tikhomirov@10: /*
tikhomirov@10:  * Copyright (c) 2010 Artem Tikhomirov 
tikhomirov@10:  */
tikhomirov@10: package com.tmate.hgkit.fs;
tikhomirov@10: 
tikhomirov@10: import java.io.File;
tikhomirov@10: import java.io.FileInputStream;
tikhomirov@10: import java.io.IOException;
tikhomirov@10: import java.nio.ByteBuffer;
tikhomirov@10: import java.nio.MappedByteBuffer;
tikhomirov@10: import java.nio.channels.FileChannel;
tikhomirov@10: 
tikhomirov@10: /**
tikhomirov@10:  *
tikhomirov@10:  * @author artem
tikhomirov@10:  */
tikhomirov@10: public class DataAccessProvider {
tikhomirov@10: 
tikhomirov@10: 	private final int mapioMagicBoundary;
tikhomirov@10: 	private final int bufferSize;
tikhomirov@10: 
tikhomirov@10: 	public DataAccessProvider() {
tikhomirov@10: 		mapioMagicBoundary = 100 * 1024;
tikhomirov@10: 		bufferSize = 8 * 1024;
tikhomirov@10: 	}
tikhomirov@10: 
tikhomirov@10: 	public DataAccess create(File f) {
tikhomirov@10: 		if (!f.exists()) {
tikhomirov@10: 			return new DataAccess();
tikhomirov@10: 		}
tikhomirov@10: 		try {
tikhomirov@10: 			FileChannel fc = new FileInputStream(f).getChannel();
tikhomirov@10: 			if (fc.size() > mapioMagicBoundary) {
tikhomirov@10: 				return new MemoryMapFileAccess(fc, fc.size());
tikhomirov@10: 			} else {
tikhomirov@10: 				// XXX once implementation is more or less stable,
tikhomirov@10: 				// may want to try ByteBuffer.allocateDirect() to see
tikhomirov@10: 				// if there's any performance gain. 
tikhomirov@10: 				boolean useDirectBuffer = false;
tikhomirov@10: 				return new FileAccess(fc, fc.size(), bufferSize, useDirectBuffer);
tikhomirov@10: 			}
tikhomirov@10: 		} catch (IOException ex) {
tikhomirov@10: 			// unlikely to happen, we've made sure file exists.
tikhomirov@10: 			ex.printStackTrace(); // FIXME log error
tikhomirov@10: 		}
tikhomirov@10: 		return new DataAccess(); // non-null, empty.
tikhomirov@10: 	}
tikhomirov@10: 
tikhomirov@10: 	// DOESN'T WORK YET 
tikhomirov@10: 	private static class MemoryMapFileAccess extends DataAccess {
tikhomirov@10: 		private FileChannel fileChannel;
tikhomirov@10: 		private final long size;
tikhomirov@10: 		private long position = 0;
tikhomirov@10: 
tikhomirov@10: 		public MemoryMapFileAccess(FileChannel fc, long channelSize) {
tikhomirov@10: 			fileChannel = fc;
tikhomirov@10: 			size = channelSize;
tikhomirov@10: 		}
tikhomirov@10: 
tikhomirov@10: 		@Override
tikhomirov@10: 		public void seek(long offset) {
tikhomirov@10: 			position = offset;
tikhomirov@10: 		}
tikhomirov@10: 
tikhomirov@10: 		@Override
tikhomirov@10: 		public void skip(int bytes) throws IOException {
tikhomirov@10: 			position += bytes;
tikhomirov@10: 		}
tikhomirov@10: 
tikhomirov@10: 		private boolean fill() throws IOException {
tikhomirov@10: 			final int BUFFER_SIZE = 8 * 1024;
tikhomirov@10: 			long left = size - position;
tikhomirov@10: 			MappedByteBuffer rv = fileChannel.map(FileChannel.MapMode.READ_ONLY, position, left < BUFFER_SIZE ? left : BUFFER_SIZE);
tikhomirov@10: 			position += rv.capacity();
tikhomirov@10: 			return rv.hasRemaining();
tikhomirov@10: 		}
tikhomirov@10: 
tikhomirov@10: 		@Override
tikhomirov@10: 		public void done() {
tikhomirov@10: 			if (fileChannel != null) {
tikhomirov@10: 				try {
tikhomirov@10: 					fileChannel.close();
tikhomirov@10: 				} catch (IOException ex) {
tikhomirov@10: 					ex.printStackTrace(); // log debug
tikhomirov@10: 				}
tikhomirov@10: 				fileChannel = null;
tikhomirov@10: 			}
tikhomirov@10: 		}
tikhomirov@10: 	}
tikhomirov@10: 
tikhomirov@10: 	// (almost) regular file access - FileChannel and buffers.
tikhomirov@10: 	private static class FileAccess extends DataAccess {
tikhomirov@10: 		private FileChannel fileChannel;
tikhomirov@10: 		private final long size;
tikhomirov@10: 		private ByteBuffer buffer;
tikhomirov@10: 		private long bufferStartInFile = 0; // offset of this.buffer in the file.
