Safe fs.ReadStream and fs.WriteStream using the same fd.
Let's say that you want to perform a parallel upload of a file to a remote
server. To do this, we want to create multiple read streams. The first
thing you might think of is to use the {start: 0, end: 0} API of
fs.createReadStream. This gives you two choices:
1. Use the same file descriptor for all fs.ReadStream objects.
2. Open the file multiple times, resulting in a separate file descriptor
for each read stream.
Neither of these are acceptable options. The first one is a severe bug,
because the API docs for fs.write state:
Note that it is unsafe to use fs.write multiple times on the same file
> without waiting for the callback. For this scenario, fs.createWriteStream
> is strongly recommended.
fs.createWriteStream will solve the problem if you only create one of them
for the file descriptor, but it will exhibit this unsafety if you create
multiple write streams per file descriptor.
The second option suffers from a race condition. For each additional time
the file is opened after the first, it is possible that the file is
modified. So in our parallel uploading example, we might upload a corrupt
file that never existed on the client's computer. We want multiple streams
to use the same file descriptor.
This module solves this problem by providing createReadStream and
createWriteStream that operate on a shared file descriptor and provides the
convenient stream API while still allowing slicing and dicing.
https://npmjs.org/package/fd-slicer
https://github.com/andrewrk/node-fd-slicer
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