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18-Nov-2017 |
Michael Wachenschwanz <mwachens@google.com> |
Disallow reading object data from Parcels with non-object reads
The check added to each non-object reads adds an overhead. If the
objects (binders and file descriptors) were written to the Parcel in
sequential order then check adds a small O(1) overhead to each read,
plus an O(N) overhead to the first read (to verify the N objects were
added in order).
If the objects were written out of order (as in by jumping around the Parcel
with setDataPosition and writing Binder, DON'T DO THIS!!) (writing non
objects out of order is fine), the first read is forced to sort the objects
in the internal bookkeeping. Based on the assumption non sequential writes
are infrequent and overall Parcels are probably mostly sorted, insertion
sort was used. Worst case sorts will add an O(N^2) overhead to the first
non object read from the Parcel.
Test: run cts -m CtsOsTestCases -t android.os.cts.ParcelTest
Bug: 29833520
Change-Id: I82de8eb5f5eb56f869542d5358e96884c24301b2
/frameworks/native/libs/binder/include/binder/Parcel.h
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