Serialize and Back

C/C++

Last updated on 2019-10-20

Write a struct to the disk and read it back again. Serialization has alot of gotchas that I don’t attempt to address here. You might want to consider ProtoBuf-C if you are going to be doing anything heavyweight.

This snippet will write struct some_data to the disk, and then read it back again into an instance of some_data.

/* serialize.c */

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

struct some_data {
  int i,j,k;
};

void
serialize(const struct some_data *in) {
  FILE *f = fopen("dump.data", "wb");

  if(!f) {
    printf("Failed to serialize.\n");
    return;
  }

  const unsigned char *data = (const unsigned char *)in;
  int count = sizeof(*in);
  int i;

  for(i = 0; i < count; ++i) {
    fprintf(f, "%c", data[i]);
  }

  fclose(f);
}

void
de_serialize(struct some_data *out) {
  FILE *f = fopen("dump.data", "rb");

  if(!f) {
    printf("Failed to de-serialize.\n");
    return;
  }

  fread(out,sizeof(*out),1,f);

  fclose(f);
}

void
output_obj(const struct some_data *o) {
  printf("%d, %d, %d\n", o->i, o->j, o->k);
}

int
main() {

  /* serialize */
  struct some_data data_to_serialize;
  data_to_serialize.i = 123;
  data_to_serialize.j = 234;
  data_to_serialize.k = 345;

  serialize(&data_to_serialize);
  output_obj(&data_to_serialize);

  /* de-serialize */

  struct some_data data_to_deserailize;

  de_serialize(&data_to_deserailize);
  output_obj(&data_to_deserailize);

  return 0;
}

Outputs …

123, 234, 345
123, 234, 345

Compile and run with GCC

gcc serialize.c && ./a.out

or Clang

clang serialize.c && ./a.out