object: string: add front, back, and pop_back functions

object/string.c

@@ -324,6 +324,38 @@ size_t b_string_get_capacity(const struct b_string *str)
 	return str->s_max;
 }
 
+char b_string_front(const struct b_string *str)
+{
+	if (str->s_len == 0) {
+		return 0;
+	}
+
+	const char *s = b_string_ptr(str);
+	return s[0];
+}
+
+char b_string_back(const struct b_string *str)
+{
+	if (str->s_len == 0) {
+		return 0;
+	}
+
+	const char *s = b_string_ptr(str);
+	return s[str->s_len - 1];
+}
+
+void b_string_pop_back(struct b_string *str)
+{
+	if (str->s_len == 0) {
+		return;
+	}
+
+	char *s = string_ptr(str);
+
+	s[str->s_len - 1] = '\0';
+	str->s_len--;
+}
+
 const char *b_string_ptr(const struct b_string *str)
 {
 	if (string_is_inline(str)) {