c - 使用 fwrite 将结构数组写入二进制文件

Question

我有:

pointfile = fopen("points.bin", "wb");
void    savepoints(point points[], int n, FILE f){
    fwrite(&points, sizeof(point), n, &f);
    return;
}
fclose(pointfile);

其中 typedef struct {float x; float y;} 点;

并由 savepoints(buffer, npoints, *pointfile); 调用

但是没有任何内容写入文件。谁能发现我的错误？我看不出如何解决这个问题，我发现其他人的搜索要么不相关，要么只是让我走到这一步。

Answer 1

需要传递一个 FILE * 作为参数，例如:

测试.c

#include <stdio.h>
#include <stdlib.h>

typedef struct 
{
  float x,
        y;
}point;

/* function to save points data to myfile */
void save_points(point *points, int num_points, FILE *myfile)
{
  /* have to use points not (&points) here */
  fwrite(points, sizeof(point), num_points, myfile);
}

int main()
{
  FILE *pointfile;
  point *points; int num_points, index;
  pointfile = fopen("points.txt", "w");
  if(!pointfile)
  {
    fprintf(stderr, "failed to create file 'points.txt'\n");
    goto err0;
  }
  num_points = 10;
  points = malloc(num_points * sizeof(point));
  if(!points)
  {
    fprintf(stderr, "failed to alloc `points`\n");
    goto err1;
  }
  /* points are uninitialized but can still write uninitialized memory to file to test.. */
  save_points(points, num_points, pointfile);
  free(points);
  fclose(pointfile);
  return 0;

err1:
  fclose(pointfile);
err0:
  return 0;
}

结果

$ ./test
$ ls -l points.txt 
-rw-r--r-- 1 me me 80 Dec 14 22:24 points.txt