C - Read struct in file - c

Question

Hi I want to read some information in a struct that i wrote in file with fwrite but there's a problem I can't extract these information. I got 2 file
tttfs.h :
#include <stdlib.h>
#include <stdio.h>
#include <stdint.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
typedef struct _disk disk;
typedef struct _block block;
struct _block{
uint8_t *unBlock;
};
struct _disk{
int id;
block *diskBlock;
};
tfs_create.c :
#include "tttfs.h"
uint8_t little[4];
int tttfs_create(int size, char *name);
void inttolitend(uint32_t x, uint8_t* lit_int);
int main(){
tttfs_create(7, "disk.tfs");
int f = 0;
if((f=open("disk.tfs",O_RDONLY)) < -1) //I took this from an example.
return 1;
disk *d = malloc(sizeof(disk)); //Create a disk
d->diskBlock = malloc(1024); //The block where I want to write the information from the file.
lseek(f,0,SEEK_SET);//I want to read from the beginning
read(f,d->diskBlock,1024); //I write all the information from the beginning to 1024th byte of my file
int i;
for(i=0; i<4; i++){
printf("%d\n", (uint8_t)&d->diskBlock[i]);//print my result.
}
}
int tttfs_create(int size, char *name){
FILE *f = NULL;
if ((f = fopen(name, "wb"))!=NULL) /** si ouverture ok **/
{
disk *d = malloc(sizeof(disk));
d->diskBlock = malloc(sizeof(block) * size);
d->id = 1;
int i;
for(i = 0; i<size; i++){
d->diskBlock[i].unBlock = malloc(sizeof(uint8_t) * 1024);
}
inttolitend(size, little);
for(i = 0; i<4; i++){
d->diskBlock[0].unBlock[i] = little[i];
}
for(i = 0; i<size; i++){
fwrite(&d->diskBlock[i],sizeof(block),1,f);
}
}
else
printf("Erreur\n\n");
return 0;
}
void inttolitend(uint32_t x, uint8_t* lit_int){
lit_int[3] = (uint8_t)x / (256*256*256);
lit_int[2] = (uint8_t)(x % (256*256*256)) / (256*256);
lit_int[1] = (uint8_t)((x % (256*256*256)) % (256*256)) / 256;
lit_int[0] = (uint8_t)((x % (256*256*256)) % (256*256)) % 256;
}
With this I create a disk with 7 block and I write all 7 block in my file. In my first block I wrote the size of my disk (7) in little endian. So block[0] = 00, block[1] = 00, block[2] = 01, block[3] = 11 or something like that.
But when I print my result I get :
0
8
16
24
Not what I expected I try without readand i got the same result. So my programm didn't write the information from the disk. Or there's a problem when I write my block in the disk ?

Answer 1

i can not be so sure what you want exactly but this should work
#define BLOCK_BUFF_SIZE (1024*sizeof(block))
int tttfs_create(int size, char *name);
int tttfs_load(char *fname, disk *pdisk)
void inttolitend(uint32_t x, uint8_t* lit_int);
int tttfs_load(char *fname, disk *pdisk){
int fd;
unsigned int n;
int i;
fd = open("disk.tfs",_O_RDONLY);
if(fd==-1){
perror("tttfs_load.open");
return -1;
}
n=lseek (fd,0,SEEK_END);
lseek(fd,0,SEEK_SET);
if(n==(unsigned int)-1){
close(fd);
return -1;
}
if(n){
n/=(BLOCK_BUFF_SIZE);
pdisk->diskBlock=malloc(n*sizeof(block));
for(i=0;i<n;i++){
pdisk->diskBlock[i].unBlock=malloc(BLOCK_BUFF_SIZE);
read(fd,pdisk->diskBlock[i].unBlock,BLOCK_BUFF_SIZE);
}
}
close(fd);
return n;
}
int main(){
unsigned int n;
disk d;
int i;
tttfs_create(7, "disk.tfs");
n=tttfs_load("disk.tfs",&d);
if(!n || n==(-1)) return -1;
for(i=0; i<4; i++){
printf("%d\n", (uint8_t)(d.diskBlock->unBlock[i]));//print my result.
}
}
int tttfs_create(int size, char *name){
FILE *f = NULL;
disk d;
int i;
if (!(f = fopen(name, "wb"))) {
perror("tttfs_create:open()");
return 0;
}
d.diskBlock = malloc(sizeof(block) * size);
d.id = 1;
for(i = 0; i<size; i++){
d.diskBlock[i].unBlock = malloc(BLOCK_BUFF_SIZE);
}
inttolitend(size, (uint8_t*)(d.diskBlock->unBlock));
for(i=0;i<size;i++){
fwrite(d.diskBlock[i].unBlock ,BLOCK_BUFF_SIZE,1,f);
}
return 1;
}
void inttolitend(uint32_t x, uint8_t* lit_int){
lit_int[3] = ((x<<24) & 0xff);
lit_int[2] = ((x<<16) & 0xff);
lit_int[1] = ((x<<8) & 0xff);
lit_int[0] = ((x<<0) & 0xff);
}