dbbuffer.html

数据库实现的一个源码包

          int pageID,
          <A HREF="../../neustore/base/DBPage.html" title="class in neustore.base">DBPage</A>&nbsp;dbpage)</CODE>

<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Writes a DBPage to buffer.</TD>
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<TD><B>Methods inherited from class java.lang.Object</B></TD>
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<TD><CODE>equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait</CODE></TD>
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<A NAME="DBBuffer(int, int)"><!-- --></A><H3>
DBBuffer</H3>
<PRE>
public <B>DBBuffer</B>(int&nbsp;bufferSize,
                int&nbsp;pageSize)</PRE>
<DL>
<DD>Opens an existing Database file.
<P>
<DT><B>Parameters:</B><DD><CODE>bufferSize</CODE> - total number of buffer pages<DD><CODE>pageSize</CODE> - page size</DL>

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<A NAME="getIOs()"><!-- --></A><H3>
getIOs</H3>
<PRE>
public int[] <B>getIOs</B>()</PRE>
<DL>
<DD>Reports the disk/buffer I/Os. There are four I/Os reported:
 <i>disk-read</i>, <i>disk-write</i>, <i>buffer-read</i> and
 <i>buffer-write</i>. They are stored in the integer array in
 the above order.
<P>
<DD><DL>

<DT><B>Returns:</B><DD>the four I/Os</DL>
</DD>
</DL>
<HR>

<A NAME="clearIOs()"><!-- --></A><H3>
clearIOs</H3>
<PRE>
public void <B>clearIOs</B>()</PRE>
<DL>
<DD>Resets the four counters <code>bufferReadIO</code>, etc.
<P>
<DD><DL>
</DL>
</DD>
</DL>
<HR>

<A NAME="readPage(java.io.RandomAccessFile, int)"><!-- --></A><H3>
readPage</H3>
<PRE>
public <A HREF="../../neustore/base/DBBufferReturnElement.html" title="class in neustore.base">DBBufferReturnElement</A> <B>readPage</B>(java.io.RandomAccessFile&nbsp;file,
                                      int&nbsp;pageID)
                               throws java.io.IOException</PRE>
<DL>
<DD>Returns a buffered page. If it is in buffer, returns it. Otherwise,
 loads it from disk and then returns it. Increases <code>bufferReadIO</code>.
<P>
<DD><DL>
<DT><B>Parameters:</B><DD><CODE>file</CODE> - which file<DD><CODE>pageID</CODE> - page ID
<DT><B>Returns:</B><DD>the buffered page
<DT><B>Throws:</B>
<DD><CODE>java.io.IOException</CODE></DL>
</DD>
</DL>
<HR>

<A NAME="writePage(java.io.RandomAccessFile, int, neustore.base.DBPage)"><!-- --></A><H3>
writePage</H3>
<PRE>
public void <B>writePage</B>(java.io.RandomAccessFile&nbsp;file,
                      int&nbsp;pageID,
                      <A HREF="../../neustore/base/DBPage.html" title="class in neustore.base">DBPage</A>&nbsp;dbpage)
               throws java.io.IOException</PRE>
<DL>
<DD>Writes a DBPage to buffer.
<P>
<DD><DL>
<DT><B>Parameters:</B><DD><CODE>file</CODE> - the file<DD><CODE>pageID</CODE> - the page ID<DD><CODE>dbpage</CODE> - the DBPage object
<DT><B>Throws:</B>
<DD><CODE>java.io.IOException</CODE></DL>
</DD>
</DL>
<HR>

<A NAME="pin(java.io.RandomAccessFile, int)"><!-- --></A><H3>
pin</H3>
<PRE>
public void <B>pin</B>(java.io.RandomAccessFile&nbsp;file,
                int&nbsp;pageID)</PRE>
<DL>
<DD>Pins a page. 
 Such pages can not be swapped out of the buffer. The pinCount 
 in DBBufferStoredElement is increased by 1.
<P>
<DD><DL>
<DT><B>Parameters:</B><DD><CODE>file</CODE> - the file<DD><CODE>pageID</CODE> - the page ID of the page to be pinned</DL>
</DD>
</DL>
<HR>

<A NAME="unpin(java.io.RandomAccessFile, int)"><!-- --></A><H3>
unpin</H3>
<PRE>
public void <B>unpin</B>(java.io.RandomAccessFile&nbsp;file,
                  int&nbsp;pageID)</PRE>
<DL>
<DD>Unpins a page. 
 The pinCount in DBBufferStoredElement is decreased by 1.
<P>
<DD><DL>
<DT><B>Parameters:</B><DD><CODE>file</CODE> - the file<DD><CODE>pageID</CODE> - the page ID of the page to be unpinned</DL>
</DD>
</DL>
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