以可视c ++格式读取文件的行为与在C程序中读取行为不同

Question

I'm build a graphical program using visual c++ form. I'm trying to read a file to a string. The contents of the file is simple html code.

Now, if i create a blank project and create a .c file with this code:

FILE *f;
int tamanho;
char *asd;

f=fopen("mail.txt","r");
if(f==NULL)
    erro("Erro abrir file");

fseek(f,0,SEEK_END);
tamanho=ftell(f);
rewind(f);
asd=(char *)malloc(tamanho+1);
fread(asd,1,tamanho,f);

It copies the whole to the string.

However if I create a windows form application and write the same code it only copies a few lines of my file.

Answer 1

fread() does not guarantee to read everything you ask for.

You need to check the return value to see how much was actually read.
You may need to do this in a loop until you have read everything you want.

size_t  read = 0;
while(read != tamanho)
{
    size_t amount = fread(asd + read,1,tamanho - read,f);

    if (amount == 0)
    {    // You may want to check for read errors here
    }

    read += amount;
}

Answer 2

Missing a while loop? That way u make sure u reach end of file properly