Golang bytes.buffer
原文链接：https://www.kancloud.cn/digest/batu-go/153538
bytes.buffer是一个缓冲byte类型的缓冲器存放着都是byte
Buffer 是 bytes 包中的一个 type Buffer struct{…}
A buffer is a variable-sized buffer of bytes with Read and Write methods. The zero value for Buffer is an empty buffer ready to use.
（是一个变长的 buffer，具有 Read 和Write 方法。 Buffer 的 零值 是一个 空的 buffer，但是可以使用）
Buffer 就像一个集装箱容器，可以存东西，取东西（存取数据）
- 创建 一个 Buffer （其实底层就是一个 []byte， 字节切片）
- 向其中写入数据 (Write mtheods)
- 从其中读取数据 (Write methods)
创建 Buffer缓冲器
var b bytes.Buffer //直接定义一个 Buffer 变量，而不用初始化
b.Writer([]byte("Hello ")) // 可以直接使用
b1 := new(bytes.Buffer) //直接使用 new 初始化，可以直接使用
// 其它两种定义方式
func NewBuffer(buf []byte) *Buffer
func NewBufferString(s string) *Buffer
NewBuffer
// NewBuffer creates and initializes a new Buffer using buf as its initial
// contents. It is intended to prepare a Buffer to read existing data. It
// can also be used to size the internal buffer for writing. To do that,
// buf should have the desired capacity but a length of zero.
//
// In most cases, new(Buffer) (or just declaring a Buffer variable) is
// sufficient to initialize a Buffer.
func NewBuffer(buf []byte) *Buffer { return &Buffer{buf: buf} }
- NewBuffer使用buf作为参数初始化Buffer，
- Buffer既可以被读也可以被写
- 如果是读Buffer，buf需填充一定的数据
- 如果是写，buf需有一定的容量(capacity)，当然也可以通过new(Buffer)来初始化Buffer。另外一个方法NewBufferString用一个string来初始化可读Buffer，并用string的内容填充Buffer.
func IntToBytes(n int) []byte {
x := int32(n)
//创建一个内容是[]byte的slice的缓冲器
//与bytes.NewBufferString("")等效
bytesBuffer := bytes.NewBuffer([]byte{})
binary.Write(bytesBuffer, binary.BigEndian, x)
return bytesBuffer.Bytes()
}
NewBufferString
- 方法NewBufferString用一个string来初始化可读Buffer，并用string的内容填充Buffer.
- 用法和NewBuffer没有太大区别
// NewBufferString creates and initializes a new Buffer using string s as its
// initial contents. It is intended to prepare a buffer to read an existing
// string.
//
// In most cases, new(Buffer) (or just declaring a Buffer variable) is
// sufficient to initialize a Buffer.
func NewBufferString(s string) *Buffer {
return &Buffer{buf: []byte(s)}
}
func TestBufferString(){
buf1:=bytes.NewBufferString("swift")
buf2:=bytes.NewBuffer([]byte("swift"))
buf3:=bytes.NewBuffer([]byte{'s','w','i','f','t'})
fmt.Println("===========以下buf1,buf2,buf3等效=========")
fmt.Println("buf1:", buf1)
fmt.Println("buf2:", buf2)
fmt.Println("buf3:", buf3)
fmt.Println("===========以下创建空的缓冲器等效=========")
buf4:=bytes.NewBufferString("")
buf5:=bytes.NewBuffer([]byte{})
fmt.Println("buf4:", buf4)
fmt.Println("buf5:", buf5)
}
输出：
===========以下buf1,buf2,buf3等效=========
buf1: swift
buf2: swift
buf3: swift
===========以下创建空的缓冲器等效=========
buf4:
buf5:
向 Buffer 中写入数据
Write
把字节切片 p 写入到buffer中去。
// Write appends the contents of p to the buffer, growing the buffer as
// needed. The return value n is the length of p; err is always nil. If the
// buffer becomes too large, Write will panic with ErrTooLarge.
func (b *Buffer) Write(p []byte) (n int, err error) {
b.lastRead = opInvalid
m := b.grow(len(p))
return copy(b.buf[m:], p), nil
}
fmt.Println("===========以下通过Write把swift写入Learning缓冲器尾部=========")
newBytes := []byte("swift")
//创建一个内容Learning的缓冲器
buf := bytes.NewBuffer([]byte("Learning"))
//打印为Learning
fmt.Println(buf.String())
//将newBytes这个slice写到buf的尾部
buf.Write(newBytes)
fmt.Println(buf.String())
打印：
===========以下通过Write把swift写入Learning缓冲器尾部=========
Learning
Learningswift
WriteString
使用WriteString方法，将一个字符串放到缓冲器的尾部
// WriteString appends the contents of s to the buffer, growing the buffer as
// needed. The return value n is the length of s; err is always nil. If the
// buffer becomes too large, WriteString will panic with ErrTooLarge.
