Thread: Writing data to file

Actually Title is not clear enough i will try to ask on a example code

Code:

typedef struct{
char name[10];
int no;
}TAM;

typedef struct{
char name[10];
char ch;
}HARF;


typedef struct{
TAM *i;
CHAR *c;
}DENEME;


main(){
FILE *f1;
DENEME *d;
d=(DENEME *) malloc(sizeof(DENEME)*2);
int i;

d[0].i=(TAM *) malloc(sizeof(TAM)*2);
d[0].c=(HARF *) malloc(sizeof(HARF)*2);
d[1].i=(TAM *) malloc(sizeof(TAM)*2);
d[1].c=(HARF *) malloc(sizeof(HARF)*2);

/* Every think ok for now  i can get info from user like  (d[0].i[0].name,d[0].i[0].no) */

f1=fopen("c:\\deneme.txt","w+b");

/* i just wnt to write d[i] to File*/
for(i=0;i<2;i++){

fwrite(d[i],sizeof(DENEME),1,f1); //if i try like this  there  is an error'cannot convert  '

fwrite(&d[i],sizeof(DENEME),1,f1) // if i try like this  this time it writes the value of pointers 




fwrite(d[i],sizeof(TAM)*2+sizeof(HARF)*2,1,f1)// finally i try this but it gives  error agin 
}


}

im able to write like this
fwrite((d+0)->i,sizeof(TAM),2,f1);
fwrite((d+0)->c,sizeof(HARF),2,f1);
but i doesnot help for my algorithms cause i want to read d[i] so that with one read i can have d[i].i[j].name

hope im could explain my problem clearly..

sorry for my english :P

1. Where are all your #includes?

2. main(){
main returns an int. You should really get into the habit of being specific about your return types. The new C standard doesn't allow implicit types anymore.

3. d=(DENEME *) malloc(sizeof(DENEME)*2);
Dont cast the return result of malloc in C - see the FAQ

4. int i;
This is after a statement, C doesn't (yet) allow mixed declarations and statements.
Move it above your malloc call.

5. d[0].c=(HARF *) malloc(sizeof(HARF)*2);
But c is a CHAR * (which isn't defined), not a HARF *

> /* i just wnt to write d[i] to File*/
Then it would be
fwrite ( d[i].i, sizeof *d[i].i, 2, fp );
fwrite ( d[i].c, sizeof *d[i].c, 2, fp );

sorry

it should be like

Code:

typedef struct{
TAM *i;
HARF *c;
}DENEME;

thanx for other suggestions 

but  i already did 
fwrite ( d[i].i, sizeof *d[i].i, 2, fp );
fwrite ( d[i].c, sizeof *d[i].c, 2, fp );

but it isnot good solution for my algorthm
if i write like this;  later while reading  i cant read  like
fread(d[0],sizeof(DENEME),1,f1);
i need to do this 
hope im clear enough..

Yes, you are being clear - but it isn't going to happen.
Each pointer needs to be followed EXPLICITLY when dealing with the likes of fwrite, since it has no idea what is a pointer, nor how much it might point to.

Lose all the pointers in the struct (and all but your first malloc), I can see no reason for them

Code:

typedef struct{
   TAM i;
   HARF c;
}DENEME;

Then you'll be able to
fread(&d[0],sizeof(DENEME),1,f1);

the reason why i use pointer we dont know how many TAM or HARf we will use its up to user i mean he will write to promt and we will write according to that informations

its like database if he writes 2 TAm whose name are PHone values 1234 and ID the values 11 it will be like

d[0].i[o].name="Phone "
d[0].i[o].no="1234 "


d[0].i[1].name="ID "
d[0].i[1].no="11 "

if i write like u said

fwrite ( d[i].i, sizeof *d[i].i, 2, fp );
fwrite ( d[i].c, sizeof *d[i].c, 2, fp );

it will write first i and then c and later when i need to get information abot someone i need to make confused calculating to read info of then but if i wirte like
fwrite ( d[i], sizeof *d[i], 1, fp );
with one read and without confusing calculations i can have all information about d[i]

amm i right?

Then for each block of memory which you malloc, and which can be variable in size, you need to also write this size information to the file, and read it back again.

