yumaojun03
aa35d086f8
feat(interface): 添加Go语言接口教程和示例代码 添加了完整的Go语言接口教学内容，包括： - README.md中详细介绍了Go语言接口的概念和特性 - 包含解耦、多态、扩展性等接口优势说明 - 提供面向接口编程的完整示例代码 - 展示了标准库中Reader、Writer等常用接口 - 实现了一个支持Reader和Writer接口的Buffer示例 - 在main.go中演示了接口的实际应用和类型断言用法 ```
313 lines
8.8 KiB
Markdown
313 lines
8.8 KiB
Markdown
# Go语言接口
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[课件](https://gitee.com/infraboard/go-course/blob/master/zh-cn/base/interface.md)
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+ 解耦（Decoupling）：调用者不需要知道具体类型，只需要知道接口
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+ 多态（Polymorphism）：不同类型可以有相同的接口，统一处理
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+ 扩展性（Extensibility）：新增类型时，不需要修改已有代码
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## 面向接口
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```go
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package main
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import "fmt"
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func main() {
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//
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dog := Dog{Name: "旺财"}
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fmt.Println(dog.Speak())
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//
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cat := Cat{Name: "招财猫"}
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fmt.Println(cat.Speak())
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//
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cow := Cow{Name: "小牛"}
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fmt.Println(cow.Speak())
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// 必须知道对象的对象, 才能调用, 面向具体类型来编写代码, 依赖具体类型, 耦合度高
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// 没有一层统一抽象，上层业务逻辑，需要知道对象，才能调用，非常麻烦，高耦合
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// speakers := []interface{}{dog, cat, cow}
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// for _, speaker := range speakers {
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// switch speaker.(type) {
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// case Dog:
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// fmt.Println(speaker.(Dog).Speak())
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// case Cat:
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// fmt.Println(speaker.(Cat).Speak())
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// case Cow:
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// fmt.Println(speaker.(Cow).Speak())
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// }
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// //...
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// }
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// 管理员，组织这些演技者，进行演讲
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// interface 先制定规范， 底层系统按照规范进行实现，上层业务代码的编写将会是透明的，简单高效
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// 这里的Speaker 和 Dog Cat Cow 都是type 他们是一种东西吗？
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// speakers = []Dog{}{dog1,dog2, dog3}
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// Speaker 是一种约束, 约束放入这个slice里面的对象，必须实现这个接口的所有方法
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speakers := []Speaker{dog, cat, cow}
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for _, speaker := range speakers {
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fmt.Println(speaker.Speak())
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}
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// 只关注 方法(接口), 不关注 对象的编程的方式，就是面向接口
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}
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// 任何一个结构体 实现了这个接口的所有方法, 就实现了这个接口
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// 接口是一层抽象, 只要实现了这个接口的所有方法, 就可以被当做这个接口来使用，屏蔽了底层系统
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type Speaker interface {
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Speak() string // 说话方法
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GetName() string // 获取名字方法
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}
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// 2. 定义不同的类型
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type Dog struct {
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Name string
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}
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// 3. 实现接口方法
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func (d Dog) Speak() string {
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return "汪汪汪"
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}
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func (d Dog) GetName() string {
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return d.Name
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}
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type Cat struct {
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Name string
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}
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func (c Cat) Speak() string {
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return "喵喵喵"
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}
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func (c Cat) GetName() string {
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return c.Name
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}
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type Cow struct {
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Name string
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}
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func (c Cow) Speak() string {
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return "哞哞哞"
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}
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func (c Cow) GetName() string {
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return c.Name
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}
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```
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+ 解耦: 调用者不需要知道具体类型，只需要知道接口, fmt.Println(speaker.Speak())
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+ 多态（Polymorphism）：不同类型可以有相同的接口，统一处理, []Speaker{dog, cat, cow}
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+ 扩展性（Extensibility）：新增类型时，不需要修改已有代码
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+ Go语言的接口实现是隐式的, 底层系统按照规范进行实现，上层业务代码的编写将会是透明的，简单高效
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## 面向接口
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```go
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type Reader interface {
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Read(p []byte) (n int, err error)
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}
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// Writer is the interface that wraps the basic Write method.
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//
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// Write writes len(p) bytes from p to the underlying data stream.
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// It returns the number of bytes written from p (0 <= n <= len(p))
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// and any error encountered that caused the write to stop early.
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// Write must return a non-nil error if it returns n < len(p).
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// Write must not modify the slice data, even temporarily.
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//
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// Implementations must not retain p.
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type Writer interface {
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Write(p []byte) (n int, err error)
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}
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// Closer is the interface that wraps the basic Close method.
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//
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// The behavior of Close after the first call is undefined.
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// Specific implementations may document their own behavior.
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type Closer interface {
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Close() error
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}
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// Seeker is the interface that wraps the basic Seek method.
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//
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// Seek sets the offset for the next Read or Write to offset,
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// interpreted according to whence:
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// [SeekStart] means relative to the start of the file,
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// [SeekCurrent] means relative to the current offset, and
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// [SeekEnd] means relative to the end
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// (for example, offset = -2 specifies the penultimate byte of the file).
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// Seek returns the new offset relative to the start of the
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// file or an error, if any.
