libluna/CString: Implement strspn and strcspn, and using those implement strtok

libluna/include/luna/CString.h

@@ -13,6 +13,11 @@ extern "C"
 
     int strcmp(const char* a, const char* b);
 
+    usize strspn(const char* str, const char* accept);
+    usize strcspn(const char* str, const char* reject);
+
+    char* strtok(char* str, const char* delim);
+
     usize wcslen(const wchar_t* str);
 
     char* strdup(const char* str);

libluna/src/CString.cpp

@@ -136,4 +136,71 @@ extern "C"
         dest[copy_len] = 0;
         return src_len;
     }
+
+    usize strcspn(const char* str, const char* reject)
+    {
+        const char* s = str;
+        while (*s)
+        {
+            const char* rp = reject;
+            while (*rp)
+            {
+                if (*s == *rp) return (usize)(s - str);
+                rp++;
+            }
+            s++;
+        }
+        return (usize)(s - str);
+    }
+
+    usize strspn(const char* str, const char* accept)
+    {
+        const char* s = str;
+        while (*s)
+        {
+            const char* ap = accept;
+            bool match = false;
+            while (*ap)
+            {
+                if (*s == *ap)
+                {
+                    match = true;
+                    break;
+                }
+                ap++;
+            }
+            if (!match) return (usize)(s - str);
+            s++;
+        }
+        return (usize)(s - str);
+    }
+
+    char* strtok(char* str, const char* delim)
+    {
+        static char* s = nullptr;
+        if (str) s = str;
+        if (!s) return nullptr;
+
+        if (*s)
+        {
+            usize skip = strspn(s, delim);
+            s += skip;
+
+            if (*s == 0) return nullptr;
+
+            usize use = strcspn(s, delim);
+            char* result = s;
+
+            if (s[use] != 0)
+            {
+                s[use] = 0;
+                s += (use + 1);
+            }
+            else { s = nullptr; }
+
+            return result;
+        }
+
+        return nullptr;
+    }
 }