concurrenthashmap.java

来自「SRI international 发布的OAA框架软件」· Java 代码 · 共 1,427 行 · 第 1/4 页

    /**
     * Returns an enumeration of the values in this table.
     *
     * @return  an enumeration of the values in this table.
     * @see     #values
     */
    public Enumeration elements() {
        return new ValueIterator();
    }

    /* ---------------- Iterator Support -------------- */

    abstract class HashIterator {
        int nextSegmentIndex;
        int nextTableIndex;
        HashEntry[] currentTable;
        HashEntry nextEntry;
        HashEntry lastReturned;

        HashIterator() {
            nextSegmentIndex = segments.length - 1;
            nextTableIndex = -1;
            advance();
        }

        public boolean hasMoreElements() { return hasNext(); }

        final void advance() {
            if (nextEntry != null && (nextEntry = nextEntry.next) != null)
                return;

            while (nextTableIndex >= 0) {
                if ( (nextEntry = (HashEntry)currentTable[nextTableIndex--]) != null)
                    return;
            }

            while (nextSegmentIndex >= 0) {
                Segment seg = (Segment)segments[nextSegmentIndex--];
                if (seg.count != 0) {
                    currentTable = seg.table;
                    for (int j = currentTable.length - 1; j >= 0; --j) {
                        if ( (nextEntry = (HashEntry)currentTable[j]) != null) {
                            nextTableIndex = j - 1;
                            return;
                        }
                    }
                }
            }
        }

        public boolean hasNext() { return nextEntry != null; }

        HashEntry nextEntry() {
            if (nextEntry == null)
                throw new NoSuchElementException();
            lastReturned = nextEntry;
            advance();
            return lastReturned;
        }

        public void remove() {
            if (lastReturned == null)
                throw new IllegalStateException();
            ConcurrentHashMap.this.remove(lastReturned.key);
            lastReturned = null;
        }
    }

    final class KeyIterator extends HashIterator implements Iterator, Enumeration {
        public Object next() { return super.nextEntry().key; }
        public Object nextElement() { return super.nextEntry().key; }
    }

    final class ValueIterator extends HashIterator implements Iterator, Enumeration {
        public Object next() { return super.nextEntry().value; }
        public Object nextElement() { return super.nextEntry().value; }
    }



    /**
     * Entry iterator. Exported Entry objects must write-through
     * changes in setValue, even if the nodes have been cloned. So we
     * cannot return internal HashEntry objects. Instead, the iterator
     * itself acts as a forwarding pseudo-entry.
     */
    final class EntryIterator extends HashIterator implements Map.Entry, Iterator {
        public Object next() {
            nextEntry();
            return this;
        }

        public Object getKey() {
            if (lastReturned == null)
                throw new IllegalStateException("Entry was removed");
            return lastReturned.key;
        }

        public Object getValue() {
            if (lastReturned == null)
                throw new IllegalStateException("Entry was removed");
            return ConcurrentHashMap.this.get(lastReturned.key);
        }

        public Object setValue(Object value) {
            if (lastReturned == null)
                throw new IllegalStateException("Entry was removed");
            return ConcurrentHashMap.this.put(lastReturned.key, value);
        }

        public boolean equals(Object o) {
            // If not acting as entry, just use default.
            if (lastReturned == null)
                return super.equals(o);
            if (!(o instanceof Map.Entry))
                return false;
            Map.Entry e = (Map.Entry)o;
            return eq(getKey(), e.getKey()) && eq(getValue(), e.getValue());
        }

        public int hashCode() {
            // If not acting as entry, just use default.
            if (lastReturned == null)
                return super.hashCode();

            Object k = getKey();
            Object v = getValue();
            return ((k == null) ? 0 : k.hashCode()) ^
                   ((v == null) ? 0 : v.hashCode());
        }

        public String toString() {
            // If not acting as entry, just use default.
            if (lastReturned == null)
                return super.toString();
            else
                return getKey() + "=" + getValue();
        }

        boolean eq(Object o1, Object o2) {
            return (o1 == null ? o2 == null : o1.equals(o2));
        }

    }

    final class KeySet extends AbstractSet {
        public Iterator iterator() {
            return new KeyIterator();
        }
        public int size() {
            return ConcurrentHashMap.this.size();
        }
        public boolean contains(Object o) {
            return ConcurrentHashMap.this.containsKey(o);
        }
        public boolean remove(Object o) {
            return ConcurrentHashMap.this.remove(o) != null;
        }
        public void clear() {
            ConcurrentHashMap.this.clear();
        }
        public Object[] toArray() {
            Collection c = new ArrayList();
            for (Iterator i = iterator(); i.hasNext(); )
                c.add(i.next());
            return c.toArray();
        }
        public Object[] toArray(Object[] a) {
            Collection c = new ArrayList();
            for (Iterator i = iterator(); i.hasNext(); )
                c.add(i.next());
            return c.toArray(a);
        }
    }

