reading writing to a file system

[hrishiS]

Anyone please help me to read write 3 differnt structure to a file...and read them searching the file....like struct A { int id; int data; }; struct B { int id; float data; }; struct C { int id; double data; int data2 };

----------------------------- I am a beginner

[Adam Roderick J]

I think you to check with serialization. Please check A serialization primer - Part 1[^]

Величие не Бога может быть недооценена.

[Rajesh R Subramanian]

You mean plain text? You could keep every such struct as a "section" and use an .inf file to store the values. For example, for a string value, you could use WritePrivateProfileString[^] (and there's an 'int' variant, and so on). For reading, use GetPrivateProfileString[^]. This would be plain text and readable. If you need encryption, you must take care of it. You might as well serialize[^] your data.

“Follow your bliss.” – Joseph Campbell

[hrishiS]

thanks a lot...but i need a file system only ...not INI file...preferably a binary file

----------------------------- I am a beginner

[hrishiS]

thanks... I quickly read the article, its somewhat interesting...I need to write the different type of class..not only the one....in that case please help me ... One more important thing is that I am not using MFC...its a pure C++ console based application

----------------------------- I am a beginner

modified on Thursday, December 17, 2009 12:42 AM

[Adam Roderick J]

Just check this http://www.osix.net/modules/article/?id=348[^]

Величие не Бога может быть недооценена.

[CPallini]

I already gave you some code, but OK, it was incomplete. Let's try a plain, not object oriented, C-Like approach:

#include

enum SerialType
{
eTYPE_UNRECOGNIZED,
eTYPE_A,
eTYPE_B,
eTYPE_C,
eTYPES
};

struct A
{
int id;
int data;
};

struct B
{
int id;
float data;
};

struct C
{
int id;
double data;
int data2;
};

size_t getSize(SerialType st)
{
switch( st)
{
case eTYPE_A:
return sizeof(A);
case eTYPE_B:
return sizeof(B);
case eTYPE_C:
return sizeof(C);
default:
return 0;
}
}

bool store( SerialType st, void * pData, FILE * fp)
{
int type = st;
size_t size = getSize(st);

if (!fp || !pData || !size) return false;
fwrite(&type, sizeof(type), 1, fp);
fwrite(pData, size,1,fp);
return true;
}

SerialType readType( FILE * fp)
{
SerialType type;
if (!fp ) return eTYPE_UNRECOGNIZED;

if ( fread(&type, sizeof(type), 1, fp) == 0 ) return eTYPE_UNRECOGNIZED;
return type;
}

bool readData( SerialType st, void * pData, FILE * fp)
{
size_t size = getSize(st);
if ( !fp || !pData || !size ) return false;
fread(pData, size, 1, fp);
return true;
}

void main()
{
SerialType type;

A a[2];
B b;
C c1,c2;

A * pa=NULL;
B * pb=NULL;
C * pc=NULL;

// define some variables
a[0].data = 5;
a[0].id = 12;

a[1].data = 6;
a[1].id = 13;

b.data=25.75f;
b.id=100;

c1.data = 27;
c1.data2=35;
c1.id = 7;

c2.data=1000.372;
c2.data2=1000;
c2.id=1;

FILE * fp = fopen("data.raw", "wb");

// store some of the defined variables
store(eTYPE_C, &c2, fp);
store(eTYPE_A, &a[1], fp);
store(eTYPE_B, &b, fp);
store(eTYPE_A, &a[0], fp);

fclose(fp);

// read the variables from the storage, printing their values.
fp = fopen("data.raw", "rb");

while ((type=readType(fp)) != eTYPE_UNRECOGNIZED)
{
switch (type)
{
case eTYPE_A:
pa = new A();
readData(type, pa, fp);
printf("type A, id=%d, data=%d.\n", pa->id, pa->data);
delete pa;
break;
case eTYPE_B:
pb = new B();
readData(type, pb, fp);
printf("type B, id=%d, data=%g.\n", pb->id, pb->data);
delete pb;
break;
case eTYPE_C:
pc = new C();
readData(type, pc, fp);
printf("type C, id=%d, data=%g, data2=%d.\n", pc->id, pc->data, pc->data2);
delete pb;
break;
}
}
fclose(fp);
}
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