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Lars Kolb commented on IO-288: ------------------------------ * [Web|http://svn.apache.org/viewvc/hadoop/common/trunk/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/LineReader.java?view=log] * [SVN|http://hadoop.apache.org/common/version_control.html] Basically, it would be required to support: {code} FSDataInputStream is= FileSystem.get(conf); is.seek(offset); //constructor takes (positioned) Input stream public ReversedLinesFileReader(InputStream is) { //do not seek to end of file, simply start reading from is } public int readLine(Text text) { //return bytes read and store line in text //alternatively one could return a Pair<String,Integer> to not depend on org.apache.hadoop.io.Text } {code} > Supply a ReversedLinesFileReader > --------------------------------- > > Key: IO-288 > URL: https://issues.apache.org/jira/browse/IO-288 > Project: Commons IO > Issue Type: New Feature > Components: Utilities > Reporter: Georg Henzler > Fix For: 2.2 > > Attachments: ReversedLinesFileReader0.3.zip > > > I needed to analyse a log file today and I was looking for a > ReversedLinesFileReader: A class that behaves exactly like BufferedReader > except that it goes from bottom to top when readLine() is called. I didn't > find it in IOUtils and the internet didn't help a lot either, e.g. > http://www.java2s.com/Tutorial/Java/0180__File/ReversingaFile.htm is a fairly > inefficient - the log files I'm analysing are huge and it is not a good idea > to load the whole content in the memory. > So I ended up writing an implementation myself using little memory and the > class RandomAccessFile - see attached file. It's used as follows: > int blockSize = 4096; // only that much memory is needed, no matter how big > the file is > ReversedLinesFileReader reversedLinesFileReader = new ReversedLinesFileReader > (myFile, blockSize, "UTF-8"); // encoding is supported > String line = null; > while((line=reversedLinesFileReader.readLine())!=null) { > ... // use the line > if(enoughLinesSeen) { > break; > } > } > reversedLinesFileReader.close(); > I believe this could be useful for other people as well! -- This message is automatically generated by JIRA. If you think it was sent incorrectly, please contact your JIRA administrators: https://issues.apache.org/jira/secure/ContactAdministrators!default.jspa For more information on JIRA, see: http://www.atlassian.com/software/jira