 545df914af3830d29bfabd12e2264fec493b2b75..3fef013fb1b21ba2f2fb52845ee318e6f962a278 100644 (file)
--- a/transform/urlreplacers/absurlreplacer.go
+++ b/transform/urlreplacers/absurlreplacer.go
@@ -41,6 +41,28 @@ type prefix struct {
        disabled bool
        b        []byte
        f        func(l *absurllexer)
+
+       nextPos int
+}
+
+func (p *prefix) find(bs []byte, start int) bool {
+       if p.disabled {
+               return false
+       }
+
+       if p.nextPos == -1 {
+               idx := bytes.Index(bs[start:], p.b)
+
+               if idx == -1 {
+                       p.disabled = true
+                       // Find the closest match
+                       return false
+               }
+
+               p.nextPos = start + idx + len(p.b)
+       }
+
+       return true
 }
 
 func newPrefixState() []*prefix {
@@ -179,35 +201,28 @@ func (l *absurllexer) replace() {
                        break
                }
 
-               nextPos := -1
-
                var match *prefix
 
                for _, p := range prefixes {
-                       if p.disabled {
+                       if !p.find(l.content, l.pos) {
                                continue
                        }
-                       idx := bytes.Index(l.content[l.pos:], p.b)
 
-                       if idx == -1 {
-                               p.disabled = true
-                               // Find the closest match
-                       } else if nextPos == -1 || idx < nextPos {
-                               nextPos = idx
+                       if match == nil || p.nextPos < match.nextPos {
                                match = p
                        }
                }
 
-               if nextPos == -1 {
+               if match == nil {
                        // Done!
                        l.pos = contentLength
                        break
                } else {
-                       l.pos += nextPos + len(match.b)
+                       l.pos = match.nextPos
+                       match.nextPos = -1
                        match.f(l)
                }
        }
-
        // Done!
        if l.pos > l.start {
                l.emit()