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

["Gary D. Gregory (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/IO-818?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Gary D. Gregory resolved IO-818.
--------------------------------
    Fix Version/s: 2.16.0
       Resolution: Fixed

> 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
>            Priority: Major
>             Fix For: 2.16.0
>
>
> 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{color:#de350b} the read(...) method should return -1 if the end of file has been reached and throwEofException is set to false{color}. However, its code doesn't check throwEofException flag before it throws the IOException:
> {noformat}
> public int read() throws IOException {
>     if (eof) {
>        throw new IOException("Read after end of file");
>     }
>     ....
> }{noformat}
> 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:
> {noformat}
> 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");
>         }
>     }
> }{noformat}



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