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Date: Fri, 21 Sep 2012 16:48:08 +1100 (NCT)
From: "Harsh J (JIRA)" <jira@apache.org>
To: common-issues@hadoop.apache.org
Message-ID: <765376368.106339.1348206488053.JavaMail.jiratomcat@arcas>
Subject: [jira] [Created] (HADOOP-8833) fs -text should make sure to call
 inputstream.seek(0) before using input stream
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Harsh J created HADOOP-8833:
-------------------------------

             Summary: fs -text should make sure to call inputstream.seek(0) before using input stream
                 Key: HADOOP-8833
                 URL: https://issues.apache.org/jira/browse/HADOOP-8833
             Project: Hadoop Common
          Issue Type: Bug
          Components: fs
    Affects Versions: 2.0.2-alpha
            Reporter: Harsh J
            Assignee: Harsh J


>From Muddy Dixon on HADOOP-8449:

Hi
We found the changes in order of switch and guard block in
{code}
private InputStream forMagic(Path p, FileSystem srcFs) throws IOException
{code}
Because of this change, return value of
{code}
codec.createInputStream(i)
{code}
is changed if codec exists.

{code}
private InputStream forMagic(Path p, FileSystem srcFs) throws IOException {
    FSDataInputStream i = srcFs.open(p);

    // check codecs
    CompressionCodecFactory cf = new CompressionCodecFactory(getConf());
    CompressionCodec codec = cf.getCodec(p);
    if (codec != null) {
      return codec.createInputStream(i);
    }

    switch(i.readShort()) {
       // cases
    }
{code}

New:

{code}
private InputStream forMagic(Path p, FileSystem srcFs) throws IOException {
    FSDataInputStream i = srcFs.open(p);

    switch(i.readShort()) { // <=== index (or pointer) processes!!
      // cases
      default: {
        // Check the type of compression instead, depending on Codec class's
        // own detection methods, based on the provided path.
        CompressionCodecFactory cf = new CompressionCodecFactory(getConf());
        CompressionCodec codec = cf.getCodec(p);
        if (codec != null) {
          return codec.createInputStream(i);
        }
        break;
      }
    }

    // File is non-compressed, or not a file container we know.
    i.seek(0);
    return i;
  }
{code}

Fix is to use i.seek(0) before we use i anywhere. I missed that.

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