[jira] [Commented] (CODEC-130) Base64InputStream.skip skips underlying stream, not output

["Thomas Neidhart (Commented) (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CODEC-130?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13231575#comment-13231575 ] 

Thomas Neidhart commented on CODEC-130:
---------------------------------------

Imho the request for change has some merit.

If looking at the InflaterInputStream (which is also a derived FilterInputStream), the skip method is implemented to skip uncompressed bytes:

{noformat}
Skips specified number of bytes of uncompressed data. 
{noformat}
                
> Base64InputStream.skip skips underlying stream, not output
> ----------------------------------------------------------
>
>                 Key: CODEC-130
>                 URL: https://issues.apache.org/jira/browse/CODEC-130
>             Project: Commons Codec
>          Issue Type: Bug
>    Affects Versions: 1.5
>            Reporter: James Pickering
>            Priority: Minor
>         Attachments: base64snippet.java
>
>
> Base64InputStream.skip() skips within underlying stream, leading to unexpected behaviour.
> The following code will reproduce the issue:
> @Test
> public void testSkip() throws Throwable {
>     InputStream ins =
>             new ByteArrayInputStream("AAAA////".getBytes("ISO-8859-1"));//should decode to {0, 0, 0, 255, 255, 255}
>     Base64InputStream instance = new Base64InputStream(ins);
>     assertEquals(3L, instance.skip(3L)); //should skip 3 decoded characters, or 4 encoded characters
>     assertEquals(255, instance.read()); //Currently returns 3, as it is decoding "A/", not "//" 
> }
> The following code, if added to Base64InputStream, or (BaseNCodecInputStream in the dev build) would resolve the issue:
> @Override
> public long skip(long n) throws IOException {
>     //delegate to read()
>     long bytesRead = 0;
>     while ((bytesRead < n) && (read() != -1)) {
>         bytesRead++;
>     }
>     return bytesRead;
> }
> More efficient code may be possible.

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