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// ==++==
//
// Copyright (c) Microsoft Corporation. All rights reserved.
//
// ==--==
// =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
//
// HashLookup.cs
//
// <OWNER>Microsoft</OWNER>
//
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
using System.Collections.Generic;
using System.Diagnostics.Contracts;
namespace System.Linq.Parallel
{
/// <summary>
/// A simple hash map data structure, derived from the LINQ set we also use.
/// </summary>
/// <typeparam name="TKey">The kind of keys contained within.</typeparam>
/// <typeparam name="TValue">The kind of values contained within.</typeparam>
internal class HashLookup<TKey, TValue>
{
int[] buckets;
Slot[] slots;
int count;
int freeList;
IEqualityComparer<TKey> comparer;
internal HashLookup() : this(null)
{
}
internal HashLookup(IEqualityComparer<TKey> comparer)
{
this.comparer = comparer;
buckets = new int[7];
slots = new Slot[7];
freeList = -1;
}
// If value is not in set, add it and return true; otherwise return false
internal bool Add(TKey key, TValue value)
{
return !Find(key, true, false, ref value);
}
// Check whether value is in set
internal bool TryGetValue(TKey key, ref TValue value)
{
return Find(key, false, false, ref value);
}
internal TValue this[TKey key]
{
set
{
TValue v = value;
Find(key, false, true, ref v);
}
}
private int GetKeyHashCode(TKey key)
{
return 0x7fffffff &
(comparer == null ?
(key == null ? 0 : key.GetHashCode()) :
comparer.GetHashCode(key));
}
private bool AreKeysEqual(TKey key1, TKey key2)
{
return
(comparer == null ?
((key1 == null && key2 == null) || (key1 != null && key1.Equals(key2))) :
comparer.Equals(key1, key2));
}
// If value is in set, remove it and return true; otherwise return false
internal bool Remove(TKey key)
{
int hashCode = GetKeyHashCode(key);
int bucket = hashCode % buckets.Length;
int last = -1;
for (int i = buckets[bucket] - 1; i >= 0; last = i, i = slots[i].next)
{
if (slots[i].hashCode == hashCode && AreKeysEqual(slots[i].key, key))
{
if (last < 0)
{
buckets[bucket] = slots[i].next + 1;
}
else
{
slots[last].next = slots[i].next;
}
slots[i].hashCode = -1;
slots[i].key = default(TKey);
slots[i].value = default(TValue);
slots[i].next = freeList;
freeList = i;
return true;
}
}
return false;
}
private bool Find(TKey key, bool add, bool set, ref TValue value)
{
int hashCode = GetKeyHashCode(key);
for (int i = buckets[hashCode % buckets.Length] - 1; i >= 0; i = slots[i].next)
{
if (slots[i].hashCode == hashCode && AreKeysEqual(slots[i].key, key))
{
if (set)
{
slots[i].value = value;
return true;
}
else
{
value = slots[i].value;
return true;
}
}
}
if (add)
{
int index;
if (freeList >= 0)
{
index = freeList;
freeList = slots[index].next;
}
else
{
if (count == slots.Length) Resize();
index = count;
count++;
}
int bucket = hashCode % buckets.Length;
slots[index].hashCode = hashCode;
slots[index].key = key;
slots[index].value = value;
slots[index].next = buckets[bucket] - 1;
buckets[bucket] = index + 1;
}
return false;
}
void Resize()
{
int newSize = checked(count * 2 + 1);
int[] newBuckets = new int[newSize];
Slot[] newSlots = new Slot[newSize];
Array.Copy(slots, 0, newSlots, 0, count);
for (int i = 0; i < count; i++)
{
int bucket = newSlots[i].hashCode % newSize;
newSlots[i].next = newBuckets[bucket] - 1;
newBuckets[bucket] = i + 1;
}
buckets = newBuckets;
slots = newSlots;
}
internal int Count
{
get { return count; }
}
internal KeyValuePair<TKey, TValue> this[int index]
{
get { return new KeyValuePair<TKey, TValue>(slots[index].key, slots[index].value); }
}
internal struct Slot
{
internal int hashCode;
internal TKey key;
internal TValue value;
internal int next;
}
}
}
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