bufio: Reader swallows 0-length reads #17059
Description
I have a package that uses bufio.Reader to decode protocol messages. It implements
trace debugging by writing all messages through an io.Pipe(). I was surprised to find
that the first 100 0-length writes were ignored by the bufio.Reader.fill method, as
the documentation explicitly states
The bytes are taken from at most one Read on the underlying Reader, hence
n may be less than len(p).
I would like to suggest a documentation change to indicate that zero-length reads are
not counted.
What version of Go are you using (go version)?
go version go1.7 linux/amd64
What operating system and processor architecture are you using (go env)?
GOARCH="amd64"
GOBIN="/usr/local/bin"
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/"
GORACE=""
GOROOT="/go"
GOTOOLDIR="/go/pkg/tool/linux_amd64"
CC="gcc"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build706953720=/tmp/go-build -gno-record-gcc-switches"
CXX="g++"
CGO_ENABLED="1"
What did you do?
A zero-length write to an io.PipeWriter, whose corresponding
io.PipeReader was read through a bufio.Reader. The following
simplified program illustrates the issue: https://play.golang.org/p/lI14R5CMQ-
What did you expect to see?
The program should print one item for every write to the pipe:
1 foo
2 bar
3
4
5
6 baz
What did you see instead?
The bufio.Reader ignored the 0-byte reads.
1 foo
2 bar
3 baz