0,0 → 1,618 |
// Protocol Buffers - Google's data interchange format |
// Copyright 2008 Google Inc. All rights reserved. |
// http://code.google.com/p/protobuf/ |
// |
// Redistribution and use in source and binary forms, with or without |
// modification, are permitted provided that the following conditions are |
// met: |
// |
// * Redistributions of source code must retain the above copyright |
// notice, this list of conditions and the following disclaimer. |
// * Redistributions in binary form must reproduce the above |
// copyright notice, this list of conditions and the following disclaimer |
// in the documentation and/or other materials provided with the |
// distribution. |
// * Neither the name of Google Inc. nor the names of its |
// contributors may be used to endorse or promote products derived from |
// this software without specific prior written permission. |
// |
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT |
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
|
package com.google.protobuf; |
|
import java.util.AbstractMap; |
import java.util.AbstractSet; |
import java.util.ArrayList; |
import java.util.Collections; |
import java.util.Iterator; |
import java.util.TreeMap; |
import java.util.List; |
import java.util.Map; |
import java.util.NoSuchElementException; |
import java.util.Set; |
import java.util.SortedMap; |
|
/** |
* A custom map implementation from FieldDescriptor to Object optimized to |
* minimize the number of memory allocations for instances with a small number |
* of mappings. The implementation stores the first {@code k} mappings in an |
* array for a configurable value of {@code k}, allowing direct access to the |
* corresponding {@code Entry}s without the need to create an Iterator. The |
* remaining entries are stored in an overflow map. Iteration over the entries |
* in the map should be done as follows: |
* |
* <pre> |
* for (int i = 0; i < fieldMap.getNumArrayEntries(); i++) { |
* process(fieldMap.getArrayEntryAt(i)); |
* } |
* for (Map.Entry<K, V> entry : fieldMap.getOverflowEntries()) { |
* process(entry); |
* } |
* </pre> |
* |
* The resulting iteration is in order of ascending field tag number. The |
* object returned by {@link #entrySet()} adheres to the same contract but is |
* less efficient as it necessarily involves creating an object for iteration. |
* <p> |
* The tradeoff for this memory efficiency is that the worst case running time |
* of the {@code put()} operation is {@code O(k + lg n)}, which happens when |
* entries are added in descending order. {@code k} should be chosen such that |
* it covers enough common cases without adversely affecting larger maps. In |
* practice, the worst case scenario does not happen for extensions because |
* extension fields are serialized and deserialized in order of ascending tag |
* number, but the worst case scenario can happen for DynamicMessages. |
* <p> |
* The running time for all other operations is similar to that of |
* {@code TreeMap}. |
* <p> |
* Instances are not thread-safe until {@link #makeImmutable()} is called, |
* after which any modifying operation will result in an |
* {@link UnsupportedOperationException}. |
* |
* @author darick@google.com Darick Tong |
*/ |
// This class is final for all intents and purposes because the constructor is |
// private. However, the FieldDescriptor-specific logic is encapsulated in |
// a subclass to aid testability of the core logic. |
class SmallSortedMap<K extends Comparable<K>, V> extends AbstractMap<K, V> { |
|
/** |
* Creates a new instance for mapping FieldDescriptors to their values. |
* The {@link #makeImmutable()} implementation will convert the List values |
* of any repeated fields to unmodifiable lists. |
* |
* @param arraySize The size of the entry array containing the |
* lexicographically smallest mappings. |
*/ |
static <FieldDescriptorType extends |
FieldSet.FieldDescriptorLite<FieldDescriptorType>> |
SmallSortedMap<FieldDescriptorType, Object> newFieldMap(int arraySize) { |
return new SmallSortedMap<FieldDescriptorType, Object>(arraySize) { |
@Override |
@SuppressWarnings("unchecked") |
public void makeImmutable() { |
if (!isImmutable()) { |
for (int i = 0; i < getNumArrayEntries(); i++) { |
final Map.Entry<FieldDescriptorType, Object> entry = |
getArrayEntryAt(i); |
if (entry.getKey().isRepeated()) { |
final List value = (List) entry.getValue(); |
entry.setValue(Collections.unmodifiableList(value)); |
} |
} |
for (Map.Entry<FieldDescriptorType, Object> entry : |
