Refactoring org.bdgenomics.adam.io package.

* Added documentation to all classes, methods, and fields that were missing
  descriptions.
* Factored duplicated code from `SingleFastqRecordReader` and
  `InterleavedFastqRecordReader` out into a new abstract base class
  `FastqRecordReader`.
* Tightened up access modifiers where possible. Sadly, the two input formats
  cannot be made more private, since Java has a more restricted form of
  package-private than scala, and the input formats are used from inside of
  `org.bdgenomics.adam.rdd`.
* Removed `@author` tags.

adam-core/src/main/java/org/bdgenomics/adam/io/FastqRecordReader.java

@@ -0,0 +1,336 @@
+/**
+ * Licensed to Big Data Genomics (BDG) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The BDG licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.bdgenomics.adam.io;
+
+import java.io.EOFException;
+import java.io.IOException;
+import java.io.InputStream;
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.fs.FSDataInputStream;
+import org.apache.hadoop.fs.FileSystem;
+import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.io.Text;
+import org.apache.hadoop.io.compress.CompressionCodec;
+import org.apache.hadoop.io.compress.CompressionCodecFactory;
+import org.apache.hadoop.mapreduce.InputSplit;
+import org.apache.hadoop.mapreduce.RecordReader;
+import org.apache.hadoop.mapreduce.TaskAttemptContext;
+import org.apache.hadoop.mapreduce.lib.input.FileSplit;
+import org.apache.hadoop.util.LineReader;
+
+/**
+ * A record reader for the interleaved FASTQ format.
+ *
+ * Reads over an input file and parses interleaved FASTQ read pairs into
+ * a single Text output. This is then fed into the FastqConverter, which
+ * converts the single Text instance into two AlignmentRecords.
+ */
+abstract class FastqRecordReader extends RecordReader<Void,Text> {
+    /*
+     * fastq format:
+     * <fastq>  :=  <block>+
+     * <block>  :=  @<seqname>\n<seq>\n\+[<seqname>]\n<qual>\n
+     * <seqname>  :=  [A-Za-z0-9_.:-]+
+     * <seq>  :=  [A-Za-z\n\.~]+
+     * <qual> :=  [!-~\n]+
+     *
+     * LP: this format is broken, no?  You can have multi-line sequence and quality strings,
+     * and the quality encoding includes '@' in its valid character range.  So how should one
+     * distinguish between \n@ as a record delimiter and and \n@ as part of a multi-line
+     * quality string?
+     *
+     * For now I'm going to assume single-line sequences.  This works for our sequencing
+     * application.  We'll see if someone complains in other applications.
+     */
+
+    /**
+     * First valid data index in the stream.
+     */
+    private long start;
+
+    /**
+     * First index value beyond the slice, i.e. slice is in range [start,end).
+     */
+    protected long end;
+
+    /**
+     * Current position in file.
+     */
+    protected long pos;
+
+    /**
+     * Path of the file being parsed.
+     */
+    private Path file;
+
+    /**
+     * The line reader we are using to read the file.
+     */
+    private LineReader lineReader;
+
+    /**
+     * The input stream we are using to read the file.
+     */
+    private InputStream inputStream;
+
+    /**
+     * The text for a single record pair we have parsed out.
+     * Hadoop's RecordReader contract requires us to save this as state.
+     */
+    private Text currentValue;
+
+    /**
+     * Newline string for matching on.
+     */
+    private static final byte[] newline = "\n".getBytes();
+
+    /**
+     * Maximum length for a read string.
+     */
+    private static final int MAX_LINE_LENGTH = 10000;
+
+    /**
+     * Builds a new record reader given a config file and an input split.
+     *
+     * @param conf The Hadoop configuration object. Used for gaining access
+     *   to the underlying file system.
+     * @param split The file split to read.
+     */
+    public FastqRecordReader(Configuration conf, FileSplit split) throws IOException {
+        file = split.getPath();
+        start = split.getStart();
+        end = start + split.getLength();
+
+        FileSystem fs = file.getFileSystem(conf);
+        FSDataInputStream fileIn = fs.open(file);
+
+        CompressionCodecFactory codecFactory = new CompressionCodecFactory(conf);
+        CompressionCodec        codec        = codecFactory.getCodec(file);
+
+        if (codec == null) { // no codec.  Uncompressed file.
+            positionAtFirstRecord(fileIn);
+            inputStream = fileIn;
+        } else { 
+            // compressed file
+            if (start != 0) {
+                throw new RuntimeException("Start position for compressed file is not 0! (found " + start + ")");
+            }
+
+            inputStream = codec.createInputStream(fileIn);
+            end = Long.MAX_VALUE; // read until the end of the file
+        }
+
+        lineReader = new LineReader(inputStream);
+    }
+
+    /**
+     * Checks to see whether the buffer is positioned at a valid record.
+     *
+     * @param bufferLength The length of the line currently in the buffer.
+     * @param buffer A buffer containing a peek at the first line in the current
+     *   stream.
+     * @return Returns true if the buffer contains the first line of a properly
+     *   formatted FASTQ record.
+     */
+    abstract protected boolean checkBuffer(int bufferLength, Text buffer);
+
+    /**
+     * Position the input stream at the start of the first record.
+     *
+     * @param stream The stream to reposition.
+     */
+    protected void positionAtFirstRecord(FSDataInputStream stream) throws IOException {
+        Text buffer = new Text();
+
+        if (true) { // (start > 0) // use start>0 to assume that files start with valid data
+            // Advance to the start of the first record that ends with /1
+            // We use a temporary LineReader to read lines until we find the
