From 8e6f1f1740ee9f7c8e3832bc2340a099e88b05bd Mon Sep 17 00:00:00 2001
From: John <john@johng.cn>
Date: Mon, 25 May 2020 23:39:09 +0800
Subject: [PATCH] improve performance of random buffer usage for package grand

---
 .example/other/test.go     | 10 ++++++++++
 .example/util/guid/guid.go |  5 +----
 util/grand/grand_buffer.go | 26 +++++++++++++++++++++-----
 3 files changed, 32 insertions(+), 9 deletions(-)

diff --git a/.example/other/test.go b/.example/other/test.go
index 233938c85..f6e15be50 100644
--- a/.example/other/test.go
+++ b/.example/other/test.go
@@ -3,8 +3,18 @@ package main
 import (
 	"fmt"
 	"github.com/gogf/gf/encoding/gjson"
+	"github.com/gogf/gf/net/ghttp"
+	"github.com/gogf/gf/util/guid"
 )
 
+func CreateSessionId(r *ghttp.Request) string {
+	var (
+		agent   = r.UserAgent()
+		address = r.RemoteAddr
+		cookie  = r.Header.Get("Cookie")
+	)
+	return guid.S([]byte(agent), []byte(address), []byte(cookie))
+}
 func main() {
 	body := "{\"id\": 413231383385427875}"
 	if dat, err := gjson.DecodeToJson(body); err == nil {
diff --git a/.example/util/guid/guid.go b/.example/util/guid/guid.go
index 39bbdc6b3..439cf9869 100644
--- a/.example/util/guid/guid.go
+++ b/.example/util/guid/guid.go
@@ -6,8 +6,5 @@ import (
 )
 
 func main() {
-	for i := 0; i < 1000; i++ {
-		s := guid.S()
-		fmt.Println(s, len(s))
-	}
+	fmt.Printf("TraceId: %s\n", guid.S())
 }
diff --git a/util/grand/grand_buffer.go b/util/grand/grand_buffer.go
index 95c658444..d83801edb 100644
--- a/util/grand/grand_buffer.go
+++ b/util/grand/grand_buffer.go
@@ -29,15 +29,31 @@ func init() {
 // to produce the random bytes, and a buffer chan to store the random bytes.
 // So it has high performance to generate random numbers.
 func asyncProducingRandomBufferBytesLoop() {
-	buffer := make([]byte, 1024)
+	var step int
 	for {
+		buffer := make([]byte, 1024)
 		if n, err := rand.Read(buffer); err != nil {
 			panic(err)
 		} else {
-			for i := 0; i < n-4; i += 4 {
-				b := make([]byte, 4)
-				copy(b, buffer[i:i+4])
-				bufferChan <- b
+			// The random buffer from system is very expensive,
+			// so fully reuse the random buffer by changing
+			// the step with a different prime number can
+			// improve the performance a lot.
+			step = 4
+			for i := 0; i < n-4; i += step {
+				bufferChan <- buffer[i : i+4]
+			}
+			step = 5
+			for i := 0; i < n-4; i += step {
+				bufferChan <- buffer[i : i+4]
+			}
+			step = 7
+			for i := 0; i < n-4; i += step {
+				bufferChan <- buffer[i : i+4]
+			}
+			step = 13
+			for i := 0; i < n-4; i += step {
+				bufferChan <- buffer[i : i+4]
 			}
 		}
 	}