From 0855c8a7b1fccea7a83e271a658636d4b0e07e39 Mon Sep 17 00:00:00 2001
From: Fabrice Vaillant <fabrice.vaillant@adevinta.com>
Date: Fri, 14 Apr 2023 11:41:37 +0200
Subject: [PATCH] Also precompute hook in decoder

---
 mapstructure.go | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/mapstructure.go b/mapstructure.go
index 4b54fae..39c555d 100644
--- a/mapstructure.go
+++ b/mapstructure.go
@@ -283,7 +283,8 @@ type DecoderConfig struct {
 // structure. The top-level Decode method is just a convenience that sets
 // up the most basic Decoder.
 type Decoder struct {
-	config *DecoderConfig
+	config           *DecoderConfig
+	cachedDecodeHook func(from reflect.Value, to reflect.Value) (interface{}, error)
 }
 
 // Metadata contains information about decoding a structure that
@@ -408,6 +409,9 @@ func NewDecoder(config *DecoderConfig) (*Decoder, error) {
 	result := &Decoder{
 		config: config,
 	}
+	if config.DecodeHook != nil {
+		result.cachedDecodeHook = cachedDecodeHook(config.DecodeHook)
+	}
 
 	return result, nil
 }
@@ -462,10 +466,10 @@ func (d *Decoder) decode(name string, input interface{}, outVal reflect.Value) e
 		return nil
 	}
 
-	if d.config.DecodeHook != nil {
+	if d.cachedDecodeHook != nil {
 		// We have a DecodeHook, so let's pre-process the input.
 		var err error
-		input, err = DecodeHookExec(d.config.DecodeHook, inputVal, outVal)
+		input, err = d.cachedDecodeHook(inputVal, outVal)
 		if err != nil {
 			return fmt.Errorf("error decoding '%s': %w", name, err)
 		}