Michael Dirks
7cc0788e8b
- Update Example08.bb to be more detailed - Added function to grab Type pointers (would previously crash).
119 lines
4.6 KiB
BlitzBasic
119 lines
4.6 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 6 - Direct Memory Access
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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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; Prerequisite: Example 5
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; --!-!!!-!--
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; This Example is aimed at Experts. You will most likely never need this.
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; --!-!!!-!--
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; BlitzPointer ships with functions for direct memory access, allowing you to
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; modify things that were previously out of reach. The functions follow the
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; typical style of Bank access, Peek and Poke:
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; PeekMemoryByte%(MemoryAddress%) / PokeMemoryByte(MemoryAddress%, Value%)
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; PeekMemoryShort%(MemoryAddress%) / PokeMemoryShort(MemoryAddress%, Value%)
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; PeekMemoryInt%(MemoryAddress%) / PokeMemoryInt(MemoryAddress%, Value%)
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; PeekMemoryFloat#(MemoryAddress%) / PokeMemoryFloat(MemoryAddress%, Value#)
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; PeekMemory%(MemoryAddress%, Length%, Bank%) / PokeMemory%(MemoryAddress%, Length%, Bank%)
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; This function allows you to directly read and write from memory into a Bank
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; or from a Bank, saving you a few instructions per access. It will only read
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; or write as many bytes as your Bank holds and returns the amount of read or
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; written bytes.
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; These allow us to do simple direct memory modification, allowing us to do some
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; things that were previously only possible using MemMove and MemCopy from
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; the Windows libraries.
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; For example, Types in Blitz follow this structure:
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; ---------------------------------------------------------------------------- ;
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; Offset Type Description
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; ---------------------------------------------------------------------------- ;
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; 0 Pointer Pointer to Field Data
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; 4 Pointer Next Type Object or Type Structure (Last Element Signal)
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; 8 Pointer Prev Type Object or Type Structure (First Element Signal)
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; 12 Pointer Type Structure
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; 16 Integer Reference Count
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; 20+ ... Your Field Data usually follows here.
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;
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; We can do some fun stuff with this information.
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; If you want to know more about the internal structure of Blitz, there are some
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; resources that people have compiled in addition to the official source:
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; Structures: http://www.blitzforum.de/forum/viewtopic.php?t=4320
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; Source Code: http://github.com/blitz-research/
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Include "Example_Shared.bb"
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ExampleInit()
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; Our Type will hold one of every Element.
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Type EverythingType
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Field MyInt%
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Field MyFloat#
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Field MyString$
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Field MyObject.EverythingType
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; It is important to note that Blitz doesn't consider Arrays as pointers, but
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; as solid blocks in memory instead. This is why we can't make them dynamic,
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; and have to use Dim or Banks.
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Field MyIntArray%[5]
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Field MyFloatArray#[5]
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Field MyStringArray$[5]
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Field MyObjectArray.EverythingType[5]
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End Type
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; And create a function that modifies only using pointers.
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Global fpMyPointerFunction% = 0
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Function MyPointerFunction(Pointer%)
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If fpMyPointerFunction = 0 Then
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fpMyPointerFunction = BP_GetFunctionPointer()
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Return
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EndIf
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; Simple Memory modification
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PokeMemoryInt Pointer + 20, PeekMemoryInt(Pointer + 20) + 1
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PokeMemoryFloat Pointer + 24, PeekMemoryFloat(Pointer + 24) + 1
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; Sick of reference counting? Do Circular References without incrementing that!
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PokeMemoryInt Pointer + 32, Pointer
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End Function
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MyPointerFunction(0)
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Local Instance.EverythingType = New EverythingType
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While Not KeyHit(1)
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ExampleUpdate()
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MyPointerFunction(Int(Instance))
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Text 0, 0, "\MyInt"
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Text 200, 0, Instance\MyInt
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Text 0,15, "\MyFloat"
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Text 200,15, Instance\MyFloat
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; Circular Reference
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Text 0,45, "\MyObject\MyInt"
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Text 200,45, Instance\MyObject\MyInt
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Text 0,60, "\MyObject\MyObject\MyInt"
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Text 200,60, Instance\MyObject\MyObject\MyInt
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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 |