feature: use pool for EscapeHTML (bytedance#866)

Author: bimoadityar

internal/encoder/encoder.go

@@ -21,7 +21,6 @@ import (
 	"encoding/json"
 	"reflect"
 	"runtime"
-	"unsafe"
 
 	"github.com/bytedance/sonic/utf8"
 	"github.com/bytedance/sonic/internal/encoder/alg"
@@ -181,16 +180,7 @@ func Encode(val interface{}, opts Options) ([]byte, error) {
     }
 
     /* htmlescape or correct UTF-8 if opts enable */
-    old := buf
-    *buf = encodeFinish(*old, opts)
-    pbuf := ((*rt.GoSlice)(unsafe.Pointer(buf))).Ptr
-    pold := ((*rt.GoSlice)(unsafe.Pointer(old))).Ptr
-
-    /* return when allocated a new buffer */
-    if pbuf != pold {
-        vars.FreeBytes(old)
-        return *buf, nil
-    }
+    encodeFinishWithPool(buf, opts)
 
     /* make a copy of the result */
     if rt.CanSizeResue(cap(*buf)) {
@@ -243,6 +233,20 @@ func encodeFinish(buf []byte, opts Options) []byte {
     return buf
 }
 
+func encodeFinishWithPool(buf *[]byte, opts Options) {
+    if opts & EscapeHTML != 0 {
+        dst := vars.NewBytes()
+        // put the result bytes to buf and the old buf to dst to return to the pool.
+        // we cannot return buf to the pool because it will be used by the caller.
+        *buf, *dst = HTMLEscape(*dst, *buf), *buf
+        vars.FreeBytes(dst)
+    }
+    if (opts & ValidateString != 0) && !utf8.Validate(*buf) {
+        dst := vars.NewBytes()
+        *buf, *dst = utf8.CorrectWith(*dst, *buf, `\ufffd`), *buf
+        vars.FreeBytes(dst)
+    }
+}
 
 // HTMLEscape appends to dst the JSON-encoded src with <, >, &, U+2028 and U+2029
 // characters inside string literals changed to \u003c, \u003e, \u0026, \u2028, \u2029