[jira] [Created] (IO-818) NullInputStream breaks InputStream's read method contract

["X Liu (Jira)" <ji...@apache.org>]

X Liu created IO-818:
------------------------

             Summary: NullInputStream breaks InputStream's read method contract
                 Key: IO-818
                 URL: https://issues.apache.org/jira/browse/IO-818
             Project: Commons IO
          Issue Type: Bug
          Components: Streams/Writers
    Affects Versions: 2.13.0
         Environment: JDK 17.0

Apache commons-io-2.13.0, but it looks like this apply to 2.15.0 too.
            Reporter: X Liu


A java.io.InputStream instance's read(...) method will always return -1 after it reaches its end.

 
However, after a NullInputStream instance reaches its end, if you call its read(...) method again, you'll get IOException with message {{{}Read after end of file{}}}. It's document says the read(...) method should {{{}return -1 if the end of file has been reached and throwEofException is set to false{}}}. However, its code doesn't check throwEofException flag before it throws the IOException:
public int read() throws IOException \{
        if (eof) {
            throw new IOException("Read after end of file");
        }
I'm not sure whether its read method should strictly follow what InputStream does, i.e., always return -1 after it reaches end, or should it check throwEofException flag before it throws an IOException.

Following is a snippet that can reproduce this problem:
import org.apache.commons.io.input.NullInputStream;

import java.io.ByteArrayInputStream;
import java.io.InputStream;

public class InputStreamTest \{

    private static void testOneStream(InputStream inputStream) throws Exception {
        final byte[] buffer = new byte[4096];
        int readLen;
        while ((readLen = inputStream.read(buffer)) != -1) {
            // do nothing
        }
        readLen = inputStream.read(buffer);
        if (readLen != -1) \{
            throw new Exception("Failed to read after reaching the end of the stream.");
        }
    }

    public static void main(String[] args) \{
        try { // Test ByteArrayInputStream
            final InputStream byteArrayInputStream = new ByteArrayInputStream(new byte[1024]);
            testOneStream(byteArrayInputStream);
            System.out.println("ByteArrayInputStream succeeded.");
        } catch (Exception e) \{
            System.out.println("ByteArrayInputStream failed");
        }
        try \{ //Test NullInputStream
            final InputStream nullInputStream = new NullInputStream(1024, true, false);
            testOneStream(nullInputStream);
            System.out.println("NullInputStream succeeded.");
        } catch (Exception e) \{
            System.out.println("NullInputStream failed");
        }
    }
}
 



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