Use overlapped interface with NamedPipe

[cjubb39]

This pull request has two primary changes:

1. Using GetOverlappedResult instead of lpNumberOfBytes{Read,Written} in ReadFile and WriteFile for read_overlapped and write_overlapped, respectively. According to https://docs.microsoft.com/en-us/windows/desktop/api/fileapi/nf-fileapi-readfile and https://docs.microsoft.com/en-us/windows/desktop/api/fileapi/nf-fileapi-writefile, if the file was opened with FILE_FLAG_OVERLAPPED,

The lpNumberOfBytesWritten parameter should be set to NULL. To get the number of bytes written, use the GetOverlappedResult function.

2. Noting that all NamedPipes are created with FILE_FLAG_OVERLAPPED, their read and write implementations should use the lpOverlapped parameter. Create a variant that will wait for the completion before returning to satisfy the simple read and write interface.

This seemed the simplest change that didn't break the interface defaults but am open to suggestions / alternate solutions that use the overlapped interface with handles opened using FILE_FLAG_OVERLAPPED.

[alexcrichton]

Thanks! The only suggestion I'd have is that for the blocking read/write impls could this perhaps use a thread local cached even to avoid recreating one on each call?

[cjubb39]

good suggestion -- I've made it use a threadlocal!

[alexcrichton]

Thanks!

[cjubb39]

Do you mind cutting a new release with this included when you get a chance? Not a huge rush for me :)

[alexcrichton]

Sure thing, done now!