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Frank,<br><br>Exactly the answer I was looking for, I was hoping the MemFileHandler wasn't used directly by the VSISubFileHandler. You are constantly adding features right before I need them. Keep up the great work!<br><br>-- dan<br><br>> Date: Mon, 9 Feb 2009 15:21:04 -0500<br>> From: warmerdam@pobox.com<br>> To: grevedan@hotmail.com<br>> CC: gdal-dev@lists.osgeo.org<br>> Subject: Re: [gdal-dev] concerning VSIInstallSubFileHandler<br>> <br>> Dan Greve wrote:<br>> > Greetings,<br>> > <br>> > I am currently accessing datasets which are embedded inside a single <br>> > file. Each dataset is a given file offset and length inside of the <br>> > larger file. <br>> > <br>> > I saw in the latest doxy-docs here <br>> > <http://www.gdal.org/ogr/cpl__vsi_8h.html> that there is a <br>> > VSIInstallSubFileHandler for doing just that, and look forward to <br>> > testing it out. My concern with it, as well as the normal <br>> > VSIMemFileHandler, is in accessing large files. I have 2 GB images, <br>> > embedded within files that are up to 100 GB in size. Does the <br>> > VSIMemFileHandler do any sort of paging so that the entire source image <br>> > is not read into memory?<br>> <br>> Dan,<br>> <br>> The VSIMemFileHandler treats a memory buffer as a file. There is no support<br>> in it for paging from a file so it is only suitable when you are prepared<br>> to load the object into RAM.<br>> <br>> The VSISubFileHandler on the other hand just manages access to a file through<br>> regular file access handle, but keeping track of an offset to the sub file.<br>> So it does not use appreciably more memory than a normal file access.<br>> <br>> I believe the subfilehandler would be the suitable tool for you. I believe it<br>> is only available in GDAL trunk, not 1.6.x.<br>> <br>> Best regards,<br>> -- <br>> ---------------------------------------+--------------------------------------<br>> I set the clouds in motion - turn up | Frank Warmerdam, warmerdam@pobox.com<br>> light and sound - activate the windows | http://pobox.com/~warmerdam<br>> and watch the world go round - Rush | Geospatial Programmer for Rent<br>> <br><br /><hr />Windows Live™: E-mail. Chat. Share. Get more ways to connect. <a href='http://windowslive.com/howitworks?ocid=TXT_TAGLM_WL_t2_allup_howitworks_022009' target='_new'>See how it works.</a></body>
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