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Brian Matzon
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<html>
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<head>
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<title>OpenAL Tutoral</title>
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<meta http-equiv="content-type" content="text/html; charset=windows-1252">
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<meta name="author" content="Brian Matzon">
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<meta name="description" content="Basic sound using OpenAL">
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</head>
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<body>
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<h1 align="center">Array Conversion<br>
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<font size="-1">(by Brian Matzon <<a href="mailto:brian@matzon.dk">brian@matzon.dk</a>>)</font><br>
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</h1>
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<b>1.0 About this document</b><br>
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This document describes the typical rules for converting arrays often used in
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C/C++ OpenAL (and indeed OpenGL too) code.<br>
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It is not bullet proof, but should handle most cases.<br>
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<br>
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<b>1.1 Array to ByteBuffer<br>
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</b>When using an array of some data type in C/C++
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you will typically convert that<br>
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to the corresponding ByteBuffer type. ie:<p
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style="border-style: solid; border-width: 1px; padding: 3px; background-color: rgb(255,255,204);"><tt>ALfloat
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floatv[3];</tt></p>
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<p>becomes</p>
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<p
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style="border-style: solid; border-width: 1px; padding: 3px; background-color: rgb(255,255,204);"><tt>
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FloatBuffer floatv = createFloatBuffer(3);</tt></p>
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<p>In this example, <tt>createFloatBuffer</tt>
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is this utility method:</p>
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<p
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style="border-style: solid; border-width: 1px; padding: 3px; background-color: rgb(255,255,204);"><tt>
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public FloatBuffer createFloatBuffer(int size) {<br>
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//allocate bytebuffer, using 4 bytes per float<br>
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ByteBuffer temp = ByteBuffer.allocateDirect(4*size);<br>
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temp.order(ByteOrder.nativeOrder());<br>
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<br>
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return temp.asFloatBuffer();<br>
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}</tt></p>
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<p>
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<b>1.2 Examples</b><br>
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Using the above FloatBuffer, you would typically use it like this (examples
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taken from altest.c/ALTest.java):</p>
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<p>
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<b>1.2.1 Example 1</b></p>
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<p
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style="border-style: solid; border-width: 1px; padding: 3px; background-color: rgb(255,255,204);"><tt>
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alGetListenerfv(AL_POSITION, floatv);</tt></p>
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<p>
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becomes</p>
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<p
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style="border-style: solid; border-width: 1px; padding: 3px; background-color: rgb(255,255,204);"><tt>
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al.getListenerfv(AL.POSITION, Sys.getDirectBufferAddress(floatv));</tt></p>
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<p><b>1.2.2 Example 2</b></p>
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<p
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style="border-style: solid; border-width: 1px; padding: 3px; background-color: rgb(255,255,204);"><tt>
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if (floatv[0] != 100.0)) {</tt></p>
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<p>becomes:</p>
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<p
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style="border-style: solid; border-width: 1px; padding: 3px; background-color: rgb(255,255,204);"><tt>
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if (floatv.get(0) != 100.0f) {</tt></p>
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<p><b>1.2.3 Example 3</b></p>
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<p
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style="border-style: solid; border-width: 1px; padding: 3px; background-color: rgb(255,255,204);"><tt>
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alGetListener3f(AL_POSITION, &floatv[0], <br>
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&floatv[1], <br>
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&floatv[2]);</tt></p>
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<p>becomes</p>
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<p
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style="border-style: solid; border-width: 1px; padding: 3px; background-color: rgb(255,255,204);"><tt>
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al.getListener3f(AL.POSITION, Sys.getDirectBufferAddress(floatv), <br>
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Sys.getDirectBufferAddress(floatv) + 4, <br>
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Sys.getDirectBufferAddress(floatv) + 8);</tt></p>
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<p>the last case is a bit special, since we start of by getting the base
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address of the buffer, and then add the datatype size to the base address<br>
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to get the address of that specific index. This is just how it has to
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be in Java.</p>
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</body>
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</html>
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@ -1,45 +0,0 @@
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Author: Brian Matzon <brian@matzon.dk>
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When converting C/C++ OpenAL code to Java the following
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conversion rules, typically apply:
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When using an array of some data type in C/C++ you will typically convert that
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to the corresponding ByteBuffer type. ie:
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ALfloat floatv[3];
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becomes
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FloatBuffer floatv = createFloatBuffer(3);
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In this example, createFloatBuffer is this utility method:
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public FloatBuffer createFloatBuffer(int size) {
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//allocate bytebuffer, using 4 bytes per float
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ByteBuffer temp = ByteBuffer.allocateDirect(4*size);
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temp.order(ByteOrder.nativeOrder());
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return temp.asFloatBuffer();
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}
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Using the above FloatBuffer, you would typically use it like this:
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(examples taken from altest.c/ALTest.java):
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example 1:
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alGetListenerfv(AL_POSITION, floatv);
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becomes
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al.getListenerfv(AL.POSITION, Sys.getDirectBufferAddress(floatv));
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example 2:
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if (floatv[0] != 100.0)) {
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becomes:
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if (floatv.get(0) != 100.0f) {
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example 3:
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alGetListener3f(AL_POSITION, &floatv[0],
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&floatv[1],
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&floatv[2]);
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becomes
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al.getListener3f(AL.POSITION, Sys.getDirectBufferAddress(floatv),
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Sys.getDirectBufferAddress(floatv) + 4,
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Sys.getDirectBufferAddress(floatv) + 8);
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the last case is a bit special, since we start of by getting the base
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address of the buffer, and then add the datatype size to the base address
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to get the address of that specific index. This is just how it has to
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be in Java.
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