C++ Convert bytes to string ( Bytes, KB, MB, GB, TB )

[pDevice]

Hello, This function serves to convert a size of a module for example, string, and shows the size, in bytes, KB, MB, GB, or TB ...

char* BytesToSize( float Bytes )        {
             float tb = 1099511627776;
             float gb = 1073741824;
             float mb = 1048576;
             float kb = 1024;


             char returnSize[256];


             if( Bytes >= tb )
                 sprintf(returnSize, "%.2f TB", (float)Bytes/tb);        
             else if( Bytes >= gb && Bytes < tb )
                 sprintf(returnSize, "%.2f GB", (float)Bytes/gb);
             else if( Bytes >= mb && Bytes < gb )
                 sprintf(returnSize, "%.2f MB", (float)Bytes/mb);   
             else if( Bytes >= kb && Bytes < mb )
                 sprintf(returnSize, "%.2f KB", (float)Bytes/kb);
             else if ( Bytes < kb)
                 sprintf(returnSize, "%.2f Bytes", Bytes);
             else
                 sprintf(returnSize, "%.2f Bytes", Bytes);


             return returnSize;
         }

[abuckau907]

You're returning the address of a local variable of the function.

Char* x = function(4000);
Char* y = function(8000);

Both point to the same char array. Not what you'd expect.

[pDevice]

You're returning the address of a local variable of the function.

Char* x = function(4000);
Char* y = function(8000);

Both point to the same char array. Not what you'd expect.

Works fine for me

[Fovea]

It works fine because the program you have written for verification is simple. In the real world, your function will break because what is returned exists on the stack and it will be overwritten eventually.

[Harava]

Fix'd.

#include <cstdio>
#include <windows.h>

bool BytesToSize( double Bytes , char * ByteString , int BufSize )
{
    float tb = 1099511627776.0f;
    float gb = 1073741824.0f;
    float mb = 1048576.0f;
    float kb = 1024.0f;

    char * returnSize = (char *)malloc(BufSize);
    if(returnSize == NULL)
        return false;

    if( Bytes >= tb )
        sprintf(returnSize, "%.2lf TB", (double)Bytes/tb);
    else if( Bytes >= gb && Bytes < tb )
        sprintf(returnSize, "%.2lf GB", (double)Bytes/gb);
    else if( Bytes >= mb && Bytes < gb )
        sprintf(returnSize, "%.2lf MB", (double)Bytes/mb);
    else if( Bytes >= kb && Bytes < mb )
        sprintf(returnSize, "%.2lf KB", (double)Bytes/kb);
    else if ( Bytes < kb)
        sprintf(returnSize, "%.2lf Bytes", Bytes);
    else
        sprintf(returnSize, "%.2lf Bytes", Bytes);

    memcpy((void *)ByteString, (void *)returnSize, BufSize);
    free(returnSize);
    return true;
}

int main()
{
    double baits = 9999999999999999999999.0f;
    char ByteString[512];
    if(BytesToSize(baits, ByteString, sizeof(ByteString)))
        printf("%lf Bytes are %s \n", baits, ByteString);
    return 0;
}

[abuckau907]

Thanks @Harava


@OP
One more thing ..

if( Bytes >= tb )
...
else if( Bytes >= gb && Bytes < tb )
...
else if( Bytes >= mb && Bytes < gb )
...
else if( Bytes >= kb && Bytes < mb )
...
else if ( Bytes < kb)
...
else

If the first IF branch is not taken, that means bytes < tb --> No need to test for bytes < tb in the 2nd if clause.
Same thing continues down -- all the conditions to the right of && were proven true in the previous if statement : P

if( Bytes >= tb )
...
else if( Bytes >= gb)
...
else if( Bytes >= mb)
...
else if( Bytes >= kb )
...
else