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7IntAllocator
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90com.rabbitmq.utility</FONT>
91<BR>
92Class IntAllocator</H2>
93<PRE>
94java.lang.Object
95  <IMG SRC="../../../resources/inherit.gif" ALT="extended by "><B>com.rabbitmq.utility.IntAllocator</B>
96</PRE>
97<HR>
98<DL>
99<DT><PRE>public class <B>IntAllocator</B><DT>extends java.lang.Object</DL>
100</PRE>
101
102<P>
103A class for allocating integers from a given range that uses a
104 <CODE>BitSet</CODE> representation of the free integers.
105
106 <p/><strong>Concurrent Semantics:</strong><br />
107 This class is <b><i>not</i></b> thread safe.
108
109 <p/><b>Implementation notes:</b>
110 <br/>This was originally an ordered chain of non-overlapping Intervals,
111 together with a fixed size array cache for freed integers.
112 <br/><A HREF="../../../com/rabbitmq/utility/IntAllocator.html#reserve(int)"><CODE>reserve(int)</CODE></A> was expensive in this scheme, whereas in the
113 present implementation it is O(1), as is <A HREF="../../../com/rabbitmq/utility/IntAllocator.html#free(int)"><CODE>free(int)</CODE></A>.
114 <p>Although <A HREF="../../../com/rabbitmq/utility/IntAllocator.html#allocate()"><CODE>allocate()</CODE></A> is slightly slower than O(1) and in the
115 worst case could be O(N), the use of a "<code>lastIndex</code>" field
116 for starting the next scan for free integers means this is negligible.
117 </p>
118 <p>The data representation overhead is O(N) where N is the size of the
119 allocation range. One <code>long</code> is used for every 64 integers in the
120 range.
121 </p>
122 <p>Very little Object creation and destruction occurs in use.</p>
123<P>
124
125<P>
126<HR>
127
128<P>
129
130<!-- ======== CONSTRUCTOR SUMMARY ======== -->
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135<TH ALIGN="left" COLSPAN="2"><FONT SIZE="+2">
136<B>Constructor Summary</B></FONT></TH>
137</TR>
138<TR BGCOLOR="white" CLASS="TableRowColor">
139<TD><CODE><B><A HREF="../../../com/rabbitmq/utility/IntAllocator.html#IntAllocator(int, int)">IntAllocator</A></B>(int&nbsp;bottom,
140             int&nbsp;top)</CODE>
141
142<BR>
143&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Creates an IntAllocator allocating integer IDs within the
144 inclusive range [<code>bottom</code>, <code>top</code>].</TD>
145</TR>
146</TABLE>
147&nbsp;
148<!-- ========== METHOD SUMMARY =========== -->
149
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154<B>Method Summary</B></FONT></TH>
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157<TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1">
158<CODE>&nbsp;int</CODE></FONT></TD>
159<TD><CODE><B><A HREF="../../../com/rabbitmq/utility/IntAllocator.html#allocate()">allocate</A></B>()</CODE>
160
161<BR>
162&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Allocate an unallocated integer from the range, or return -1 if no
163 more integers are available.</TD>
164</TR>
165<TR BGCOLOR="white" CLASS="TableRowColor">
166<TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1">
167<CODE>&nbsp;void</CODE></FONT></TD>
168<TD><CODE><B><A HREF="../../../com/rabbitmq/utility/IntAllocator.html#free(int)">free</A></B>(int&nbsp;reservation)</CODE>
169
170<BR>
171&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Make the provided integer available for allocation again.</TD>
172</TR>
173<TR BGCOLOR="white" CLASS="TableRowColor">
174<TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1">
175<CODE>&nbsp;boolean</CODE></FONT></TD>
176<TD><CODE><B><A HREF="../../../com/rabbitmq/utility/IntAllocator.html#reserve(int)">reserve</A></B>(int&nbsp;reservation)</CODE>
177
178<BR>
179&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Attempt to reserve the provided ID as if it had been allocated.</TD>
180</TR>
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182<TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1">
183<CODE>&nbsp;java.lang.String</CODE></FONT></TD>
184<TD><CODE><B><A HREF="../../../com/rabbitmq/utility/IntAllocator.html#toString()">toString</A></B>()</CODE>
185
186<BR>
187&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</TD>
188</TR>
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193<TH ALIGN="left"><B>Methods inherited from class java.lang.Object</B></TH>
194</TR>
195<TR BGCOLOR="white" CLASS="TableRowColor">
196<TD><CODE>clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait</CODE></TD>
197</TR>
198</TABLE>
199&nbsp;
200<P>
201
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207<TH ALIGN="left" COLSPAN="1"><FONT SIZE="+2">
208<B>Constructor Detail</B></FONT></TH>
209</TR>
210</TABLE>
211
212<A NAME="IntAllocator(int, int)"><!-- --></A><H3>
213IntAllocator</H3>
214<PRE>
215public <B>IntAllocator</B>(int&nbsp;bottom,
216                    int&nbsp;top)</PRE>
217<DL>
218<DD>Creates an IntAllocator allocating integer IDs within the
219 inclusive range [<code>bottom</code>, <code>top</code>].
220<P>
221<DL>
222<DT><B>Parameters:</B><DD><CODE>bottom</CODE> - lower end of range<DD><CODE>top</CODE> - upper end of range (inclusive)</DL>
223</DL>
224
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231<B>Method Detail</B></FONT></TH>
232</TR>
233</TABLE>
234
235<A NAME="allocate()"><!-- --></A><H3>
236allocate</H3>
237<PRE>
238public int <B>allocate</B>()</PRE>
239<DL>
240<DD>Allocate an unallocated integer from the range, or return -1 if no
241 more integers are available.
242<P>
243<DD><DL>
244
245<DT><B>Returns:</B><DD>the allocated integer, or -1</DL>
246</DD>
247</DL>
248<HR>
249
250<A NAME="free(int)"><!-- --></A><H3>
251free</H3>
252<PRE>
253public void <B>free</B>(int&nbsp;reservation)</PRE>
254<DL>
255<DD>Make the provided integer available for allocation again. This operation
256 runs in O(1) time.
257 <br/>No error checking is performed, so if you double free or free an
258 integer that was not originally allocated the results are undefined.
259<P>
260<DD><DL>
261<DT><B>Parameters:</B><DD><CODE>reservation</CODE> - the previously allocated integer to free</DL>
262</DD>
263</DL>
264<HR>
265
266<A NAME="reserve(int)"><!-- --></A><H3>
267reserve</H3>
268<PRE>
269public boolean <B>reserve</B>(int&nbsp;reservation)</PRE>
270<DL>
271<DD>Attempt to reserve the provided ID as if it had been allocated. Returns
272 true if it is available, false otherwise.
273 <br/>
274 This operation runs in O(1) time.
275<P>
276<DD><DL>
277<DT><B>Parameters:</B><DD><CODE>reservation</CODE> - the integer to be allocated, if possible
278<DT><B>Returns:</B><DD><code><b>true</b></code> if allocated, <code><b>false</b></code>
279 if already allocated</DL>
280</DD>
281</DL>
282<HR>
283
284<A NAME="toString()"><!-- --></A><H3>
285toString</H3>
286<PRE>
287public java.lang.String <B>toString</B>()</PRE>
288<DL>
289<DD><DL>
290<DT><B>Overrides:</B><DD><CODE>toString</CODE> in class <CODE>java.lang.Object</CODE></DL>
291</DD>
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