bug #8702; r=ftang, cata; fixed performance problems in UTF8 Unicode decoder

intl/uconv/ucvlatin/nsUTF8ToUnicode.cpp

@@ -22,29 +22,18 @@
 
 #include "nsUTF8ToUnicode.h"
 
-//----------------------------------------------------------------------
-// Global functions and data [declaration]
-
-static PRUint16 g_UTF8MappingTable[] = {
-  0x0001, 0x0004, 0x0005, 0x0008, 0x0000, 0x0000, 0xFFFF, 0x0000
-};
-
-static PRInt16 g_UTF8ShiftTable[] =  {
-  3, uMultibytesCharset, 
-  ShiftCell(u1ByteChar,       1, 0x00, 0x7F, 0x00, 0x00, 0x00, 0x7F), 
-  ShiftCell(u2BytesUTF8,      2, 0xC0, 0xDF, 0x00, 0x00, 0x07, 0xFF), 
-  ShiftCell(u3BytesUTF8,      3, 0xE0, 0xEF, 0x08, 0x00, 0xFF, 0xFF) 
-};
 
 //----------------------------------------------------------------------
 // Class nsUTF8ToUnicode [implementation]
 
 nsUTF8ToUnicode::nsUTF8ToUnicode() 
-: nsTableDecoderSupport((uShiftTable*) &g_UTF8ShiftTable, 
-                        (uMappingTable*) &g_UTF8MappingTable)
+: nsBasicDecoderSupport()
+
 {
+	Reset();
 }
 
+
 nsresult nsUTF8ToUnicode::CreateInstance(nsISupports ** aResult) 
 {
   *aResult = new nsUTF8ToUnicode();
@@ -61,3 +50,132 @@ NS_IMETHODIMP nsUTF8ToUnicode::GetMaxLength(const char * aSrc,
   *aDestLength = aSrcLength;
   return NS_OK;
 }
+
+
+//----------------------------------------------------------------------
+// Subclassing of nsBasicDecoderSupport class [implementation]
+
+ NS_IMETHODIMP nsUTF8ToUnicode::Reset()
+{
+
+	mState = 0;			// cached expected number of bytes per UTF8 character sequence
+	mUcs4  = 0;			// cached Unicode character
+	return NS_OK;
+
+}
+
+//----------------------------------------------------------------------
+// Subclassing of nsBasicDecoderSupport class [implementation]
+
+ 
+ NS_IMETHODIMP nsUTF8ToUnicode::Convert(const char * aSrc, 
+                                                    PRInt32 * aSrcLength, 
+                                                    PRUnichar * aDest, 
+                                                    PRInt32 * aDestLength)
+ {
+   
+   PRUint32 aSrcLen   = (PRUint32) (*aSrcLength);
+   PRUint32 aDestLen = (PRUint32) (*aDestLength);
+   
+   const char *in, *inend;
+   inend = aSrc + aSrcLen;
+   
+   PRUnichar *out, *outend;
+   outend = aDest + aDestLen;
+
+   nsresult res;	// conversion result
+
+   for(in=aSrc,out=aDest,res=nsnull;((in < inend) && (out < outend)); in++)
+   {
+      if(0 == mState) {
+         if( 0 == (0x80 & (*in))) {
+             // ASCII
+             *out++ = (PRUnichar)*in;
+         } else if( 0xC0 == (0xE0 & (*in))) {
+             // 2 bytes UTF8
+             mUcs4 = (PRUint32)(*in);
+             mUcs4 = (mUcs4 << 6) & 0x000007C0L;
+             mState=1;
+         } else if( 0xE0 == (0xF0 & (*in))) {
+			 // 3 bytes UTF8
+             mUcs4 = (PRUint32)(*in);
+             mUcs4 = (mUcs4 << 12) & 0x0000F000L;
+             mState=2;
+         } else if( 0xF0 == (0xF8 & (*in))) {
+			 // 4 bytes UTF8
+             mUcs4 = (PRUint32)(*in);
+             mUcs4 = (mUcs4 << 18) & 0x001F0000L;
+             mState=3;
+         } else if( 0xF8 == (0xFC & (*in))) {
+			 // 5 bytes UTF8
+             mUcs4 = (PRUint32)(*in);
+             mUcs4 = (mUcs4 << 24) & 0x03000000L;
+             mState=4;
+         } else if( 0xFC == (0xFE & (*in))) {
+			 // 6 bytes UTF8
+             mUcs4 = (PRUint32)(*in);
+             mUcs4 = (mUcs4 << 30) & 0x40000000L;
+             mState=5;
+         } else {
+			 
+			 //NS_ASSERTION(0, "The input string is not in utf8");
+
+	  		 //unexpected octet, put in a replacement char, 
+			 //flush and refill the buffer, reset state
+			 res = NS_ERROR_UNEXPECTED;
+			 break;
+
+         }
+
+	 } else {
+
+		 if(0x80 == (0xC0 & (*in)))
+         {
+             PRUint32 tmp = (*in);
+             int shift = (mState-1) * 6;
+             tmp = (tmp << shift ) & ( 0x0000003FL << shift);
+             mUcs4 |= tmp;
+			 if(0 == --mState)
+             {
+                 if(mUcs4 >= 0x00010000) {
+                    if(mUcs4 >= 0x001F0000) {
+                      *out++ = 0xFFFD;
+                    } else {
+                      mUcs4 -= 0x00010000;
+                      *out++ = 0xD800 | (0x000003FF & (mUcs4 >> 10));
+                      *out++ = 0xDC00 | (0x000003FF & mUcs4);
+                    }
+                 } else {
+                    *out++ = mUcs4;
+                 }
+                 
+				 //initialize UTF8 cache
+				 Reset();
+             }
+
+         } else {
+
+			 //NS_ASSERTION(0, "The input string is not in utf8");
+	
+	  		 //unexpected octet, put in a replacement char, 
+			 //flush and refill the buffer, reset state
+			 res = NS_ERROR_UNEXPECTED;
+			 break;
+
+         }
+     }
+   }
+
+   //output not finished, output buffer too short
+   if ((in < inend) && (out >= outend)) res = NS_OK_UDEC_MOREOUTPUT;
+
+   //last USC4 is incomplete, make sure the caller 
+   //returns with properly aligned continuation of the buffer
+   if (mState != 0) res = NS_OK_UDEC_MOREINPUT;
+
+   *aSrcLength = in - aSrc;
+   *aDestLength  = out - aDest;
+   
+   return(res);
+
+ }

