fixed memory corruption in the stuff I added to moreUTF8. This fixes GetEscapement crashes. The rest of the file needs reviewing as well, but I wanted to commit this ASAP

git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@13155 a95241bf-73f2-0310-859d-f6bbb57e9c96

headers/private/interface/moreUTF8.h

@@ -1,22 +1,20 @@
 #ifndef __MOREUTF8
 #define __MOREUTF8
 
+#include <stdio.h>
 
 static inline bool
 IsInsideGlyph(uchar ch)
 {
 	return (ch & 0xC0) == 0x80;
+//	return (ch & 0x80);
 }
 
-
 static inline uint32
-UTF8NextCharLen(const char *text)
+UTF8NextCharLenUnsafe(const char *text)
 {
 	const char *ptr = text;
-	
-	if (ptr == NULL || *ptr == 0)
-		return 0;
-	
+
 	do {
 		ptr++;
 	} while (IsInsideGlyph(*ptr));
@@ -24,6 +22,15 @@ UTF8NextCharLen(const char *text)
 	return ptr - text;
 }
 
+static inline uint32
+UTF8NextCharLen(const char *text)
+{
+	if (text == NULL || *text == 0)
+		return 0;
+
+	return UTF8NextCharLenUnsafe(text);
+}
+
 static inline uint32
 UTF8PreviousCharLen(const char *text, const char *limit)
 {
@@ -41,17 +48,39 @@ UTF8PreviousCharLen(const char *text, const char *limit)
 	return text - ptr;
 }
 
+// TODO: use this function in other places of this file...
+static inline uint32
+count_utf8_bytes(uchar ch)
+{
+	// the number of high bits set until the first
+	// unset bit determine the count of bytes used for
+	// this glyph from this byte on
+	uchar bit = 1 << 7;
+	uint32 count = 1;
+	if (ch & bit) {
+		bit = bit >> 1;
+		while (ch & bit) {
+			count++;
+			bit = bit >> 1;
+		}
+	}
+	return count;
+}
+
 static inline uint32
 UTF8CountBytes(const char *text, uint32 numChars)
 {
-	const char *ptr = text;
-
-	while (numChars) {
-		ptr += UTF8NextCharLen(ptr);
-		numChars--;
+	if (text) {
+		// iterate over numChars glyphs incrementing ptr by the
+		// number of bytes for each glyph, which is encoded in
+		// the first byte of any glyph.
+		const char *ptr = text;
+		while (numChars--) {
+			ptr += count_utf8_bytes(*ptr);
+		}
+		return ptr - text;
 	}
-
-	return ptr - text;
+	return 0;
 }
 
 static inline uint32