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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"><head><meta http-equiv="content-type" content="text/html; charset=UTF-8" /><title>PieceTable xref</title><link type="text/css" rel="stylesheet" href="../../../../stylesheet.css" /></head><body><div id="overview"><a href="../../../../../apidocs/org/archive/util/ms/PieceTable.html">View Javadoc</a></div><pre><a name="1" href="#1">1</a> <em class="comment">/*<em class="comment"> PieceTable</em></em><a name="2" href="#2">2</a> <em class="comment">*</em><a name="3" href="#3">3</a> <em class="comment">* Created on September 12, 2006</em><a name="4" href="#4">4</a> <em class="comment">*</em><a name="5" href="#5">5</a> <em class="comment">* Copyright (C) 2006 Internet Archive.</em><a name="6" href="#6">6</a> <em class="comment">*</em><a name="7" href="#7">7</a> <em class="comment">* This file is part of the Heritrix web crawler (crawler.archive.org).</em><a name="8" href="#8">8</a> <em class="comment">*</em><a name="9" href="#9">9</a> <em class="comment">* Heritrix is free software; you can redistribute it and/or modify</em><a name="10" href="#10">10</a> <em class="comment">* it under the terms of the GNU Lesser Public License as published by</em><a name="11" href="#11">11</a> <em class="comment">* the Free Software Foundation; either version 2.1 of the License, or</em><a name="12" href="#12">12</a> <em class="comment">* any later version.</em><a name="13" href="#13">13</a> <em class="comment">*</em><a name="14" href="#14">14</a> <em class="comment">* Heritrix is distributed in the hope that it will be useful,</em><a name="15" href="#15">15</a> <em class="comment">* but WITHOUT ANY WARRANTY; without even the implied warranty of</em><a name="16" href="#16">16</a> <em class="comment">* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the</em><a name="17" href="#17">17</a> <em class="comment">* GNU Lesser Public License for more details.</em><a name="18" href="#18">18</a> <em class="comment">*</em><a name="19" href="#19">19</a> <em class="comment">* You should have received a copy of the GNU Lesser Public License</em><a name="20" href="#20">20</a> <em class="comment">* along with Heritrix; if not, write to the Free Software</em><a name="21" href="#21">21</a> <em class="comment">* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA</em><a name="22" href="#22">22</a> <em class="comment">*/</em><a name="23" href="#23">23</a> <strong>package</strong> <a href="../../../../org/archive/util/ms/package-summary.html">org.archive.util.ms</a>;<a name="24" href="#24">24</a> <a name="25" href="#25">25</a> <strong>import</strong> java.io.IOException;<a name="26" href="#26">26</a> <strong>import</strong> java.util.logging.Level;<a name="27" href="#27">27</a> <strong>import</strong> java.util.logging.Logger;<a name="28" href="#28">28</a> <a name="29" href="#29">29</a> <strong>import</strong> org.archive.io.BufferedSeekInputStream;<a name="30" href="#30">30</a> <strong>import</strong> org.archive.io.Endian;<a name="31" href="#31">31</a> <strong>import</strong> org.archive.io.OriginSeekInputStream;<a name="32" href="#32">32</a> <strong>import</strong> org.archive.io.SafeSeekInputStream;<a name="33" href="#33">33</a> <strong>import</strong> org.archive.io.SeekInputStream;<a name="34" href="#34">34</a> <a name="35" href="#35">35</a> <a name="36" href="#36">36</a> <em>/**<em>*</em></em><a name="37" href="#37">37</a> <em> * The piece table of a .doc file. </em><a name="38" href="#38">38</a> <em> * </em><a name="39" href="#39">39</a> <em> * <p>The piece table maps logical character positions of a document's text</em><a name="40" href="#40">40</a> <em> * stream to actual file stream positions. The piece table is stored as two</em><a name="41" href="#41">41</a> <em> * parallel arrays. The first array contains 32-bit integers representing</em><a name="42" href="#42">42</a> <em> * the logical character positions. The second array contains 64-bit data</em><a name="43" href="#43">43</a> <em> * structures that are mostly mysterious to me, except that they contain a</em><a name="44" href="#44">44</a> <em> * 32-bit subfile offset. The second array is stored immediately after the</em><a name="45" href="#45">45</a> <em> * first array. I call the first array the <i>charPos</i> array and the </em><a name="46" href="#46">46</a> <em> * second array the <i>filePos</i> array.