Summary:
The loop took care to advance `b` to match the amount
of data that it had processed, but was still passing `buf`
(the unadjusted start of the buffer) to the syscalls.
This meant that in situations where a `readFull` might
encounter a partial read, it would scribble over the start
of the buffer and leave junk at the end.
For example:
write("hell");
write("o");
could produce "oell?" in the buffer when `readFull` consumes
the other end of the pipe.
Reviewed By: xavierd
Differential Revision: D23486270
fbshipit-source-id: 0848f6789b44421b609b91fe08890768ff59f7f5
Summary:
This commit introduces a few types from the watchman codebase:
`FileDescriptor` which is on posix systems represents a file descriptor,
and on Windows is a HANDLE (which can be a file, pipe or socket descriptor).
`Pipe` is a convenience struct that holds the read and write ends of a Pipe.
Note that we have a conceptual class with a windows specific Pipe type under
eden/fs/win/utils/Pipe.h; I remove that in the next diff in the stack.
There are a couple of differences from the watchman code
Reviewed By: chadaustin
Differential Revision: D23287819
fbshipit-source-id: 6ca90ba345037c6c3e308f588d690a899c9866a5
