add: strjoin and strmerger

src/str/str.h

@@ -1,4 +1,6 @@
 #pragma once
+
+#include <stdarg.h>
 #include <stddef.h>
 #include <string.h>
 #include <stdlib.h>
@@ -6,3 +8,5 @@
 char **split(const char *str, const char *delimiter);
 void str_shift(char *str, int shift);
 int str_contain_only(const char *str, const char *charset);
+char* str_merger(size_t arg_len, ...);
+char* str_join(const char* s1, const char* s2);

src/str/str_join.c

@@ -0,0 +1,14 @@
+#include "str.h"
+#include <string.h>
+
+char *str_join(const char *s1, const char *s2)
+{
+	char *out;
+	
+	out = malloc((strlen(s1) + strlen(s2) + 1) * sizeof(char));
+	if (out == NULL)
+		return (NULL);
+	strcpy(out, s1);
+	strcat(out, s2);
+	return out;
+}

src/str/str_merger.c

@@ -0,0 +1,21 @@
+#include "str.h"
+
+char	*str_merger(size_t arg_len, ...)
+{
+	va_list	va;
+	char	*out;
+	char	*temp;
+
+	va_start(va, arg_len);
+	out = str_join(va_arg(va, char *), va_arg(va, char *));
+	while (arg_len > 2)
+	{
+		temp = str_join(out, va_arg(va, char *));
+		free(out);
+		if (temp == NULL)
+			return (NULL);
+		out = temp;
+		arg_len--;
+	}
+	return out;
+}