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When a file is downloaded, specifying the file location is optional. If it isn't specified the file is placed in a default 'cache folder'. The organization of the file cache is:
<cache root>/ <folder> <intermediate folder> / <file handle id>/<file name>
where <folder> where <intermediate folder> 's name is <file handle id> mod 1000. (This extra level is to reduce fan-out when the number of downloaded files is much greater than 1000.)
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There is a file for each Synapse FileHandle ID that has been downloaded or uploaded. The file has the path:
<cache root> / <folder> <intermediate folder> / <file handle id> / .cacheMap
where <folder> where <intermediate folder> 's name is <file handle id> mod 1000
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