Michael Dirks
7cc0788e8b
- Update Example08.bb to be more detailed - Added function to grab Type pointers (would previously crash).
72 lines
2.8 KiB
BlitzBasic
72 lines
2.8 KiB
BlitzBasic
; BlitzPointer - Adding Pointers to Blitz.
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; Copyright (C) 2015 Xaymar (Michael Fabian Dirks)
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;
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; This program is free software: you can redistribute it and/or modify
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; it under the terms of the GNU Lesser General Public License as
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; published by the Free Software Foundation, either version 3 of the
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; License, or (at your option) any later version.
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;
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; This program is distributed in the hope that it will be useful,
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; but WITHOUT ANY WARRANTY; without even the implied warranty of
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; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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; GNU General Public License for more details.
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;
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; You should have received a copy of the GNU Lesser General Public License
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; along with this program. If not, see <http:;www.gnu.org/licenses/>.
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; ---------------------------------------------------------------------------- ;
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; Example 1 - Retrieving Function Pointers
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; ---------------------------------------------------------------------------- ;
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; License: Creative Commons Attribution 2.0
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; Author: Michael Fabian Dirks<michael.dirks@realitybends.de>
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; If you don't know what a pointer is, I recommend googling it.
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; Blitz doesn't offer native ways of getting function pointers, nor would they
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; work with anything but tailored ASM calls. So what can they be useful for?
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; Here are some examples on what you can do:
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; * Footprint-only Callbacks (no longer need to override functions)
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; * Creating APIs that support multiple versions.
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Include "Example_Shared.bb"
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ExampleInit()
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; We begin by initalizing a variable to hold our pointer. Globals work best for
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; this task as we don't have to use a function parameter.
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Global fpOurFunction = 0
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; Our function can be anything we want, however we must be able to call it once
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; without effect before we can actually retrieve the function pointer. Why?
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; Simple! The BP_GetFunctionPointer traces the return address for the
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; Blitz function signature - and thus can't work outside a function.
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Function OurFunction()
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; Let's begin by checking if we already have the pointer. Not required, but
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; we do it anyway to save some scanning time on every call.
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If fpOurFunction = 0 Then
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; Now let us call the above mentioned function to retrieve the pointer.
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fpOurFunction = BP_GetFunctionPointer()
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; Weether you use a Return or an Else is up to you. Return is technically
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; faster in Blitz, as using Else causes a complex ASM construction.
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Return
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EndIf
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; For proof reasons, we show the pointer on the screen.
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Text 0, 0, "Function Pointer"
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Text 0,15, " 0x" + Replace(RSet(Hex(fpOurFunction),8)," ","0")
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End Function
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; Now we call our function once. Since there is no function pointer assigned
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; it will return almost immediately.
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OurFunction()
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While Not KeyHit(1)
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ExampleUpdate()
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OurFunction()
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ExampleLoop()
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Wend
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End
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;~IDEal Editor Parameters:
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;~C#Blitz3D |