Golang之bytes.buffer
2016-08-05 16:33
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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("===========以下通过Write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())
}
func BufferWriteByte(){
fmt.Println("===========以下通过WriteByte把swift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())
}
func BufferWriteRune(){
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())
}
向 Buffer 中读取数据
Read
给Read方法一个容器p,读完后,p就满了,缓冲器相应的减少了,返回的n为成功读的数量// Read reads the next len(p) bytes from the buffer or until the buffer // is drained. The return value n is the number of bytes read. If the // buffer has no data to return, err is io.EOF (unless len(p) is zero); // otherwise it is nil. func (b *Buffer) Read(p []byte) (n int, err error) {}
func Read(){ bufs := bytes.NewBufferString("Learning swift.") fmt.Println(bufs.String()) //声明一个空的slice,容量为8 l := make([]byte, 8) //把bufs的内容读入到l内,因为l容量为8,所以只读了8个过来 bufs.Read(l) fmt.Println("::bufs缓冲器内容::") fmt.Println(bufs.String()) //空的l被写入了8个字符,所以为 Learning fmt.Println("::l的slice内容::") fmt.Println(string(l)) //把bufs的内容读入到l内,原来的l的内容被覆盖了 bufs.Read(l) fmt.Println("::bufs缓冲器被第二次读取后剩余的内容::") fmt.Println(bufs.String()) fmt.Println("::l的slice内容被覆盖,由于bufs只有7个了,因此最后一个g被留下来了::") fmt.Println(string(l)) }
打印:
=======Read=======
Learning swift.
::bufs缓冲器内容::
swift.
::l的slice内容::
Learning
::bufs缓冲器被第二次读取后剩余的内容::
::l的slice内容被覆盖::
swift.g
ReadByte
返回缓冲器头部的第一个byte,缓冲器头部第一个byte被拿掉// ReadByte reads and returns the next byte from the buffer. // If no byte is available, it returns error io.EOF. func (b *Buffer) ReadByte() (c byte, err error) {}
func ReadByte(){ bufs := bytes.NewBufferString("Learning swift.") fmt.Println(bufs.String()) //读取第一个byte,赋值给b b, _ := bufs.ReadByte() fmt.Println(bufs.String()) fmt.Println(string(b)) }
打印:
=======ReadByte===
Learning swift.
earning swift.
L
ReadRune
ReadRune和ReadByte很像 返回缓冲器头部的第一个rune,缓冲器头部第一个rune被拿掉
// ReadRune reads and returns the next UTF-8-encoded // Unicode code point from the buffer. // If no bytes are available, the error returned is io.EOF. // If the bytes are an erroneous UTF-8 encoding, it // consumes one byte and returns U+FFFD, 1. func (b *Buffer) ReadRune() (r rune, size int, err error) {}
func ReadRune(){ bufs := bytes.NewBufferString("学swift.") fmt.Println(bufs.String()) //读取第一个rune,赋值给r r,z,_ := bufs.ReadRune() //打印中文"学",缓冲器头部第一个被拿走 fmt.Println(bufs.String()) //打印"学","学"作为utf8储存占3个byte fmt.Println("r=",string(r),",z=",z) }
ReadBytes
ReadBytes需要一个byte作为分隔符,读的时候从缓冲器里找第一个出现的分隔符(delim),找到后,把从缓冲器头部开始到分隔符之间的所有byte进行返回,作为byte类型的slice,返回后,缓冲器也会空掉一部分// ReadBytes reads until the first occurrence of delim in the input, // returning a slice containing the data up to and including the delimiter. // If ReadBytes encounters an error before finding a delimiter, // it returns the data read before the error and the error itself (often io.EOF). // ReadBytes returns err != nil if and only if the returned data does not end in // delim. func (b *Buffer) ReadBytes(delim byte) (line []byte, err error) {}
func ReadBytes(){ bufs := bytes.NewBufferString("现在开始 Learning swift.") fmt.Println(bufs.String()) var delim byte = 'L' line, _ := bufs.ReadBytes(delim) fmt.Println(bufs.String()) fmt.Println(string(line)) }
打印:
=======ReadBytes==
现在开始 Learning swift.
earning swift.
现在开始 L
ReadString
ReadString需要一个byte作为分隔符,读的时候从缓冲器里找第一个出现的分隔符(delim),找到后,把从缓冲器头部开始到分隔符之间的所有byte进行返回,作为字符串,返回后,缓冲器也会空掉一部分 和ReadBytes类似
// ReadString reads until the first occurrence of delim in the input, // returning a string containing the data up to and including the delimiter. // If ReadString encounters an error before finding a delimiter, // it returns the data read before the error and the error itself (often io.EOF). // ReadString returns err != nil if and only if the returned data does not end // in delim. func (b *Buffer) ReadString(delim byte) (line string, err error) {}
ReadFrom
从一个实现io.Reader接口的r,把r里的内容读到缓冲器里,n返回读的数量// ReadFrom reads data from r until EOF and appends it to the buffer, growing // the buffer as needed. The return value n is the number of bytes read. Any // error except io.EOF encountered during the read is also returned. If the // buffer becomes too large, ReadFrom will panic with ErrTooLarge. func (b *Buffer) ReadFrom(r io.Reader) (n int64, err error) {}
func ReadFrom(){ //test.txt 内容是 "未来" file, _ := os.Open("learngo/bytes/text.txt") buf := bytes.NewBufferString("Learning swift.") buf.ReadFrom(file) //将text.txt内容追加到缓冲器的尾部 fmt.Println(buf.String()) }
打印:
=======ReadFrom===
Learning swift.未来
Reset
将数据清空,没有数据可读// Reset resets the buffer so it has no content. // b.Reset() is the same as b.Truncate(0). func (b *Buffer) Reset() { b.Truncate(0) }
func Reset(){ bufs := bytes.NewBufferString("现在开始 Learning swift.") fmt.Println(bufs.String()) bufs.Reset() fmt.Println("::已经清空了bufs的缓冲内容::") fmt.Println(bufs.String()) }
打印:
=======Reset======
现在开始 Learning swift.
::已经清空了bufs的缓冲内容::
string
将未读取的数据返回成 string// String returns the contents of the unread portion of the buffer // as a string. If the Buffer is a nil pointer, it returns "<nil>". func (b *Buffer) String() string {}
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