将 FILE 指针传递到 C 函数

Question

我的 C 函数采用 FILE 指针的地址（指向指针的指针）。我从Go调用此方法。有人可以给我一个在Go中调用约定的示例代码行吗？FILE **fp

C 库代码（将创建 .so 文件）：

int fileOpen(char *filename, char* mode, FILE **fp){

*fp  = fopen (filename, mode);

 if (*fp ==NULL)

   return -1;

 return 0;

}

int fileread(FILE *fp,char *buff ){

        if((fp!=NULL)&&( fgets ( buff, 50, fp) != NULL ) )

        {

                return 0;

        }

  return -1;

}

int fileclose(FILE *fp){

  fclose(fp);

  return 0;

}

import "C"

type (

        fileptr C.FILE

)

func opencfile(name string, mode string) int {

        var fp *fileptr

        return (int)(C.fileOpen(C.CString(name), C.CString(mode), C.FILE(&fp)));

}

我收到错误

无法将_cgoBase2（类型 **fileptr） 转换为类型 _Ctype_struct__IO_FILE

问题：

这是调用 C 方法的正确方法吗？

如何从Go传递文件指针的地址？或如何解决上述错误。

所谓的“C”方法原型是：

int fileOpen(char *filename, char* mode, FILE **fp);

更新：这是我的最新代码：

C 代码（.c 文件）

#include "fileOp_lib.h"

int fileOpen(char *filename, char* mode, fileptr *out){

    FILE *fp  = fopen(filename, mode);

    if (fp == NULL) {

        *out = 0;

        return -1;

    }

    *out = (fileptr) fp;

    return 0;

}

int fileread(fileptr fp, char *buff){

    if( (fp != 0) && (fgets(buff, 50, (FILE*)fp) != NULL) )

        return 0;

    return -1;

}

int fileclose(fileptr fp){

    fclose((FILE*)fp);

    return 0;

}

头文件（.h 文件）

#include <stdio.h>

typedef unsigned int fileptr;

int fileOpen(char *filename, char* mode, fileptr *out);

//int fileread(FILE *fp,char *buff ); temp. commented

//int fileclose(FILE *fp);

围棋代码

package main

/*

#cgo LDFLAGS: -L./SAMPLE/ -lfileop

#include "fileOp_lib.h"

*/

import "C"

type (

        fileptr uintptr

)

func opencfile(name string, mode string) int {

        var fp fileptr;

        return (int)(C.fileOpen(C.CString(name), C.CString(mode), (&fp)));

}

func main(){

        var e int;

        e = opencfile("data.txt","r");

}

Answer 1

与其搞砸更多的层，不如从Go正确调用原始C代码。请参阅 JimB 的评论或下面的示例。请注意，原始的C代码是...不是很好，而且考虑到除了C代码之外什么都没有，使用Go I / O例程可能会更好，这些例程更安全，更容易正确。想必无论你拥有什么真正的C代码都要复杂得多。您遗漏的部分可能需要对C和Go都有深入的了解才能连接。下面是编译和运行（并创建一个空）的代码。file.txtpackage main// #include <stdio.h>// #include <stdlib.h>// int fileOpen(char *filename, char *mode, FILE **fp) {//&nbsp; &nbsp; &nbsp; *fp = fopen(filename, mode);//&nbsp; &nbsp; &nbsp; if (*fp == NULL)//&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; return -1;//&nbsp; &nbsp; &nbsp; return 0;// }//// int fileread(FILE *fp, char *buff) {//&nbsp; &nbsp; &nbsp; if ((fp != NULL) && (fgets(buff, 50, fp) != NULL)) {//&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; return 0;//&nbsp; &nbsp; &nbsp; }//&nbsp; &nbsp; &nbsp; return -1;// }//// int fileclose(FILE *fp) {//&nbsp; &nbsp; &nbsp; fclose(fp);//&nbsp; &nbsp; &nbsp; return 0;// }import "C"import (&nbsp; &nbsp; &nbsp; &nbsp; "fmt"&nbsp; &nbsp; &nbsp; &nbsp; "unsafe")func opencfile(name string, mode string) (ret int, fp *C.FILE) {&nbsp; &nbsp; &nbsp; &nbsp; cname := C.CString(name)&nbsp; &nbsp; &nbsp; &nbsp; defer C.free(unsafe.Pointer(cname))&nbsp; &nbsp; &nbsp; &nbsp; cmode := C.CString(mode)&nbsp; &nbsp; &nbsp; &nbsp; defer C.free(unsafe.Pointer(cmode))&nbsp; &nbsp; &nbsp; &nbsp; ret = int(C.fileOpen(cname, cmode, &fp))&nbsp; &nbsp; &nbsp; &nbsp; return}func main() {&nbsp; &nbsp; &nbsp; &nbsp; ret, fp := opencfile("file.txt", "w")&nbsp; &nbsp; &nbsp; &nbsp; if ret >= 0 {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; defer C.fileclose(fp)&nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; fmt.Printf("result of opencfile was %d\n", ret)}

Answer 2

我不知道将a从Go传递到C的正确语法（如果可能的话）。但是，如果您可以更改C代码，我建议您不要公开对互操作不兼容类型的直接访问。我会建议更像这样的东西：FILE**FILE#include <stdint.h>typedef uintptr_t fileptr;int fileOpen(char *filename, char* mode, fileptr *out){&nbsp; &nbsp; FILE *fp&nbsp; = fopen(filename, mode);&nbsp; &nbsp; if (*fp == NULL) {&nbsp; &nbsp; &nbsp; &nbsp; *out = 0;&nbsp; &nbsp; &nbsp; &nbsp; return -1;&nbsp; &nbsp; }&nbsp; &nbsp; *out = (fileptr) fp;&nbsp; &nbsp; return 0;}int fileread(fileptr fp, char *buff){&nbsp; &nbsp; if( (fp != 0) && (fgets(buff, 50, (FILE*)fp) != NULL) )&nbsp; &nbsp; &nbsp; &nbsp; return 0;&nbsp; &nbsp; return -1;}int fileclose(fileptr fp){&nbsp; &nbsp; fclose((FILE*)fp);&nbsp; &nbsp; return 0;}import "C"...var fp uintptrC.fileOpen(..., &fp);...c.fileRead(fp, ...);...C.fileClose(fp);