Two small performance issue in COSString, these are not bugs
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Key: PDFBOX-410
URL: https://issues.apache.org/jira/browse/PDFBOX-410
Project: PDFBox
Issue Type: Improvement
Affects Versions: 0.8.0-incubator
Environment: All
Reporter: [email protected]
Priority: Trivial
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;)
{
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