Replace ViewCursor with SliceCursor.

2 files changed, 167 insertions, 110 deletions

diff --git a/src/main/java/com/amazon/carbonado/cursor/SliceCursor.java b/src/main/java/com/amazon/carbonado/cursor/SliceCursor.java
new file mode 100644
index 0000000..882932f
--- /dev/null
+++ b/src/main/java/com/amazon/carbonado/cursor/SliceCursor.java
@@ -0,0 +1,167 @@
+/*

+ * Copyright 2007 Amazon Technologies, Inc. or its affiliates.

+ * Amazon, Amazon.com and Carbonado are trademarks or registered trademarks

+ * of Amazon Technologies, Inc. or its affiliates.  All rights reserved.

+ *

+ * Licensed under the Apache License, Version 2.0 (the "License");

+ * you may not use this file except in compliance with the License.

+ * You may obtain a copy of the License at

+ *

+ *     http://www.apache.org/licenses/LICENSE-2.0

+ *

+ * Unless required by applicable law or agreed to in writing, software

+ * distributed under the License is distributed on an "AS IS" BASIS,

+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

+ * See the License for the specific language governing permissions and

+ * limitations under the License.

+ */

+

+package com.amazon.carbonado.cursor;

+

+import java.util.NoSuchElementException;

+

+import com.amazon.carbonado.Cursor;

+import com.amazon.carbonado.FetchException;

+

+/**

+ * Wraps another cursor and only produces a range of elements. The actual range

+ * might be smaller if the source cursor doesn't have enough elements.

+ *

+ * @author Brian S O'Neill

+ * @since 1.2

+ */

+public abstract class SliceCursor<S> extends AbstractCursor<S> {

+    /**

+     * @param from zero-based element to start from, inclusive

+     * @param to zero-based element to end at, exclusive

+     * @throws IllegalArgumentException if source is null, from is negative or

+     * if from is more than to

+     */

+    public static <S> Cursor<S> slice(Cursor<S> source, long from, long to) {

+	return slice(source, (Long) from, (Long) to);

+    }

+

+    /**

+     * @param from optional zero-based element to start from, inclusive

+     * @param to optional zero-based element to end at, exclusive

+     * @throws IllegalArgumentException if source is null, from is negative or

+     * if from is more than to

+     */

+    public static <S> Cursor<S> slice(Cursor<S> source, Long from, Long to) {

+        if (source == null) {

+            throw new IllegalArgumentException("Source is null");

+        }

+

+	long actualFrom;

+

+	if (from == null) {

+	    actualFrom = 0;

+	} else if (from >= 0) {

+	    if ((actualFrom = from) > 0) {

+		source = new Skip<S>(source, actualFrom);

+	    }

+	} else {

+            throw new IllegalArgumentException("Slice from is negative: " + from);

+	}

+

+	long remaining;

+

+	if (to == null) {

+	    return source;

+	} else if ((remaining = to - actualFrom) < 0) {

+	    throw new IllegalArgumentException("Slice from is more than to: " + from + " > " + to);

+	}

+

+	return new Limit<S>(source, remaining);

+    }

+

+    final Cursor<S> mSource;

+

+    SliceCursor(Cursor<S> source) {

+	mSource = source;

+    }

+

+    public void close() throws FetchException {

+        mSource.close();

+    }

+

+    private static class Skip<S> extends SliceCursor<S> {

+	private volatile long mSkip;

+

+	Skip(Cursor<S> source, long skip) {

+	    super(source);

+	    mSkip = skip;

+	}

+

+	public boolean hasNext() throws FetchException {

+	    doSkip();

+	    return mSource.hasNext();

+	}

+

+	public S next() throws FetchException {

+	    doSkip();

+	    return mSource.next();

+	}

+

+	@Override

+	public int skipNext(int amount) throws FetchException {

+	    doSkip();

+	    return mSource.skipNext(amount);

+	}

+

+	private void doSkip() throws FetchException {

+	    if (mSkip > 0) {

+		while (mSkip > Integer.MAX_VALUE) {

+		    mSkip -= mSource.skipNext(Integer.MAX_VALUE);

+		}

+		mSource.skipNext((int) mSkip);

+		mSkip = 0;

+	    }

+	}

+    }

+

+    private static class Limit<S> extends SliceCursor<S> {

+	private volatile long mRemaining;

+

+	Limit(Cursor<S> source, long remaining) {

+	    super(source);

+	    mRemaining = remaining;