Code:

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

typedef struct{
  char  name[10];
  int   no;
}TAM;

typedef struct{
  char  name[10];
  char  ch;
}HARF;


typedef struct{
  int   numTams;
  int   numHarfs;
  TAM   *tams;
  HARF  *harfs;
}DENEME;

int main(void)
{
  int     numDenemes = 2; /* some number */
  DENEME  *d = malloc ( numDenemes * sizeof *d );
  FILE    *fp;
  int     i;

  // an initial database of some sort
  d[0].numTams  = 1;
  d[0].tams     = malloc(sizeof(TAM)*d[0].numTams);
  d[0].numHarfs = 2;
  d[0].harfs    = malloc(sizeof(HARF)*d[0].numHarfs);
  d[1].numTams  = 3;
  d[1].tams     = malloc(sizeof(TAM)*d[1].numTams);
  d[1].numHarfs = 4;
  d[1].harfs    = malloc(sizeof(HARF)*d[1].numHarfs);

  // writing
  fwrite ( &numDenemes, sizeof numDenemes, 1, fp ); /* total number */
  for ( i = 0 ; i < numDenemes ; i++ ) {
    /* write out how many of each record we have */
    fwrite ( &d[i].numTams,   sizeof d[i].numTams,  1, fp );
    fwrite ( &d[i].numHarfs,  sizeof d[i].numHarfs, 1, fp );
    /* write out the records */
    fwrite ( d[i].tams,   sizeof *d[i].tams,  d[i].numTams,  fp );
    fwrite ( d[i].harfs,  sizeof *d[i].harfs, d[i].numHarfs, fp );
  }

  // reading (assuming nothing has been malloc'ed yet)
  fread ( &numDenemes, sizeof numDenemes, 1, fp ); /* total number */
  d = malloc ( numDenemes * sizeof *d );
  for ( i = 0 ; i < numDenemes ; i++ ) {
    /* read in how many of each record we have */
    fread ( &d[i].numTams,  sizeof d[i].numTams,  1, fp );
    fread ( &d[i].numHarfs, sizeof d[i].numHarfs, 1, fp );

    /* allocate space for the records we're about to read */
    d[i].tams  = malloc(sizeof(TAM)*d[i].numTams);
    d[i].harfs = malloc(sizeof(TAM)*d[i].numHarfs);

    /* read in the records */
    fread ( d[i].tams,  sizeof *d[i].tams,  d[i].numTams,  fp );
    fread ( d[i].harfs, sizeof *d[i].harfs, d[i].numHarfs, fp );
  }

  return 0;
}

first of all really thanx for your interest

actually im plannng to store info like
int numTams;
int numHarfs;
numDenemes;
in another file because of futurer properties (teher may be lots of file so its not logical to open ever file and get the information)
any way


im sory if im wrong but
if we read like
fread ( d[i].tams, sizeof *d[i].tams, d[i].numTams, fp );
printf("%s \n ",d[1].tams[0].name);
it will give us some strage characters that pointer has

if we read like
fread ( &d[i].tams, sizeof *d[i].tams, d[i].numTams, fp );
tahts allright but go and look to your file there will be again the pointers i mean when we close the program and when we just try to read data like

f1=fopen("c:\\deneme.txt","r+b");

fread(d[0].tams,sizeof *d[i].tams,1,f1);

printf("%s \n ",d[3].i[0].name);
printf("%d \n",d[3].i[0].no);

there will be again only strange chars

am i doing right ?

im really confused

Ok, real example, and some output.
Error checks on malloc, fopen and fread have been omitted for brevity.

Code:

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

typedef struct {
  char  name[10];
  int   no;
} TAM;

typedef struct {
  char  name[10];
  char  ch;
} HARF;

typedef struct {
  int   numTams;
  int   numHarfs;
  TAM   *tams;
  HARF  *harfs;
} DENEME;

DENEME *allocDenemes ( int numDenemes ) {
  int      i, j;
  DENEME  *d = malloc ( numDenemes * sizeof *d );
  for ( i = 0 ; i < numDenemes ; i++ ) {
    d[i].numTams = i + 1;
    d[i].numHarfs= i + 2;
    d[i].tams    = malloc ( d[i].numTams * sizeof *d[i].tams );
    d[i].harfs   = malloc ( d[i].numHarfs* sizeof *d[i].harfs );
    for ( j = 0 ; j < d[i].numTams ; j++ ) {
      sprintf( d[i].tams[j].name, "Name %d", i + j );
      d[i].tams[j].no = i + j;
    }
    for ( j = 0 ; j < d[i].numHarfs ; j++ ) {
      sprintf( d[i].harfs[j].name, "Name %d", i + j );
      d[i].harfs[j].ch = i + j + 'a';
    }
  }
  return d;
}

