Most of computers have the shift left instruction.
Shifting the bits by “x” positions to left, is equivalent to multiplication by x^2.
In this case…
int a = 4;
int b = 0;
b = a<<1;
/* Now, b value is 8 */
b = a<<2;
/* Now, b value is 16 */
That’s all folks!
Usually I need to open a file stream or a file descriptor to write something in that.
I used to create a new string, concatenating the directory (usually some macro) with the file name.
Something like this:
#define DIR "/tmp/alice/files/"
FILE *fs = NULL;
char filename[500] = {0};
snprintf(filename, 500, "%s/file.txt", DIR);
fs = fopen(filename, "a+");
But an easy way to do that is to use the facility of constant strings:
#define DIR "/tmp/alice/files/"
FILE *fs = NULL;
fs = fopen(DIR "file.txt", "a+");
In my opinion, this way is easier to read and certainly faster.
Bruno Soares.
One thing that I like in GLib is this macro: “g_return_if_fail” and “g_return_val_if_fail”.
But if you don’t use GLib or you have your own trace system, you can create your own macro, something like this:
#define return_if_fail(expr) if (!(expr)) {trace("[%s] - expr '%s' failed", __FUNCTION__, #expr); return;};
#define return_val_if_fail(expr, val) if (!(expr)) {trace("[%s] - expr '%s' failed", __FUNCTION__, #expr); return val;};
And with this macro, you can change your way to check the intergrity of your variables:
Common way:
if(var == NULL) {
printf("var == NULL\n");
return 1;
}
You can use:
return_val_if_fail(var != NULL, 1);
PS.: if you don’t have your own trace function, you can just change the “trace” for “printf” or “fprintf” function.
This is an easy, fast and nice way to trace the problems.
I would like to say that… let’s try it again!
New blog with another focus. We’ll try write somethings about C, Linux, Embedded, etc.
I invited some friends to write over here, they are very good professionals and experts in their areas.
So… let’s do it!
Some C Tips 