fixed #2: Procedures for reading an utf8 string incorrectly read some utf-8 characters.

Those characters were treated as invalid characters.

UTF8ToInt_FirstOctet incorrectly checked if the first octed is zero (after removing first bits).
This is a case only if the utf-8 character consists of two bytes. For 3 or 4 bytes
the first part can have all bits equal zero.

utf8/utf8.cpp

@@ -56,6 +56,42 @@ bool UTF8_CheckRange(int c)
 }
 
 
+/*!
+	returns true if 'c' is a correct unicode character
+
+	this method is used when reading from an utf8 string
+	how_many_bytes - means how many bytes from the utf8 string were read
+*/
+bool UTF8_CheckRange(int c, int how_many_bytes)
+{
+	if( c >= 0x0000 && c <= 0x007f && how_many_bytes == 1 )
+	{
+		return true;
+	}
+
+	if( c >= 0x0080 && c <= 0x07ff && how_many_bytes == 2 )
+	{
+		return true;
+	}
+
+	if( c >= 0x0800 && c < 0xD800 && how_many_bytes == 3)
+	{
+		return true;
+	}
+
+	if( c > 0xDFFF && c <= 0xffff && how_many_bytes == 3)
+	{
+		return true;
+	}
+
+	if( c >= 0x10000 && c <= 0x10FFFF && how_many_bytes == 4 )
+	{
+		return true;
+	}
+
+return false;
+}
+
 
 
 /*!
@@ -97,7 +133,7 @@ size_t i, len;
 			return i;
 	}
 
-	if( UTF8_CheckRange(res) )
+	if( UTF8_CheckRange(res, len) )
 		correct = true;
 
 return len;
@@ -141,7 +177,7 @@ size_t i, len;
 			return i;
 	}
 
-	if( UTF8_CheckRange(res) )
+	if( UTF8_CheckRange(res, len) )
 		correct = true;
 
 return len;
@@ -210,7 +246,7 @@ unsigned char uz;
 			return i;
 	}
 
-	if( UTF8_CheckRange(res) )
+	if( UTF8_CheckRange(res, len) )
 		correct = true;
 
 return len;

utf8/utf8.h

@@ -64,6 +64,14 @@ namespace PT
 bool UTF8_CheckRange(int c);
 
 
+/*!
+	returns true if 'c' is a correct unicode character
+
+	this method is used when reading from an utf8 string
+	how_many_chars - means how many characters from utf8 string were read
+*/
+bool UTF8_CheckRange(int c, int how_many_bytes);
+
 
 /*
  *

utf8/utf8_private.cpp

@@ -52,7 +52,7 @@ bool UTF8ToInt_FirstOctet(unsigned char uz, size_t & len, int & res)
 	for(len=0 ; (uz & 0x80) != 0 ; ++len)
 		uz <<= 1;
 
-	if( len == 1 )
+	if( len == 1 || len > 4 )
 		return false;
 
 	res = uz;
@@ -60,9 +60,6 @@ bool UTF8ToInt_FirstOctet(unsigned char uz, size_t & len, int & res)
 	if( len > 0 )
 		res >>= len;
 
-	if( res == 0 )
-		return false;
-
 	if( len == 0 )
 		len = 1;