</em><a name="47" href="#47">47</a> <em> * </em><a name="48" href="#48">48</a> <em> * <p>The arrays are preceded by a special tag byte (2), followed by the</em><a name="49" href="#49">49</a> <em> * combined size of both arrays in bytes. The number of piece table entries </em><a name="50" href="#50">50</a> <em> * must be deduced from this byte size. </em><a name="51" href="#51">51</a> <em> * </em><a name="52" href="#52">52</a> <em> * <p>Because of this bizarre structure, caching piece table entries is </em><a name="53" href="#53">53</a> <em> * something of a challenge. A single piece table entry is actually located</em><a name="54" href="#54">54</a> <em> * in two different file locations. If there are many piece table entries,</em><a name="55" href="#55">55</a> <em> * then the charPos and filePos information may be separated by many bytes,</em><a name="56" href="#56">56</a> <em> * potentially crossing block boundaries. The approach I took was to use</em><a name="57" href="#57">57</a> <em> * two different buffered streams. Up to n charPos offsets and n filePos</em><a name="58" href="#58">58</a> <em> * structures can be buffered in the two streams, preventing any file seeking</em><a name="59" href="#59">59</a> <em> * from occurring when looking up piece information. (File seeking must </em><a name="60" href="#60">60</a> <em> * still occur to jump from one piece to the next.)</em><a name="61" href="#61">61</a> <em> * </em><a name="62" href="#62">62</a> <em> * <p>Note that the vast majority of .doc files in the world will have exactly</em><a name="63" href="#63">63</a> <em> * 1 piece table entry, representing the complete text of the document. Only</em><a name="64" href="#64">64</a> <em> * those documents that were "fast-saved" should have multiple pieces.</em><a name="65" href="#65">65</a> <em> * </em><a name="66" href="#66">66</a> <em> * <p>Finally, the text contained in a .doc file can either contain 16-bit</em><a name="67" href="#67">67</a> <em> * unicode characters (charset UTF-16LE) or 8-bit CP1252 characters. One</em><a name="68" href="#68">68</a> <em> * .doc file can contain both kinds of pieces. Whether or not a piece is</em><a name="69" href="#69">69</a> <em> * Cp1252 is stored as a flag in the filePos value, bizarrely enough. If</em><a name="70" href="#70">70</a> <em> * the flag is set, then the actual file position is the filePos with the</em><a name="71" href="#71">71</a> <em> * flag cleared, then divided by 2.</em><a name="72" href="#72">72</a> <em> * </em><a name="73" href="#73">73</a> <em> * @author pjack</em><a name="74" href="#74">74</a> <em> */</em><a name="75" href="#75">75</a> <strong>class</strong> <a href="../../../../org/archive/util/ms/PieceTable.html">PieceTable</a> {<a name="76" href="#76">76</a> <a name="77" href="#77">77</a> <strong>final</strong> <strong>static</strong> Logger LOGGER<a name="78" href="#78">78</a> = Logger.getLogger(PieceTable.<strong>class</strong>.getName());<a name="79" href="#79">79</a> <a name="80" href="#80">80</a> <em>/**<em>* The bit that indicates if a piece uses Cp1252 or unicode. */</em></em><a name="81" href="#81">81</a> <strong>final</strong> <strong>static</strong> <strong>int</strong> CP1252_INDICATOR = 1 << 30;<a name="82" href="#82">82</a> <a name="83" href="#83">83</a> <em>/**<em>* The mask to use to clear the Cp1252 flag bit. */</em></em><a name="84" href="#84">84</a> <strong>final</strong> <strong>static</strong> <strong>int</strong> CP1252_MASK = ~(3 << 30);<a name="85" href="#85">85</a> <a name="86" href="#86">86</a> <em>/**<em>* The total number of pieces in the table. */</em></em><a name="87" href="#87">87</a> <strong>private</strong> <strong>int</strong> count;<a name="88" href="#88">88</a> <a name="89" href="#89">89</a> <em>/**<em>* The total number of characters in the text stream. */</em></em><a name="90" href="#90">90</a> <strong>private</strong> <strong>int</strong> maxCharPos;<a