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//
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// Seeking to an offset before the start of the file is an error.
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// Seeking to any positive offset may be allowed, but if the new offset exceeds
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// the size of the underlying object the behavior of subsequent I/O operations
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// is implementation-dependent.
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type Seeker interface {
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Seek(offset int64, whence int) (int64, error)
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}
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// ReadWriter is the interface that groups the basic Read and Write methods.
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type ReadWriter interface {
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Reader
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Writer
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}
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// ReadCloser is the interface that groups the basic Read and Close methods.
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type ReadCloser interface {
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Reader
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Closer
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}
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// WriteCloser is the interface that groups the basic Write and Close methods.
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type WriteCloser interface {
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Writer
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Closer
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}
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// ReadWriteCloser is the interface that groups the basic Read, Write and Close methods.
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type ReadWriteCloser interface {
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Reader
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Writer
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Closer
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}
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// ReadSeeker is the interface that groups the basic Read and Seek methods.
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type ReadSeeker interface {
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Reader
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Seeker
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}
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// ReadSeekCloser is the interface that groups the basic Read, Seek and Close
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// methods.
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type ReadSeekCloser interface {
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Reader
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Seeker
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Closer
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}
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// WriteSeeker is the interface that groups the basic Write and Seek methods.
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type WriteSeeker interface {
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Writer
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Seeker
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}
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// ReadWriteSeeker is the interface that groups the basic Read, Write and Seek methods.
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type ReadWriteSeeker interface {
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Reader
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Writer
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Seeker
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}
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```
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Io Reader和Writer接口
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```go
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// Reader is the interface that wraps the basic Read method.
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//
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// Read reads up to len(p) bytes into p. It returns the number of bytes
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// read (0 <= n <= len(p)) and any error encountered. Even if Read
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// returns n < len(p), it may use all of p as scratch space during the call.
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// If some data is available but not len(p) bytes, Read conventionally
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// returns what is available instead of waiting for more.
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//
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// When Read encounters an error or end-of-file condition after
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// successfully reading n > 0 bytes, it returns the number of
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// bytes read. It may return the (non-nil) error from the same call
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// or return the error (and n == 0) from a subsequent call.
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// An instance of this general case is that a Reader returning
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// a non-zero number of bytes at the end of the input stream may
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// return either err == EOF or err == nil. The next Read should
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// return 0, EOF.
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//
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// Callers should always process the n > 0 bytes returned before
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// considering the error err. Doing so correctly handles I/O errors
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// that happen after reading some bytes and also both of the
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// allowed EOF behaviors.
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//
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// If len(p) == 0, Read should always return n == 0. It may return a
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// non-nil error if some error condition is known, such as EOF.
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//
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// Implementations of Read are discouraged from returning a
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// zero byte count with a nil error, except when len(p) == 0.
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// Callers should treat a return of 0 and nil as indicating that
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// nothing happened; in particular it does not indicate EOF.
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//
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// Implementations must not retain p.
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type Reader interface {
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Read(p []byte) (n int, err error)
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}
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// Writer is the interface that wraps the basic Write method.
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//
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// Write writes len(p) bytes from p to the underlying data stream.
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// It returns the number of bytes written from p (0 <= n <= len(p))
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// and any error encountered that caused the write to stop early.
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// Write must return a non-nil error if it returns n < len(p).
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// Write must not modify the slice data, even temporarily.
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//
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// Implementations must not retain p.
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type Writer interface {
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Write(p []byte) (n int, err error)
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}
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```
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如何实现一个buf
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```go
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func NewBuffer() *Buffer {
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return &Buffer{
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// 固定 1k 大小的缓冲区
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buf: make([]byte, 1024),
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dataLen: 0,
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}
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}
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// 实现 Reader和 Writer方法
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type Buffer struct {
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buf []byte // 固定大小的缓冲区
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dataLen int // 当前缓冲区中的数据量
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}
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func (b *Buffer) Read(p []byte) (n int, err error) {
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if b.dataLen == 0 {
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return 0, io.EOF
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}
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// 读取缓冲区中的数据
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n = copy(p, b.buf[:b.dataLen])
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fmt.Println("read: ", n)
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// 移除已读数据（将未读数据前移）
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copy(b.buf, b.buf[n:b.dataLen])
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b.dataLen -= n
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return n, nil
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}
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func (b *Buffer) Write(p []byte) (n int, err error) {
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// 计算剩余空间
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available := len(b.buf) - b.dataLen
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if available == 0 {
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// 缓冲区已满
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return 0, io.ErrShortBuffer
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}
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// 只写入缓冲区能容纳的数据（固定大小，不扩展）
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n = copy(b.buf[b.dataLen:], p)
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b.dataLen += n
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fmt.Printf("write: %d 字节, 缓冲区使用: %d/%d\n", n, b.dataLen, len(b.buf))
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// 如果没能写入全部数据，返回 ErrShortBuffer
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if n < len(p) {
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return n, io.ErrShortBuffer
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}
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return n, nil
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}
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func (b *Buffer) String() string {
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return string(b.buf[:b.dataLen])
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}
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// Reset 清空缓冲区
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func (b *Buffer) Reset() {
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b.dataLen = 0
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}
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``` |