getOverflowEntries()) { |
if (entry.getKey().isRepeated()) { |
final List value = (List) entry.getValue(); |
entry.setValue(Collections.unmodifiableList(value)); |
} |
} |
} |
super.makeImmutable(); |
} |
}; |
} |
|
/** |
* Creates a new instance for testing. |
* |
* @param arraySize The size of the entry array containing the |
* lexicographically smallest mappings. |
*/ |
static <K extends Comparable<K>, V> SmallSortedMap<K, V> newInstanceForTest( |
int arraySize) { |
return new SmallSortedMap<K, V>(arraySize); |
} |
|
private final int maxArraySize; |
// The "entry array" is actually a List because generic arrays are not |
// allowed. ArrayList also nicely handles the entry shifting on inserts and |
// removes. |
private List<Entry> entryList; |
private Map<K, V> overflowEntries; |
private boolean isImmutable; |
// The EntrySet is a stateless view of the Map. It's initialized the first |
// time it is requested and reused henceforth. |
private volatile EntrySet lazyEntrySet; |
|
/** |
* @code arraySize Size of the array in which the lexicographically smallest |
* mappings are stored. (i.e. the {@code k} referred to in the class |
* documentation). |
*/ |
private SmallSortedMap(int arraySize) { |
this.maxArraySize = arraySize; |
this.entryList = Collections.emptyList(); |
this.overflowEntries = Collections.emptyMap(); |
} |
|
/** Make this map immutable from this point forward. */ |
public void makeImmutable() { |
if (!isImmutable) { |
// Note: There's no need to wrap the entryList in an unmodifiableList |
// because none of the list's accessors are exposed. The iterator() of |
// overflowEntries, on the other hand, is exposed so it must be made |
// unmodifiable. |
overflowEntries = overflowEntries.isEmpty() ? |
Collections.<K, V>emptyMap() : |
Collections.unmodifiableMap(overflowEntries); |
isImmutable = true; |
} |
} |
|
/** @return Whether {@link #makeImmutable()} has been called. */ |
public boolean isImmutable() { |
return isImmutable; |
} |
|
/** @return The number of entries in the entry array. */ |
public int getNumArrayEntries() { |
return entryList.size(); |
} |
|
/** @return The array entry at the given {@code index}. */ |
public Map.Entry<K, V> getArrayEntryAt(int index) { |
return entryList.get(index); |
} |
|
/** @return There number of overflow entries. */ |
public int getNumOverflowEntries() { |
return overflowEntries.size(); |
} |
|
/** @return An iterable over the overflow entries. */ |
public Iterable<Map.Entry<K, V>> getOverflowEntries() { |
return overflowEntries.isEmpty() ? |
EmptySet.<Map.Entry<K, V>>iterable() : |
overflowEntries.entrySet(); |
} |
|
@Override |
public int size() { |
return entryList.size() + overflowEntries.size(); |
} |
|
/** |
* The implementation throws a {@code ClassCastException} if o is not an |
* object of type {@code K}. |
* |
* {@inheritDoc} |
*/ |
@Override |
public boolean containsKey(Object o) { |
@SuppressWarnings("unchecked") |
final K key = (K) o; |
return binarySearchInArray(key) >= 0 || overflowEntries.containsKey(key); |
} |
|
/** |
* The implementation throws a {@code ClassCastException} if o is not an |
* object of type {@code K}. |
* |
* {@inheritDoc} |
*/ |
@Override |
public V get(Object o) { |
@SuppressWarnings("unchecked") |
final K key = (K) o; |
final int index = binarySearchInArray(key); |
if (index >= 0) { |
return entryList.get(index).getValue(); |
} |
return overflowEntries.get(key); |
} |
|
@Override |
public V put(K key, V value) { |
checkMutable(); |
final int index = binarySearchInArray(key); |
if (index >= 0) { |
// Replace existing array entry. |
return entryList.get(index).setValue(value); |
} |
ensureEntryArrayMutable(); |
final int insertionPoint = -(index + 1); |
if (insertionPoint >= maxArraySize) { |
// Put directly in overflow. |
return getOverflowEntriesMutable().put(key, value); |
} |
// Insert new Entry in array. |
if (entryList.size() == maxArraySize) { |
// Shift the last array entry into overflow. |
final Entry lastEntryInArray = entryList.remove(maxArraySize - 1); |
getOverflowEntriesMutable().put(lastEntryInArray.getKey(), |
lastEntryInArray.getValue()); |
} |
entryList.add(insertionPoint, new Entry(key, value)); |
return null; |
} |
|
@Override |
public void clear() { |
checkMutable(); |
if (!entryList.isEmpty()) { |
entryList.clear(); |
} |
if (!overflowEntries.isEmpty()) { |
overflowEntries.clear(); |
} |
} |
|
/** |
* The implementation throws a {@code ClassCastException} if o is not an |