func (b *Buffer) WriteString(s string) (n int, err error) {
b.lastRead = opInvalid
m := b.grow(len(s))
return copy(b.buf[m:], s), nil
}
fmt.Println("===========以下通过WriteString把swift写入Learning缓冲器尾部=========")
newString := "swift"
//创建一个string内容Learning的缓冲器
buf := bytes.NewBufferString("Learning")
//打印为Learning
fmt.Println(buf.String())
//将newString这个string写到buf的尾部
buf.WriteString(newString)
fmt.Println(buf.String())
打印：
===========以下通过Write把swift写入Learning缓冲器尾部=========
Learning
Learningswift
WriteByte
将一个byte类型的数据放到缓冲器的尾部
// WriteByte appends the byte c to the buffer, growing the buffer as needed.
// The returned error is always nil, but is included to match bufio.Writer's
// WriteByte. If the buffer becomes too large, WriteByte will panic with
// ErrTooLarge.
func (b *Buffer) WriteByte(c byte) error {
b.lastRead = opInvalid
m := b.grow(1)
b.buf[m] = c
return nil
}
fmt.Println("===========以下通过WriteByte把!写入Learning缓冲器尾部=========")
var newByte byte = '!'
//创建一个string内容Learning的缓冲器
buf := bytes.NewBufferString("Learning")
//打印为Learning
fmt.Println(buf.String())
//将newString这个string写到buf的尾部
buf.WriteByte(newByte)
fmt.Println(buf.String())
打印：
===========以下通过WriteByte把swift写入Learning缓冲器尾部=========
Learning
Learning!
WriteRune
将一个rune类型的数据放到缓冲器的尾部
// WriteRune appends the UTF-8 encoding of Unicode code point r to the
// buffer, returning its length and an error, which is always nil but is
// included to match bufio.Writer's WriteRune. The buffer is grown as needed;
// if it becomes too large, WriteRune will panic with ErrTooLarge.
func (b *Buffer) WriteRune(r rune) (n int, err error) {
if r < utf8.RuneSelf {
b.WriteByte(byte(r))
return 1, nil
}
n = utf8.EncodeRune(b.runeBytes[0:], r)
b.Write(b.runeBytes[0:n])
return n, nil
}
fmt.Println("===========以下通过WriteRune把\"好\"写入Learning缓冲器尾部=========")
var newRune = '好'
//创建一个string内容Learning的缓冲器
buf := bytes.NewBufferString("Learning")
//打印为Learning
fmt.Println(buf.String())
//将newString这个string写到buf的尾部
buf.WriteRune(newRune)
fmt.Println(buf.String())
打印：
===========以下通过WriteRune把”好”写入Learning缓冲器尾部=========
Learning
Learning好
完整示例
package main
import (
"bytes"
"encoding/binary"
"fmt"
)
func main() {
//newBuffer 整形转换成字节
var n int = 10000
intToBytes := IntToBytes(n)
fmt.Println("==========int to bytes========")
fmt.Println(intToBytes)
//NewBufferString
TestBufferString()
//write
BufferWrite()
//WriteString
BufferWriteString()
//WriteByte
BufferWriteByte()
//WriteRune
BufferWriteRune()
}
func IntToBytes(n int) []byte {
x := int32(n)
//创建一个内容是[]byte的slice的缓冲器
//与bytes.NewBufferString("")等效
bytesBuffer := bytes.NewBuffer([]byte{})
binary.Write(bytesBuffer, binary.BigEndian, x)
return bytesBuffer.Bytes()
}
func TestBufferString(){
buf1:=bytes.NewBufferString("swift")
buf2:=bytes.NewBuffer([]byte("swift"))
buf3:=bytes.NewBuffer([]byte{'s','w','i','f','t'})
fmt.Println("===========以下buf1,buf2,buf3等效=========")
fmt.Println("buf1:", buf1)
fmt.Println("buf2:", buf2)
fmt.Println("buf3:", buf3)
fmt.Println("===========以下创建空的缓冲器等效=========")
buf4:=bytes.NewBufferString("")
buf5:=bytes.NewBuffer([]byte{})
fmt.Println("buf4:", buf4)
fmt.Println("buf5:", buf5)
}
func BufferWrite(){
fmt.Println("===========以下通过Write把swift写入Learning缓冲器尾部=========")
newBytes := []byte("swift")
//创建一个内容Learning的缓冲器
buf := bytes.NewBuffer([]byte("Learning"))
//打印为Learning
fmt.Println(buf.String())
//将newBytes这个slice写到buf的尾部
buf.Write(newBytes)
fmt.Println(buf.String())
}
func BufferWriteString(){
fmt.Println(