void freeDenemes ( DENEME *d, int numDenemes ) {
  int i;
  for ( i = 0 ; i < numDenemes; i++ ) {
    free ( d[i].tams );
    free ( d[i].harfs );
  }
  free ( d );
}

void printDenemes ( DENEME *d, int numDenemes ) {
  int i, j;
  for ( i = 0 ; i < numDenemes; i++ ) {
    printf( "TAMS for %d\n", i );
    for ( j = 0 ; j < d[i].numTams ; j++ ) {
      printf ( "-- Name=%s, no=%d\n",
               d[i].tams[j].name, d[i].tams[j].no );
    }
    printf( "HARFS for %d\n", i );
    for ( j = 0 ; j < d[i].numHarfs ; j++ ) {
      printf ( "-- Name=%s, ch=%c\n",
               d[i].harfs[j].name, d[i].harfs[j].ch );
    }
  }
}

void saveDenemes ( DENEME *d, int numDenemes, const char *filename ) {
  int i;
  FILE *fp = fopen ( filename, "wb" );

  fwrite ( &numDenemes, sizeof numDenemes, 1, fp ); /* total number */
  for ( i = 0 ; i < numDenemes ; i++ ) {
    /* write out how many of each record we have */
    fwrite ( &d[i].numTams,   sizeof d[i].numTams,  1, fp );
    fwrite ( &d[i].numHarfs,  sizeof d[i].numHarfs, 1, fp );
    /* write out the records */
    fwrite ( d[i].tams,   sizeof *d[i].tams,  d[i].numTams,  fp );
    fwrite ( d[i].harfs,  sizeof *d[i].harfs, d[i].numHarfs, fp );
  }
  fclose ( fp );
}

DENEME *loadDenemes ( int *numDenemes, const char *filename ) {
  int i;
  FILE *fp = fopen ( filename, "rb" );
  DENEME  *d;

  fread ( numDenemes, sizeof *numDenemes, 1, fp ); /* total number */
  d = malloc ( *numDenemes * sizeof *d );
  for ( i = 0 ; i < *numDenemes ; i++ ) {
    /* read in how many of each record we have */
    fread ( &d[i].numTams,  sizeof d[i].numTams,  1, fp );
    fread ( &d[i].numHarfs, sizeof d[i].numHarfs, 1, fp );

    /* allocate space for the records we're about to read */
    d[i].tams  = malloc(sizeof(TAM)*d[i].numTams);
    d[i].harfs = malloc(sizeof(TAM)*d[i].numHarfs);

    /* read in the records */
    fread ( d[i].tams,  sizeof *d[i].tams,  d[i].numTams,  fp );
    fread ( d[i].harfs, sizeof *d[i].harfs, d[i].numHarfs, fp );
  }
  fclose ( fp );
  return d;
}

int main ( void ) {
  const char *filename = "savedata.dat";
  int         numDenemes = 2; /* some number */
  DENEME     *d;

  printf( "Initialise, print it, save it and free\n" );
  d = allocDenemes ( numDenemes );
  printDenemes ( d, numDenemes );
  saveDenemes ( d, numDenemes, filename );
  freeDenemes ( d, numDenemes );

  printf( "\nLoad it, print it and free\n" );
  d = loadDenemes ( &numDenemes, filename );
  printDenemes ( d, numDenemes );
  freeDenemes ( d, numDenemes );

  return 0;
}


$ ./a.out
Initialise, print it, save it and free
TAMS for 0
-- Name=Name 0, no=0
HARFS for 0
-- Name=Name 0, ch=a
-- Name=Name 1, ch=b
TAMS for 1
-- Name=Name 1, no=1
-- Name=Name 2, no=2
HARFS for 1
-- Name=Name 1, ch=b
-- Name=Name 2, ch=c
-- Name=Name 3, ch=d

Load it, print it and free
TAMS for 0
-- Name=Name 0, no=0
HARFS for 0
-- Name=Name 0, ch=a
-- Name=Name 1, ch=b
TAMS for 1
-- Name=Name 1, no=1
-- Name=Name 2, no=2
HARFS for 1
-- Name=Name 1, ch=b
-- Name=Name 2, ch=c
-- Name=Name 3, ch=d

Thanks for your interest & help Salem your code helped me alot hope someother friends also should have lookto this code