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iFilter4Archives

Description

This library uses 7-Zip to provide an iFilter for various archive formats, including (but not limited to) .7z, .rar, .tar and .gz files, allowing Windows Search and other programs (e.g. SQL Server) to find compressed files and archives based on their content.

Build

The build system uses cmake and requires at least version 3.15. It creates iFilter4Archives.dll in ./out/build/[platform]-[configuration]/, which is statically linked to the MSVC runtime.

To build the Windows Installer package, which bundles 7-Zip together with the iFilter, the Windows Installer Toolset version 3.10 or later is required. Also, the contents of 7-Zip's .exe installer must be extracted to either ./installer/src/x86/ or ./installer/src/x64/, depending on the targeted architecture.

The installer is not MUI. Each ./installer/7-Zip.[culture].wxl file results in a ./out/build/[platform]-[configuration]/installer/[culture]/7-Zip.msi.

Installation

Either build the Windows Installer package and install it or copy the 7z.dll library from a 7-Zip installation or 7-Zip's .exe installer together with iFilter4Archives.dll into a directory of your choice and run

regsvr32 iFilter4Archives.dll

in that directory.

Settings

Under HKEY_LOCAL_MACHINE\SOFTWARE\iFilter4Archives a couple of tweaks can be set using the following DWORD values:

  • ConcurrentFilterThreads: Sets the amount of threads the library uses per input file, i.e. the number of contained files it scans simultaneously. Defaults to the number of available hardware threads.
  • MaximumFileSize: Specified the maximum size up to which a contained file will be scanned, in megabytes. This should be equal to the Windows Search setting MaxDownloadSize. Defaults to 16 megabytes.
  • MaximumBufferSize: Specified the maximum size up to which a contained file will be placed in memory, in bytes. Files above that size will be temporarily extracted to disk instead. This value, multiplied by ConcurrentFilterThreads, should not exceed the Windows Search setting FilterProcessMemoryQuota. Default to 4194304 bytes.
  • RecursionDepthLimit: Limits the amount of archive file recursions, after which no additionally contained archive file will be scanned. Defaults to 1.

The iFilter that used to scan a contained file depends on the following settings and in that order:

  • IgnoreRegisteredPersistentHandlerIfArchive: If set to 1, 7-Zip will be used to scan the contained file if it's a known compressed or archive type, ignoring any other iFilter that might be registered with that type. Defaults to 0.
  • IgnoreNullPersistentHandler: If set to 1, which is the default, the Windows "Dummy iFilter", which only collects file properties, will not be invoked even if a type is associated with that handler. These properties are of no use since they only apply for a single file, e.g. the last time a file was modified.
  • UseInternalPersistentHandlerIfNoneRegistered: If set to 1, which is the default, 7-Zip will be used if no iFilter is associated with a contained file and it's a known compressed or archive type.