remove string copies from cgo ref pool

Signed-off-by: Eliott Bouhana <[email protected]>

cgo_ref_pool.go

@@ -20,7 +20,7 @@ import (
 // wafObject are either arrays (for maps, structs and arrays) or string (for all ints, booleans and strings),
 // we can store 2 slices of arrays and use runtime.KeepAlive in each code path to protect them from the GC.
 type cgoRefPool struct {
-	stringRefs [][]byte
+	stringRefs []string
 	arrayRefs  [][]wafObject
 }
 
@@ -30,12 +30,9 @@ func (refPool *cgoRefPool) append(newRefs cgoRefPool) {
 }
 
 func (refPool *cgoRefPool) AllocCString(str string) uintptr {
-	goArray := make([]byte, len(str)+1)
-	copy(goArray, str)
-	refPool.stringRefs = append(refPool.stringRefs, goArray)
-	goArray[len(str)] = 0 // Null termination byte for C strings
-
-	return sliceToUintptr(goArray)
+	nullTerminated := str + "\x00"
+	refPool.stringRefs = append(refPool.stringRefs, nullTerminated)
+	return nativeStringUnwrap(nullTerminated).Data
 }
 
 func (refPool *cgoRefPool) AllocWafString(obj *wafObject, str string) {
@@ -47,12 +44,10 @@ func (refPool *cgoRefPool) AllocWafString(obj *wafObject, str string) {
 		return
 	}
 
-	goArray := make([]byte, len(str))
-	copy(goArray, str)
-	refPool.stringRefs = append(refPool.stringRefs, goArray)
-
-	obj.value = sliceToUintptr(goArray)
-	obj.nbEntries = uint64(len(goArray))
+	refPool.stringRefs = append(refPool.stringRefs, str)
+	stringHeader := nativeStringUnwrap(str)
+	obj.value = stringHeader.Data
+	obj.nbEntries = uint64(stringHeader.Len)
 }
 
 func (refPool *cgoRefPool) AllocWafArray(obj *wafObject, typ wafObjectType, size uint64) []wafObject {
@@ -81,10 +76,8 @@ func (refPool *cgoRefPool) AllocWafMapKey(obj *wafObject, str string) {
 		return
 	}
 
-	goArray := make([]byte, len(str))
-	copy(goArray, str)
-	refPool.stringRefs = append(refPool.stringRefs, goArray)
-
-	obj.parameterName = sliceToUintptr(goArray)
-	obj.parameterNameLength = uint64(len(goArray))
+	refPool.stringRefs = append(refPool.stringRefs, str)
+	stringHeader := nativeStringUnwrap(str)
+	obj.parameterName = stringHeader.Data
+	obj.parameterNameLength = uint64(stringHeader.Len)
 }

ctypes.go

@@ -114,6 +114,11 @@ func gostring(ptr *byte) string {
 	return string(unsafe.Slice(ptr, length))
 }
 
+// nativeStringUnwrap cast a native string type into it's runtime value. Exported as the struct reflect.StringHeader
+func nativeStringUnwrap(str string) reflect.StringHeader {
+	return *(*reflect.StringHeader)(unsafe.Pointer(&str))
+}
+
 func gostringSized(ptr *byte, size uint64) string {
 	if ptr == nil {
 		return ""

waf_test.go

@@ -1453,6 +1453,7 @@ func BenchmarkEncoder(b *testing.B) {
 			containerMaxSize: 100,
 		}
 		b.Run(fmt.Sprintf("%d", l), func(b *testing.B) {
+			b.ReportAllocs()
 			str := fullstr[:l]
 			slice := []string{str, str, str, str, str, str, str, str, str, str}
 			data := map[string]interface{}{