* object of type {@code K}. |
* |
* {@inheritDoc} |
*/ |
@Override |
public V remove(Object o) { |
checkMutable(); |
@SuppressWarnings("unchecked") |
final K key = (K) o; |
final int index = binarySearchInArray(key); |
if (index >= 0) { |
return removeArrayEntryAt(index); |
} |
// overflowEntries might be Collections.unmodifiableMap(), so only |
// call remove() if it is non-empty. |
if (overflowEntries.isEmpty()) { |
return null; |
} else { |
return overflowEntries.remove(key); |
} |
} |
|
private V removeArrayEntryAt(int index) { |
checkMutable(); |
final V removed = entryList.remove(index).getValue(); |
if (!overflowEntries.isEmpty()) { |
// Shift the first entry in the overflow to be the last entry in the |
// array. |
final Iterator<Map.Entry<K, V>> iterator = |
getOverflowEntriesMutable().entrySet().iterator(); |
entryList.add(new Entry(iterator.next())); |
iterator.remove(); |
} |
return removed; |
} |
|
/** |
* @param key The key to find in the entry array. |
* @return The returned integer position follows the same semantics as the |
* value returned by {@link java.util.Arrays#binarySearch()}. |
*/ |
private int binarySearchInArray(K key) { |
int left = 0; |
int right = entryList.size() - 1; |
|
// Optimization: For the common case in which entries are added in |
// ascending tag order, check the largest element in the array before |
// doing a full binary search. |
if (right >= 0) { |
int cmp = key.compareTo(entryList.get(right).getKey()); |
if (cmp > 0) { |
return -(right + 2); // Insert point is after "right". |
} else if (cmp == 0) { |
return right; |
} |
} |
|
while (left <= right) { |
int mid = (left + right) / 2; |
int cmp = key.compareTo(entryList.get(mid).getKey()); |
if (cmp < 0) { |
right = mid - 1; |
} else if (cmp > 0) { |
left = mid + 1; |
} else { |
return mid; |
} |
} |
return -(left + 1); |
} |
|
/** |
* Similar to the AbstractMap implementation of {@code keySet()} and |
* {@code values()}, the entry set is created the first time this method is |
* called, and returned in response to all subsequent calls. |
* |
* {@inheritDoc} |
*/ |
@Override |
public Set<Map.Entry<K, V>> entrySet() { |
if (lazyEntrySet == null) { |
lazyEntrySet = new EntrySet(); |
} |
return lazyEntrySet; |
} |
|
/** |
* @throws UnsupportedOperationException if {@link #makeImmutable()} has |
* has been called. |
*/ |
private void checkMutable() { |
if (isImmutable) { |
throw new UnsupportedOperationException(); |
} |
} |
|
/** |
* @return a {@link SortedMap} to which overflow entries mappings can be |
* added or removed. |
* @throws UnsupportedOperationException if {@link #makeImmutable()} has been |
* called. |
*/ |
@SuppressWarnings("unchecked") |
private SortedMap<K, V> getOverflowEntriesMutable() { |
checkMutable(); |
if (overflowEntries.isEmpty() && !(overflowEntries instanceof TreeMap)) { |
overflowEntries = new TreeMap<K, V>(); |
} |
return (SortedMap<K, V>) overflowEntries; |
} |
|
/** |
* Lazily creates the entry list. Any code that adds to the list must first |
* call this method. |
*/ |
private void ensureEntryArrayMutable() { |
checkMutable(); |
if (entryList.isEmpty() && !(entryList instanceof ArrayList)) { |
entryList = new ArrayList<Entry>(maxArraySize); |
} |
} |
|
/** |
* Entry implementation that implements Comparable in order to support |
* binary search witin the entry array. Also checks mutability in |
* {@link #setValue()}. |
*/ |
private class Entry implements Map.Entry<K, V>, Comparable<Entry> { |
|
private final K key; |
private V value; |
|
Entry(Map.Entry<K, V> copy) { |
this(copy.getKey(), copy.getValue()); |
} |
|
Entry(K key, V value) { |
this.key = key; |
this.value = value; |
} |
|
//@Override (Java 1.6 override semantics, but we must support 1.5) |
public K getKey() { |
return key; |
} |
|
//@Override (Java 1.6 override semantics, but we must support 1.5) |
public V getValue() { |
return value; |
} |
|
//@Override (Java 1.6 override semantics, but we must support 1.5) |
public int compareTo(Entry other) { |
return getKey().compareTo(other.getKey()); |
} |
|
//@Override (Java 1.6 override semantics, but we must support 1.5) |
public V setValue(V newValue) { |
checkMutable(); |
final V oldValue = this.value; |
this.value = newValue; |
return oldValue; |
} |
|
@Override |
public boolean equals(Object o) { |
if (o == this) { |
return true; |
} |
if (!(o instanceof Map.Entry)) { |
return false; |
} |
@SuppressWarnings("unchecked") |
Map.Entry<?, ?> other = (Map.Entry<?, ?>) o; |