+            // position of the right one.  We then seek the file to that position.
+            stream.seek(start);
+            LineReader reader = new LineReader(stream);
+
+            int bytesRead = 0;
+            do {
+                bytesRead = reader.readLine(buffer, (int)Math.min(MAX_LINE_LENGTH, end - start));
+                int bufferLength = buffer.getLength();
+                if (bytesRead > 0 && !checkBuffer(bufferLength, buffer)) {
+                    start += bytesRead;
+                } else {
+                    // line starts with @.  Read two more and verify that it starts with a +
+                    //
+                    // If this isn't the start of a record, we want to backtrack to its end
+                    long backtrackPosition = start + bytesRead;
+
+                    bytesRead = reader.readLine(buffer, (int)Math.min(MAX_LINE_LENGTH, end - start));
+                    bytesRead = reader.readLine(buffer, (int)Math.min(MAX_LINE_LENGTH, end - start));
+                    if (bytesRead > 0 && buffer.getLength() > 0 && buffer.getBytes()[0] == '+') {
+                        break; // all good!
+                    } else {
+                        // backtrack to the end of the record we thought was the start.
+                        start = backtrackPosition;
+                        stream.seek(start);
+                        reader = new LineReader(stream);
+                    }
+                }
+            } while (bytesRead > 0);
+
+            stream.seek(start);
+        }
+
+        pos = start;
+    }
+
+    /**
+     * Method is a no-op.
+     *
+     * @param split The input split that we will parse.
+     * @param context The Hadoop task context.
+     */
+    public void initialize(InputSplit split, TaskAttemptContext context) throws IOException, InterruptedException {}
+
+    /**
+     * FASTQ has no keys, so we return null.
+     *
+     * @return Always returns null.
+     */
+    public Void getCurrentKey() {
+        return null;
+    }
+
+    /**
+     * Returns the last interleaved FASTQ record.
+     *
+     * @return The text corresponding to the last read pair.
+     */
+    public Text getCurrentValue() {
+        return currentValue;
+    }
+
+    /**
+     * Seeks ahead in our split to the next key-value pair.
+     *
+     * Triggers the read of an interleaved FASTQ read pair, and populates
+     * internal state.
+     *
+     * @return True if reading the next read pair succeeded.
+     */
+    public boolean nextKeyValue() throws IOException, InterruptedException {
+        currentValue = new Text();
+
+        return next(currentValue);
+    }
+
+    /**
+     * Close this RecordReader to future operations.
+     */
+    public void close() throws IOException {
+        inputStream.close();
+    }
+
+    /**
+     * How much of the input has the RecordReader consumed?
+     *
+     * @return Returns a value on [0.0, 1.0] that notes how many bytes we
+     *   have read so far out of the total bytes to read.
+     */
+    public float getProgress() {
+        if (start == end)
+            return 1.0f;
+        else
+            return Math.min(1.0f, (pos - start) / (float)(end - start));
+    }
+
+    /**
+     * Produces a debugging message with the file position.
+     *
+     * @return Returns a string containing {filename}:{index}.
+     */
+    protected String makePositionMessage() {
+        return file.toString() + ":" + pos;
+    }
+
+    /**
+     * Parses a read from an interleaved FASTQ file.
+     *
+     * Only reads a single record.
+     *
+     * @param readName Text record containing read name. Output parameter.
+     * @param value Text record containing full record. Output parameter.
+     * @return Returns true if read was successful (did not hit EOF).
+     *
+     * @throws RuntimeException Throws exception if FASTQ record doesn't
+     *   have proper formatting (e.g., record doesn't start with @).
+     */
+    protected boolean lowLevelFastqRead(Text readName, Text value) throws IOException {
+        // ID line
+        readName.clear();
+        long skipped = appendLineInto(readName, true);
+        pos += skipped;
+        if (skipped == 0)
+            return false; // EOF
+        if (readName.getBytes()[0] != '@')
+            throw new RuntimeException("unexpected fastq record didn't start with '@' at " + makePositionMessage() + ". Line: " + readName + ". \n");
+
+        value.append(readName.getBytes(), 0, readName.getLength());
+
+        // sequence
+        appendLineInto(value, false);
+
+        // separator line
+        appendLineInto(value, false);
+
+        // quality
+        appendLineInto(value, false);
+
+        return true;
+    }
+
+    /**
+     * Reads from the input split.
+     *
+     * @param value Text record to write input value into.
+     * @return Returns whether this read was successful or not.
+     *
+     * @see lowLevelFastqRead
+     */
+    abstract protected boolean next(Text value) throws IOException;
+
+    /**
+     * Reads a newline into a text record from the underlying line reader.
+     *
+     * @param dest Text record to read line into.
+     * @param eofOk Whether an EOF is acceptable in this line.
+     * @return Returns the number of bytes read.
+     *
+     * @throws EOFException Throws if eofOk was false and we hit an EOF in
+     *    the current line.
+     */
+    private int appendLineInto(Text dest, boolean eofOk) throws EOFException, IOException {
+        Text buf = new Text();
+        int bytesRead = lineReader.readLine(buf, MAX_LINE_LENGTH);
+
+        if (bytesRead < 0 || (bytesRead == 0 && !eofOk))
+            throw new EOFException();
+
+        dest.append(buf.getBytes(), 0, buf.getLength());
+        dest.append(newline, 0, 1);
+        pos += bytesRead;
+
+        return bytesRead;
+    }
+}