[Java-game-lib-cvs] CVS: LWJGL/doc openal_c-to-java.txt,NONE,1.1

[Brian M. <ma...@us...>]

Update of /cvsroot/java-game-lib/LWJGL/doc
In directory usw-pr-cvs1:/tmp/cvs-serv26864

Added Files:
	openal_c-to-java.txt 
Log Message:
initial import of basic OpenAL conversion from c/c++ to Java

--- NEW FILE: openal_c-to-java.txt ---
CVS Browser:
http://cvs.sourceforge.net/cgi-bin/viewcvs.cgi/java-game-lib/LWJGL/doc/openal_c-to-java.txt
Author: Brian Matzon <br...@ma...>

When converting C/C++ OpenAL code to Java the following 
conversion rules, typically apply:

When using an array of some data type in C/C++ you will typically convert that
to the corresponding ByteBuffer type. ie:
 ALfloat floatv[3];
becomes
 FloatBuffer floatv = createFloatBuffer(3);

In this example, createFloatBuffer is this utility method:
public FloatBuffer createFloatBuffer(int size) {
  //allocate bytebuffer, using 4 bytes per float
  ByteBuffer temp = ByteBuffer.allocateDirect(4*size);
  temp.order(ByteOrder.nativeOrder());
        
  return temp.asFloatBuffer();
}

Using the above FloatBuffer, you would typically use it like this:
(examples taken from altest.c/ALTest.java):
example 1:
 alGetListenerfv(AL_POSITION, floatv);
becomes
 al.getListenerfv(AL.POSITION, Sys.getDirectBufferAddress(floatv));

example 2:
 if (floatv[0] != 100.0)) {
becomes:
 if (floatv.get(0) != 100.0f) {

example 3:
 alGetListener3f(AL_POSITION, &floatv[0], 
                                &floatv[1], 
                                &floatv[2]);
becomes
 al.getListener3f(AL.POSITION, Sys.getDirectBufferAddress(floatv), 
                                Sys.getDirectBufferAddress(floatv) + 4, 
                                Sys.getDirectBufferAddress(floatv) + 8);

the last case is a bit special, since we start of by getting the base 
address of the buffer, and then add the datatype size to the base address
to get the address of that specific index. This is just how it has to 
be in Java.