    final class Values extends AbstractCollection {
        public Iterator iterator() {
            return new ValueIterator();
        }
        public int size() {
            return ConcurrentHashMap.this.size();
        }
        public boolean contains(Object o) {
            return ConcurrentHashMap.this.containsValue(o);
        }
        public void clear() {
            ConcurrentHashMap.this.clear();
        }
        public Object[] toArray() {
            Collection c = new ArrayList();
            for (Iterator i = iterator(); i.hasNext(); )
                c.add(i.next());
            return c.toArray();
        }
        public Object[] toArray(Object[] a) {
            Collection c = new ArrayList();
            for (Iterator i = iterator(); i.hasNext(); )
                c.add(i.next());
            return c.toArray(a);
        }
    }

    final class EntrySet extends AbstractSet {
        public Iterator iterator() {
            return new EntryIterator();
        }
        public boolean contains(Object o) {
            if (!(o instanceof Map.Entry))
                return false;
            Map.Entry e = (Map.Entry)o;
            Object v = ConcurrentHashMap.this.get(e.getKey());
            return v != null && v.equals(e.getValue());
        }
        public boolean remove(Object o) {
            if (!(o instanceof Map.Entry))
                return false;
            Map.Entry e = (Map.Entry)o;
            return ConcurrentHashMap.this.remove(e.getKey(), e.getValue());
        }
        public int size() {
            return ConcurrentHashMap.this.size();
        }
        public void clear() {
            ConcurrentHashMap.this.clear();
        }
        public Object[] toArray() {
            // Since we don't ordinarily have distinct Entry objects, we
            // must pack elements using exportable SimpleEntry
            Collection c = new ArrayList(size());
            for (Iterator i = iterator(); i.hasNext(); )
                c.add(new SimpleEntry((Entry)i.next()));
            return c.toArray();
        }
        public  Object[] toArray(Object[] a) {
            Collection c = new ArrayList(size());
            for (Iterator i = iterator(); i.hasNext(); )
                c.add(new SimpleEntry((Entry)i.next()));
            return c.toArray(a);
        }

    }

    /**
     * This duplicates java.util.AbstractMap.SimpleEntry until this class
     * is made accessible.
     */
    static final class SimpleEntry implements Entry {
        Object key;
        Object value;

        public SimpleEntry(Object key, Object value) {
            this.key   = key;
            this.value = value;
        }

        public SimpleEntry(Entry e) {
            this.key   = e.getKey();
            this.value = e.getValue();
        }

        public Object getKey() {
            return key;
        }

        public Object getValue() {
            return value;
        }

        public Object setValue(Object value) {
            Object oldValue = this.value;
            this.value = value;
            return oldValue;
        }

        public boolean equals(Object o) {
            if (!(o instanceof Map.Entry))
                return false;
            Map.Entry e = (Map.Entry)o;
            return eq(key, e.getKey()) && eq(value, e.getValue());
        }

        public int hashCode() {
            return ((key   == null)   ? 0 :   key.hashCode()) ^
                   ((value == null)   ? 0 : value.hashCode());
        }

        public String toString() {
            return key + "=" + value;
        }

        static boolean eq(Object o1, Object o2) {
            return (o1 == null ? o2 == null : o1.equals(o2));
        }
    }

    /* ---------------- Serialization Support -------------- */

    /**
     * Save the state of the <tt>ConcurrentHashMap</tt>
     * instance to a stream (i.e.,
     * serialize it).
     * @param s the stream
     * @serialData
     * the key (Object) and value (Object)
     * for each key-value mapping, followed by a null pair.
     * The key-value mappings are emitted in no particular order.
     */
    private void writeObject(java.io.ObjectOutputStream s) throws IOException  {
        s.defaultWriteObject();

        for (int k = 0; k < segments.length; ++k) {
            Segment seg = (Segment)segments[k];
            seg.lock();
            try {
                HashEntry[] tab = seg.table;
                for (int i = 0; i < tab.length; ++i) {
                    for (HashEntry e = (HashEntry)tab[i]; e != null; e = e.next) {
                        s.writeObject(e.key);
                        s.writeObject(e.value);
                    }
                }
            } finally {
                seg.unlock();
            }
        }
        s.writeObject(null);
        s.writeObject(null);
    }

    /**
     * Reconstitute the <tt>ConcurrentHashMap</tt>
     * instance from a stream (i.e.,
     * deserialize it).
     * @param s the stream
     */
    private void readObject(java.io.ObjectInputStream s)
        throws IOException, ClassNotFoundException  {
        s.defaultReadObject();

        // Initialize each segment to be minimally sized, and let grow.
        for (int i = 0; i < segments.length; ++i) {
            segments[i].setTable(new HashEntry[1]);
        }

        // Read the keys and values, and put the mappings in the table
        for (;;) {
            Object key = (Object) s.readObject();
            Object value = (Object) s.readObject();
            if (key == null)
                break;
            put(key, value);
        }
    }
}