diff --git a/mozilla/string/obsolete/nsStr.cpp b/mozilla/string/obsolete/nsStr.cpp
index 50b0ca1e1ea..5974b5c5c83 100644
--- a/mozilla/string/obsolete/nsStr.cpp
+++ b/mozilla/string/obsolete/nsStr.cpp
@@ -438,23 +438,31 @@ void nsStr::CompressSet(nsStr& aDest,const char* aSet,PRUint32 aChar,PRBool aEli
 
 
 PRInt32 nsStr::FindSubstr(const nsStr& aDest,const nsStr& aTarget, PRBool aIgnoreCase,PRUint32 anOffset) {
-  PRUint32 index=anOffset-1;
-  PRUint32 theMax=aDest.mLength-aTarget.mLength;
   if((aDest.mLength>0) && (aTarget.mLength>0) && (anOffset<aTarget.mLength)){
-    PRUint32 theNewStartPos=-1;
-    PRUnichar theFirstTargetChar=GetCharAt(aTarget,0);
-    PRUnichar theLastTargetChar=GetCharAt(aTarget,aTarget.mLength-1);
-    PRUint32 theTargetMax=aTarget.mLength;
-    while(++index<=theMax) {
-      PRUint32 theSubIndex=-1;
-      PRBool  matches=PR_TRUE;
-      while((++theSubIndex<theTargetMax) && (matches)){
-        PRUnichar theChar=GetCharAt(aDest,index+theSubIndex);
-        PRUnichar theTargetChar=GetCharAt(aTarget,theSubIndex);
-        matches=PRBool(theChar==theTargetChar);
+
+      //This little block of code builds up the boyer-moore skip table.
+      //It might be nicer if this could be generated externally as passed in to improve performance.
+    const int theSize=256;
+    int theSkipTable[theSize];
+    PRUint32 theIndex=0;
+    for (theIndex=0;theIndex<theSize;++theIndex) {
+      theSkipTable[theIndex]=aTarget.mLength;
+    }
+    for (theIndex=0;theIndex<aTarget.mLength-1;++theIndex) {
+      theSkipTable[(PRUint32)GetCharAt(aTarget,theIndex)]=(aTarget.mLength-theIndex-1);
+    }
+
+      //and now we do the actual searching.      
+    PRUint32 theMaxIndex=aDest.mLength-anOffset;
+    for (theIndex=aTarget.mLength-1; theIndex< theMaxIndex; theIndex+= theSkipTable[(unsigned char)GetCharAt(aDest,theIndex)]) {
+      int theBufIndex=theIndex;
+      int thePatIndex=aTarget.mLength-1;
+      while((thePatIndex>=0) && (GetCharAt(aDest,theBufIndex)==GetCharAt(aTarget,thePatIndex))){
+        --theBufIndex;
+        --thePatIndex;
       }
-      if(matches) {
-        return index;
+      if(-1==thePatIndex){
+        return anOffset+theBufIndex+1;
       }
     }
   }//if
diff --git a/mozilla/xpcom/ds/nsStr.cpp b/mozilla/xpcom/ds/nsStr.cpp
index 50b0ca1e1ea..5974b5c5c83 100644
--- a/mozilla/xpcom/ds/nsStr.cpp
+++ b/mozilla/xpcom/ds/nsStr.cpp
@@ -438,23 +438,31 @@ void nsStr::CompressSet(nsStr& aDest,const char* aSet,PRUint32 aChar,PRBool aEli
 
