[PATCH] D66471: [Support] Improve readNativeFile(Slice) interface

[Alexandre Ganea via Phabricator via llvm-commits]

aganea added inline comments.


================
Comment at: lib/Support/MemoryBuffer.cpp:467
+    Expected<size_t> ReadBytes =
+        sys::fs::readNativeFileSlice(FD, Buf->getBuffer(), Offset);
+    if (!ReadBytes)
----------------
labath wrote:
> aganea wrote:
> > Shouldn't we use `ToRead` here instead of `Buf->getBuffer()`? Could you please test two sequential reads in the unittests?
> Woops, indeed it should. Thanks for catching that!
> 
> As for the test, I am not sure how I could force the read syscall to return partial data here. For the non-slice version, I suppose I could make this read from a pipe, and then make sure I write to the pipe very slowly. However, the slice version requires a seekable fd, and I don't know what to do there... Do you have any suggestion?
You can probably call `MemoryBuffer::getOpenFile` with a smaller `FileSize` & `MapSize` and `IsVolatile = true`? And then a subsequent call by setting `Offset` > 0? Would that work?


Repository:
  rL LLVM

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https://reviews.llvm.org/D66471