| /* |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you 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 org.apache.datasketches.memory.internal; |
| |
| import org.apache.datasketches.memory.BaseBuffer; |
| import org.apache.datasketches.memory.BufferPositionInvariantsException; |
| |
| /** |
| * A new positional API. This is different from and simpler than Java Buffer positional approach. |
| * <ul><li>All based on longs instead of ints.</li> |
| * <li>Eliminated "mark". Rarely used and confusing with its silent side effects.</li> |
| * <li>The invariants are {@code 0 <= start <= position <= end <= capacity}.</li> |
| * <li>It always starts up as (0, 0, capacity, capacity).</li> |
| * <li>You set (start, position, end) in one call with |
| * {@link #setStartPositionEnd(long, long, long)}</li> |
| * <li>Position can be set directly or indirectly when using the positional get/put methods. |
| * <li>Added incrementPosition(long), which is much easier when you know the increment.</li> |
| * <li>This approach eliminated a number of methods and checks, and has no unseen side effects, |
| * e.g., mark being invalidated.</li> |
| * <li>Clearer method naming (IMHO).</li> |
| * </ul> |
| * |
| * @author Lee Rhodes |
| */ |
| public abstract class BaseBufferImpl extends ResourceImpl implements BaseBuffer { |
| private long capacity; |
| private long start = 0; |
| private long pos = 0; |
| private long end; |
| |
| //Pass-through constructor |
| BaseBufferImpl(final long capacityBytes) { |
| super(); |
| capacity = end = capacityBytes; |
| } |
| |
| @Override |
| public final BaseBufferImpl incrementPosition(final long increment) { |
| incrementAndCheckPositionForRead(pos, increment); |
| return this; |
| } |
| |
| @Override |
| public final BaseBufferImpl incrementAndCheckPosition(final long increment) { |
| incrementAndCheckPositionForRead(pos, increment); |
| return this; |
| } |
| |
| @Override |
| public final long getEnd() { |
| return end; |
| } |
| |
| @Override |
| public final long getPosition() { |
| return pos; |
| } |
| |
| @Override |
| public final long getStart() { |
| return start; |
| } |
| |
| @Override |
| public final long getRemaining() { |
| return end - pos; |
| } |
| |
| @Override |
| public final boolean hasRemaining() { |
| return (end - pos) > 0; |
| } |
| |
| @Override |
| public final BaseBufferImpl resetPosition() { |
| pos = start; |
| return this; |
| } |
| |
| @Override |
| public final BaseBufferImpl setPosition(final long position) { |
| return setStartPositionEnd(start, position, end); |
| } |
| |
| @Override |
| public final BaseBufferImpl setStartPositionEnd(final long start, final long position, final long end) { |
| checkValid(); |
| checkInvariants(start, position, end, capacity); |
| this.start = start; |
| this.end = end; |
| pos = position; |
| return this; |
| } |
| |
| //RESTRICTED |
| |
| //used for buffer arrays and apply at runtime |
| final void incrementAndCheckPositionForRead(final long position, final long increment) { |
| checkValid(); |
| final long newPos = position + increment; |
| checkInvariants(start, newPos, end, capacity); |
| pos = newPos; |
| } |
| |
| //used for buffer arrays and apply at runtime |
| final void incrementAndCheckPositionForWrite(final long position, final long increment) { |
| checkNotReadOnly(); |
| incrementAndCheckPositionForRead(position, increment); |
| } |
| |
| /** |
| * The invariants equation is: {@code 0 <= start <= position <= end <= capacity}. |
| * If this equation is violated a <i>BufferPositionInvariantsException</i> will be thrown. |
| * @param start the lowest start position |
| * @param pos the current position |
| * @param end the highest position |
| * @param cap the capacity of the backing buffer. |
| */ |
| static final void checkInvariants(final long start, final long pos, final long end, final long cap) { |
| if ((start | pos | end | cap | (pos - start) | (end - pos) | (cap - end) ) < 0L) { |
| throw new BufferPositionInvariantsException( |
| "Violation of Invariants: " |
| + "start: " + start |
| + " <= pos: " + pos |
| + " <= end: " + end |
| + " <= cap: " + cap |
| + "; (pos - start): " + (pos - start) |
| + ", (end - pos): " + (end - pos) |
| + ", (cap - end): " + (cap - end) |
| ); |
| } |
| } |
| |
| } |