[jira] [Closed] (IO-428) BOMInputStream.skip returns wrong count if stream contains no BOM

["Kristian Rosenvold (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/IO-428?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Kristian Rosenvold closed IO-428.
---------------------------------
       Resolution: Fixed
    Fix Version/s: 2.5
         Assignee: Kristian Rosenvold

> BOMInputStream.skip returns wrong count if stream contains no BOM
> -----------------------------------------------------------------
>
>                 Key: IO-428
>                 URL: https://issues.apache.org/jira/browse/IO-428
>             Project: Commons IO
>          Issue Type: Bug
>          Components: Streams/Writers
>    Affects Versions: 2.0.1
>            Reporter: Stefan Gmeiner
>            Assignee: Kristian Rosenvold
>            Priority: Minor
>             Fix For: 2.5
>
>
> If the {{skip}} method of {{BOMInputStream}} is used on a stream without a BOM, {{skip}} returns the wrong number of bytes (n - max(BOM-length)). This can lead to problems if the return value is evaluated for example from guava {{ByteStreams.skipFully}}.
> {code:title=BomTest.java}
> public class BomTest {
> 	private static InputStream createInputStream(boolean addBOM) {
> 		ByteBuffer bb = ByteBuffer.allocate(64);
> 		if (addBOM) {
> 			// UTF-8 BOM
> 			bb.put(new byte[] { (byte) 0xEF, (byte) 0xBB, (byte) 0xBF });
> 		}
> 		bb.put((byte) 0x31);
> 		bb.put((byte) 0x32);
> 		bb.put((byte) 0x33);
> 		return new ByteArrayInputStream(bb.array());
> 	}
> 	
> 	public static void main(String[] args) throws IOException {
> 		BOMInputStream is1 = new BOMInputStream(createInputStream(true));
> 		assertEquals(2, is1.skip(2));
> 		assertEquals((byte) 0x33, is1.read());
> 		
> 		BOMInputStream is2 = new BOMInputStream(createInputStream(false));
> 		assertEquals(2, is2.skip(2)); // fails here - skip returns 0
> 		assertEquals((byte) 0x33, is2.read());
> 	}
> 	
> }
> {code}
> I catched this bug in 2.0.1, but as far as I can see on the source 2.5 is still affected.
> I suggest the following change to the {{skip}} method:
> {code:title=BOMInputStream.java}
>     public long skip(long n) throws IOException {
>     	int skipped = 0;
>         while ((n > skipped) && (readFirstBytes() >= 0)) {
>             skipped++;
>         }
>         return in.skip(n - skipped) + skipped;
>     }
> {code}



--
This message was sent by Atlassian JIRA
(v6.3.4#6332)