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+Frontend Interfaces
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+===================
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+
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+This file will try to document some of the interfaces that dpkg makes
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+available to frontends or that expects them to use, which are currently
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+not covered by any other type of documentation.
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+
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+
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+Database Locking
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+----------------
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+
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+Any frontend needing to make sure no write operation is currently happening,
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+should lock the dpkg database by locking the file «<admindir>/lock» using
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+file record locks (i.e. fcntl(2) advisory locking). The whole file should
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+be locked, as that's the most portable way to perform this operation; this
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+can be achieved by using start=0, len=0 and whence=SEEK_SET.
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+
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+Take into account there will be a race condition between the frontend
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+unlocking the database and the invoked dpkg locking it again, in which
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+another process could lock it.
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+
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+In the future this functionality will be available through a shared libdpkg
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+library, and all frontends will be expected to switch to that instead,
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+because this will fix the aforementioned race condition.
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Guillem Jover