From 93441d04fd3a9f4eedad13ee4d6d58cd4b75ffdc Mon Sep 17 00:00:00 2001
From: asahi <mikiyashiki@outlook.com>
Date: Sat, 18 Jan 2025 01:45:05 +0800
Subject: [PATCH] =?UTF-8?q?=E9=98=85=E8=AF=BBbuffered=20io=E6=96=87?=
 =?UTF-8?q?=E6=A1=A3?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 Golang/Golang Document.md | 95 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 95 insertions(+)

diff --git a/Golang/Golang Document.md b/Golang/Golang Document.md
index 016808b..be5ba21 100644
--- a/Golang/Golang Document.md	
+++ b/Golang/Golang Document.md	
@@ -70,6 +70,8 @@
 		- [compare time](#compare-time)
 		- [Sub](#sub)
 		- [time.Duration](#timeduration)
+	- [Bufio](#bufio)
+		- [Buffered Reader](#buffered-reader)
 	- [syntax](#syntax)
 		- [iota](#iota)
 
@@ -1475,6 +1477,99 @@ const (
 2010-12-17 19:03:32 +0000 UTC
 ```
 
+## Bufio
+`bufio`为golang中的一个包，提供了带缓冲的读写功能。
+
+### Buffered Reader
+如果要创建一个buffered reader，可以使用`bufio.NewReader`方法，该方法接受一个`io.Reader`作为参数，返回类型则是`*bufio.Reader`。
+
+常用的`bufio.NewReader`的入参为`os.File`, `strings.Reader`, `bytes.Buffer`。
+
+使用带缓冲区io和不带缓冲区io，针对`10M`的文件，性能差别如下所示。
+
+测试文件如下，大小为`10M`
+```bash
+$ ls -lh random.file
+-rw-r--r-- 1 Asahi 197609 10M Jan 18 01:24 random.file
+```
+
+带缓冲和不带缓冲代码如下：
+```go
+func CountWithoutBuf(filename string, b byte) (cnt uint64) {
+	file, err := os.OpenFile(filename, os.O_RDONLY, 0)
+	if err != nil {
+		panic(any(err))
+	}
+	defer file.Close()
+	cnt = 0
+	bs := []byte{0}
+	for {
+		_,err = file.Read(bs)
+		if err == io.EOF {
+			break
+		} else if err != nil {
+			panic(any(err))
+		} else if bs[0] == b {
+			cnt++
+		}
+	}
+	return
+}
+
+func CountWithBuf(filename string, b byte) (cnt uint64) {
+	file, err := os.OpenFile(filename, os.O_RDONLY, 0)
+	if err != nil {
+		panic(any(err))
+	}
+	defer file.Close()
+	cnt = 0
+	bs := []byte{0}
+	br := bufio.NewReader(file)
+	for {
+		_,err = br.Read(bs)
+		if err == io.EOF {
+			break
+		} else if err != nil {
+			panic(any(err))
+		} else if bs[0] == b {
+			cnt++
+		}
+	}
+	return
+}
+```
+
+benchmark测试代码如下：
+```go
+func BenchmarkCountWithBuf(b *testing.B) {
+	CountWithBuf(FileName, B)
+}
+
+func BenchmarkCountWithoutBuf(b *testing.B) {
+	CountWithoutBuf(FileName, B)
+}
+```
+执行benchmark命令：
+```bash
+go test -bench=.*
+```
+
+测试结果返回如下：
+```
+goos: windows
+goarch: amd64
+pkg: git.kazusa.red/asahi/bufio
+cpu: AMD Ryzen 9 7950X 16-Core Processor
+BenchmarkCountWithBuf-32        1000000000               0.03209 ns/op
+BenchmarkCountWithoutBuf-32            1        8937341700 ns/op
+PASS
+ok      git.kazusa.red/asahi/bufio      9.254s
+```
+可知，带缓冲场景下10M文件每次读取花费`0.03209 ns`，而不带缓冲按字节读取时每次读取花费`8.93s`。
+
+
+
+
 
 ## syntax
 ### iota