name="91" href="#91">91</a> <a name="92" href="#92">92</a> <em>/**<em>* The index of the current piece. */</em></em><a name="93" href="#93">93</a> <strong>private</strong> <strong>int</strong> current;<a name="94" href="#94">94</a> <a name="95" href="#95">95</a> <em>/**<em>* The most recently returned piece from this table. */</em></em><a name="96" href="#96">96</a> <strong>private</strong> <a href="../../../../org/archive/util/ms/Piece.html">Piece</a> currentPiece;<a name="97" href="#97">97</a> <a name="98" href="#98">98</a> <a name="99" href="#99">99</a> <em>/**<em>* The buffered stream that provides character position information. */</em></em><a name="100" href="#100">100</a> <strong>private</strong> <a href="../../../../org/archive/io/SeekInputStream.html">SeekInputStream</a> charPos;<a name="101" href="#101">101</a> <a name="102" href="#102">102</a> <em>/**<em>* The buffered stream that provides file pointer information. */</em></em><a name="103" href="#103">103</a> <strong>private</strong> <a href="../../../../org/archive/io/SeekInputStream.html">SeekInputStream</a> filePos;<a name="104" href="#104">104</a> <a name="105" href="#105">105</a> <a name="106" href="#106">106</a> <em>/**<em>*</em></em><a name="107" href="#107">107</a> <em> * Constructor.</em><a name="108" href="#108">108</a> <em> * </em><a name="109" href="#109">109</a> <em> * @param tableStream the stream containing the piece table</em><a name="110" href="#110">110</a> <em> * @param offset the starting offset of the piece table</em><a name="111" href="#111">111</a> <em> * @param maxCharPos the total number of characters in the document</em><a name="112" href="#112">112</a> <em> * @param cachedRecords the number of piece table entries to cache</em><a name="113" href="#113">113</a> <em> * @throws IOException if an IO error occurs</em><a name="114" href="#114">114</a> <em> */</em><a name="115" href="#115">115</a> <strong>public</strong> <a href="../../../../org/archive/util/ms/PieceTable.html">PieceTable</a>(<a href="../../../../org/archive/io/SeekInputStream.html">SeekInputStream</a> tableStream, <strong>int</strong> offset, <a name="116" href="#116">116</a> <strong>int</strong> maxCharPos, <strong>int</strong> cachedRecords) throws IOException {<a name="117" href="#117">117</a> tableStream.position(offset);<a name="118" href="#118">118</a> skipProperties(tableStream);<a name="119" href="#119">119</a> <strong>int</strong> sizeInBytes = Endian.littleInt(tableStream);<a name="120" href="#120">120</a> <strong>this</strong>.count = (sizeInBytes - 4) / 12;<a name="121" href="#121">121</a> cachedRecords = Math.min(cachedRecords, count);<a name="122" href="#122">122</a> <strong>long</strong> tp = tableStream.position() + 4;<a name="123" href="#123">123</a> <strong>long</strong> charPosStart = tp;<a name="124" href="#124">124</a> <strong>long</strong> filePosStart = tp + count * 4 + 2;<a name="125" href="#125">125</a> <a name="126" href="#126">126</a> <strong>this</strong>.filePos = wrap(tableStream, filePosStart, cachedRecords * 8);<a name="127" href="#127">127</a> <strong>this</strong>.charPos = wrap(tableStream, charPosStart, cachedRecords * 4);<a name="128" href="#128">128</a> <strong>this</strong>.maxCharPos = maxCharPos;<a name="129" href="#129">129</a> <a name="130" href="#130">130</a> <strong>if</strong> (LOGGER.isLoggable(Level.FINEST)) {<a name="131" href="#131">131</a> LOGGER.finest(<span class="string">"Size in bytes: "</span> + sizeInBytes);<a name="132" href="#132">132</a> LOGGER.finest(<span class="string">"Piece table count: "</span> + count);<a name="133" href="#133">133</a> <strong>for</strong> (Piece piece = next(); piece != <strong>null</strong>; piece = next()) {<a name="134" href="#134">134</a> LOGGER.finest(<span class="string">"#"</span> + current + <span class="string">": "</span> + piece.toString());<a name="135" href="#135">135</a> }<a name="136" href="#136">136</a> current = 0;<a name="137" href="#137">137</a> }<a name="138" href="#138">138</a> }<a name="139" href="#139">139</a> <a name="140" href="#140">140</a> ⌨️ 快捷键说明
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