Well, it's *supposed* to work as you say. But honestly, this code has not
been tested with blocking streams, since that's not how we use it in Google.
It's possible that there is a bug. But the code appears to be correct
AFAICT.
When CodedInputStream needs more data, it calls Refresh(), which looks like
this:
bool CodedInputStream::Refresh() {
DCHECK_EQ(buffer_size_, 0);
if (buffer_size_after_limit_ > 0 || overflow_bytes_ > 0 ||
total_bytes_read_ == current_limit_) {
// ...
return false;
}
// ...
}
In your case, total_bytes_read_ should be equal to current_limit_ -- both
should be 17. Therefore, it *should* be returning false, not trying to read
more.
What are you seeing? If you can't figure it out, can you write a small demo
program? Just make the demo program abort if CodedInputStream tries to read
too much. Then I can debug it.
On Tue, Jun 30, 2009 at 10:57 AM, Matthews <heav...@gmail.com> wrote:
>
> I am writing a Java server and C++ client and trying to use Protocol
> Buffers for encoding the socket communication. I have written the Java
> server and tested it with a Java based client and all is well.
> However, I am having some difficulty with the C++ portion.
>
> I've wrapped the socket code in my own CopyingInputStream and
> CopyingOutputStream sub-classes and am using those with the
> CopyingInputStreamAdaptor and CopyingOutputStreamAdapdtor classes.
> These classes are further wrapped in CodedInputStream and
> CodedOutputStream instances for reading/writing the serialized data.
>
> When I send messages I encode the message type and size as varints
> then the message itself. When reading the server response in the C++
> code I read the message type and size then pass the size to
> CodedInputStream.PushLimit(). My server response is very small, 17
> bytes so the initial read gets all the data (I verified that by
> stepping through the code in the debugger).
>
> In this case the type and size are each encoded as 1 byte so that
> leaves 15 bytes for the message. What I am finding is that even after
> the call to PushLimit() with the value 15 the CodedInputStream is
> trying to read more bytes. Again, stepping through the code in the
> debugger I can see that the 15 bytes are already buffered. I've poured
> through the C++ docs and the description of limits states that
> PushLimit will prevent CodedInputStream from reading any additional
> bytes.
>
> This is a problem as the socket is doing a blocking read so it is
> waiting for bytes that will not be sent.
>
> Am I mis-understanding the behavior of PushLimit?
>
> Thanks,
> Michael
> >
>
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