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<pre><span class="sourceLineNo">001</span>/*<a name="line.1"></a>
<span class="sourceLineNo">002</span> * Copyright Aduna (http://www.aduna-software.com/) (c) 2008-2009.<a name="line.2"></a>
<span class="sourceLineNo">003</span> *<a name="line.3"></a>
<span class="sourceLineNo">004</span> * Licensed under the Aduna BSD-style license.<a name="line.4"></a>
<span class="sourceLineNo">005</span> */<a name="line.5"></a>
<span class="sourceLineNo">006</span>package com.fluidops.fedx.evaluation.iterator;<a name="line.6"></a>
<span class="sourceLineNo">007</span><a name="line.7"></a>
<span class="sourceLineNo">008</span><a name="line.8"></a>
<span class="sourceLineNo">009</span><a name="line.9"></a>
<span class="sourceLineNo">010</span>import info.aduna.iteration.LookAheadIteration;<a name="line.10"></a>
<span class="sourceLineNo">011</span><a name="line.11"></a>
<span class="sourceLineNo">012</span>import java.util.ArrayList;<a name="line.12"></a>
<span class="sourceLineNo">013</span>import java.util.Arrays;<a name="line.13"></a>
<span class="sourceLineNo">014</span>import java.util.LinkedList;<a name="line.14"></a>
<span class="sourceLineNo">015</span>import java.util.List;<a name="line.15"></a>
<span class="sourceLineNo">016</span>import java.util.Queue;<a name="line.16"></a>
<span class="sourceLineNo">017</span>import java.util.concurrent.ArrayBlockingQueue;<a name="line.17"></a>
<span class="sourceLineNo">018</span>import java.util.concurrent.BlockingQueue;<a name="line.18"></a>
<span class="sourceLineNo">019</span><a name="line.19"></a>
<span class="sourceLineNo">020</span>import org.openrdf.query.QueryEvaluationException;<a name="line.20"></a>
<span class="sourceLineNo">021</span><a name="line.21"></a>
<span class="sourceLineNo">022</span>/**<a name="line.22"></a>
<span class="sourceLineNo">023</span> * Makes working with a queue easier by adding the methods {@link #done()} and<a name="line.23"></a>
<span class="sourceLineNo">024</span> * {@link #toss(Exception)} and automatically converting the exception into a<a name="line.24"></a>
<span class="sourceLineNo">025</span> * QueryEvaluationException with an appropriate stack trace.<a name="line.25"></a>
<span class="sourceLineNo">026</span> * <a name="line.26"></a>
<span class="sourceLineNo">027</span> * @author James Leigh<a name="line.27"></a>
<span class="sourceLineNo">028</span> */<a name="line.28"></a>
<span class="sourceLineNo">029</span>public class QueueCursor&lt;E&gt; extends LookAheadIteration&lt;E, QueryEvaluationException&gt; {<a name="line.29"></a>
<span class="sourceLineNo">030</span><a name="line.30"></a>
<span class="sourceLineNo">031</span>        private volatile boolean done;<a name="line.31"></a>
<span class="sourceLineNo">032</span><a name="line.32"></a>
<span class="sourceLineNo">033</span>        private BlockingQueue&lt;E&gt; queue;<a name="line.33"></a>
<span class="sourceLineNo">034</span><a name="line.34"></a>
<span class="sourceLineNo">035</span>        private E afterLast = createAfterLast();<a name="line.35"></a>
<span class="sourceLineNo">036</span><a name="line.36"></a>
<span class="sourceLineNo">037</span>        private volatile Queue&lt;Throwable&gt; exceptions = new LinkedList&lt;Throwable&gt;();<a name="line.37"></a>
<span class="sourceLineNo">038</span><a name="line.38"></a>
<span class="sourceLineNo">039</span>        /**<a name="line.39"></a>
<span class="sourceLineNo">040</span>         * Creates an &lt;tt&gt;QueueCursor&lt;/tt&gt; with the given (fixed) capacity and<a name="line.40"></a>
<span class="sourceLineNo">041</span>         * default access policy.<a name="line.41"></a>
<span class="sourceLineNo">042</span>         * <a name="line.42"></a>
<span class="sourceLineNo">043</span>         * @param capacity<a name="line.43"></a>
<span class="sourceLineNo">044</span>         *        the capacity of this queue<a name="line.44"></a>
<span class="sourceLineNo">045</span>         */<a name="line.45"></a>
<span class="sourceLineNo">046</span>        public QueueCursor(int capacity) {<a name="line.46"></a>
<span class="sourceLineNo">047</span>                this(capacity, false);<a name="line.47"></a>
<span class="sourceLineNo">048</span>        }<a name="line.48"></a>
