Add log2

Library/Convert.cpp

@@ -593,6 +593,43 @@ EXTERNC char *ultoa(unsigned long Value, char *Buffer, int Base)
     return reverse(Buffer, 0, i - 1);
 }
 
+EXTERNC int log2(unsigned int n)
+{
+    if (n == 0)
+    {
+        error("log2(0) is undefined.");
+        return -1;
+    }
+
+    int log = 0;
+    
+    if ((n & 0xFFFF0000) != 0)
+    {
+        n >>= 16;
+        log = 16;
+    }
+    
+    if (n >= 256)
+    {
+        n >>= 8;
+        log += 8;
+    }
+
+    if (n >= 16)
+    {
+        n >>= 4;
+        log += 4;
+    }
+
+    if (n >= 4)
+    {
+        n >>= 2;
+        log += 2;
+    }
+    
+    return log + (n >> 1);
+}
+
 EXTERNC void __chk_fail(void) __attribute__((__noreturn__));
 
 __noreturn __always_inline static inline void __convert_chk_fail(void)

include/convert.h

@@ -74,6 +74,7 @@ extern "C"
     int strcasecmp(const char *lhs, const char *rhs);
     char *strtok(char *src, const char *delim);
     long int strtol(const char *str, char **endptr, int base);
+    int log2(unsigned int n);
 
     void *__memcpy_chk(void *dest, const void *src, size_t len, size_t slen);
     void *__memset_chk(void *dest, int val, size_t len, size_t slen);