return equals(key, other.getKey()) && equals(value, other.getValue()); |
} |
|
@Override |
public int hashCode() { |
return (key == null ? 0 : key.hashCode()) ^ |
(value == null ? 0 : value.hashCode()); |
} |
|
@Override |
public String toString() { |
return key + "=" + value; |
} |
|
/** equals() that handles null values. */ |
private boolean equals(Object o1, Object o2) { |
return o1 == null ? o2 == null : o1.equals(o2); |
} |
} |
|
/** |
* Stateless view of the entries in the field map. |
*/ |
private class EntrySet extends AbstractSet<Map.Entry<K, V>> { |
|
@Override |
public Iterator<Map.Entry<K, V>> iterator() { |
return new EntryIterator(); |
} |
|
@Override |
public int size() { |
return SmallSortedMap.this.size(); |
} |
|
/** |
* Throws a {@link ClassCastException} if o is not of the expected type. |
* |
* {@inheritDoc} |
*/ |
@Override |
public boolean contains(Object o) { |
@SuppressWarnings("unchecked") |
final Map.Entry<K, V> entry = (Map.Entry<K, V>) o; |
final V existing = get(entry.getKey()); |
final V value = entry.getValue(); |
return existing == value || |
(existing != null && existing.equals(value)); |
} |
|
@Override |
public boolean add(Map.Entry<K, V> entry) { |
if (!contains(entry)) { |
put(entry.getKey(), entry.getValue()); |
return true; |
} |
return false; |
} |
|
/** |
* Throws a {@link ClassCastException} if o is not of the expected type. |
* |
* {@inheritDoc} |
*/ |
@Override |
public boolean remove(Object o) { |
@SuppressWarnings("unchecked") |
final Map.Entry<K, V> entry = (Map.Entry<K, V>) o; |
if (contains(entry)) { |
SmallSortedMap.this.remove(entry.getKey()); |
return true; |
} |
return false; |
} |
|
@Override |
public void clear() { |
SmallSortedMap.this.clear(); |
} |
} |
|
/** |
* Iterator implementation that switches from the entry array to the overflow |
* entries appropriately. |
*/ |
private class EntryIterator implements Iterator<Map.Entry<K, V>> { |
|
private int pos = -1; |
private boolean nextCalledBeforeRemove; |
private Iterator<Map.Entry<K, V>> lazyOverflowIterator; |
|
//@Override (Java 1.6 override semantics, but we must support 1.5) |
public boolean hasNext() { |
return (pos + 1) < entryList.size() || |
getOverflowIterator().hasNext(); |
} |
|
//@Override (Java 1.6 override semantics, but we must support 1.5) |
public Map.Entry<K, V> next() { |
nextCalledBeforeRemove = true; |
// Always increment pos so that we know whether the last returned value |
// was from the array or from overflow. |
if (++pos < entryList.size()) { |
return entryList.get(pos); |
} |
return getOverflowIterator().next(); |
} |
|
//@Override (Java 1.6 override semantics, but we must support 1.5) |
public void remove() { |
if (!nextCalledBeforeRemove) { |
throw new IllegalStateException("remove() was called before next()"); |
} |
nextCalledBeforeRemove = false; |
checkMutable(); |
|
if (pos < entryList.size()) { |
removeArrayEntryAt(pos--); |
} else { |
getOverflowIterator().remove(); |
} |
} |
|
/** |
* It is important to create the overflow iterator only after the array |
* entries have been iterated over because the overflow entry set changes |
* when the client calls remove() on the array entries, which invalidates |
* any existing iterators. |
*/ |
private Iterator<Map.Entry<K, V>> getOverflowIterator() { |
if (lazyOverflowIterator == null) { |
lazyOverflowIterator = overflowEntries.entrySet().iterator(); |
} |
return lazyOverflowIterator; |
} |
} |
|
/** |
* Helper class that holds immutable instances of an Iterable/Iterator that |
* we return when the overflow entries is empty. This eliminates the creation |
* of an Iterator object when there is nothing to iterate over. |
*/ |
private static class EmptySet { |
|
private static final Iterator<Object> ITERATOR = new Iterator<Object>() { |
//@Override (Java 1.6 override semantics, but we must support 1.5) |
public boolean hasNext() { |
return false; |
} |
//@Override (Java 1.6 override semantics, but we must support 1.5) |
public Object next() { |
throw new NoSuchElementException(); |
} |
//@Override (Java 1.6 override semantics, but we must support 1.5) |
public void remove() { |
throw new UnsupportedOperationException(); |
} |
}; |
|
private static final Iterable<Object> ITERABLE = new Iterable<Object>() { |
//@Override (Java 1.6 override semantics, but we must support 1.5) |
public Iterator<Object> iterator() { |
return ITERATOR; |
} |
}; |
|
@SuppressWarnings("unchecked") |
static <T> Iterable<T> iterable() { |
return (Iterable<T>) ITERABLE; |
} |
} |
} |