tikhomirov@10: 
tikhomirov@10: 		public FileAccess(FileChannel fc, long channelSize, int bufferSizeHint, boolean useDirect) {
tikhomirov@10: 			fileChannel = fc;
tikhomirov@10: 			size = channelSize;
tikhomirov@10: 			final int capacity = size < bufferSizeHint ? (int) size : bufferSizeHint;
tikhomirov@10: 			buffer = useDirect ? ByteBuffer.allocateDirect(capacity) : ByteBuffer.allocate(capacity);
tikhomirov@10: 			buffer.flip(); // or .limit(0) to indicate it's empty
tikhomirov@10: 		}
tikhomirov@10: 		
tikhomirov@10: 		@Override
tikhomirov@10: 		public boolean isEmpty() {
tikhomirov@10: 			return bufferStartInFile + buffer.position() >= size;
tikhomirov@10: 		}
tikhomirov@10: 		
tikhomirov@10: 		@Override
tikhomirov@10: 		public void seek(long offset) throws IOException {
tikhomirov@10: 			if (offset < bufferStartInFile + buffer.limit() && offset >= bufferStartInFile) {
tikhomirov@10: 				buffer.position((int) (offset - bufferStartInFile));
tikhomirov@10: 			} else {
tikhomirov@10: 				// out of current buffer, invalidate it (force re-read) 
tikhomirov@10: 				// XXX or ever re-read it right away?
tikhomirov@10: 				bufferStartInFile = offset;
tikhomirov@10: 				buffer.clear();
tikhomirov@10: 				buffer.limit(0); // or .flip() to indicate we switch to reading
tikhomirov@10: 				fileChannel.position(offset);
tikhomirov@10: 			}
tikhomirov@10: 		}
tikhomirov@10: 
tikhomirov@10: 		@Override
tikhomirov@10: 		public void skip(int bytes) throws IOException {
tikhomirov@10: 			final int newPos = buffer.position() + bytes;
tikhomirov@10: 			if (newPos >= 0 && newPos < buffer.limit()) {
tikhomirov@10: 				// no need to move file pointer, just rewind/seek buffer 
tikhomirov@10: 				buffer.position(newPos);
tikhomirov@10: 			} else {
tikhomirov@10: 				//
tikhomirov@10: 				seek(fileChannel.position()+ bytes);
tikhomirov@10: 			}
tikhomirov@10: 		}
tikhomirov@10: 
tikhomirov@10: 		private boolean fill() throws IOException {
tikhomirov@10: 			if (!buffer.hasRemaining()) {
tikhomirov@10: 				bufferStartInFile += buffer.limit();
tikhomirov@10: 				buffer.clear();
tikhomirov@10: 				if (bufferStartInFile < size) { // just in case there'd be any exception on EOF, not -1 
tikhomirov@10: 					fileChannel.read(buffer);
tikhomirov@10: 					// may return -1 when EOF, but empty will reflect this, hence no explicit support here   
tikhomirov@10: 				}
tikhomirov@10: 				buffer.flip();
tikhomirov@10: 			}
tikhomirov@10: 			return buffer.hasRemaining();
tikhomirov@10: 		}
tikhomirov@10: 
tikhomirov@10: 		@Override
tikhomirov@10: 		public void readBytes(byte[] buf, int offset, int length) throws IOException {
tikhomirov@10: 			final int tail = buffer.remaining();
tikhomirov@10: 			if (tail >= length) {
tikhomirov@10: 				buffer.get(buf, offset, length);
tikhomirov@10: 			} else {
tikhomirov@10: 				buffer.get(buf, offset, tail);
tikhomirov@10: 				if (fill()) {
tikhomirov@10: 					buffer.get(buf, offset + tail, length - tail);
tikhomirov@10: 				} else {
tikhomirov@10: 					throw new IOException(); // shall not happen provided stream contains expected data and no attempts to read past nonEmpty() == false are made. 
tikhomirov@10: 				}
tikhomirov@10: 			}
tikhomirov@10: 		}
tikhomirov@10: 
tikhomirov@10: 		@Override
tikhomirov@10: 		public byte readByte() throws IOException {
tikhomirov@10: 			if (buffer.hasRemaining()) {
tikhomirov@10: 				return buffer.get();
tikhomirov@10: 			}
tikhomirov@10: 			if (fill()) {
tikhomirov@10: 				return buffer.get();
tikhomirov@10: 			}
tikhomirov@10: 			throw new IOException();
tikhomirov@10: 		}
tikhomirov@10: 
tikhomirov@10: 		@Override
tikhomirov@10: 		public void done() {
tikhomirov@10: 			if (buffer != null) {
tikhomirov@10: 				buffer = null;
tikhomirov@10: 			}
tikhomirov@10: 			if (fileChannel != null) {
tikhomirov@10: 				try {
tikhomirov@10: 					fileChannel.close();
tikhomirov@10: 				} catch (IOException ex) {
tikhomirov@10: 					ex.printStackTrace(); // log debug
tikhomirov@10: 				}
tikhomirov@10: 				fileChannel = null;
tikhomirov@10: 			}
tikhomirov@10: 		}
tikhomirov@10: 	}
tikhomirov@10: }