Revert "Merge pull request #460 from thesnowgoose/master"

This reverts commit f5ba7ae197, reversing
changes made to 0fe1bbcd91.

The change fails for /foo/../../bar paths, as it returns bar rather than null

jetty-util/src/main/java/org/eclipse/jetty/util/URIUtil.java

@@ -20,11 +20,6 @@ package org.eclipse.jetty.util;
 
 import java.nio.charset.Charset;
 import java.nio.charset.StandardCharsets;
-import java.util.Collections;
-import java.util.LinkedList;
-import java.util.List;
-import java.util.ListIterator;
-import java.util.regex.Pattern;
 
 import org.eclipse.jetty.util.Utf8Appendable.NotUtf8Exception;
 import org.eclipse.jetty.util.log.Log;
@@ -54,7 +49,6 @@ public class URIUtil
     public static final String HTTP_COLON="http:";
     public static final String HTTPS="https";
     public static final String HTTPS_COLON="https:";
-    private static final Pattern __PATH_SPLIT = Pattern.compile("(?<=\\/)");
 
     // Use UTF-8 as per http://www.w3.org/TR/html40/appendix/notes.html#non-ascii-chars
     public static final Charset __CHARSET=StandardCharsets.UTF_8 ;
@@ -509,40 +503,130 @@ public class URIUtil
      */
     public static String canonicalPath(String path)
     {
-        if (path == null || path.isEmpty() || !path.contains("."))
+        if (path==null || path.length()==0)
             return path;
 
-        if(path.startsWith("/.."))
+        int end=path.length();
-            return null;
+        int start = path.lastIndexOf('/', end);
 
-        List<String> directories = new LinkedList<>();
+    search:
-        Collections.addAll(directories, __PATH_SPLIT.split(path));
+        while (end>0)
-
-        for(ListIterator<String> iterator = directories.listIterator(); iterator.hasNext();)
         {
-            switch (iterator.next()) {
+            switch(end-start)
-                case "./":
+            {
-                case ".":
+              case 2: // possible single dot
-                    if (iterator.hasNext() && directories.get(iterator.nextIndex()).equals("/")) {
+                  if (path.charAt(start+1)!='.')
+                      break;
+                  break search;
+              case 3: // possible double dot
+                  if (path.charAt(start+1)!='.' || path.charAt(start+2)!='.')
+                      break;
+                  break search;
+            }
+            
+            end=start;
+            start=path.lastIndexOf('/',end-1);
+        }
+
+        // If we have checked the entire string
+        if (start>=end)
+            return path;
+        
+        StringBuilder buf = new StringBuilder(path);
+        int delStart=-1;
+        int delEnd=-1;
+        int skip=0;
+        
+        while (end>0)
+        {
+            switch(end-start)
+            {       
+              case 2: // possible single dot
+                  if (buf.charAt(start+1)!='.')
+                  {
+                      if (skip>0 && --skip==0)
+                      {   
+                          delStart=start>=0?start:0;
+                          if(delStart>0 && delEnd==buf.length() && buf.charAt(delEnd-1)=='.')
+                              delStart++;
+                      }
                       break;
                   }
-                    iterator.remove();
+                  
+                  if(start<0 && buf.length()>2 && buf.charAt(1)=='/' && buf.charAt(2)=='/')
                       break;
-                case "../":
+                  
-                case "..":
+                  if(delEnd<0)
-                    if(iterator.previousIndex() == 0) {
+                      delEnd=end;
-                        return null;
+                  delStart=start;
-                    }
+                  if (delStart<0 || delStart==0&&buf.charAt(delStart)=='/')
-                    iterator.remove();
+                  {
-                    iterator.previous();
+                      delStart++;
-                    iterator.remove();
+                      if (delEnd<buf.length() && buf.charAt(delEnd)=='/')
+                          delEnd++;
                       break;
                   }
+                  if (end==buf.length())
+                      delStart++;
+                  
+                  end=start--;
+                  while (start>=0 && buf.charAt(start)!='/')
+                      start--;
+                  continue;
+                  
+              case 3: // possible double dot
+                  if (buf.charAt(start+1)!='.' || buf.charAt(start+2)!='.')
+                  {
+                      if (skip>0 && --skip==0)
+                      {   delStart=start>=0?start:0;
+                          if(delStart>0 && delEnd==buf.length() && buf.charAt(delEnd-1)=='.')
+                              delStart++;
                       }
-        if (directories.isEmpty() && path.startsWith("/"))
+                      break;
+                  }
+                  
+                  delStart=start;
+                  if (delEnd<0)
+                      delEnd=end;
+
+                  skip++;
+                  end=start--;
+                  while (start>=0 && buf.charAt(start)!='/')
+                      start--;
+                  continue;
+
+              default:
+                  if (skip>0 && --skip==0)
+                  {
+                      delStart=start>=0?start:0;
+                      if(delEnd==buf.length() && buf.charAt(delEnd-1)=='.')
+                          delStart++;
+                  }
+            }     
+            
+            // Do the delete
+            if (skip<=0 && delStart>=0 && delEnd>=delStart)
+            {  
+                buf.delete(delStart,delEnd);
+                delStart=delEnd=-1;
+                if (skip>0)
+                    delEnd=end;
+            }
+            
+            end=start--;
+            while (start>=0 && buf.charAt(start)!='/')
+                start--;
+        }      
+
+        // Too many ..
+        if (skip>0)
             return null;
         
-        return String.join("", directories);
+        // Do the delete
+        if (delEnd>=0)
+            buf.delete(delStart,delEnd);
+
+        return buf.toString();
     }
 
     /* ------------------------------------------------------------ */