缓冲区大小和文件读取

Question

I already asked a similiar question but I think now the problem is different.. Im writing in C on eclipse ,linux machine.

I need to read the testfile and each time to try with different buffer size... I know I need to run on the buffer several times if the size of the buffer is too small but im not sure how to do this...

this is my code ( when im running on buffer with size 67108864 im getting segmentation fault. * I edited my code

int main(void)
{   int fd;
    char* buff = malloc (67108864);
    if (buff){
    fd = open("testfile.txt", O_RDONLY);
    if (fd >= 0) {
        while (read(fd,buff,67108864)!=0){}
        close(fd);
    }
    }
free(buff);
return 0;
}

Answer 1

This is not a char[] :

char* buff[67108864];

but is an array of char* . Change to:

char buff[67108864];

Also, the size of buff may be too large for the stack. The typical size of the stack is 1MB (1048576 bytes) but the size of buff far exceeds (64MB!) that which would result in a stack overflow error. If you wish to use a buffer of this dynamically allocate it, using malloc() , and release it later, using free() :

char* buff = malloc(67108864);
if (buff)
{
    /* Use 'buff' and then release it. */

    free(buff);
}

Answer 2

Remove * , you are declaring an array of pointers, but you need an array of characters.

   char buff[67108864];

I'm not sure about 67108864 it's too big for stack. Try to make it on heap.