LUCENE-2816: MMapDirectory speedups

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1050737 13f79535-47bb-0310-9956-ffa450edef68

lucene/src/java/org/apache/lucene/store/MMapDirectory.java

@@ -242,7 +242,34 @@ public class MMapDirectory extends FSDirectory {
         throw new IOException("read past EOF");
       }
     }
+    
+    @Override
+    public short readShort() throws IOException {
+      try {
+        return buffer.getShort();
+      } catch (BufferUnderflowException e) {
+        throw new IOException("read past EOF");
+      }
+    }
 
+    @Override
+    public int readInt() throws IOException {
+      try {
+        return buffer.getInt();
+      } catch (BufferUnderflowException e) {
+        throw new IOException("read past EOF");
+      }
+    }
+
+    @Override
+    public long readLong() throws IOException {
+      try {
+        return buffer.getLong();
+      } catch (BufferUnderflowException e) {
+        throw new IOException("read past EOF");
+      }
+    }
+    
     @Override
     public long getFilePointer() {
       return buffer.position();
@@ -294,7 +321,6 @@ public class MMapDirectory extends FSDirectory {
     private final int maxBufSize;
   
     private ByteBuffer curBuf; // redundant for speed: buffers[curBufIndex]
-    private int curAvail; // redundant for speed: (bufSizes[curBufIndex] - curBuf.position())
   
     private boolean isClone = false;
     
@@ -333,37 +359,66 @@ public class MMapDirectory extends FSDirectory {
   
     @Override
     public byte readByte() throws IOException {
-      // Performance might be improved by reading ahead into an array of
-      // e.g. 128 bytes and readByte() from there.
-      if (curAvail == 0) {
+      try {
+        return curBuf.get();
+      } catch (BufferUnderflowException e) {
         curBufIndex++;
         if (curBufIndex >= buffers.length)
           throw new IOException("read past EOF");
         curBuf = buffers[curBufIndex];
         curBuf.position(0);
-        curAvail = bufSizes[curBufIndex];
+        return curBuf.get();
       }
-      curAvail--;
-      return curBuf.get();
     }
   
     @Override
     public void readBytes(byte[] b, int offset, int len) throws IOException {
-      while (len > curAvail) {
-        curBuf.get(b, offset, curAvail);
-        len -= curAvail;
-        offset += curAvail;
-        curBufIndex++;
-        if (curBufIndex >= buffers.length)
-          throw new IOException("read past EOF");
-        curBuf = buffers[curBufIndex];
-        curBuf.position(0);
-        curAvail = bufSizes[curBufIndex];
+      try {
+        curBuf.get(b, offset, len);
+      } catch (BufferUnderflowException e) {
+        int curAvail = curBuf.remaining();
+        while (len > curAvail) {
+          curBuf.get(b, offset, curAvail);
+          len -= curAvail;
+          offset += curAvail;
+          curBufIndex++;
+          if (curBufIndex >= buffers.length)
+            throw new IOException("read past EOF");
+          curBuf = buffers[curBufIndex];
+          curBuf.position(0);
+          curAvail = curBuf.remaining();
+        }
+        curBuf.get(b, offset, len);
       }
-      curBuf.get(b, offset, len);
-      curAvail -= len;
     }
   
+    @Override
+    public short readShort() throws IOException {
+      try {
+        return curBuf.getShort();
+      } catch (BufferUnderflowException e) {
+        return super.readShort();
+      }
+    }
+
+    @Override
+    public int readInt() throws IOException {
+      try {
+        return curBuf.getInt();
+      } catch (BufferUnderflowException e) {
+        return super.readInt();
+      }
+    }
+
+    @Override
+    public long readLong() throws IOException {
+      try {
+        return curBuf.getLong();
+      } catch (BufferUnderflowException e) {
+        return super.readLong();
+      }
+    }
+    
     @Override
     public long getFilePointer() {
       return ((long) curBufIndex * maxBufSize) + curBuf.position();
@@ -375,7 +430,6 @@ public class MMapDirectory extends FSDirectory {
       curBuf = buffers[curBufIndex];
       int bufOffset = (int) (pos - ((long) curBufIndex * maxBufSize));
       curBuf.position(bufOffset);
-      curAvail = bufSizes[curBufIndex] - bufOffset;
     }
   
     @Override