C strtrim function: Trims leading and trailing whitespace from a string in-place

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        DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE 
                    Version 2, December 2004 

 Copyright (C) 2025 Iuri Diniz <iuridiniz-at-EMAIL-BIG-G.com> 

 Everyone is permitted to copy and distribute verbatim or modified 
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 as the name is changed. 

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  0. You just DO WHAT THE FUCK YOU WANT TO.

strtrim.c

#include <ctype.h>
#include <string.h>
/**
 * @brief Trims leading and trailing whitespace from a string in-place.
 * 
 * This function modifies the input string to remove any leading and trailing
 * whitespace characters (as defined by isspace).
 *
 * @param str The character string to trim. The string must be modifiable.
 * @return A pointer to the first non-whitespace character in the string.
 *
 * If the string is NULL, empty, or contains only whitespace, it returns
 * a pointer to the beginning of the (now empty) string.
 */
static inline char *strtrim(char *str) {
	char *start;
	char *end;

	// 1. Handle edge cases: If the string is NULL or already empty, do nothing.
	if (!str || *str == '\0') {
		return str;
	}

	// 2. Find the first non-whitespace character.
	// The `start` pointer will be moved forward until it points to a
	// character that is not a space.
	start = str;
	while (isspace((unsigned char)*start)) {
		start++;
	}

	// 3. Handle strings that contain ONLY whitespace.
	// If `start` now points to the end of the string ('\0'), it means
	// the entire string was whitespace. We make the original string empty.
	if (*start == '\0') {
		*str = '\0';
		return str;
	}

	// 4. Find the last non-whitespace character.
	// The `end` pointer starts at the end of the string and moves
	// backward until it finds a non-whitespace character.
	end = str + strlen(str) - 1;
	while (end > start && isspace((unsigned char)*end)) {
		end--;
	}

	// 5. Add the null terminator.
	// Place the null terminator right after the last non-whitespace character
	// to officially end the string there.
	*(end + 1) = '\0';

	// 6. Return the new start of the string.
	return start;
}