[Mulgara-svn] r871 - in projects/xa2/object-pool/src: . scheduler

[andrae at mulgara.org]

Author: andrae
Date: 2008-04-30 01:59:06 -0700 (Wed, 30 Apr 2008)
New Revision: 871

Added:
   projects/xa2/object-pool/src/scheduler/
   projects/xa2/object-pool/src/scheduler/Block.java
   projects/xa2/object-pool/src/scheduler/FileCache.java
   projects/xa2/object-pool/src/scheduler/FileHandle.java
   projects/xa2/object-pool/src/scheduler/FileHandleFactory.java
   projects/xa2/object-pool/src/scheduler/IOScheduler.java
Log:
Incomplete initial cut at an io-scheduler sufficient to start work on ISAM-Tree.



Added: projects/xa2/object-pool/src/scheduler/Block.java
===================================================================
--- projects/xa2/object-pool/src/scheduler/Block.java	                        (rev 0)
+++ projects/xa2/object-pool/src/scheduler/Block.java	2008-04-30 08:59:06 UTC (rev 871)
@@ -0,0 +1,28 @@
+/*
+ * Copyright Topaz Foundation 2008
+ * Author Andrae Muys
+ * Date 30th April 2008
+ */
+package scheduler;
+
+import java.lang.ref.SoftReference;
+import java.util.HashMap;
+import java.util.Map;
+
+public class Block {
+  private FileHandle handle;
+  private Long position;
+
+  public Block(FileHandle handle, Long position) {
+    this.handle = handle;
+    this.position = position;
+  }
+
+  public FileHandle getHandle() {
+    return handle;
+  }
+
+  public Long getPosition() {
+    return position;
+  }
+}

Added: projects/xa2/object-pool/src/scheduler/FileCache.java
===================================================================
--- projects/xa2/object-pool/src/scheduler/FileCache.java	                        (rev 0)
+++ projects/xa2/object-pool/src/scheduler/FileCache.java	2008-04-30 08:59:06 UTC (rev 871)
@@ -0,0 +1,51 @@
+/*
+ * Copyright Topaz Foundation 2008
+ * Author Andrae Muys
+ * Date 30th April 2008
+ */
+package scheduler;
+
+import java.io.File;
+import java.ref.SoftReference;
+import java.util.WeakHashMap;
+
+public class FileCache {
+  private FileHandle handle;
+  // The Block object is required to maintain a strong reference to the Long key obj.
+  private WeakHashMap<Long, SoftReference<Block>> blockCache;
+
+  private static final int LOG2_BLOCK_SIZE = 21;
+
+  FileCache(FileHandle handle) {
+    this.handle = handle;
+    this.blockCache = new WeakHashMap
+  }
+
+  public File getFile() {
+    return file;
+  }
+
+  public Block getBlock(long position) {
+    Long pos = new Long(position >> handle.log2BlockSize());
+    SoftReference<Block> blockRef = blockCache.get(pos);
+    if (blockRef != null) {
+      Block block = blockRef.get();
+      if (block != null) {
+
+        return block;
+      } else {
+        // Note that the combination of soft and weak references means that we need this double check.
+        // Because soft-references prevent weak-references from being reaped it is legal for the gc to reap
+        // the block and the key in subsequent passes.
+        // Here we remove the stale entry so it can be reentered.
+        blockCache.remove(pos);
+      }
+    }
+    Block newBlock = handle.getBlock(pos);
+    // Note we use the newBlock's position, not pos - this ensures the map's entry will be retained until
+    // memory pressure forces the SoftReference to be reaped.
+    blockCache.put(newBlock.getPosition(), new SoftReference(newBlock));
+
+    return newBlock;
+  }
+}

Added: projects/xa2/object-pool/src/scheduler/FileHandle.java
===================================================================
--- projects/xa2/object-pool/src/scheduler/FileHandle.java	                        (rev 0)
+++ projects/xa2/object-pool/src/scheduler/FileHandle.java	2008-04-30 08:59:06 UTC (rev 871)
@@ -0,0 +1,40 @@
+/*
+ * Copyright Topaz Foundation 2008
+ * Author Andrae Muys
+ * Date 30th April 2008
+ */
+package scheduler;
+
+import java.io.File;
+
+public class FileHandle {
+  private File file;
+  private FileHandleCMap fhmap;
+  private FileChannel channel;
+
+  private long seeks;
+
+  FileHandle(File file, FileHandleCMap fhmap) {
+    this.file = file;
+    this.fhmap = fhmap;
+    this.seeks = 0;
+
+    this.channel = file.exists() ?
+        new FileInputStream(file).getChannel() :
+        new FileOutputStream(file).getChannel();
+  }
+
+  public File getFile() {
+    return file;
+  }
+
+  Block getBlock(Long blockId) {
+    long position = blockId.longValue();
+    if (channel.position() != position) {
+      seeks++;
+      channel.position(position);
+    }
+
+
+  }
+}

Added: projects/xa2/object-pool/src/scheduler/FileHandleFactory.java
===================================================================
--- projects/xa2/object-pool/src/scheduler/FileHandleFactory.java	                        (rev 0)
+++ projects/xa2/object-pool/src/scheduler/FileHandleFactory.java	2008-04-30 08:59:06 UTC (rev 871)
@@ -0,0 +1,30 @@
+/*
+ * Copyright Topaz Foundation 2008
+ * Author Andrae Muys
+ * Date 30th April 2008
+ */
+package scheduler;
+
+import java.io.File;
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * A canonical mapping of File objects to FileHandles.
+ */
+public class FileHandleCMap {
+  private Map<File, FileHandle> handles;
+
+  public FileHandleCMap() {
+    this.handles = new HashMap<File, FileHandle>();
+  }
+
+  public FileHandle getHandle(File file) {
+    FileHandle result = handles.get(file);
+    if (result == null) {
+      result = new FileHandle(file, this);
+      handles.put(result);
+    }
+    return result;
+  }
+}

Added: projects/xa2/object-pool/src/scheduler/IOScheduler.java
===================================================================
--- projects/xa2/object-pool/src/scheduler/IOScheduler.java	                        (rev 0)
+++ projects/xa2/object-pool/src/scheduler/IOScheduler.java	2008-04-30 08:59:06 UTC (rev 871)
@@ -0,0 +1,18 @@
+/*
+ * Copyright Topaz Foundation 2008
+ * Author Andrae Muys
+ * Date 30th April 2008
+ */
+package scheduler;
+
+import java.lang.ref.SoftReference;
+import java.util.HashMap;
+import java.util.Map;
+
+public class IOScheduler {
+  private Map<FileHandle, FileCache> fileCache;
+
+  public IOScheduler() {
+    fileCache = new HashMap<FileHandle, FileCache>();
+  }
+}