Fix utf8.h

SourceX/utf8.h

@@ -24,8 +24,8 @@
  * occurs, this pointer will be a guess that depends on the particular
  * error, but it will always advance at least one byte.
  */
-inline void *
-utf8_decode(void *buf, uint32_t *c, int *e)
+inline const unsigned char *
+utf8_decode(const unsigned char *buf, uint32_t *c, int *e)
 {
     static const char lengths[] = {
         1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
@@ -36,14 +36,14 @@ utf8_decode(void *buf, uint32_t *c, int *e)
     static const int shiftc[] = {0, 18, 12, 6, 0};
     static const int shifte[] = {0, 6, 4, 2, 0};
 
-    unsigned char *s = static_cast<unsigned char*>(buf);
+    const unsigned char *s = buf;
     int len = lengths[s[0] >> 3];
 
     /* Compute the pointer to the next character early so that the next
      * iteration can start working on the next character. Neither Clang
      * nor GCC figure out this reordering on their own.
      */
-    unsigned char *next = s + len + !len;
+    const unsigned char *next = s + len + !len;
 
     /* Assume a four-byte character and load four bytes. Unused bits are
      * shifted out.
@@ -71,7 +71,7 @@ inline std::string utf8_to_latin1(const char* in)
 {
 	std::string instr(in);
 	instr.resize(instr.size() + 4);
-	const char* buf = instr.data();
+	const unsigned char* buf = reinterpret_cast<const unsigned char*>(instr.data());
 	std::string ret;
 	uint32_t next;
 	int error;