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241 lines
9.0 KiB
241 lines
9.0 KiB
#import "HashMap.h"
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/**
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* <p>Hash table and linked list implementation of the <tt>Map</tt> interface,
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* with predictable iteration order. This implementation differs from
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* <tt>HashMap</tt> in that it maintains a doubly-linked list running through
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* all of its entries. This linked list defines the iteration ordering,
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* which is normally the order in which keys were inserted into the map
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* (<i>insertion-order</i>). Note that insertion order is not affected
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* if a key is <i>re-inserted</i> into the map. (A key <tt>k</tt> is
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* reinserted into a map <tt>m</tt> if <tt>m.put(k, v)</tt> is invoked when
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* <tt>m.containsKey(k)</tt> would return <tt>true</tt> immediately prior to
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* the invocation.)
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*
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* <p>This implementation spares its clients from the unspecified, generally
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* chaotic ordering provided by {@link HashMap} (and {@link Hashtable}),
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* without incurring the increased cost associated with {@link TreeMap}. It
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* can be used to produce a copy of a map that has the same order as the
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* original, regardless of the original map's implementation:
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* <pre>
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* void foo(Map m) {
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* Map copy = new LinkedHashMap(m);
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* ...
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* }
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* </pre>
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* This technique is particularly useful if a module takes a map on input,
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* copies it, and later returns results whose order is determined by that of
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* the copy. (Clients generally appreciate having things returned in the same
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* order they were presented.)
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*
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* <p>A special {@link #LinkedHashMap(NSInteger,float,boolean) constructor} is
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* provided to create a linked hash map whose order of iteration is the order
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* in which its entries were last accessed, from least-recently accessed to
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* most-recently (<i>access-order</i>). This kind of map is well-suited to
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* building LRU caches. Invoking the <tt>put</tt> or <tt>get</tt> method
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* results in an access to the corresponding entry (assuming it exists after
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* the invocation completes). The <tt>putAll</tt> method generates one entry
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* access for each mapping in the specified map, in the order that key-value
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* mappings are provided by the specified map's entry set iterator. <i>No
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* other methods generate entry accesses.</i> In particular, operations on
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* collection-views do <i>not</i> affect the order of iteration of the backing
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* map.
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*
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* <p>The {@link #removeEldestEntry(Map.Entry)} method may be overridden to
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* impose a policy for removing stale mappings automatically when new mappings
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* are added to the map.
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*
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* <p>This class provides all of the optional <tt>Map</tt> operations, and
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* permits null elements. Like <tt>HashMap</tt>, it provides constant-time
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* performance for the basic operations (<tt>add</tt>, <tt>contains</tt> and
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* <tt>remove</tt>), assuming the hash function disperses elements
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* properly among the buckets. Performance is likely to be just slightly
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* below that of <tt>HashMap</tt>, due to the added expense of maintaining the
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* linked list, with one exception: Iteration over the collection-views
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* of a <tt>LinkedHashMap</tt> requires time proportional to the <i>size</i>
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* of the map, regardless of its capacity. Iteration over a <tt>HashMap</tt>
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* is likely to be more expensive, requiring time proportional to its
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* <i>capacity</i>.
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*
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* <p>A linked hash map has two parameters that affect its performance:
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* <i>initial capacity</i> and <i>load factor</i>. They are defined precisely
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* as for <tt>HashMap</tt>. Note, however, that the penalty for choosing an
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* excessively high value for initial capacity is less severe for this class
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* than for <tt>HashMap</tt>, as iteration times for this class are unaffected
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* by capacity.
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*
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* <p><strong>Note that this implementation is not synchronized.</strong>
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* If multiple threads access a linked hash map concurrently, and at least
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* one of the threads modifies the map structurally, it <em>must</em> be
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* synchronized externally. This is typically accomplished by
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* synchronizing on some object that naturally encapsulates the map.
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*
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* If no such object exists, the map should be "wrapped" using the
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* {@link Collections#synchronizedMap Collections.synchronizedMap}
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* method. This is best done at creation time, to prevent accidental
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* unsynchronized access to the map:<pre>
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* Map m = Collections.synchronizedMap(new LinkedHashMap(...));</pre>
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*
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* A structural modification is any operation that adds or deletes one or more
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* mappings or, in the case of access-ordered linked hash maps, affects
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* iteration order. In insertion-ordered linked hash maps, merely changing
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* the value associated with a key that is already contained in the map is not
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* a structural modification. <strong>In access-ordered linked hash maps,
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* merely querying the map with <tt>get</tt> is a structural
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* modification.</strong>)
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*
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* <p>The iterators returned by the <tt>iterator</tt> method of the collections
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* returned by all of this class's collection view methods are
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* <em>fail-fast</em>: if the map is structurally modified at any time after
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* the iterator is created, in any way except through the iterator's own
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* <tt>remove</tt> method, the iterator will throw a {@link
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* ConcurrentModificationException}. Thus, in the face of concurrent
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* modification, the iterator fails quickly and cleanly, rather than risking
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* arbitrary, non-deterministic behavior at an undetermined time in the future.
