implement multi-page long value writing

git-svn-id: https://svn.code.sf.net/p/jackcess/code/jackcess/trunk@127 f203690c-595d-4dc9-a70b-905162fa7fd2

1 files changed, 18 insertions, 0 deletions

diff --git a/src/java/com/healthmarketscience/jackcess/PageChannel.java b/src/java/com/healthmarketscience/jackcess/PageChannel.java
index 0acaad8..3865394 100644
--- a/src/java/com/healthmarketscience/jackcess/PageChannel.java
+++ b/src/java/com/healthmarketscience/jackcess/PageChannel.java
@@ -44,6 +44,9 @@ public class PageChannel implements Channel {
   private static final Log LOG = LogFactory.getLog(PageChannel.class);
   
   static final int INVALID_PAGE_NUMBER = -1;
+
+  /** dummy buffer used when allocating new pages */
+  private static final ByteBuffer FORCE_BYTES = ByteBuffer.allocate(1);
   
   /** Global usage map always lives on page 1 */
   private static final int PAGE_GLOBAL_USAGE_MAP = 1;
@@ -113,6 +116,21 @@ public class PageChannel implements Channel {
     _globalUsageMap.removePageNumber(pageNumber);  //force is done here
     return pageNumber;
   }
+
+  /**
+   * Allocates a new page in the database.  Data in the page is undefined
+   * until it is written in a call to {@link #writePage}.
+   */
+  public int allocateNewPage() throws IOException {
+    long size = _channel.size();
+    FORCE_BYTES.rewind();
+    long offset = size + _format.PAGE_SIZE - FORCE_BYTES.remaining();
+    // this will force the file to be extended with mostly undefined bytes
+    _channel.write(FORCE_BYTES, offset);
+    int pageNumber = (int) (size / _format.PAGE_SIZE);
+    _globalUsageMap.removePageNumber(pageNumber);  //force is done here
+    return pageNumber;
+  }
   
   /**
    * @return Number of pages in the database