src/share/classes/java/util/IdentityHashMap.java
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@@ -1,7 +1,7 @@
/*
- * Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2014, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
@@ -23,11 +23,10 @@
* questions.
*/
package java.util;
-import java.io.*;
import java.lang.reflect.Array;
import java.util.function.BiConsumer;
import java.util.function.BiFunction;
import java.util.function.Consumer;
@@ -72,11 +71,11 @@
* this parameter is used to determine the number of buckets initially
* comprising the hash table. The precise relationship between the expected
* maximum size and the number of buckets is unspecified.
*
* <p>If the size of the map (the number of key-value mappings) sufficiently
- * exceeds the expected maximum size, the number of buckets is increased
+ * exceeds the expected maximum size, the number of buckets is increased.
* Increasing the number of buckets ("rehashing") may be fairly expensive, so
* it pays to create identity hash maps with a sufficiently large expected
* maximum size. On the other hand, iteration over collection views requires
* time proportional to the number of buckets in the hash table, so it
* pays not to set the expected maximum size too high if you are especially
@@ -155,18 +154,19 @@
* MUST be a power of two.
*/
private static final int MINIMUM_CAPACITY = 4;
/**
- * The maximum capacity, used if a higher value is implicitly specified
- * by either of the constructors with arguments.
- * MUST be a power of two <= 1<<29.
+ * The maximum capacity (3 << 28), used if a higher value
+ * is implicitly specified by either of the constructors with arguments.
+ * MAXIMUM_CAPACITY / 3 must be an integer and power of two.
*/
- private static final int MAXIMUM_CAPACITY = 1 << 29;
+ private static final int MAXIMUM_CAPACITY = 3 << 28;
/**
- * The table, resized as necessary. Length MUST always be a power of two.
+ * The table, resized as necessary. Length MUST always be a power of two
+ * or 2 * MAXIMUM_CAPACITY
*/
transient Object[] table; // non-private to simplify nested class access
/**
* The number of key-value mappings contained in this identity hash map.
@@ -179,15 +179,10 @@
* The number of modifications, to support fast-fail iterators
*/
transient int modCount;
/**
- * The next size value at which to resize (capacity * load factor).
- */
- private transient int threshold;
-
- /**
* Value representing null keys inside tables.
*/
static final Object NULL_KEY = new Object();
/**
@@ -227,44 +222,40 @@
+ expectedMaxSize);
init(capacity(expectedMaxSize));
}
/**
- * Returns the appropriate capacity for the specified expected maximum
- * size. Returns the smallest power of two between MINIMUM_CAPACITY
- * and MAXIMUM_CAPACITY, inclusive, that is greater than
- * (3 * expectedMaxSize)/2, if such a number exists. Otherwise
- * returns MAXIMUM_CAPACITY. If (3 * expectedMaxSize)/2 is negative, it
- * is assumed that overflow has occurred, and MAXIMUM_CAPACITY is returned.
- */
- private int capacity(int expectedMaxSize) {
- // Compute min capacity for expectedMaxSize given a load factor of 2/3
- int minCapacity = (3 * expectedMaxSize)/2;
-
- // Compute the appropriate capacity
- int result;
- if (minCapacity > MAXIMUM_CAPACITY || minCapacity < 0) {
- result = MAXIMUM_CAPACITY;
- } else {
- result = MINIMUM_CAPACITY;
- while (result < minCapacity)
- result <<= 1;
- }
- return result;
+ * Returns the appropriate capacity for the given expected maximum size.
+ * Returns the smallest power of two between MINIMUM_CAPACITY and
+ * MAXIMUM_CAPACITY, inclusive, that is greater than (3 *
+ * expectedMaxSize)/2, if such a number exists. Otherwise returns
+ * MAXIMUM_CAPACITY.
