EnableExplicit

#HashMap_InitialPower = 9
#HashMap_InsertIterations = 100000

;{

Structure ChainedHashMapBucket
	*BucketData
	*Next.ChainedHashMapBucket
	Hash.q
EndStructure

Structure ChainedHashMap
	EntryCount.i
	Capacity.i
	SizePower.a
	*Buckets.ChainedHashMapBucket[0]
EndStructure


Prototype CbFree(*Data)

Procedure.l MakeBitMask(BitCount.b)
	EnableASM
	MOV eax, $00000001
	MOV cl, BitCount
	SHL eax, cl
	DEC eax
	ProcedureReturn
	DisableASM
EndProcedure

Procedure.i CHM_Create(SizePower.b)
	Protected *CHM.ChainedHashMap = AllocateMemory(SizeOf(ChainedHashMap) + (SizeOf(Integer) * (MakeBitMask(SizePower) + 1)))
	
	If *CHM <> #Null
		*CHM\EntryCount = 0
		*CHM\SizePower = SizePower
		
		Protected iBucket 
		For iBucket = 0 To MakeBitMask(SizePower)
			*CHM\Buckets[iBucket] = #Null
		Next
	EndIf
	
	ProcedureReturn *CHM
EndProcedure

Procedure.i CHM_GetByHash(*CHM.ChainedHashMap, Hash.q)
	If *CHM <> #Null
		Protected *CurrentBucket.ChainedHashMapBucket = *CHM\Buckets[(Hash & MakeBitMask(*CHM\SizePower))]
		
		While *CurrentBucket <> #Null
			If *CurrentBucket\Hash = Hash
				ProcedureReturn *CurrentBucket\BucketData
			EndIf
			*CurrentBucket = *CurrentBucket\Next
		Wend
	EndIf
	
	ProcedureReturn #Null
EndProcedure

Procedure.b CHM_OverwriteByHash(*CHM.ChainedHashMap, *Data, Hash.q, *FreeingCallback.CbFree = #Null)
	If *CHM <> #Null
		Protected *PreviousBucket.ChainedHashMapBucket = #Null
		Protected *CurrentBucket.ChainedHashMapBucket = *CHM\Buckets[(Hash & MakeBitMask(*CHM\SizePower))]
		
		; We iterate over the bucket chain until we find a collision or an in-between.
		While *CurrentBucket <> #Null
			If *CurrentBucket\Hash >= Hash
				Break
			EndIf
			*PreviousBucket = *CurrentBucket
			*CurrentBucket = *CurrentBucket\Next
		Wend
		
		If *CurrentBucket = #Null Or *CurrentBucket\Hash <> Hash
			; We either reached the end of the list, or no buckets was in the current slot.
			; Or, we have an in-between, or we are at the start of the list.
			Protected *NewBucket.ChainedHashMapBucket = AllocateMemory(SizeOf(ChainedHashMapBucket))
			
			If *NewBucket <> #Null
				*NewBucket\Next = *CurrentBucket
				*NewBucket\BucketData = *Data
				*NewBucket\Hash = Hash
				
				If *PreviousBucket <> #Null
					; In-between, or we are at the start of the List.
					*PreviousBucket\Next = *NewBucket
				Else
					; Start of the list.
					*CHM\Buckets[(Hash & MakeBitMask(*CHM\SizePower))] = *NewBucket
				EndIf
				
				*CHM\EntryCount = *CHM\EntryCount + 1
				ProcedureReturn #True
			EndIf
		ElseIf *FreeingCallback <> #Null
			; Handling collision.
			CallFunctionFast(*FreeingCallback, *CurrentBucket\BucketData)
			*CurrentBucket\BucketData = *Data
			ProcedureReturn #True
		EndIf
		; Implied else: Handling collision while forbidden to overwrite => doing nothing.
	EndIf
	
	ProcedureReturn #False
EndProcedure

Procedure CHM_DeleteByHash(*CHM.ChainedHashMap, Hash.q)
	
EndProcedure

Procedure CHM_Free(*CHM.ChainedHashMap)
	
EndProcedure

Procedure NoopFree(*Data) : EndProcedure