Example usage for java.nio CharBuffer charAt

Introduction

In this page you can find the example usage for java.nio CharBuffer charAt.

Prototype

public final char charAt(int index) 

Source Link

Document

Returns the character located at the specified index in the buffer.

Usage

From source file:pyromaniac.IO.MMFastqImporter.java

/**
 * Helper function for init(). Scans this.fastq file for sequence starts and records their position.
 * Multiple MappedByteBuffers are used to handle large files.
 * @throws Exceptions relating to file reading and decoding.
 *//*from  w ww.ja v  a2s  .  c o  m*/
private void _initFile() throws Exception {
    FileInputStream tempStream = new FileInputStream(new File(this.fastqFile));
    FileChannel fcSeq = tempStream.getChannel();
    this.seqSizeLong = fcSeq.size();
    this.recordStarts = new ArrayList<Pair<Integer, Long>>();

    int state = -1;

    for (long startPosition = 0L; startPosition < this.seqSizeLong; startPosition += HALF_GIGA) {
        MappedByteBuffer recordBuffer = fcSeq.map(FileChannel.MapMode.READ_ONLY, startPosition,
                Math.min(this.seqSizeLong - startPosition, HALF_GIGA));
        this.recordBuffers.add(recordBuffer);

        int sbf_pos = this.recordBuffers.size() - 1;

        int maxBuffer = 2048;
        int bufferSize = (recordBuffer.capacity() > maxBuffer) ? maxBuffer : recordBuffer.capacity();

        recordBuffer.limit(bufferSize);
        recordBuffer.position(0);

        while (recordBuffer.position() != recordBuffer.capacity()) {
            int prevPos = recordBuffer.position();
            CharBuffer result = decoder.decode(recordBuffer);
            recordBuffer.position(prevPos);

            for (int i = 0; i < result.capacity(); i++) {
                char curr = result.charAt(i);
                int posInFile = prevPos + i;

                //I see a fastq header, I am either at beginning of file, or last saw the quality line...
                if (curr == BEGINNING_FASTQ_SEQ && (state == -1 || state == 4)) {
                    this.recordStarts.add(new Pair<Integer, Long>(sbf_pos, new Long(posInFile)));
                    state = 1;

                } else if (curr == BEGINNING_FASTQ_QUAL && (state == 1)) {
                    state = 2;
                } else if ((curr == '\n' || curr == '\r') & state == 2) {
                    state = 3;
                } else if ((curr == '\n' || curr == '\r') & state == 3) {
                    state = 4;
                }
            }

            int newPos = recordBuffer.limit();

            if (recordBuffer.limit() + bufferSize > recordBuffer.capacity())
                recordBuffer.limit(recordBuffer.capacity());
            else
                recordBuffer.limit(recordBuffer.limit() + bufferSize);
            recordBuffer.position(newPos);
        }
        recordBuffer.rewind();
    }
}

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