69 lines
3.4 KiB
Plaintext
69 lines
3.4 KiB
Plaintext
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This DLL is an example of how to write a component which obtains ratings for
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URLs from some external source. The sample is quite primitive and merely
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reads the ratings from a file, RATINGS.INI. Obviously a real product would
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have more work to do.
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To use this component, copy SAMPLE.DLL into the system directory (usually
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C:\WINDOWS\SYSTEM). Then run "regsvr32 sample.dll" from there; this will
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install the appropriate registry keys. Finally, create RATINGS.INI in the
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Windows directory, with contents something like this:
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[Ratings]
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http://www.microsoft.com=l 0 n 0 s 0 v 0
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http://www.playboy.com=l 4 n 4 s 3 v 0
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[Allow]
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http://www.playboy.com/allowme.htm=1
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[Deny]
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http://www.disney.com/denyanyway.htm=1
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Then, when you browse to any sites listed in RATINGS.INI, the ratings provided
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there will override any ratings found at the site itself. The [Allow] and
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[Deny] sections list URLs which should have access explicitly allowed or
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denied, no matter what the user's rating restrictions are. This simulates
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an inclusion/exclusion list.
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To modify this DLL for your own purposes:
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The source is packaged as a Microsoft Developer Studio project.
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Change the name of the component to something other than SAMPLE.DLL (this
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should be done in the build environment, in the resource file version stamps,
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in the .DEF file, and the string szDLLNAME in comobj.cpp).
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Run the GUIDGEN utility (supplied with Microsoft Developer Studio, or the
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Win32 SDK) to generate a CLSID for your component. Replace the definitions
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of CLSID_Sample and szOurGUID with this GUID. Do not omit this step and just
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use the GUID provided, otherwise your component may collide with that of
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another ISV if they also omit this step.
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Modify the code in getlabel.cpp, CSampleObtainRating::ObtainRating to retrieve
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the rating for a URL from the source of your choosing. Memory for the rating
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label should be allocated using the IMalloc interface provided.
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If WaitForSingleObject(hAbortEvent, 0) returns WAIT_OBJECT_0, then the user
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has cancelled the download and any attempt to obtain a rating should also be
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cancelled. If obtaining the rating is a relatively quick operation (such as
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reading from a local file) and is not easily divided into substeps for polling
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the event, then this event can be ignored.
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Also modify CSampleObtainRating::GetSortOrder to determine the priority of
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your rating obtainer's ratings relative to other installable rating obtainers.
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Rating obtainers with lower sort orders are called before those with higher
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sort orders. Thus, if Microsoft's label bureau obtainer (whose sort order
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is 0x80000000) is called and obtains a rating for a site, then any obtainer
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with a higher sort order will not even be called for that site. If the bureau
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was unable to obtain a rating, then further obtainers would be called until
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a rating was found.
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Microsoft's label bureau obtainer's sort order is 0x80000000. If Microsoft
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produces an obtainer which fetches from a local exclusion list, its sort order
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will be 0xC0000000. Note that a rating obtained from an installable DLL will
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always override any rating found in the HTML document itself.
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Install your DLL in the Windows system directory. Run "regsvr32 <yourdll>.DLL"
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or load it and call its DllRegisterServer entrypoint to install its registry
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keys. Currently the user must log off and back on (or restart the system) for
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the installation of this component to take effect.
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