tikhomirov@10: /*
tikhomirov@23:  * Copyright (c) 2010, 2011 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@27: 		this(100 * 1024, 8 * 1024);
tikhomirov@27: 	}
tikhomirov@27: 
tikhomirov@27: 	public DataAccessProvider(int mapioBoundary, int regularBufferSize) {
tikhomirov@27: 		mapioMagicBoundary = mapioBoundary;
tikhomirov@27: 		bufferSize = regularBufferSize;
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@26: 				// TESTS: bufLen of 1024 was used to test MemMapFileAccess
tikhomirov@26: 				return new MemoryMapFileAccess(fc, fc.size(), mapioMagicBoundary);
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@26: 				// TESTS: bufferSize of 100 was used to check buffer underflow states when readBytes reads chunks bigger than bufSize 
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@26: 		private long position = 0; // always points to buffer's absolute position in the file
tikhomirov@26: 		private final int memBufferSize;
tikhomirov@26: 		private MappedByteBuffer buffer;
tikhomirov@10: 
tikhomirov@26: 		public MemoryMapFileAccess(FileChannel fc, long channelSize, int /*long?*/ bufferSize) {
tikhomirov@10: 			fileChannel = fc;
tikhomirov@10: 			size = channelSize;
tikhomirov@26: 			memBufferSize = bufferSize;
tikhomirov@10: 		}
tikhomirov@10: 
tikhomirov@10: 		@Override
tikhomirov@26: 		public boolean isEmpty() {
tikhomirov@26: 			return position + (buffer == null ? 0 : buffer.position()) >= size;
tikhomirov@26: 		}
tikhomirov@26: 		
tikhomirov@26: 		@Override
tikhomirov@51: 		public long length() {
tikhomirov@51: 			return size;
tikhomirov@51: 		}
tikhomirov@51: 		
tikhomirov@51: 		@Override
tikhomirov@51: 		public void reset() throws IOException {
tikhomirov@51: 			seek(0);
tikhomirov@51: 		}
tikhomirov@51: 		
tikhomirov@51: 		@Override
tikhomirov@10: 		public void seek(long offset) {
tikhomirov@26: 			assert offset >= 0;
tikhomirov@26: 			// offset may not necessarily be further than current position in the file (e.g. rewind) 
tikhomirov@26: 			if (buffer != null && /*offset is within buffer*/ offset >= position && (offset - position) < buffer.limit()) {
tikhomirov@26: 				buffer.position((int) (offset - position));
tikhomirov@26: 			} else {
tikhomirov@26: 				position = offset;
tikhomirov@26: 				buffer = null;
tikhomirov@26: 			}
tikhomirov@10: 		}
tikhomirov@10: 
tikhomirov@10: 		@Override
tikhomirov@10: 		public void skip(int bytes) throws IOException {
tikhomirov@26: 			assert bytes >= 0;
tikhomirov@26: 			if (buffer == null) {
tikhomirov@26: 				position += bytes;
tikhomirov@26: 				return;
tikhomirov@26: 			}
tikhomirov@26: 			if (buffer.remaining() > bytes) {
tikhomirov@26: 				buffer.position(buffer.position() + bytes);
tikhomirov@26: 			} else {
tikhomirov@26: 				position += buffer.position() + bytes;
tikhomirov@26: 				buffer = null;
tikhomirov@26: 			}
tikhomirov@10: 		}
tikhomirov@10: 
tikhomirov@26: 		private void fill() throws IOException {
tikhomirov@26: 			if (buffer != null) {
tikhomirov@26: 				position += buffer.position(); 
tikhomirov@26: 			}
tikhomirov@10: 			long left = size - position;
tikhomirov@26: 			buffer = fileChannel.map(FileChannel.MapMode.READ_ONLY, position, left < memBufferSize ? left : memBufferSize);
tikhomirov@26: 		}
tikhomirov@26: 
tikhomirov@26: 		@Override
tikhomirov@26: 		public void readBytes(byte[] buf, int offset, int length) throws IOException {
tikhomirov@26: 			if (buffer == null || !buffer.hasRemaining()) {
tikhomirov@26: 				fill();
tikhomirov@26: 			}
tikhomirov@26: 			// XXX in fact, we may try to create a MappedByteBuffer of exactly length size here, and read right away
tikhomirov@26: 			while (length > 0) {
tikhomirov@26: 				int tail = buffer.remaining();
tikhomirov@26: 				if (tail == 0) {
tikhomirov@26: 					throw new IOException();
tikhomirov@26: 				}
tikhomirov@26: 				if (tail >= length) {
tikhomirov@26: 					buffer.get(buf, offset, length);
tikhomirov@26: 				} else {
tikhomirov@26: 					buffer.get(buf, offset, tail);
tikhomirov@26: 					fill();
tikhomirov@26: 				}
tikhomirov@26: 				offset += tail;
tikhomirov@26: 				length -= tail;
tikhomirov@26: 			}
tikhomirov@26: 		}
tikhomirov@26: 
tikhomirov@26: 		@Override
tikhomirov@26: 		public byte readByte() throws IOException {
tikhomirov@26: 			if (buffer == null || !buffer.hasRemaining()) {
tikhomirov@26: 				fill();
tikhomirov@26: 			}
tikhomirov@26: 			if (buffer.hasRemaining()) {
tikhomirov@26: 				return buffer.get();
tikhomirov@26: 			}
tikhomirov@26: 			throw new IOException();
tikhomirov@10: 		}
tikhomirov@10: 
tikhomirov@10: 		@Override
tikhomirov@10: 		public void done() {
tikhomirov@26: 			buffer = null;
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@51: 		public long length() {
tikhomirov@51: 			return size;
tikhomirov@51: 		}
tikhomirov@51: 		
tikhomirov@51: 		@Override
tikhomirov@51: 		public void reset() throws IOException {
tikhomirov@51: 			seek(0);
tikhomirov@51: 		}
tikhomirov@51: 		
tikhomirov@51: 		@Override
tikhomirov@10: 		public void seek(long offset) throws IOException {
tikhomirov@23: 			if (offset > size) {
tikhomirov@23: 				throw new IllegalArgumentException();
tikhomirov@23: 			}
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@23: 				seek(bufferStartInFile + newPos);
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@26: 			if (!buffer.hasRemaining()) {
tikhomirov@26: 				fill();
tikhomirov@26: 			}
tikhomirov@26: 			while (length > 0) {
tikhomirov@26: 				int tail = buffer.remaining();
tikhomirov@26: 				if (tail == 0) {
tikhomirov@26: 					throw new IOException(); // shall not happen provided stream contains expected data and no attempts to read past isEmpty() == true are made.
tikhomirov@26: 				}
tikhomirov@26: 				if (tail >= length) {
tikhomirov@26: 					buffer.get(buf, offset, length);
tikhomirov@10: 				} else {
tikhomirov@26: 					buffer.get(buf, offset, tail);
tikhomirov@26: 					fill();
tikhomirov@10: 				}
tikhomirov@26: 				offset += tail;
tikhomirov@26: 				length -= tail;
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: }