<span class="sourceLineNo">049</span><a name="line.49"></a>
<span class="sourceLineNo">050</span>        /**<a name="line.50"></a>
<span class="sourceLineNo">051</span>         * Creates an &lt;tt&gt;QueueCursor&lt;/tt&gt; with the given (fixed) capacity and the<a name="line.51"></a>
<span class="sourceLineNo">052</span>         * specified access policy.<a name="line.52"></a>
<span class="sourceLineNo">053</span>         * <a name="line.53"></a>
<span class="sourceLineNo">054</span>         * @param capacity<a name="line.54"></a>
<span class="sourceLineNo">055</span>         *        the capacity of this queue<a name="line.55"></a>
<span class="sourceLineNo">056</span>         * @param fair<a name="line.56"></a>
<span class="sourceLineNo">057</span>         *        if &lt;tt&gt;true&lt;/tt&gt; then queue accesses for threads blocked on<a name="line.57"></a>
<span class="sourceLineNo">058</span>         *        insertion or removal, are processed in FIFO order; if<a name="line.58"></a>
<span class="sourceLineNo">059</span>         *        &lt;tt&gt;false&lt;/tt&gt; the access order is unspecified.<a name="line.59"></a>
<span class="sourceLineNo">060</span>         */<a name="line.60"></a>
<span class="sourceLineNo">061</span>        public QueueCursor(int capacity, boolean fair) {<a name="line.61"></a>
<span class="sourceLineNo">062</span>                this.queue = new ArrayBlockingQueue&lt;E&gt;(capacity, fair);<a name="line.62"></a>
<span class="sourceLineNo">063</span>        }<a name="line.63"></a>
<span class="sourceLineNo">064</span><a name="line.64"></a>
<span class="sourceLineNo">065</span>        /**<a name="line.65"></a>
<span class="sourceLineNo">066</span>         * The next time {@link #next()} is called this exception will be thrown. If<a name="line.66"></a>
<span class="sourceLineNo">067</span>         * it is not a QueryEvaluationException or RuntimeException it will be wrapped in a<a name="line.67"></a>
<span class="sourceLineNo">068</span>         * QueryEvaluationException.<a name="line.68"></a>
<span class="sourceLineNo">069</span>         */<a name="line.69"></a>
<span class="sourceLineNo">070</span>        public void toss(Exception exception) {<a name="line.70"></a>
<span class="sourceLineNo">071</span>                synchronized (exceptions) {<a name="line.71"></a>
<span class="sourceLineNo">072</span>                        exceptions.add(exception);<a name="line.72"></a>
<span class="sourceLineNo">073</span>                }<a name="line.73"></a>
<span class="sourceLineNo">074</span>        }<a name="line.74"></a>
<span class="sourceLineNo">075</span><a name="line.75"></a>
<span class="sourceLineNo">076</span>        /**<a name="line.76"></a>
<span class="sourceLineNo">077</span>         * Adds another item to the queue, blocking while the queue is full.<a name="line.77"></a>
<span class="sourceLineNo">078</span>         */<a name="line.78"></a>
<span class="sourceLineNo">079</span>        public void put(E st)<a name="line.79"></a>
<span class="sourceLineNo">080</span>                throws InterruptedException<a name="line.80"></a>
<span class="sourceLineNo">081</span>        {<a name="line.81"></a>
<span class="sourceLineNo">082</span>                queue.put(st);<a name="line.82"></a>
<span class="sourceLineNo">083</span>        }<a name="line.83"></a>
<span class="sourceLineNo">084</span><a name="line.84"></a>
<span class="sourceLineNo">085</span>        /**<a name="line.85"></a>
<span class="sourceLineNo">086</span>         * Indicates the method {@link #put(Object)} will not be called in the queue<a name="line.86"></a>
<span class="sourceLineNo">087</span>         * anymore.<a name="line.87"></a>
<span class="sourceLineNo">088</span>         */<a name="line.88"></a>
<span class="sourceLineNo">089</span>        public void done() {<a name="line.89"></a>
<span class="sourceLineNo">090</span>                done = true;<a name="line.90"></a>
<span class="sourceLineNo">091</span>                try {<a name="line.91"></a>
<span class="sourceLineNo">092</span>                        queue.add(afterLast);<a name="line.92"></a>
<span class="sourceLineNo">093</span>                }<a name="line.93"></a>
<span class="sourceLineNo">094</span>                catch (IllegalStateException e) {<a name="line.94"></a>