+	}

+

+	public boolean hasNext() throws FetchException {

+	    if (mSource.hasNext()) {

+		if (mRemaining > 0) {

+		    return true;

+		}

+		mSource.close();

+	    }

+	    return false;

+	}

+

+	public S next() throws FetchException {

+	    if (mRemaining <= 0) {

+		throw new NoSuchElementException();

+	    }

+	    S next = mSource.next();

+	    if (--mRemaining <= 0) {

+		mSource.close();

+	    }

+	    return next;

+	}

+

+	@Override

+	public int skipNext(int amount) throws FetchException {

+	    if (mRemaining <= 0) {

+		return 0;

+	    }

+	    if (amount > mRemaining) {

+		amount = (int) mRemaining;

+	    }

+	    amount = mSource.skipNext(amount);

+	    if ((mRemaining -= amount) <= 0) {

+		mSource.close();

+	    }

+	    return amount;

+	}

+    }

+}

diff --git a/src/main/java/com/amazon/carbonado/cursor/ViewCursor.java b/src/main/java/com/amazon/carbonado/cursor/ViewCursor.java
deleted file mode 100644
index 01b02c3..0000000
--- a/src/main/java/com/amazon/carbonado/cursor/ViewCursor.java
+++ /dev/null
@@ -1,110 +0,0 @@
-/*

- * Copyright 2007 Amazon Technologies, Inc. or its affiliates.

- * Amazon, Amazon.com and Carbonado are trademarks or registered trademarks

- * of Amazon Technologies, Inc. or its affiliates.  All rights reserved.

- *

- * Licensed under the Apache License, Version 2.0 (the "License");

- * you may not use this file except in compliance with the License.

- * You may obtain a copy of the License at

- *

- *     http://www.apache.org/licenses/LICENSE-2.0

- *

- * Unless required by applicable law or agreed to in writing, software

- * distributed under the License is distributed on an "AS IS" BASIS,

- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

- * See the License for the specific language governing permissions and

- * limitations under the License.

- */

-

-package com.amazon.carbonado.cursor;

-

-import java.util.NoSuchElementException;

-

-import com.amazon.carbonado.Cursor;

-import com.amazon.carbonado.FetchException;

-

-/**

- * Wraps another cursor and only produces a range of elements. The range might

- * be smaller if the source cursor doesn't have enough elements.

- *

- * @author Brian S O'Neill

- * @since 1.2

- */

-public class ViewCursor<S> extends AbstractCursor<S> {

-    private final Cursor<S> mSource;

-

-    private volatile long mFrom;

-    private volatile long mRemaining;

-

-    /**

-     * @param from zero-based element to start from, inclusive

-     * @param to zero-based element to end at, exclusive

-     * @throws IllegalArgumentException if source is null, from is negative or

-     * if from is more than to

-     */

-    public ViewCursor(Cursor<S> source, long from, long to) {

-        if (source == null) {

-            throw new IllegalArgumentException("Source is null");

-        }

-        if (from < 0) {

-            throw new IllegalArgumentException("From is negative: " + from);

-        }

-        mSource = source;

-        mFrom = from;

-        mRemaining = to - from;

-        if (mRemaining <= 0) {

-            if (mRemaining < 0) {

-                throw new IllegalArgumentException("From is more than to: " + from + " > " + to);

-            }

-            // Don't bother skipping.

-            mFrom = 0;

-        }

-    }

-

-    public void close() throws FetchException {

-        mSource.close();

-    }

-

-    public boolean hasNext() throws FetchException {

-        if (mFrom > 0) {

-            while (mFrom > Integer.MAX_VALUE) {

-                mFrom -= mSource.skipNext(Integer.MAX_VALUE);

-            }

-            mSource.skipNext((int) mFrom);

-            mFrom = 0;

-        }

-        if (mSource.hasNext()) {

-            if (mRemaining > 0) {

-                return true;

-            }

-            mSource.close();

-        }

-        return false;

-    }

-

-    public S next() throws FetchException {

-        if (!hasNext()) {

-            throw new NoSuchElementException();

-        }

-        S next = mSource.next();

-        if (--mRemaining <= 0) {

-            mSource.close();

-        }

-        return next;

-    }

-

-    @Override

-    public int skipNext(int amount) throws FetchException {

-        if (!hasNext()) {

-            return 0;

-        }

-        if (amount > mRemaining) {

-            amount = (int) mRemaining;

-        }

-        amount = mSource.skipNext(amount);

-        if ((mRemaining -= amount) <= 0) {

-            mSource.close();

-        }

-        return amount;

-    }

-}