string: add and test strtok (DONE)

CMakeLists.txt

@@ -158,6 +158,7 @@ set(SOURCES
   src/libc/string/strspn.c
   src/libc/string/strstr.c
   src/libc/string/strstr_base.c
+  src/libc/string/strtok.c
   src/libc/string/strxfrm.c)
 
 if(vhex-generic IN_LIST TARGET_FOLDERS)

STATUS

@@ -127,7 +127,7 @@ DONE:       Function/symbol/macro is defined, builds, links, and is tested
      7.21.5.5  strrchr: DONE
      7.21.5.6  strspn: DONE
      7.21.5.7  strstr: DONE
-!    7.21.5.8  strtok: TODO
+     7.21.5.8  strtok: DONE
      7.21.6.1  memset: DONE
      7.21.6.2  strerror: DONE
      7.21.6.3  strlen: DONE

src/libc/string/strtok.c

@@ -0,0 +1,18 @@
+#include <string.h>
+
+char *strtok(char * restrict new_s, char const * restrict separators)
+{
+	static char *s = NULL;
+	if(new_s) s = new_s;
+
+	/* Skip leading delimiters */
+	s += strspn(s, separators);
+	if(!*s) return NULL;
+
+	/* Skip non-delimiters */
+	char *token = s;
+	s += strcspn(s, separators);
+	*s++ = 0;
+
+	return token;
+}