<span class="sourceLineNo">095</span>                        // no thread is waiting on this queue anyway<a name="line.95"></a>
<span class="sourceLineNo">096</span>                }<a name="line.96"></a>
<span class="sourceLineNo">097</span>        }<a name="line.97"></a>
<span class="sourceLineNo">098</span><a name="line.98"></a>
<span class="sourceLineNo">099</span>        /**<a name="line.99"></a>
<span class="sourceLineNo">100</span>         * Returns the next item in the queue or throws an exception.<a name="line.100"></a>
<span class="sourceLineNo">101</span>         */<a name="line.101"></a>
<span class="sourceLineNo">102</span>        @Override<a name="line.102"></a>
<span class="sourceLineNo">103</span>        public E getNextElement()<a name="line.103"></a>
<span class="sourceLineNo">104</span>                throws QueryEvaluationException<a name="line.104"></a>
<span class="sourceLineNo">105</span>        {<a name="line.105"></a>
<span class="sourceLineNo">106</span>                try {<a name="line.106"></a>
<span class="sourceLineNo">107</span>                        checkException();<a name="line.107"></a>
<span class="sourceLineNo">108</span>                        E take;<a name="line.108"></a>
<span class="sourceLineNo">109</span>                        if (done) {<a name="line.109"></a>
<span class="sourceLineNo">110</span>                                take = queue.poll();<a name="line.110"></a>
<span class="sourceLineNo">111</span>                        }<a name="line.111"></a>
<span class="sourceLineNo">112</span>                        else {<a name="line.112"></a>
<span class="sourceLineNo">113</span>                                take = queue.take();<a name="line.113"></a>
<span class="sourceLineNo">114</span>                                if (done) {<a name="line.114"></a>
<span class="sourceLineNo">115</span>                                        done(); // in case the queue was full before<a name="line.115"></a>
<span class="sourceLineNo">116</span>                                }<a name="line.116"></a>
<span class="sourceLineNo">117</span>                        }<a name="line.117"></a>
<span class="sourceLineNo">118</span>                        if (isAfterLast(take)) {<a name="line.118"></a>
<span class="sourceLineNo">119</span>                                checkException();<a name="line.119"></a>
<span class="sourceLineNo">120</span>                                done(); // put afterLast back for others<a name="line.120"></a>
<span class="sourceLineNo">121</span>                                return null;<a name="line.121"></a>
<span class="sourceLineNo">122</span>                        }<a name="line.122"></a>
<span class="sourceLineNo">123</span>                        return take;<a name="line.123"></a>
<span class="sourceLineNo">124</span>                }<a name="line.124"></a>
<span class="sourceLineNo">125</span>                catch (InterruptedException e) {<a name="line.125"></a>
<span class="sourceLineNo">126</span>                        checkException();<a name="line.126"></a>
<span class="sourceLineNo">127</span>                        throw new QueryEvaluationException(e);<a name="line.127"></a>
<span class="sourceLineNo">128</span>                }<a name="line.128"></a>
<span class="sourceLineNo">129</span>        }<a name="line.129"></a>
<span class="sourceLineNo">130</span><a name="line.130"></a>
<span class="sourceLineNo">131</span>        @Override<a name="line.131"></a>
<span class="sourceLineNo">132</span>        public void handleClose()<a name="line.132"></a>
<span class="sourceLineNo">133</span>                throws QueryEvaluationException<a name="line.133"></a>
<span class="sourceLineNo">134</span>        {<a name="line.134"></a>
<span class="sourceLineNo">135</span>                checkException();<a name="line.135"></a>
<span class="sourceLineNo">136</span>        }<a name="line.136"></a>
<span class="sourceLineNo">137</span>        public void checkException()<a name="line.137"></a>
<span class="sourceLineNo">138</span>                throws QueryEvaluationException<a name="line.138"></a>
<span class="sourceLineNo">139</span>        {<a name="line.139"></a>
<span class="sourceLineNo">140</span>                synchronized (exceptions) {<a name="line.140"></a>
