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;- Top
; -----------------------------------------------------------------------------
;  Name        : StringBuilder Interface
;  Description : Fast String concatenation
;  Author      : HeX0R
;  Date        : 2023-02-16
;  Original    : https://www.purebasic.fr/english/viewtopic.php?p=558277#p558277
;  OS          : Cross-platform
;  Forum       : https://www.purebasic.fr/english/viewtopic.php?p=595972#p595972
;
; AND...ashes on my head!!:
; Base idea from mk-soft
;              : https://www.purebasic.fr/english/viewtopic.php?t=75758
; -----------------------------------------------------------------------------

Structure struc_StringBuilder
	VTable.i
	*Address
	*Pointer
	MemSize.i
	PacketSize.i
	Length.i
EndStructure

Interface IF_StringBuilder
	Add(String.s)
	GetString.s()
	Reset(KeepMemory = #False)
	Release()
EndInterface

Procedure __SB_Reset(*THIS.struc_StringBuilder, KeepMemory = #False)
	;Reset back to initial values, for reusing the interface
	If KeepMemory = #False
		If *THIS\MemSize > *THIS\PacketSize
			*THIS\Address = ReAllocateMemory(*THIS\Address, *THIS\PacketSize, #PB_Memory_NoClear)
		EndIf
		*THIS\MemSize = *THIS\PacketSize
	EndIf
	*THIS\Pointer = *THIS\Address
	*THIS\Length  = 0
EndProcedure

Procedure __SB_Add(*THIS.struc_StringBuilder, String.s)
	Protected Len, *Add, Result = #True
	
	Len = StringByteLength(String)
	If Len + *THIS\Length + 2 > *THIS\MemSize
		*THIS\MemSize = *THIS\Length + Len + 2 + *THIS\PacketSize
		*Add          = ReAllocateMemory(*THIS\Address, *THIS\MemSize, #PB_Memory_NoClear)
		If *Add
			If *Add <> *THIS\Address
				*THIS\Pointer = *THIS\Pointer - *THIS\Address + *Add
			EndIf
			*THIS\Address = *Add
		Else
			;not enough memory?
			ProcedureReturn #False
		EndIf
	EndIf
	CopyMemoryString(@String, @*THIS\Pointer)
	*THIS\Length + Len
	
	ProcedureReturn Result
EndProcedure

Procedure.s __SB_GetString(*THIS.struc_StringBuilder)
	ProcedureReturn PeekS(*THIS\Address, *THIS\Length / SizeOf(Character))
EndProcedure

Procedure __SB_Release(*THIS.struc_StringBuilder)
	If *THIS\Address
		FreeMemory(*THIS\Address)
	EndIf
	FreeMemory(*THIS)
EndProcedure

Procedure New_StringBuilder(PacketSize.i = 65536)
	Protected *THIS.struc_StringBuilder, *Buffer
	
	*THIS        = AllocateMemory(SizeOf(struc_StringBuilder))
	*THIS\VTable = ?_VT_STRINGBUILDER_
	If *THIS = 0
		ProcedureReturn #False
	EndIf
	
	*Buffer = AllocateMemory(PacketSize, #PB_Memory_NoClear)
	If *Buffer
		*THIS\Address    = *Buffer
		*THIS\Pointer    = *Buffer
		*THIS\PacketSize = PacketSize
		*THIS\MemSize    = PacketSize
		ProcedureReturn *THIS
	Else
		FreeMemory(*THIS)
	EndIf
	ProcedureReturn #False
	
	DataSection
		_VT_STRINGBUILDER_:
		Data.i @__SB_Add()
		Data.i @__SB_GetString()
		Data.i @__SB_Reset()
		Data.i @__SB_Release()
	EndDataSection
EndProcedure

;----------------------------EOF-------------------------


CompilerIf #PB_Compiler_IsMainFile
	
	Define i, a$, b$, c$, s1, s2
	Define SB.IF_StringBuilder
	
	SB = New_StringBuilder()
	a$ = "abcdefghijklmnopqrstuvwxyz" + #CRLF$
	s1 = ElapsedMilliseconds()
	For i = 1 To 10000
		SB\Add(a$)
	Next i
	b$ = SB\GetString()
	s1 = ElapsedMilliseconds() - s1
	s2 = ElapsedMilliseconds()
	For i = 1 To 10000
		c$ + a$
	Next i
	s2 = ElapsedMilliseconds() - s2
	MessageRequester("Info", ~"Stringbuilder: \t" + Str(s1) + ~"ms\nPB-Way: \t" + Str(s2) + "ms")
	;Debug b$
	SB\Release()
	
CompilerEndIf