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Date: Mon, 15 Oct 2012 20:33:03 +0000 (UTC)
From: "Amit Gupta (JIRA)" <jira@apache.org>
To: issues@commons.apache.org
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Subject: [jira] [Updated] (IMAGING-95) Some tiff processing takes very long
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     [ https://issues.apache.org/jira/browse/IMAGING-95?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Amit Gupta updated IMAGING-95:
------------------------------

    Attachment: tiff_perf_fix.patch

patch for skipping array copy for skip operation
                
> Some tiff processing takes very long
> ------------------------------------
>
>                 Key: IMAGING-95
>                 URL: https://issues.apache.org/jira/browse/IMAGING-95
>             Project: Commons Imaging
>          Issue Type: Bug
>          Components: Format: TIFF
>    Affects Versions: 1.0
>            Reporter: Amit Gupta
>         Attachments: tiff_perf_fix.patch
>
>
> org.apache.commons.imaging.formats.tiff.TiffReader.getTiffRawImageData(ByteSource, TiffDirectory)	226635	1
> org.apache.commons.imaging.common.bytesource.ByteSourceInputStream.getBlock(int, int)	226588	5616
> org.apache.commons.imaging.common.BinaryFileFunctions.skipBytes(InputStream, int)	226526	5616
> org.apache.commons.imaging.common.BinaryFileFunctions.skipBytes(InputStream, int, String)	226526	5616
> org.apache.commons.imaging.common.bytesource.ByteSourceInputStream$CacheReadingInputStream.read(byte[], int, int)	226526	188656860
> org.apache.commons.imaging.common.bytesource.ByteSourceInputStream$CacheBlock.getNext()	64581	188651244
> skip bytes is being called repeatedly again and again, last column is invocation count in one call tree. Second column is total number of time taken by that method in that call tree..
> and skip method is not overridden org.apache.commons.imaging.common.bytesource.ByteSourceInputStream.CacheReadingInputStream and default implementation of InputStream tries to use read method (which is overridden in CacheReadingInputStream) to skip. 
> In case of a tiff, which has large number of strips, skip is repeatedly called in use of read is inefficient as it tried to do a System.arraycopy. array copy is not needed in case of skip operation, as the bytes were already read in block/cached, we can simply jump the pointer (block by block)

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