+ */
+ private static int capacity(int expectedMaxSize) {
+ // assert expectedMaxSize >= 0;
+ return Math.min(
+ MAXIMUM_CAPACITY,
+ Math.max(
+ MINIMUM_CAPACITY,
+ expectedMaxSize > Integer.MAX_VALUE / 3
+ ? MAXIMUM_CAPACITY // 3 * expectedMaxSize would overflow
+ : Integer.highestOneBit(expectedMaxSize + (expectedMaxSize << 1))
+ )
+ );
}
/**
* Initializes object to be an empty map with the specified initial
* capacity, which is assumed to be a power of two between
* MINIMUM_CAPACITY and MAXIMUM_CAPACITY inclusive.
*/
private void init(int initCapacity) {
- // assert (initCapacity & -initCapacity) == initCapacity; // power of 2
+ // assert initCapacity == MAXIMUM_CAPACITY ||
+ // (initCapacity & -initCapacity) == initCapacity; // power of 2
// assert initCapacity >= MINIMUM_CAPACITY;
// assert initCapacity <= MAXIMUM_CAPACITY;
- threshold = (initCapacity * 2)/3;
table = new Object[2 * initCapacity];
}
/**
* Constructs a new identity hash map containing the keys-value mappings
@@ -302,19 +293,29 @@
/**
* Returns index for Object x.
*/
private static int hash(Object x, int length) {
int h = System.identityHashCode(x);
- // Multiply by -127, and left-shift to use least bit as part of hash
- return ((h << 1) - (h << 8)) & (length - 1);
+ // multiply by -127
+ h -= h << 7;
+ if (length < MAXIMUM_CAPACITY * 2) { // length is 2^n
+ // left-shift to use least bit as part of hash
+ return (h << 1) & (length - 1);
+ }
+ // assert length == MAXIMUM_CAPACITY * 2
+ // clamp
+ h &= (MAXIMUM_CAPACITY / 3 * 4 - 1);
+ // Multiply by 3/2 and reset 0th bit
+ return (h + (h >> 1)) & ~1;
}
/**
* Circularly traverses table of size len.
*/
private static int nextKeyIndex(int i, int len) {
- return (i + 2 < len ? i + 2 : 0);
+ int i2 = i + 2;
+ return (i2 < len ? i2 : 0);
}
/**
* Returns the value to which the specified key is mapped,
* or {@code null} if this map contains no mapping for the key.
@@ -427,56 +428,70 @@
* @see Object#equals(Object)
* @see #get(Object)
* @see #containsKey(Object)
*/
public V put(K key, V value) {
- Object k = maskNull(key);
- Object[] tab = table;
- int len = tab.length;
+ final Object k = maskNull(key);
+
+ while (true) {
+ final Object[] tab = table;
+ final int len = tab.length;
int i = hash(k, len);
- Object item;
- while ( (item = tab[i]) != null) {
+ for (Object item; (item = tab[i]) != null;
+ i = nextKeyIndex(i, len)) {
if (item == k) {
@SuppressWarnings("unchecked")
V oldValue = (V) tab[i + 1];
tab[i + 1] = value;
return oldValue;
}
- i = nextKeyIndex(i, len);
}
+ final int s = size + 1;
+ // Use optimized form of 3 * s.
+ if (s + (s << 1) < len) {
modCount++;
tab[i] = k;
tab[i + 1] = value;
- if (++size >= threshold)
- resize(len); // len == 2 * current capacity.
+ size = s;
return null;
}
+ // Next capacity is len, 2 * current capacity.
+ resize(len);
+ }
+ }
/**
- * Resize the table to hold given capacity.
+ * Resizes the table if necessary to hold given capacity.
*
* @param newCapacity the new capacity, must be a power of two.
