浅解 go 语言的 interface

我写了一个 go interface 相关的代码转换为 C 代码的样例。也许有助于大家理解 go 的 interface。不过请注意一点，这里没有完整解析 go 语言 interface 的所有细节。

Go 代码：

package main

import "fmt"

// -------------------------------------------------------------

type IReadWriter interface {

    Read(buf *byte, cb int) int

    Write(buf *byte, cb int) int

}

// -------------------------------------------------------------

type A struct {

    a int

}

func NewA(params int) *A {

    fmt.Println("NewA:", params);

    return &A{params}

}

func (this *A) Read(buf *byte, cb int) int {

    fmt.Println("A_Read:", this.a)

    return cb

}

func (this *A) Write(buf *byte, cb int) int {

    fmt.Println("A_Write:", this.a)

    return cb

}

// -------------------------------------------------------------

type B struct {

    A

}

func NewB(params int) *B {

    fmt.Println("NewB:", params);

    return &B{A{params}}

}

func (this *B) Write(buf *byte, cb int) int {

    fmt.Println("B_Write:", this.a)

    return cb

}

func (this *B) Foo() {

    fmt.Println("B_Foo:", this.a)

}

// -------------------------------------------------------------

func main() {

    var p IReadWriter = NewB(8)

    p.Read(nil, 10)

    p.Write(nil, 10)

}

// -------------------------------------------------------------

对应的 C 代码：

#include <stdio.h>

#include <stdlib.h>

// -------------------------------------------------------------

typedef struct _TypeInfo {

    // 用于运行时取得类型信息, 比如反射机制

} TypeInfo;

typedef struct _InterfaceInfo {

    // 用于运行时取得interface信息

} InterfaceInfo;

// -------------------------------------------------------------

typedef struct _IReadWriterTbl {

    InterfaceInfo* inter;

    TypeInfo* type;

    int (*Read)(void* this, char* buf, int cb);

    int (*Write)(void* this, char* buf, int cb);

} IReadWriterTbl;

typedef struct _IReadWriter {

    IReadWriterTbl* tab;

    void* data;

} IReadWriter;

InterfaceInfo g_InterfaceInfo_IReadWriter = {

    // ...    

};

// -------------------------------------------------------------

typedef struct _A {

    int a;

} A;

int A_Read(A* this, char* buf, int cb) {

    printf("A_Read: %d\n", this->a);

    return cb;

}

int A_Write(A* this, char* buf, int cb) {

    printf("A_Write: %d\n", this->a);

    return cb;

}

TypeInfo g_TypeInfo_A = {

    // ...    

};

A* NewA(int params) {

    printf("NewA: %d\n", params);

    A* this = (A*)malloc(sizeof(A));

    this->a = params;

    return this;

}

// -------------------------------------------------------------

typedef struct _B {

    A base;

} B;

int B_Write(B* this, char* buf, int cb) {

    printf("B_Write: %d\n", this->base.a);

    return cb;

}

void B_Foo(B* this) {

    printf("B_Foo: %d\n", this->base.a);

}

TypeInfo g_TypeInfo_B = {

    // ...    

};

B* NewB(int params) {

    printf("NewB: %d\n", params);

    B* this = (B*)malloc(sizeof(B));

    this->base.a = params;

    return this;

}

// -------------------------------------------------------------

IReadWriterTbl g_Itbl_IReadWriter_B = {

    &g_InterfaceInfo_IReadWriter,

    &g_TypeInfo_B,

    (int (*)(void* this, char* buf, int cb))A_Read,

    (int (*)(void* this, char* buf, int cb))B_Write

};

int main() {

    B* unnamed = NewB(8);

    IReadWriter p = {

        &g_Itbl_IReadWriter_B,

        unnamed

    };

    p.tab->Read(p.data, NULL, 10);

    p.tab->Write(p.data, NULL, 10);

    return 0;

}

// -------------------------------------------------------------