Mercurial > jhg

annotate src/com/tmate/hgkit/fs/DataAccess.java @ 51:9429c7bd1920 wrap-data-access

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Try DataAccess to reach revision data instead of plain byte arrays
author Artem Tikhomirov <tikhomirov.artem@gmail.com>
date Sun, 16 Jan 2011 01:20:26 +0100
parents 382cfe9463db
children
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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;
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5
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6 import java.io.IOException;
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7
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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
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12 * distinct getInt() or readBytes(totalForFewInts) and parse themselves instead in an attempt to optimize.
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13 * Name: ByteSource? DataSource, DataInput, ByteInput
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14 */
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15 public class DataAccess {
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16 public boolean isEmpty() {
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17 return true;
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18 }
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19 public long length() {
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20 return 0;
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21 }
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22 // get this instance into initial state
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23 public void reset() throws IOException {
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24 // nop, empty instance is always in the initial state
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25 }
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26 // absolute positioning
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27 public void seek(long offset) throws IOException {
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28 throw new UnsupportedOperationException();
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29 }
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30 // relative positioning
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31 public void skip(int bytes) throws IOException {
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32 throw new UnsupportedOperationException();
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33 }
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34 // shall be called once this object no longer needed
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35 public void done() {
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36 // no-op in this empty implementation
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37 }
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38 public int readInt() throws IOException {
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39 byte[] b = new byte[4];
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40 readBytes(b, 0, 4);
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41 return b[0] << 24 | (b[1] & 0xFF) << 16 | (b[2] & 0xFF) << 8 | (b[3] & 0xFF);
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42 }
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43 public long readLong() throws IOException {
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44 byte[] b = new byte[8];
382cfe9463db Dirstate parsing. DataAccess refactored to allow reuse and control over constants
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45 readBytes(b, 0, 8);
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46 int i1 = b[0] << 24 | (b[1] & 0xFF) << 16 | (b[2] & 0xFF) << 8 | (b[3] & 0xFF);
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47 int i2 = b[4] << 24 | (b[5] & 0xFF) << 16 | (b[6] & 0xFF) << 8 | (b[7] & 0xFF);
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48 return ((long) i1) << 32 | ((long) i2 & 0xFFFFFFFF);
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49 }
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50 public void readBytes(byte[] buf, int offset, int length) throws IOException {
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51 throw new UnsupportedOperationException();
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52 }
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53 public byte readByte() throws IOException {
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54 throw new UnsupportedOperationException();
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55 }
51
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56
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57 // XXX decide whether may or may not change position in the DataAccess
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58 // FIXME exception handling is not right, just for the sake of quick test
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59 public byte[] byteArray() {
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60 byte[] rv = new byte[(int) length()];
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61 try {
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62 reset();
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63 readBytes(rv, 0, rv.length);
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64 } catch (IOException ex) {
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65 ex.printStackTrace();
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66 }
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67 return rv;
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68 }
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69 }