Writer adaptors should have a public method flush_outer()

Issue by kballard
Wednesday Apr 30, 2014 at 03:50 GMT

For earlier discussion, see https://github.com/rust-lang/rust/issues/13858

This issue was labelled with: in the Rust repository

All the Writer adaptors that libstd provides that have some sort of internal buffer should expose a method named .flush_outer() that flushes this internal buffer. Basically, whatever it does in .flush() besides flushing the inner writer. For example, in BufferedWriter it would be the flush_buf() method.

This would be useful when the client needs to handle errors from this shallow flush but doesn't want to flush the full writer stack. For example, before calling BufferedWriter.unwrap(), the client could use .flush_buf() to get the error, as BufferedWriter.unwrap() will fail otherwise.

Similarly, LineBufferedWriter could call self.inner.flush_outer() in write() instead of calling self.inner.flush().

Start with the earlier discussion in Rust issue #13858 and inspect the standard library's Writer adaptors, especially BufferedWriter and LineBufferedWriter. Determine which adaptors need a public flush_outer() operation and how it should interact with existing flush behavior; the work is done when the API and adaptor behavior are consistently specified and implemented.