c_cpp 在C中读写二进制数据块

Posted 2021-05-14

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

#define ASC_SIZE 128

#define BLOCK_SIZE (128 * 9)

typedef struct
{
  unsigned char data[BLOCK_SIZE];
} RootBlock;


// Gets offsetted file node from block
unsigned long 
RootBlock_get_pos(RootBlock* rb, long index)
{
  unsigned long* positions = (unsigned long*)(rb->data + ASC_SIZE);
  return positions[index];
}

int main(void) {
  
  
  FILE * pFile;
  unsigned long locations[ASC_SIZE] = {0};
  unsigned char states[ASC_SIZE] = {0};
  unsigned char beg[2] = {22, 33};
  pFile = fopen ("myfile.roots", "a+b");
  fwrite(beg, sizeof(unsigned char), sizeof(beg), pFile);
  fwrite (locations , sizeof(unsigned long), ASC_SIZE, pFile);
  fwrite (states , sizeof(unsigned char), ASC_SIZE, pFile);
    
  fclose (pFile);
  
  pFile = fopen ("myfile.roots", "rb");
  unsigned char beg_r[2];
  fread(beg_r, sizeof(unsigned char), 2, pFile);
  printf("The beginning bytes are %u and %u\n", beg_r[0], beg_r[1]);
  
  return 0;
}