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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
//*****************************************************************************
// MetaDataHash.h -- Meta data hash data structures.
//
//
// Used by Emitters and by E&C.
//
//*****************************************************************************
#ifndef _MetaDataHash_h_
#define _MetaDataHash_h_
#if _MSC_VER >= 1100
# pragma once
#endif
#include "utilcode.h"
#define REHASH_THREADSHOLD 3
//*****************************************************************************
// A hash entry list item.
//*****************************************************************************
struct TOKENHASHENTRY
{
mdToken tok;
ULONG ulHash;
ULONG iNext;
};
//*****************************************************************************
// The following is a hash class definition used for hashing MemberDef. The difference
// from the hash table above is because it is expansive to retrieve the parent for MemberDef.
//
//*****************************************************************************
struct MEMBERDEFHASHENTRY
{
mdToken tok;
mdToken tkParent;
ULONG ulHash;
ULONG iNext;
};
//*****************************************************************************
// This class is used to create transient indexes for meta data structures.
// This class is generic; one must override it to provide hashing and
// accessor methods for your specific record type. It can start out on top
// of malloc with a small memory footprint, and as you get larger, it must
// be capable of rehashing.
//*****************************************************************************
template <class Entry> class CMetaDataHashTemplate
{
public:
CMetaDataHashTemplate()
{
m_rgBuckets = 0;
m_cItems = 0;
m_iBuckets = 0;
}
~CMetaDataHashTemplate()
{
// Free the bucket list.
if (m_rgBuckets)
{
delete [] m_rgBuckets;
m_rgBuckets = 0;
m_cItems = 0;
m_iBuckets = 0;
}
}
//*****************************************************************************
// Called to allocate the hash table entries so that new data may be added.
//*****************************************************************************
HRESULT NewInit( // Return status.
int iBuckets=17) // How many buckets you want.
{
m_rgBuckets = new (nothrow) int[iBuckets];
if (!m_rgBuckets)
return (OutOfMemory());
m_iBuckets = iBuckets;
memset(m_rgBuckets, ~0, sizeof(int) * iBuckets);
return (S_OK);
}
//*****************************************************************************
// Add new items to the hash list.
//*****************************************************************************
Entry *Add( // Pointer to element to write to.
ULONG iHash) // Hash value of entry to add.
{
Entry *p = 0;
HRESULT hr;
int iBucket = iHash % m_iBuckets;
if (m_cItems > REHASH_THREADSHOLD * m_iBuckets)
{
hr = ReHash();
if (FAILED(hr))
return (0);
iBucket = iHash % m_iBuckets;
}
// Add a new item pointer.
p = m_Heap.Append();
if (!p)
return (0);
// Chain the new item to the front of the heap.
p->iNext = m_rgBuckets[iBucket];
p->ulHash = iHash;
m_cItems++;
m_rgBuckets[iBucket] = m_Heap.ItemIndex(p);
return (p);
}
//*****************************************************************************
// Grow the hash table
//*****************************************************************************
HRESULT ReHash()
{
int *rgBuckets;
int iBuckets;
int iBucket;
int index;
int iCount;
Entry *p = 0;
iBuckets = m_iBuckets*2 -1;
rgBuckets = new (nothrow) int[iBuckets];
if (!rgBuckets)
return (OutOfMemory());
memset(rgBuckets, ~0, sizeof(int) * iBuckets);
// loop through each of data and rehash them
iCount = m_Heap.Count();
for (index = 0; index < iCount; index++)
{
// get the hash value of the entry
p = m_Heap.Get(index);
// rehash the entry
iBucket = p->ulHash % iBuckets;
// Chain the item to the front of the new heap.
p->iNext = rgBuckets[iBucket];
rgBuckets[iBucket] = index;
}
// swap the hash table
delete [] m_rgBuckets;
m_rgBuckets = rgBuckets;
m_iBuckets = iBuckets;
return NOERROR;
}
//*****************************************************************************
// Find first/find next node for a chain given the hash.
//*****************************************************************************
Entry *FindFirst( // Return entry.
ULONG iHash, // The hash value for the entry.
int &POS) // Current position.
{
int iBucket = iHash % m_iBuckets;
POS = m_rgBuckets[iBucket];
return (FindNext(POS));
}
Entry *FindNext( // Return entry or 0.
int &POS) // Current location.
{
Entry *p;
if (POS == ~0)
return (0);
p = m_Heap.Get(POS);
POS = p->iNext;
return (p);
}
private:
CDynArray<Entry> m_Heap; // First heap in the list.
int *m_rgBuckets; // Bucket list.
int m_iBuckets; // How many buckets.
int m_cItems; // Number of items in the hash
};
class CMetaDataHashBase : public CMetaDataHashTemplate<TOKENHASHENTRY>
{
};
class CMemberDefHash : public CMetaDataHashTemplate<MEMBERDEFHASHENTRY>
{
};
#endif // _MetaDataHash_h_
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