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47 строки
2.5 KiB
ReStructuredText
47 строки
2.5 KiB
ReStructuredText
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.. _uri_loader_service:
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URI Loader Service
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==================
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As its name might suggest the URI loader service is responsible for loading URIs
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but it is also responsible for deciding how to handle that content, whether to
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display it as part of a DOM window or hand it off to something else.
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It is generally used when loading content for display to the user, normally from
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``nsDocShell`` for display as a webpage or ``nsObjectLoadingContent`` for display inside
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a webpage's ``<object>`` tag. The normal entrypoint is throught ``nsIURILoader::OpenURI``.
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The URI loader starts the load and registers an ``nsDocumentOpenInfo`` as a stream
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listener for the content. Once headers have been received `DispatchContent <https://searchfox.org/mozilla-central/search?q=nsDocumentOpenInfo%3A%3ADispatchContent&path=>`_
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then decides what to do with the content as it may need to be handled by something
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other than the caller. It uses a few criteria to decide this including:
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* Content-Type header.
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* Content-Disposition header.
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* Load flags.
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Part of this handling may include running the content through a registered stream
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converter to convert the content type from one to another. This is done through
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the `stream converter service <https://searchfox.org/mozilla-central/source/netwerk/streamconv>`_.
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When this happens a new ``nsDocumentOpenInfo`` is created to handle the new content
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in the same way as the current content.
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The rough flow goes as follows (though note that this can vary depending on the
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flags passed to the loader service):
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1. The caller may provide an ``nsIURIContentListener`` which can offer to handle
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the content type or a content type that we can convert the original type to).
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If so the load is passed off to the listener.
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2. Global instances of ``nsIURIContentListener`` can be registered with the URI
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loader service so these are consulted in the same way.
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3. Global instances of ``nsIURIContentListener`` can be registered in the category
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manager so these are consulted in the same way.
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4. Global instances of ``nsIContentHandler`` can be registered. If one agrees to
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handle the content then the load is handed over to it.
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5. We attempt to convert the content to a different type.
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6. The load is handed over to the :ref:`External Helper App Service <external_helper_app_service>`.
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For the most part the process ends at step 1 because nsDocShell passes a ``nsDSURIContentListener``
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for the ``nsIURIContentListener`` consulted first and it accepts most of the
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`web content types <https://searchfox.org/mozilla-central/search?q=CONTENTDLF_CATEGORIES&redirect=false>`_.
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