1 files changed, 7 insertions, 5 deletions

diff --git a/src/utf.c b/src/utf.c
index 216864f5c..083ada788 100644
--- a/src/utf.c
+++ b/src/utf.c
@@ -514,20 +514,22 @@ char *sqlite3Utf16to8(sqlite3 *db, const void *z, int nByte, u8 enc){
 }
 
 /*
-** zIn is a UTF-16 encoded unicode string at least nChar characters long.
+** zIn is a UTF-16 encoded unicode string at least nByte bytes long.
 ** Return the number of bytes in the first nChar unicode characters
-** in pZ.  nChar must be non-negative.
+** in pZ.  nChar must be non-negative.  Surrogate pairs count as a single
+** character.
 */
-int sqlite3Utf16ByteLen(const void *zIn, int nChar){
+int sqlite3Utf16ByteLen(const void *zIn, int nByte, int nChar){
   int c;
   unsigned char const *z = zIn;
+  unsigned char const *zEnd = &z[nByte-1];
   int n = 0;
   
   if( SQLITE_UTF16NATIVE==SQLITE_UTF16LE ) z++;
-  while( n<nChar ){
+  while( n<nChar && ALWAYS(z<=zEnd) ){
     c = z[0];
     z += 2;
-    if( c>=0xd8 && c<0xdc && z[0]>=0xdc && z[0]<0xe0 ) z += 2;
+    if( c>=0xd8 && c<0xdc && z<=zEnd && z[0]>=0xdc && z[0]<0xe0 ) z += 2;
     n++;
   }
   return (int)(z-(unsigned char const *)zIn)