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bufio_Writer.go
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/
bufio_Writer.go
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package main
import (
"bufio"
"bytes"
"fmt"
"strings"
)
func main() {
// Writer为io.Writer对象实现缓冲。
//如果在写入Writer时发生错误，将不再接受更多数据，并且所有后续写入和Flush都将返回错误。
//写入所有数据后，客户端应调用Flush方法以确保所有数据均已转发到基础io.Writer。
ls:=make([]byte,0)//作为buffer的参数千万不要给长度
buffer := bytes.NewBuffer(ls)//buffer实现了io.Reader和io.Writer
writer := bufio.NewWriter(buffer)
ls111:=[]byte{97,98,99,100,101,102,103}
nn, err111 := writer.Write(ls111)//将ls111写入writer的底层字节切片ls指向的地址
if err111 != nil{
fmt.Println(err111)
}
fmt.Println(nn)//7
fmt.Println(ls111)//[97 98 99 100 101 102 103]
fmt.Println(writer)//&{<nil> [97 98 99 100 101 102 103 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0....](4096字节)
//没有方法读取才死
fmt.Println(writer.WriteRune(104))
fmt.Println(writer)//&{<nil> [97 98 99 100 101 102 103 104 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0....](4096字节)
fmt.Println(writer.WriteString("ijk"))
fmt.Println(writer)//&{<nil> [97 98 99 100 101 102 103 104 105 106 107 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0....](4096字节)
fmt.Println(writer.WriteByte(108))
fmt.Println(writer)//&{<nil> [97 98 99 100 101 102 103 104 105 106 107 108 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0....](4096字节)
//err := writer.Flush()//一般都调用这个做结尾，似乎不调用也可以，除非大数据
//if err != nil{
// fmt.Println(err)
//}
// Buffered返回已写入当前缓冲区的字节数。
fmt.Println(writer.Buffered())//12,如果上面调用了flush()则会输出0，flush相当于置零了writer的计数n
fmt.Println(writer.Size())//4096
fmt.Println(writer.Available())//4084(4096-12),表示余下空间多少字节没用
writer.Flush()
fmt.Println("buffer:",buffer)//buffer: abcdefghijkl
fmt.Println("-------------------------------------")
ls333:=make([]byte,0)
buffer333 := bytes.NewBuffer(ls333)
// Reset丢弃所有未刷新的缓冲数据，清除所有错误，然后
//重置b将其输出写入w。
writer.Reset(buffer333)//重置,只是重新跟换了写入器而已，底层缓存切片没换的
writer.WriteString("ppp")
writer.Flush()
fmt.Println("==",buffer333)
fmt.Println(writer)//&{<nil> [97 98 99 100 101 102 103 104 105 106 107 108 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0...](4096字节，不知道为什么还是保留以前的数据)
fmt.Println(writer.Size())//4096
fmt.Println(writer.Available())//4096
fmt.Println(writer.Buffered())//0
fmt.Println(writer.WriteString("mno"))//3 <nil>
fmt.Println(writer)//&{<nil> [109 110 111 100 101 102 103 104 105 106 107 108 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 ...]
fmt.Println("-------------------------------------")
reader := strings.NewReader("pq")
fmt.Println(writer.ReadFrom(reader))//2 <nil>
fmt.Println(writer)//&{<nil> [109 110 111 112 113 102 103 104 105 106 107 108 0 0 0 0 0 0 0 0 0 0 0 0 0...]
