Thread: Dump C struct (object) to a file and restore it back (serialize)

Hello, I am trying to serialize a simple C struct. I am dumping it to a file then try to read and restore it. However I got wrong data. Here is my idea:

Code:

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




struct a
{
    int i;
    char str[64];
    struct
    {
        float x;
        float y;
        float z;
    } vec3;


};




static struct a setA(int i, char* s, float f1, float f2, float f3)
{
    struct a newa;
    newa.i = i;
    strcpy(newa.str, s);
    newa.vec3.x = f1;
    newa.vec3.y = f2;
    newa.vec3.z = f3;


    return newa;
}








static char* dumpA(struct a* pa)
{
    union dmp {
        struct a m_a;
        char c[sizeof(struct a)];
    } ;


    union dmp d;


    d.m_a.i = pa->i;
    strcpy(d.m_a.str, pa->str);
    d.m_a.vec3.x = pa->vec3.x;
    d.m_a.vec3.y = pa->vec3.y;
    d.m_a.vec3.z = pa->vec3.z;


    int i =0;
    static char dumped[sizeof(union dmp)];


    FILE* fp = fopen("serialized", "wb");
    if (!fp) {
        return 0;
    }


    for(i=0; i < sizeof(d); i++) {
        fprintf(fp, "%0x", d.c[i]);
        dumped[i] = d.c[i];
    }
    fclose(fp);
    return &dumped;
}








static void printA(struct a* pa)
{
    printf("[%d][%s][%f;%f;%f]\n", pa->i, pa->str,
           pa->vec3.x, pa->vec3.y, pa->vec3.z);
}




struct a* restoreA(char* fname)
{
    return 0;
}


int main(int argc, char *argv[])
{
    struct a newa = setA(1, "bla bla bla", 1.0, 2.0, 3.0);
    printA(&newa);


    char* odump = dumpA(&newa);


    FILE *fp = fopen("serialized", "r");
    char buff[256]={0};
    while(fgets(buff, 256, fp)) {


    }


    union dm {
        struct a ma;
        char c[sizeof(struct a)];
    };


    union dm d;
    memset(d.c, 0, sizeof(struct a));
    strcpy(d.c, buff);


    printf("[%d][%s][%f,%f,%f]\n", d.ma.i, d.ma.str,
           d.ma.vec3.x, d.ma.vec3.y, d.ma.vec3.z);

    fclose(fp);
    return 0;
}

When I read it back it seems filled with data but the data is bad. In first time I don`t know if it is dumped correctly.

I`ve found a way to restore the object via the cast from the buffer:
After reading the object to a char buffer with a sufficiet size:

Code:

struct a* pa = (struct a*) buff;

Also the serialize procedure must dump the object in a %c char not in hex as I did

Code:

fprintf(fp, "%c", c);