Two small performance issue in COSString, these are not bugs

[Pe...@ibi.com]

There were 2 small issues here. Both performance related, but I assume
that this method createFromHexString is called a lot.

These are not bugs.

 

 

>From this article:
http://www.javaworld.com/javaworld/jw-04-1997/jw-04-optimize.html?page=5

 

Comparing against zero is almost always more efficient in any language
since the underlying tests are based on < 0,<= 0, == 0, != 0, >= 0 and >
0. 

 

 

 

package org.apache.pdfbox.cos;

 

// original code.

 

public static COSString createFromHexString( String hex ) throws
IOException

 

        COSString retval = new COSString();

        StringBuffer hexBuffer = new StringBuffer( hex.trim() );

        //if odd number then the last hex digit is assumed to be 0

        if( hexBuffer.length() % 2 == 1 )

        {

            hexBuffer.append( "0" );

        }

        for( int i=0; i<hexBuffer.length();)

        {

 

// Same code with 3 small changes applied.

// test for null optional, since it should never happen

// compare to zero instead of 1

// added loop invariant variable hexBufferLength

 

public static COSString createFromHexString( String hex ) throws
IOException

 

        COSString retval = new COSString();

         // should you add a test for null here?

         if (hex == null)  // this should never happen

   return null; 

            // or 

               return retval; // ??

 

        StringBuffer hexBuffer = new StringBuffer( hex.trim() );

 

 

 

// slightly changed code to improve effiency of the loop.

int hexBufferLength= hexBuffer.length();

 

 

if( hexBufferLength % 2 != 0 )  // add comparison against zero values of
mod 2 can only be 0 or 1

        {

            hexBuffer.append( "0" );

        }

 

// hexBuffer.length() is a loop invariant, and will not change within
the loop,

// calling the method on each iteration is not efficient.

// better to create a local variable and reference it at the top of the
loop.

for( int i=0; i<hexBufferLength;)

{