 
 PRInt32 nsStr::FindSubstr(const nsStr& aDest,const nsStr& aTarget, PRBool aIgnoreCase,PRUint32 anOffset) {
-  PRUint32 index=anOffset-1;
-  PRUint32 theMax=aDest.mLength-aTarget.mLength;
   if((aDest.mLength>0) && (aTarget.mLength>0) && (anOffset<aTarget.mLength)){
-    PRUint32 theNewStartPos=-1;
-    PRUnichar theFirstTargetChar=GetCharAt(aTarget,0);
-    PRUnichar theLastTargetChar=GetCharAt(aTarget,aTarget.mLength-1);
-    PRUint32 theTargetMax=aTarget.mLength;
-    while(++index<=theMax) {
-      PRUint32 theSubIndex=-1;
-      PRBool  matches=PR_TRUE;
-      while((++theSubIndex<theTargetMax) && (matches)){
-        PRUnichar theChar=GetCharAt(aDest,index+theSubIndex);
-        PRUnichar theTargetChar=GetCharAt(aTarget,theSubIndex);
-        matches=PRBool(theChar==theTargetChar);
+
+      //This little block of code builds up the boyer-moore skip table.
+      //It might be nicer if this could be generated externally as passed in to improve performance.
+    const int theSize=256;
+    int theSkipTable[theSize];
+    PRUint32 theIndex=0;
+    for (theIndex=0;theIndex<theSize;++theIndex) {
+      theSkipTable[theIndex]=aTarget.mLength;
+    }
+    for (theIndex=0;theIndex<aTarget.mLength-1;++theIndex) {
+      theSkipTable[(PRUint32)GetCharAt(aTarget,theIndex)]=(aTarget.mLength-theIndex-1);
+    }
+
+      //and now we do the actual searching.      
+    PRUint32 theMaxIndex=aDest.mLength-anOffset;
+    for (theIndex=aTarget.mLength-1; theIndex< theMaxIndex; theIndex+= theSkipTable[(unsigned char)GetCharAt(aDest,theIndex)]) {
+      int theBufIndex=theIndex;
+      int thePatIndex=aTarget.mLength-1;
+      while((thePatIndex>=0) && (GetCharAt(aDest,theBufIndex)==GetCharAt(aTarget,thePatIndex))){
+        --theBufIndex;
+        --thePatIndex;
       }
-      if(matches) {
-        return index;
+      if(-1==thePatIndex){
+        return anOffset+theBufIndex+1;
       }
     }
   }//if
diff --git a/mozilla/xpcom/string/obsolete/nsStr.cpp b/mozilla/xpcom/string/obsolete/nsStr.cpp
index 50b0ca1e1ea..5974b5c5c83 100644
--- a/mozilla/xpcom/string/obsolete/nsStr.cpp
+++ b/mozilla/xpcom/string/obsolete/nsStr.cpp
@@ -438,23 +438,31 @@ void nsStr::CompressSet(nsStr& aDest,const char* aSet,PRUint32 aChar,PRBool aEli
 
 
 PRInt32 nsStr::FindSubstr(const nsStr& aDest,const nsStr& aTarget, PRBool aIgnoreCase,PRUint32 anOffset) {
-  PRUint32 index=anOffset-1;
-  PRUint32 theMax=aDest.mLength-aTarget.mLength;
   if((aDest.mLength>0) && (aTarget.mLength>0) && (anOffset<aTarget.mLength)){
-    PRUint32 theNewStartPos=-1;
-    PRUnichar theFirstTargetChar=GetCharAt(aTarget,0);
-    PRUnichar theLastTargetChar=GetCharAt(aTarget,aTarget.mLength-1);
-    PRUint32 theTargetMax=aTarget.mLength;
-    while(++index<=theMax) {
-      PRUint32 theSubIndex=-1;
-      PRBool  matches=PR_TRUE;
-      while((++theSubIndex<theTargetMax) && (matches)){
-        PRUnichar theChar=GetCharAt(aDest,index+theSubIndex);
-        PRUnichar theTargetChar=GetCharAt(aTarget,theSubIndex);
-        matches=PRBool(theChar==theTargetChar);
+
+      //This little block of code builds up the boyer-moore skip table.
+      //It might be nicer if this could be generated externally as passed in to improve performance.
+    const int theSize=256;
+    int theSkipTable[theSize];
+    PRUint32 theIndex=0;
+    for (theIndex=0;theIndex<theSize;++theIndex) {
+      theSkipTable[theIndex]=aTarget.mLength;
+    }
+    for (theIndex=0;theIndex<aTarget.mLength-1;++theIndex) {
+      theSkipTable[(PRUint32)GetCharAt(aTarget,theIndex)]=(aTarget.mLength-theIndex-1);
+    }
+
+      //and now we do the actual searching.      
+    PRUint32 theMaxIndex=aDest.mLength-anOffset;
+    for (theIndex=aTarget.mLength-1; theIndex< theMaxIndex; theIndex+= theSkipTable[(unsigned char)GetCharAt(aDest,theIndex)]) {
+      int theBufIndex=theIndex;
+      int thePatIndex=aTarget.mLength-1;
+      while((thePatIndex>=0) && (GetCharAt(aDest,theBufIndex)==GetCharAt(aTarget,thePatIndex))){
+        --theBufIndex;
+        --thePatIndex;
       }
-      if(matches) {
-        return index;
+      if(-1==thePatIndex){
+        return anOffset+theBufIndex+1;
       }
     }
   }//if