读取二进制数据 - 查找最小和最大坐标

Question

我有一个二进制数据文件.有超过4百万个LIDAR数据记录.每条记录都存储为四个数字 - 三个浮点数(坐标x,y,z)和一个整数(现在不重要).我应该实现一个在每个轴上获得最小和最大坐标的函数.我编写了下面的代码,算法看起来非常简单和简单,但它不起作用(它将每个最小值返回为0.0f,每个最大值返回1.0f).我有什么不对吗？

void get_min_max(const char *filename, float *a_min_x, float *a_max_x, float *a_min_y, float *a_max_y, float *a_min_z, float *a_max_z) {
  FILE *f = NULL;
  float x, y, z;
  float min_x, min_y, min_z, max_x, max_y, max_z;
  int l_type;

  f = fopen(filename, "rb");

  if (!f) {
    printf("No binary file read!\n");
    exit(-1);
  }

  min_x = min_y = min_z =  std::numeric_limits<float>::max();
  max_x = max_y = max_z = -std::numeric_limits<float>::max();

  while (true) {
    x = fread((void*)(&x), sizeof(x), 1, f);
    y = fread((void*)(&y), sizeof(y), 1, f);
    z = fread((void*)(&z), sizeof(z), 1, f);

    min_x = fminf(x, min_x);
    min_y = fminf(y, min_y);
    min_z = fminf(z, min_z);

    max_x = fmaxf(x, max_x);
    max_y = fmaxf(y, max_y);
    max_z = fmaxf(z, max_z);

    l_type = fread((void*)(&l_type), sizeof(l_type), 1, f);

    if (feof(f)) {
      break;
    }
  }

  fclose(f);

  *a_min_x = min_x;    // = 0.0f ???
  *a_min_y = min_y;    // = 0.0f ???
  *a_min_z = min_z;    // = 0.0f ???

  *a_max_x = max_x;    // = 1.0f ???
  *a_max_y = max_y;    // = 1.0f ???
  *a_max_z = max_z;    // = 1.0f ???
}

Answer 1

您的问题是将fread结果分配给您的变量:

x = fread(&x, ...)

首先fread将数据读入x,然后返回读取的元素数(1),然后x变为1.0.

你应该真正学会如何使用调试器,你会很快看到它.