Golang 中的 io 包詳解：組合接口
io.ReadWriter
// ReadWriter is the interface that groups the basic Read and Write methods.
type ReadWriter interface {
Reader
Writer
}是對(duì)Reader和Writer接口的組合，聚合了基本的讀寫(xiě)操作。簡(jiǎn)單示例如下：
package main
import (
"bytes"
"fmt"
"io"
)
func main() {
var buf bytes.Buffer
rw := io.ReadWriter(&buf)
// 寫(xiě)入數(shù)據(jù)
_, err := rw.Write([]byte("hello world"))
if err != nil {
panic(err)
}
// 讀取數(shù)據(jù)
var data = make([]byte, 11)
_, err = rw.Read(data)
if err != nil {
panic(err)
}
fmt.Println(string(data))
}io.ReadCloser
// ReadCloser is the interface that groups the basic Read and Close methods.
type ReadCloser interface {
Reader
Closer
}是對(duì)Reader和Closer接口的組合，聚合了基本的讀操作和關(guān)閉操作。使用 ReadCloser 接口時(shí)，一般會(huì)通過(guò) NewReader 或其它方式獲取一個(gè) io.ReadCloser 對(duì)象，然后通過(guò) Read 方法不斷讀取數(shù)據(jù)，直到數(shù)據(jù)讀取結(jié)束，最后通過(guò) Close 方法釋放資源。
io.WriteCloser
// WriteCloser is the interface that groups the basic Write and Close methods.
type WriteCloser interface {
Writer
Closer
}是對(duì)Writer和Closer接口的組合，聚合了基本的寫(xiě)操作和關(guān)閉操作。使用 WriteCloser 接口時(shí)，一般會(huì)通過(guò) NewWriter 或其它方式獲取一個(gè) io.WriteCloser 對(duì)象，然后通過(guò) Write 方法不斷寫(xiě)入數(shù)據(jù)，直到數(shù)據(jù)寫(xiě)入結(jié)束，最后通過(guò) Close 方法釋放資源。簡(jiǎn)單示例如下：
package main
import (
"bufio"
"compress/gzip"
"os"
)
func main() {
f, err := os.Create("test.gz")
if err != nil {
panic(err)
}
defer f.Close()
// 通過(guò) gzip.NewWriter 方法創(chuàng)建一個(gè) io.WriteCloser 對(duì)象
// 用于將數(shù)據(jù)壓縮并寫(xiě)入文件中
w := gzip.NewWriter(f)
defer w.Close()
// 將數(shù)據(jù)寫(xiě)入到 io.WriteCloser 對(duì)象中
writer := bufio.NewWriter(w)
_, err = writer.WriteString("hello world")
if err != nil {
panic(err)
}
writer.Flush()
}首先通過(guò) os.Create 方法創(chuàng)建一個(gè)文件對(duì)象 f，然后通過(guò) gzip.NewWriter 方法創(chuàng)建一個(gè) io.WriteCloser 對(duì)象 w，該對(duì)象將數(shù)據(jù)寫(xiě)入到 f 中，并對(duì)數(shù)據(jù)進(jìn)行壓縮。接著通過(guò) bufio.NewWriter 方法創(chuàng)建一個(gè) bufio.Writer 對(duì)象 writer，該對(duì)象將數(shù)據(jù)寫(xiě)入到 io.WriteCloser 對(duì)象中。最后調(diào)用 writer.Flush 方法將緩沖區(qū)中的數(shù)據(jù)寫(xiě)入到 io.WriteCloser 對(duì)象中，然后釋放資源。
io.ReadWriteCloser
// ReadWriteCloser is the interface that groups the basic Read, Write and Close methods.
type ReadWriteCloser interface {
Reader
Writer
Closer
}是對(duì) Reader、Writer 和 Closer 接口的組合，聚合了基本的讀寫(xiě)操作和關(guān)閉操作。使用 ReadWriteCloser 接口時(shí)，可以通過(guò) Read 方法從數(shù)據(jù)源讀取數(shù)據(jù)，通過(guò) Write 方法寫(xiě)入數(shù)據(jù)到數(shù)據(jù)接收器中，最后通過(guò) Close 方法釋放資源。
io.ReadSeeker
// ReadSeeker is the interface that groups the basic Read and Seek methods.
type ReadSeeker interface {
Reader
Seeker
}是對(duì) Reader 和 Seeker 接口的組合，聚合了基本的讀取和移位操作。使用 ReadSeeker 接口時(shí)，可以通過(guò) Read 方法從數(shù)據(jù)源讀取數(shù)據(jù)，通過(guò) Seek 方法在數(shù)據(jù)源中定位讀取位置，然后再通過(guò) Read 方法繼續(xù)讀取數(shù)據(jù)。簡(jiǎn)單示例：
package main
import (
"fmt"
"io"
"strings"
)
func main() {
s := strings.NewReader("0123456789")
rs := io.ReadSeeker(s)
// 讀取前 4 個(gè)字節(jié)
var data = make([]byte, 4)
_, err := rs.Read(data)
if err != nil {
panic(err)
}
fmt.Println(string(data))
// 定位到第 6 個(gè)字節(jié)
offset, err := rs.Seek(2, io.SeekCurrent)
if err != nil {
panic(err)
}
fmt.Printf("current offset:%d\n", offset)
// 讀取后 5 個(gè)字節(jié)
data = make([]byte, 5)
_, err = rs.Read(data)
if err != nil {
panic(err)
}
fmt.Println(string(data))
}io.ReadSeekCloser
// ReadSeekCloser is the interface that groups the basic Read, Seek and Close
// methods.
type ReadSeekCloser interface {
Reader
Seeker
Closer
}是對(duì) Reader、Seeker 和 Closer 接口的組合，聚合了基本的讀操作、移位操作和關(guān)閉操作。使用 ReadSeekCloser 接口時(shí)，可以通過(guò) Read 方法從數(shù)據(jù)源讀取數(shù)據(jù)，通過(guò) Seek 方法在數(shù)據(jù)源中定位讀取位置，最后通過(guò) Close 方法釋放資源。
io.WriteSeeker
// WriteSeeker is the interface that groups the basic Write and Seek methods.
type WriteSeeker interface {
Writer
Seeker
}是對(duì) Writer 和 Seeker 接口的組合，聚合了基本的寫(xiě)操作和移位操作。
io.ReadWriteSeeker
// ReadWriteSeeker is the interface that groups the basic Read, Write and Seek methods.
type ReadWriteSeeker interface {
Reader
Writer
Seeker
}是對(duì) Reader、Writer 和 Seeker 接口的組合，聚合了基本的讀寫(xiě)操作和移位操作。