<span class="sourceLineNo">141</span>                        if (!exceptions.isEmpty()) {<a name="line.141"></a>
<span class="sourceLineNo">142</span>                                try {<a name="line.142"></a>
<span class="sourceLineNo">143</span>                                        throw exceptions.remove();<a name="line.143"></a>
<span class="sourceLineNo">144</span>                                }<a name="line.144"></a>
<span class="sourceLineNo">145</span>                                catch (QueryEvaluationException e) {<a name="line.145"></a>
<span class="sourceLineNo">146</span>                                        List&lt;StackTraceElement&gt; stack = new ArrayList&lt;StackTraceElement&gt;();<a name="line.146"></a>
<span class="sourceLineNo">147</span>                                        stack.addAll(Arrays.asList(e.getStackTrace()));<a name="line.147"></a>
<span class="sourceLineNo">148</span>                                        StackTraceElement[] thisStack = new Throwable().getStackTrace();<a name="line.148"></a>
<span class="sourceLineNo">149</span>                                        stack.addAll(Arrays.asList(thisStack).subList(1, thisStack.length));<a name="line.149"></a>
<span class="sourceLineNo">150</span>                                        e.setStackTrace(stack.toArray(new StackTraceElement[stack.size()]));<a name="line.150"></a>
<span class="sourceLineNo">151</span>                                        throw e;<a name="line.151"></a>
<span class="sourceLineNo">152</span>                                }<a name="line.152"></a>
<span class="sourceLineNo">153</span>                                catch (RuntimeException e) {<a name="line.153"></a>
<span class="sourceLineNo">154</span>                                        List&lt;StackTraceElement&gt; stack = new ArrayList&lt;StackTraceElement&gt;();<a name="line.154"></a>
<span class="sourceLineNo">155</span>                                        stack.addAll(Arrays.asList(e.getStackTrace()));<a name="line.155"></a>
<span class="sourceLineNo">156</span>                                        StackTraceElement[] thisStack = new Throwable().getStackTrace();<a name="line.156"></a>
<span class="sourceLineNo">157</span>                                        stack.addAll(Arrays.asList(thisStack));<a name="line.157"></a>
<span class="sourceLineNo">158</span>                                        e.setStackTrace(stack.toArray(new StackTraceElement[stack.size()]));<a name="line.158"></a>
<span class="sourceLineNo">159</span>                                        throw e;<a name="line.159"></a>
<span class="sourceLineNo">160</span>                                }<a name="line.160"></a>
<span class="sourceLineNo">161</span>                                catch (Throwable e) {<a name="line.161"></a>
<span class="sourceLineNo">162</span>                                        throw new QueryEvaluationException(e);<a name="line.162"></a>
<span class="sourceLineNo">163</span>                                }<a name="line.163"></a>
<span class="sourceLineNo">164</span>                        }<a name="line.164"></a>
<span class="sourceLineNo">165</span>                }<a name="line.165"></a>
<span class="sourceLineNo">166</span>        }<a name="line.166"></a>
<span class="sourceLineNo">167</span><a name="line.167"></a>
<span class="sourceLineNo">168</span>        private boolean isAfterLast(E take) {<a name="line.168"></a>
<span class="sourceLineNo">169</span>                return take == null || take == afterLast;<a name="line.169"></a>
<span class="sourceLineNo">170</span>        }<a name="line.170"></a>
<span class="sourceLineNo">171</span><a name="line.171"></a>
<span class="sourceLineNo">172</span>        @SuppressWarnings("unchecked")<a name="line.172"></a>
<span class="sourceLineNo">173</span>        private E createAfterLast() {<a name="line.173"></a>
<span class="sourceLineNo">174</span>                return (E)new Object();<a name="line.174"></a>
<span class="sourceLineNo">175</span>        }<a name="line.175"></a>
<span class="sourceLineNo">176</span><a name="line.176"></a>
<span class="sourceLineNo">177</span>}<a name="line.177"></a>




























































</pre>
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