// HASHMAP.CPP

//

// This file holds the class methods for the CHashMap

// A hash function for hash table lookup.  Assumes input data length is a multiple of 8-bits.

// 

// The original hash function was sourced from http://burtleburtle.net/bob/hash/index.html

// "By Bob Jenkins, 1996.  bob_jenkins@burtleburtle.net.  You may use this code any way you wish, 

// private, educational, or commercial.  It's free."

// portions Copyright (c) 1995 - 2010 Nokia Corporation and/or its subsidiary(-ies).

//

#include "SERVER.H"

CHashMap::CHashMap() :

	iTableSize(sizeof(iHashTable)/sizeof(CSharedBitmapObject*)),

	iMask(iTableSize-1)

	{

	}

CHashMap::~CHashMap()

	{

	for (TInt i=0; i<iTableSize; i++)

		{

		__ASSERT_DEBUG(iHashTable[i]==NULL, User::Invariant());

		}

	}

/* This function inserts a pointer to the CSharedBitmapObject into the hashmap.

The hashmap does not acquire ownership of the CSharedBitmapObject.

The key used for insertion is a pre-existing member of the CSharedBitmapObject.

The caller must ensure the key does not already exist in the hashmap prior to calling this function.

@param aBmpObj The CSharedBitmapObject to insert.

@param aHash The hash of the key of the CSharedBitmapObject.  This is provided for performance reasons explained in CFbTop::ShareBitmap.

@internalComponent

*/

void CHashMap::Insert(CSharedBitmapObject& aBmpObj, TUint aHash)

	{

	__ASSERT_DEBUG(aHash==Hash(*(aBmpObj.iKey)), User::Invariant());     // Verify the hash value

	__ASSERT_DEBUG(!Lookup(*(aBmpObj.iKey), aHash), User::Invariant());  // Duplicate keys are not allowed

	const TUint index = aHash & iMask;

	// Insert aBmpObj at head of list

	aBmpObj.iNext = iHashTable[index];

	iHashTable[index] = &aBmpObj;

	}

/* This function looks up a CSharedBitmapObject in the hashmap using a key.

Lookup is case sensitive.

@param aKey The key of the CSharedBitmapObject to be found.

@param aHash The hash of the key.  This is provided for performance reasons explained in CFbTop::ShareBitmap.

@return A pointer to the CSharedBitmapObject if the key is found.  NULL otherwise.

@internalComponent

*/

CSharedBitmapObject* CHashMap::Lookup(const TDesC& aKey, TUint aHash) const

	{

	const TUint index = aHash & iMask;

	for (CSharedBitmapObject* n=iHashTable[index]; n!=NULL; n=n->iNext) // n walks the links of the linked list.

		{

		if (n->iKey->Length()==aKey.Length() && !n->iKey->Compare(aKey))

			{

			return n;  // Key found

			}

		}

	return NULL;   // Key not found

	}

/* Removes a specific object from the hashmap.

The object is discovered using its key and address.

This function does not destroy the object.

@param aBmpObj The specific CSharedBitmapObject to be removed.

@return KErrNone if the object is found and removed.  An standard error otherwise.

@internalComponent

*/

TInt CHashMap::Remove(const CSharedBitmapObject& aBmpObj)

	{

	const TUint hash = Hash(*(aBmpObj.iKey));

	const TUint index = hash & iMask;

	for (CSharedBitmapObject** n=&iHashTable[index]; *n!=NULL; n=&((*n)->iNext))  // *n walks the links of the linked list.

		{

		if (&aBmpObj==*n)

			{

			*n = aBmpObj.iNext;  // Key found.  The link that was pointing to aBmpObj nows points to the successor of aBmpObj.

			return KErrNone;

			}	

		}

	return KErrNotFound;

	}

// Utility macro for the hash function

#define mix(a,b,c) \

{ \

  a -= b; a -= c; a ^= (c>>13); \

  b -= c; b -= a; b ^= (a<<8);  \

  c -= a; c -= b; c ^= (b>>13); \

  a -= b; a -= c; a ^= (c>>12); \

  b -= c; b -= a; b ^= (a<<16); \

  c -= a; c -= b; c ^= (b>>5);  \

  a -= b; a -= c; a ^= (c>>3);  \

  b -= c; b -= a; b ^= (a<<10); \

  c -= a; c -= b; c ^= (b>>15); \

}

/* A hash function for hash table lookup.

Assumes input data length is a multiple of 8-bits.

The original hash function was sourced from

http://burtleburtle.net/bob/hash/index.html

"By Bob Jenkins, 1996.  bob_jenkins@burtleburtle.net.  You may use this

code any way you wish, private, educational, or commercial.  It's free."

TUint CHashMap::Hash(const TDesC8& aKey)

	{

	const TUint8* k = aKey.Ptr();

	const TUint length = aKey.Length();

	const TUint initval = 0;

	TUint len = length;

	TUint a = 0x9e3779b9;

	TUint b = 0x9e3779b9;

	TUint c = initval;

	while (len >= 12)

		{

		a += (k[0] + ((TUint)k[1]<<8) + ((TUint)k[2] <<16) + ((TUint)k[3] <<24));

		b += (k[4] + ((TUint)k[5]<<8) + ((TUint)k[6] <<16) + ((TUint)k[7] <<24));

		c += (k[8] + ((TUint)k[9]<<8) + ((TUint)k[10]<<16) + ((TUint)k[11]<<24));

		mix(a,b,c);

		k += 12; len -= 12;

		}

	c += length;

	switch(len)

		{

		case 11: c+=((TUint)k[10]<<24);

		case 10: c+=((TUint)k[9]<<16);

		case 9 : c+=((TUint)k[8]<<8);

      // the first byte of c is reserved for the length

		case 8 : b+=((TUint)k[7]<<24);

		case 7 : b+=((TUint)k[6]<<16);

		case 6 : b+=((TUint)k[5]<<8);

		case 5 : b+=k[4];

		case 4 : a+=((TUint)k[3]<<24);

		case 3 : a+=((TUint)k[2]<<16);

		case 2 : a+=((TUint)k[1]<<8);

		case 1 : a+=k[0];

     // case 0: nothing left to add

		}

	mix(a,b,c);

	return c;

	}

*/

/* A hash function for hash table lookup.

Assumes input data length is a multiple of 16-bits.

@param aKey The data to be hashed

@return The hash value

@internalComponent

*/

TUint CHashMap::Hash(const TDesC16& aKey)

	{

	const TUint16* k = aKey.Ptr();

	const TUint length = aKey.Length();

	const TUint initval = 0;

	TUint len = length;

	TUint a = 0x9e3779b9;

	TUint b = 0x9e3779b9;

	TUint c = initval;

	while (len >= 6)

		{

		a += (k[0] + ((TUint)k[1]<<16));

		b += (k[2] + ((TUint)k[3]<<16));

		c += (k[4] + ((TUint)k[5]<<16));

		mix(a,b,c);

		k += 6; len -= 6;

		}

	c += length;

	switch(len)

		{

		case 5 : c+=((TUint)k[4]<<16);

      // the first byte of c is reserved for the length

		case 4 : b+=((TUint)k[3]<<16);

		case 3 : b+=k[2];

		case 2 : a+=((TUint)k[1]<<16);

		case 1 : a+=k[0];

     // case 0: nothing left to add

		}

	mix(a,b,c);

	return c;

	}