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annotate src/com/tmate/hgkit/fs/DataAccess.java @ 26:71a9ba42cee8

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Memory-mapped files for bigger files. Defect reading number of bytes greater than size of the buffer fixed
author Artem Tikhomirov <tikhomirov.artem@gmail.com>
date Sun, 09 Jan 2011 15:59:54 +0100
parents 382cfe9463db
children 9429c7bd1920
rev   line source
10
382cfe9463db Dirstate parsing. DataAccess refactored to allow reuse and control over constants
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1 /*
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2 * Copyright (c) 2010 Artem Tikhomirov
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3 */
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4 package com.tmate.hgkit.fs;
382cfe9463db Dirstate parsing. DataAccess refactored to allow reuse and control over constants
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5
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6 import java.io.IOException;
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7
382cfe9463db Dirstate parsing. DataAccess refactored to allow reuse and control over constants
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8 /**
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9 * relevant parts of DataInput, non-stream nature (seek operation), explicit check for end of data.
382cfe9463db Dirstate parsing. DataAccess refactored to allow reuse and control over constants
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10 * convenient skip (+/- bytes)
382cfe9463db Dirstate parsing. DataAccess refactored to allow reuse and control over constants
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11 * Primary goal - effective file read, so that clients don't need to care whether to call few
382cfe9463db Dirstate parsing. DataAccess refactored to allow reuse and control over constants
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12 * distinct getInt() or readBytes(totalForFewInts) and parse themselves instead in an attempt to optimize.
382cfe9463db Dirstate parsing. DataAccess refactored to allow reuse and control over constants
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13 */
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14 public class DataAccess {
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15 public boolean isEmpty() {
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16 return true;
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17 }
382cfe9463db Dirstate parsing. DataAccess refactored to allow reuse and control over constants
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18 // absolute positioning
382cfe9463db Dirstate parsing. DataAccess refactored to allow reuse and control over constants
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19 public void seek(long offset) throws IOException {
382cfe9463db Dirstate parsing. DataAccess refactored to allow reuse and control over constants
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20 throw new UnsupportedOperationException();
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21 }
382cfe9463db Dirstate parsing. DataAccess refactored to allow reuse and control over constants
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22 // relative positioning
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23 public void skip(int bytes) throws IOException {
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24 throw new UnsupportedOperationException();
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25 }
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26 // shall be called once this object no longer needed
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27 public void done() {
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28 // no-op in this empty implementation
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29 }
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30 public int readInt() throws IOException {
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31 byte[] b = new byte[4];
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32 readBytes(b, 0, 4);
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33 return b[0] << 24 | (b[1] & 0xFF) << 16 | (b[2] & 0xFF) << 8 | (b[3] & 0xFF);
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34 }
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35 public long readLong() throws IOException {
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36 byte[] b = new byte[8];
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37 readBytes(b, 0, 8);
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38 int i1 = b[0] << 24 | (b[1] & 0xFF) << 16 | (b[2] & 0xFF) << 8 | (b[3] & 0xFF);
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39 int i2 = b[4] << 24 | (b[5] & 0xFF) << 16 | (b[6] & 0xFF) << 8 | (b[7] & 0xFF);
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40 return ((long) i1) << 32 | ((long) i2 & 0xFFFFFFFF);
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41 }
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42 public void readBytes(byte[] buf, int offset, int length) throws IOException {
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43 throw new UnsupportedOperationException();
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44 }
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45 public byte readByte() throws IOException {
382cfe9463db Dirstate parsing. DataAccess refactored to allow reuse and control over constants
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46 throw new UnsupportedOperationException();
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47 }
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48 }