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1
50 package org.apache.avalon.excalibur.collections;
51
52
64 public final class VariableSizeBuffer implements Buffer
65 {
66 protected Object  [] m_buffer;
67 protected int m_head;
68 protected int m_tail;
69
70
74 public VariableSizeBuffer( int size )
75 {
76 m_buffer = new Object [ size + 1 ];
77 m_head = 0;
78 m_tail = 0;
79 }
80
81
89 public VariableSizeBuffer()
90 {
91 this( 32 );
92 }
93
94
97 public final boolean isEmpty()
98 {
99 return ( size() == 0 );
100 }
101
102
105 public final int size()
106 {
107 int size = 0;
108
109 if( m_tail < m_head )
110 {
111 size = m_buffer.length - m_head + m_tail;
112 }
113 else
114 {
115 size = m_tail - m_head;
116 }
117
118 return size;
119 }
120
121
124 public final void add( final Object o )
125 {
126 if( null == o )
127 {
128 throw new NullPointerException ( "Attempted to add null object to buffer" );
129 }
130
131 if( size() + 1 >= m_buffer.length )
132 {
133 Object [] tmp = new Object [ ( ( m_buffer.length - 1 ) * 2 ) + 1 ];
134
135 int j = 0;
136 for( int i = m_head; i != m_tail; )
137 {
138 tmp[ j ] = m_buffer[ i ];
139 m_buffer[ i ] = null;
140
141 j++;
142 i++;
143 if( i == m_buffer.length )
144 {
145 i = 0;
146 }
147 }
148
149 m_buffer = tmp;
150 m_head = 0;
151 m_tail = j;
152 }
153
154 m_buffer[ m_tail ] = o;
155 m_tail++;
156 if( m_tail >= m_buffer.length )
157 {
158 m_tail = 0;
159 }
160 }
161
162
165 public Object remove()
166 {
167 if( isEmpty() )
168 {
169 throw new BufferUnderflowException( "The buffer is already empty" );
170 }
171
172 Object element = m_buffer[ m_head ];
173
174 if( null != element )
175 {
176 m_buffer[ m_head ] = null;
177
178 m_head++;
179 if( m_head >= m_buffer.length )
180 {
181 m_head = 0;
182 }
183 }
184
185 return element;
186 }
187 }
188
189 |
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