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FirefoxOS/Device Storage/Worker Design: Difference between revisions
FirefoxOS/Device Storage/Worker Design (view source)
Revision as of 00:39, 10 June 2015
, 10 June 2015→MIME service: note nsDOMDeviceStorage::Add and MIME service dependency
(add notes on mime service) |
(→MIME service: note nsDOMDeviceStorage::Add and MIME service dependency) |
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== MIME service == | == MIME service == | ||
The MIME type of a file is queried for each file when an enumeration operation is requested. The MIME service can only be accessed on the main thread; this is problematic given that this would presently require a context switch to and from each time the user calls continue on our enumeration cursor. nsExternalHelperAppService::GetTypeFromFile extracts the file extension and check then checks that against the numerous sources of MIME information (consistent with the IDL description). We should switch to extracting the file extension ourselves, use nsExternalHelperAppService:::GetTypeFromExtension to get the MIME type on the main thread for unknown extensions as is done today, and cache the result for the duration of the enumeration cursor. This balances worker performance (i.e. very | The MIME type of a file is queried for each file when an enumeration operation is requested. The MIME service can only be accessed on the main thread; this is problematic given that this would presently require a context switch to and from each time the user calls continue on our enumeration cursor. nsExternalHelperAppService::GetTypeFromFile extracts the file extension and check then checks that against the numerous sources of MIME information (consistent with the IDL description). We should switch to extracting the file extension ourselves, use nsExternalHelperAppService:::GetTypeFromExtension to get the MIME type on the main thread for unknown extensions as is done today, and cache the result for the duration of the enumeration cursor. This balances worker performance (i.e. very likely that the number of files greatly exceeds the number of unique extensions) with accuracy (i.e. by caching only for a particular cursor request, we allow the underlying service to discover new MIME types by addition of plugins, etc if the enumeration is reattempted). | ||
It is also queried when a file is added (prior to issuing the request) via nsDOMDeviceStorage::Add in order to determine the correct file extension. This should be moved into the create request itself, after the permission check, and before the file creation itself or sending the request to the parent process (if a child process). The file path should verified again at this point to ensure its safety. | |||
''* Note that nsDOMDeviceStorage::Add indicates the file will be rejected by nsDOMDeviceStorage::Add(OrAppend)Named if the given extension is empty. The check is actually performed just before creating the WriteFileEvent object in DeviceStorageRequest::Allow.'' | |||
== Device storage IPC API with child-parent processes == | == Device storage IPC API with child-parent processes == | ||