writer.Flush()
fmt.Println("--",buffer333)//-- mnopq,不加上面的flush则是空字符串，说明数据还在写入器里面，没更新到真的接收器里面去
//写入器里面的东西随时可能被覆盖，我们要记得flush,取数据也要到buffer中去取才对、
//另外一个鲜明的例子:
fmt.Println("-------------------------------------")
b := bytes.NewBuffer(make([]byte, 0))
bw := bufio.NewWriter(b)
bw.WriteString("123")
fmt.Println("--",b)
c := bytes.NewBuffer(make([]byte, 0))
bw.Reset(c)
bw.WriteString("456")
bw.Flush()
fmt.Println("--",b)
fmt.Println(c)
//输出：
//--
//--
//456
fmt.Println("-------------------------------------")
ls6:=make([]byte,0)//作为buffer的参数千万不要给长度
buffer6 := bytes.NewBuffer(ls6)//buffer实现了io.Reader和io.Writer
writer6 := bufio.NewWriter(buffer6)
writer6.WriteString("abc")
writer6.Flush()
fmt.Println(writer6)
fmt.Println("--",buffer6)
// Len返回缓冲区未读部分的字节数；
// b.Len（）== len（b.Bytes（））。
fmt.Println("--",buffer6.Len())
fmt.Println("--",buffer6.Cap())// Cap返回缓冲区基础字节片的容量，即为缓冲区数据分配的总空间。
fmt.Println("--",ls6)
//输出：
//&{<nil> [97 98 99 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0...]
//-- abc
//-- 3
//-- 3
//-- []
fmt.Println("-------------------------------------")
//newReader("abcd")==NewReaderSize("abcd",4096)
newReader := strings.NewReader("abcd")
newReaderSize := bufio.NewReaderSize(newReader, 20)
fmt.Println(newReaderSize.Buffered())//0
fmt.Println(newReaderSize.Size())//100
ls777:=make([]byte,10)
fmt.Println(newReaderSize.Read(ls777))
fmt.Println(newReaderSize)//&{[97 98 99 100 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0] 0xc000004520 4 4 <nil> 100 -1}
fmt.Println(ls777)//[97 98 99 100 0 0 0 0 0 0]
//newWriter(newBuffer)==NewWriterSize(newBuffer,4096)
ls999:=make([]byte,0)
newBuffer := bytes.NewBuffer(ls999)
Wsize := bufio.NewWriterSize(newBuffer, 20)
i, _ := Wsize.WriteString("dcba")
Wsize.Flush()
fmt.Println(i)//4
fmt.Println(Wsize.Size())//20
fmt.Println(Wsize.Buffered())//4
fmt.Println(Wsize)//&{<nil> [100 99 98 97 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0] 0 0xc00005c420}
fmt.Println(newBuffer)//dcba
fmt.Println(ls999)//[]
fmt.Println("-------------------------------------")
// NewReadWriter分配一个新的ReadWriter，该新的ReadWriter调度到r和w。
newRd := strings.NewReader("ABCD")//读取来源处
bufio_R := bufio.NewReaderSize(newRd, 20)
ls555:=make([]byte,0)//写入接收处
newBf := bytes.NewBuffer(ls555)
bufio_W :=bufio.NewWriterSize(newBf,20)
readWriter := bufio.NewReadWriter(bufio_R, bufio_W)//读取写入器
p_ls:=make([]byte,10)
readWriter.Read(p_ls)
fmt.Println(p_ls)//[65 66 67 68 0 0 0 0 0 0]
w_n, _ := readWriter.WriteString("EFG")
fmt.Println(w_n)//3
readWriter.Flush()
fmt.Println(newBf)//EFG
fmt.Println(ls555)//[]
fmt.Println("***************************")
//将读取器和接收器(或者说是读取写入器的两头)对接
R1 := strings.NewReader("aabbcc")
bufio_R1 := bufio.NewReaderSize(R1, 15)
ls_W:=make([]byte,0)//写入接收器
newBf_W := bytes.NewBuffer(ls_W)
bufio_W1 := bufio.NewWriter(newBf_W)
newReadWriter := bufio.NewReadWriter(bufio_R1, bufio_W1)
ls_R:=make([]byte,10)//中间承接的切片
newReadWriter.Read(ls_R)
fmt.Println("ls_R:",ls_R)//ls_R: [97 97 98 98 99 99 0 0 0 0]
nn2, err22 := newReadWriter.Write(ls_R)
if err22 != nil{
fmt.Println(err22)
}
fmt.Println(nn2)//10
newReadWriter.Flush()
fmt.Println("ls_W:",ls_W)//ls_W: []
fmt.Println("newBf_W:",newBf_W)//newBf_W: aabbcc
}