[
https://issues.apache.org/jira/browse/HTTPCORE-449?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15888073#comment-15888073
]
John Flavin commented on HTTPCORE-449:
--------------------------------------
Maybe "bug" is not the right word. But it seems to me that
{{SessionInputBufferImpl#available}} is supposed to tell me if there is data
available *in the stream*, not in the buffer.
Compare to {{SessionInputBufferImpl#read(...)}} on [line
185|https://github.com/apache/httpcore/blob/4.4.x/httpcore/src/main/java/org/apache/http/impl/io/SessionInputBufferImpl.java#L185],
which first checks if the buffer has data (using
{{SessionInputBufferImpl#hasBufferedData}} method), but if the buffer is empty
it reads data directly off the stream.
That's what I want {{SessionInputBufferImpl#available}} to do: sure, as a
shortcut, first check if data is buffered, but if not then tell me if data is
available in the stream. That's the contract of {{InputStream#available}}: does
the stream have available data? The fact that the stream data is buffered or
not buffered is an implementation detail that need not be exposed to consumers.
> IdentityInputStream.available() erroneously returns 0
> -----------------------------------------------------
>
> Key: HTTPCORE-449
> URL: https://issues.apache.org/jira/browse/HTTPCORE-449
> Project: HttpComponents HttpCore
> Issue Type: Bug
> Components: HttpCore
> Affects Versions: 4.4.5, 4.4.6
> Reporter: John Flavin
>
> h5. BACKGROUND
> I have an application that reads data from a stream. When data is available,
> I can read from the stream perfectly fine. However, sometimes the stream will
> remain open with no data, in which case reading from the stream blocks. I
> would like to use the {{available()}} method on the stream to first check
> whether anything can be read before attempting to read.
> h5. PROBLEM
> When I attempt to use the {{available()}} method on my {{InputStream}}
> instance it returns {{0}}, i.e. no data available, even when I can
> successfully call {{read(...)}} and read data off the stream.
> h5. INVESTIGATION INTO PROBLEM
> I have traced the {{available()}} method on my {{InputStream}} instance
> through several layers of wrapper classes around more {{InputStream}}
> instances. Each layer's {{available()}} method simply calls into its wrapped
> {{InputStream}}'s {{available()}} method. That is, until I reach the
> {{IdentityInputStream.available()}} method. The latter does this:
> {code:java}
> @Override
> public int available() throws IOException {
> if (this.in instanceof BufferInfo) {
> return ((BufferInfo) this.in).length();
> } else {
> return 0;
> }
> }
> {code}
> The {{in}} in the above code is a {{SessionInputBufferImpl}}, which has a few
> methods that are seemingly relevant to this:
> {code:java}
> @Override
> public int capacity() {
> return this.buffer.length;
> }
> @Override
> public int length() {
> return this.bufferlen - this.bufferpos;
> }
> @Override
> public int available() {
> return capacity() - length();
> }
> {code}
> h5. QUESTION
> Why does {{IdentityInputStream.available()}} call {{((BufferInfo)
> this.in).length()}} instead of {{((BufferInfo) this.in).available()}}? The
> former returns {{0}} when I call it on a stream that has data which can be
> read, but has not been; the latter returns a number greater than {{0}}.
--
This message was sent by Atlassian JIRA
(v6.3.15#6346)
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