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*
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* <p>Note that the fail-fast behavior of an iterator cannot be guaranteed
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* as it is, generally speaking, impossible to make any hard guarantees in the
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* presence of unsynchronized concurrent modification. Fail-fast iterators
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* throw <tt>ConcurrentModificationException</tt> on a best-effort basis.
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* Therefore, it would be wrong to write a program that depended on this
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* exception for its correctness: <i>the fail-fast behavior of iterators
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* should be used only to detect bugs.</i>
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*
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* <p>This class is a member of the
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* <a href="{@docRoot}/../technotes/guides/collections/index.html">
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* Java Collections Framework</a>.
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*
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* @param <K> the type of keys maintained by this map
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* @param <V> the type of mapped values
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*
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* @author Josh Bloch
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* @see Object#hashCode()
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* @see Collection
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* @see Map
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* @see HashMap
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* @see TreeMap
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* @see Hashtable
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* @since 1.4
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*/
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@class LinkedHashMap;
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/**
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* LinkedHashMap entry.
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*/
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@interface LHMEntry : HMEntry
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{
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LHMEntry *before;
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LHMEntry *after;
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BOOL accessOrder;
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}
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@property (retain) LHMEntry *before;
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@property (retain) LHMEntry *after;
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@property (assign) BOOL accessOrder;
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- (id) newEntry:(NSInteger)aHash key:(NSString *)aKey value:(id)aValue next:(LHMEntry *)aNext;
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- (id) init:(NSInteger)hash key:(NSString *)key value:(id)value next:(LHMEntry *)next;
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- (void) recordAccess:(LinkedHashMap *)m;
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- (void) recordRemoval:(LinkedHashMap *)m;
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@end
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/**
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* LinkedHashMapIterator.
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*/
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@interface LinkedHashIterator : HashIterator
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{
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LHMEntry *nextEntry;
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LHMEntry *lastReturned;
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LinkedHashMap *lhm;
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}
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@property (retain) LHMEntry *nextEntry;
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@property (retain) LHMEntry *lastReturned;
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@property (retain) LinkedHashMap *lhm;
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+ (LinkedHashIterator *) newIterator:(LinkedHashMap *)aLHM;
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- (id) init:(LinkedHashMap *)aLHM;
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- (BOOL) hasNext;
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- (void) remove;
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- (LHMEntry *) nextEntry;
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@end
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@interface LHMEntryIterator : LinkedHashIterator
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{
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}
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+ (LHMEntryIterator *)newIterator:(LinkedHashMap *)aHM;
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- (id) init:(LinkedHashMap *)aHM;
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- (LHMEntry *) next;
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@end
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@interface LHMKeyIterator : LinkedHashIterator
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{
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}
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+ (LHMKeyIterator *)newIterator:(LinkedHashMap *)aHM;
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- (id) init:(LinkedHashMap *)aHM;
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- (NSString *) next;
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@end
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@interface LHMValueIterator : LinkedHashIterator
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{
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}
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+ (LHMValueIterator *)newIterator:(LinkedHashMap *)aHM;
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- (id) init:(LinkedHashMap *)aHM;
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- (id) next;
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@end
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@interface LinkedHashMap : HashMap
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{
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/**
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* The head of the doubly linked list.
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*/
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LHMEntry *header;
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/**
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* The iteration ordering method for this linked hash map: <tt>true</tt>
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* for access-order, <tt>false</tt> for insertion-order.
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*
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* @serial
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*/
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BOOL accessOrder;
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}
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@property (retain) LHMEntry *header;
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@property (assign) BOOL accessOrder;
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+ (id) newLinkedHashMap:(NSInteger)anInitialCapacity;
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+ (id) newLinkedHashMap:(NSInteger)anInitialCapacity
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loadFactor:(float)loadFactor;
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+ (id) newLinkedHashMap:(NSInteger)anInitialCapacity
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loadFactor:(float)loadFactor
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accessOrder:(BOOL)anAccessOrder;
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- (id) init:(NSInteger)initialCapacity loadFactor:(float)loadFactor accessOrder:(BOOL)accessOrder;
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- (id) init:(NSInteger)initialCapacity loadFactor:(float)loadFactor;
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- (id) init:(NSInteger)initialCapacity;
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- (id) init;
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- (id) initWithM:(AMutableDictionary *)m;
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- (void) transfer:(NSArray *)newTable;
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- (BOOL) containsValue:(NSObject *)value;
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- (id) get:(NSString *)key;
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- (void) clear;
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- (LHMEntryIterator *) newEntryIterator;
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- (LHMKeyIterator *) newKeyIterator;
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- (LHMValueIterator *) newValueIterator;
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- (void) addEntry:(NSInteger)hash key:(NSString *)key value:(id)value bucketIndex:(NSInteger)bucketIndex;
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- (void) createEntry:(NSInteger)hash key:(NSString *)key value:(id)value bucketIndex:(NSInteger)bucketIndex;
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- (BOOL) removeEldestEntry:(LHMEntry *)eldest;
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@end
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