ft_strlen

Subject

STRLEN(3) (simplified)

NAME
    strlen -- find length of string
SYNOPSIS
    size_t(const char *s);
DESCRIPTION
    The strlen() function computes the length of the string s.
RETURN VALUES
    The strlen() function returns the number of characters that precede the terminating NUL character.

Understandable explanation

For this function, the man is pretty self-explanatory on what the function does, but some things are new, we never seen some things before.

The strlen() function returns the number of characters before the terminating NUL (\0) character of the string.

What does this mean ?

If our string is abcde\0, strlen() will return 5.

The string we pass as parameter has the keyword const before it, this means we can't modify this string inside our function, since it's a constant value.

The returned value of strlen() is of type size_t, what is it ? Let me explain.

As said on geeksforgeeks.org, the size_t data type is a type which is used to represent the size of objects in bytes and is therefore used as the return type by the sizeof operator. It is guaranteed to be big enough to contain the size of the biggest object the host system can handle. Basically the maximum permissible size is dependent on the compiler; if the compiler is 32 bit then it is simply a typedef (i.e., alias) for unsigned int but if the compiler is 64 bit then it would be a typedef for unsigned long long. The size_t data type is never negative.

Hints

ft_strlen.c

size_t    ft_strlen(const char *s)
{
    while( /* we are not reading \0 character */)
        /* increment a counter and read next char */
    return (/* the counter */);
}

Commented solution

Come on ! You wrote this function like a hundred times during the Piscine, you really need to see the code ?

ft_strlen

ft_strlen.c

#include "libft.h"

size_t    ft_strlen(cont char *s)
{
    /* usually we declare our counter as an int, but for this one
     * we'll declare it as a size_t since size_t is bigger than int
     */
    size_t    i;
    
    i = 0;
    /* we then iterate over all the characters in the s array
     * you might think there's no exit condition on this loop but
     * there is. If the character we read is \0 then the loop
     * condition will evaluate to false, therefore not going into
     * it again.
     */
    while (s[i])
        i++;
    /* as said in the hint, we return the counter, it will be equal
     * to the number of character before the terminating \0
     * character
     */
    return (i);
}