*/
private void resize(int newCapacity) {
- // assert (newCapacity & -newCapacity) == newCapacity; // power of 2
- int newLength = newCapacity * 2;
+ // assert newCapacity == MAXIMUM_CAPACITY ||
+ // newCapacity == MAXIMUM_CAPACITY * 2 || // when adding past 66% of MAXIMUM_CAPACITY
+ // (newCapacity & -newCapacity) == newCapacity; // power of 2
+
+ // when resize is triggered from put() for 2 * MAXIMUM_CAPACITY it means
+ // that we are about to insert new element past 66% of MAXIMUM_CAPACITY
+ // (past max. size of 2^29 - 1)
+ if (newCapacity == 2 * MAXIMUM_CAPACITY) {
+ throw new OutOfMemoryError("Max. size exceeded.");
+ }
+
+ int newLength = Math.min(
+ 2 * MAXIMUM_CAPACITY,
+ newCapacity > Integer.MAX_VALUE / 2
+ ? 2 * MAXIMUM_CAPACITY // newCapacity << 1 would overflow
+ : newCapacity << 1
+ );
Object[] oldTable = table;
int oldLength = oldTable.length;
- if (oldLength == 2*MAXIMUM_CAPACITY) { // can't expand any further
- if (threshold == MAXIMUM_CAPACITY-1)
- throw new IllegalStateException("Capacity exhausted.");
- threshold = MAXIMUM_CAPACITY-1; // Gigantic map!
- return;
- }
- if (oldLength >= newLength)
- return;
+ // assert newLength > oldLength
Object[] newTable = new Object[newLength];
- threshold = newLength / 3;
for (int j = 0; j < oldLength; j += 2) {
Object key = oldTable[j];
if (key != null) {
Object value = oldTable[j+1];
@@ -502,12 +517,13 @@
*/
public void putAll(Map<? extends K, ? extends V> m) {
int n = m.size();
if (n == 0)
return;
- if (n > threshold) // conservatively pre-expand
- resize(capacity(n));
+ int c = capacity(n);
+ if (c << 1 > table.length)
+ resize(c); // conservatively pre-expand
for (Entry<? extends K, ? extends V> e : m.entrySet())
put(e.getKey(), e.getValue());
}
@@ -540,11 +556,10 @@
}
if (item == null)
return null;
i = nextKeyIndex(i, len);
}
-
}
/**
* Removes the specified key-value mapping from the map if it is present.
*
@@ -1264,12 +1279,12 @@
private static final long serialVersionUID = 8188218128353913216L;
/**
- * Save the state of the <tt>IdentityHashMap</tt> instance to a stream
- * (i.e., serialize it).
+ * Saves the state of the <tt>IdentityHashMap</tt> instance to a stream
+ * (i.e., serializes it).
*
* @serialData The <i>size</i> of the HashMap (the number of key-value
* mappings) (<tt>int</tt>), followed by the key (Object) and
* value (Object) for each key-value mapping represented by the
* IdentityHashMap. The key-value mappings are emitted in no
@@ -1293,23 +1308,24 @@
}
}
}
/**
- * Reconstitute the <tt>IdentityHashMap</tt> instance from a stream (i.e.,
- * deserialize it).
+ * Reconstitutes the <tt>IdentityHashMap</tt> instance from a stream (i.e.,
+ * deserializes it).
*/
private void readObject(java.io.ObjectInputStream s)
throws java.io.IOException, ClassNotFoundException {
// Read in any hidden stuff
s.defaultReadObject();
// Read in size (number of Mappings)
int size = s.readInt();
-
- // Allow for 33% growth (i.e., capacity is >= 2* size()).
- init(capacity((size*4)/3));
+ if (size < 0)
+ throw new java.io.StreamCorruptedException
+ ("Illegal mappings count: " + size);
+ init(capacity(size));
// Read the keys and values, and put the mappings in the table
for (int i=0; i<size; i++) {
@SuppressWarnings("unchecked")
K key = (K) s.readObject();
@@ -1322,11 +1338,11 @@
/**
* The put method for readObject. It does not resize the table,
* update modCount, etc.
*/
private void putForCreate(K key, V value)
- throws IOException
+ throws java.io.StreamCorruptedException
{
Object k = maskNull(key);
Object[] tab = table;
int len = tab.length;
int i = hash(k, len);