PLT Utilities Test Coverage (plt-20120304-r5436)

Clover coverage report - PLT Utilities Test Coverage (plt-20120304-r5436)

Coverage timestamp: Sat Mar 3 2012 22:01:56 CST

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file stats:	LOC:	161		Methods:	12
	NCLOC:	52		Classes:	1

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ExpandingBuffer.java

1		/BEGIN_COPYRIGHT_BLOCK
2
3		PLT Utilities BSD License
4
5		Copyright (c) 2007-2010 JavaPLT group at Rice University
6		All rights reserved.
7
8		Developed by: Java Programming Languages Team
9		Rice University
10		http://www.cs.rice.edu/~javaplt/
11
12		Redistribution and use in source and binary forms, with or without modification, are permitted
13		provided that the following conditions are met:
14
15		- Redistributions of source code must retain the above copyright notice, this list of conditions
16		and the following disclaimer.
17		- Redistributions in binary form must reproduce the above copyright notice, this list of
18		conditions and the following disclaimer in the documentation and/or other materials provided
19		with the distribution.
20		- Neither the name of the JavaPLT group, Rice University, nor the names of the library's
21		contributors may be used to endorse or promote products derived from this software without
22		specific prior written permission.
23
24		THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR
25		IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
26		FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS AND
27		CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
28		DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
29		DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER
30		IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
31		OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
32
33		END_COPYRIGHT_BLOCK/
34
35		package edu.rice.cs.plt.io;
36
37		import java.io.Serializable;
38		import java.util.LinkedList;
39
40		/**
41		* Abstraction of {@link ExpandingByteBuffer} and {@link ExpandingCharBuffer} to manage
42		* indices and bookeeping for these buffers from a single control point. In general, this
43		* class represents an expandable and thread safe buffer of elements of some type. {@code T} is the
44		* type of a sequence of these elements of fixed length {@link #BUFFER_SIZE}. Subclasses are responsible
45		* for managing reading and writing, but need not interact directly with the expanding queue
46		* of {@code T}s, nor with the indices used to manage this queue. Instead, the methods in
47		* this class provide the necessary tools. Synchronization should occur on the ExpandingBuffer
48		* object to prevent conflicts between threads before invoking any of this class's helper methods.
49		*/
50		public abstract class ExpandingBuffer<T> implements Serializable {
51
52		protected static final int BUFFER_SIZE = 1024;
53
54		private final LinkedList<T> _buffers;
55
56		/*
57		* The indices below are assumed to be positive longs. This assertion is not checked, and they
58		* will eventually wrap around, but this assumption holds for over 8 exabytes (8 million terabytes)
59		* of data (assuming 1 byte per element).
60		*/
61
62		/**
63		* The virtual index of {@code _buffers.getFirst()[0]} (or {@code _nextBuffer} if {@code _buffers}
64		* is empty)
65		*/
66		private long _base;
67
68		/**
69		* The virtual index of the beginning of the next buffer to be allocated -- {@code BUFFER_SIZE} after
70		* {@code _buffers.getLast()} ({@code _nextBuffer >= _base})
71		*/
72		private long _nextBuffer;
73
74		/**
75		* The virtual index of the first character in the virtual buffer ({@code _first >= _base},
76		* {@code _first <= _last})
77		*/
78		private long _first;
79
80		/**
81		* The virtual index after the last character in the virtual buffer ({@code _last >= _first},
82		* {@code _last <= _nextBuffer})
83		*/
84		private long _last;
85
86	0	public ExpandingBuffer() {
87	0	_buffers = new LinkedList<T>();
88	0	_base = 0l;
89	0	_nextBuffer = 0l;
90	0	_first = 0l;
91	0	_last = 0l;
92		}
93
94		/** Create a fixed-size sub-buffer */
95		protected abstract T allocateBuffer(int size);
96
97		/**
98		* @return the size of the buffer
99		*/
100	0	public synchronized long size() {
101	0	return _last - _first;
102		}
103
104	0	public synchronized boolean isEmpty() {
105	0	return _first == _last;
106		}
107
108
109		/**
110		* Allocate space in the buffer if none is available. Ensures that there is room for at least
111		* one new element (and that {@code _buffers} is nonempty). Should be called <em>before</em>
112		* a write is attempted.
113		* @return The amount of space now available at the end of the buffer ({@code > 0})
114		*/
115	0	protected int allocate() {
116	0	if (_last == _nextBuffer) {
117	0	_buffers.addLast(allocateBuffer(BUFFER_SIZE));
118	0	_nextBuffer += BUFFER_SIZE;
119	0	return BUFFER_SIZE;
120		}
121	0	else { return (int) (_nextBuffer - _last); }
122		}
123
124		/** Determine the number of buffered elements located in {@code _buffers.getFirst()} */
125	0	protected int elementsInFirstBuffer() {
126	0	long secondBuffer = _base + BUFFER_SIZE;
127	0	return (int) (((secondBuffer > _last) ? _last : secondBuffer) - _base);
128		}
129
130		/**
131		* Deallocate the first buffer if it is no longer needed. Return true if deallocation took place.
132		* Should be called <em>after</em> a read occurs.
133		*/
134	0	protected boolean deallocate() {
135	0	long secondBuffer = _base + BUFFER_SIZE;
136	0	if (_first >= secondBuffer) {
137	0	_buffers.removeFirst();
138	0	_base = secondBuffer;
139	0	return true;
140		}
141	0	else { return false; }
142		}
143
144		/** Access the first buffer (assuming it exists) */
145	0	protected T firstBuffer() { return _buffers.getFirst(); }
146
147		/** Calculate the first valid index in {@code firstBuffer()} (assuming it exists) */
148	0	protected int firstIndex() { return (int) (_first - _base); }
149
150		/** Access the last buffer (assuming it exists) */
151	0	protected T lastBuffer() { return _buffers.getLast(); }
152
153		/** Calculate the index after the last valid element in {@code lastBuffer()} (assuming it exists) */
154	0	protected int lastIndex() { return (int) (_last - (_nextBuffer - BUFFER_SIZE)); }
155
156		/** Adjust the indices after writing the given number of elements. */
157	0	protected void recordWrite(long written) { _last += written; }
158
159		/** Adjust the indices after reading the given number of elements. */
160	0	protected void recordRead(long read) { _first += read; }
161		}