intl/uconv/ucvlatin/nsUTF8ToUnicode.h

@@ -28,13 +28,16 @@
 //----------------------------------------------------------------------
 // Class nsUTF8ToUnicode [declaration]
 
+
 /**
  * A character set converter from UTF8 to Unicode.
  *
  * @created         18/Mar/1998
+ * @modified        04/Feb/2000
  * @author  Catalin Rotaru [CATA]
  */
-class nsUTF8ToUnicode : public nsTableDecoderSupport
+
+class nsUTF8ToUnicode : public nsBasicDecoderSupport
 {
 public:
 
@@ -43,6 +46,7 @@ public:
    */
   nsUTF8ToUnicode();
 
+
   /**
    * Static class constructor.
    */
@@ -50,11 +54,26 @@ public:
 
 protected:
 
+   PRUint32 mState;	// cached expected number of bytes per UTF8 character sequence
+   PRUint32 mUcs4;	// cached Unicode character
+
   //--------------------------------------------------------------------
   // Subclassing of nsDecoderSupport class [declaration]
 
   NS_IMETHOD GetMaxLength(const char * aSrc, PRInt32 aSrcLength, 
       PRInt32 * aDestLength);
+
+  //--------------------------------------------------------------------
+  // Subclassing of nsBasicDecoderSupport class [declaration]
+
+  NS_IMETHOD Convert(const char * aSrc, PRInt32 * aSrcLength, 
+      PRUnichar * aDest, PRInt32 * aDestLength);
+
+  //--------------------------------------------------------------------
+  // Subclassing of nsBasicDecoderSupport class [declaration]
+
+  NS_IMETHOD Reset();
+
 };
 
 #endif /* nsUTF8ToUnicode_h___ */