这是一个关于RenderScript如何使用 Struct 的文章，是学习RenderScript 一个必须要掌握的基础知识点。
大纲
- 如何定义Struct
- 如何得到指针长度并循环为指针赋值
- 整体DEMO代码
如何定义Struct
RenderScript 里面定义结构有两种定义方法，参考如下：
1.
typedef struct tempArray
{
float2 position
;
float size
;
} Array_T
;
Array_T *myArray;
2.
//定义一个struct
typedef struct __attribute__((packed, aligned(4))) tempArray {
int temp;
} Array_T;
Array_T *myArray;
RenderScript 定义Struct 成功后，会自动生成一个java文件，如上面的tempArray名称的结构，会生产这个文件:ScriptField_tempArray,代码如下：
/*
* Copyright (C) 2011 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
*
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*//*
* This file is auto-generated. DO NOT MODIFY!
* The source Renderscript file: /home/terry/workspace/RenderScriptsArray/src/com/xuzhi/renderScriptArray/array.rs
*/package com.xuzhi.renderScriptArray;
import android.renderscript.*;
import android.content.res.Resources;
/**
* @hide
*/public class ScriptField_tempArray
extends android.renderscript.Script.FieldBase {
static public class Item {
public static final int sizeof = 4;
int temp;
Item() {
}
}
private Item mItemArray[];
private FieldPacker mIOBuffer;
public static Element createElement(RenderScript rs) {
Element.Builder eb =
new Element.Builder(rs);
eb.add(Element.I32(rs), "temp");
return eb.create();
}
public ScriptField_tempArray(RenderScript rs,
int count) {
mItemArray =
null;
mIOBuffer =
null;
mElement = createElement(rs);
init(rs, count);
}
public ScriptField_tempArray(RenderScript rs,
int count,
int usages) {
mItemArray =
null;
mIOBuffer =
null;
mElement = createElement(rs);
init(rs, count, usages);
}
private void copyToArrayLocal(Item i, FieldPacker fp) {
fp.addI32(i.temp);
}
private void copyToArray(Item i,
int index) {
if (mIOBuffer ==
null) mIOBuffer =
new FieldPacker(Item.sizeof * getType().getX()
/* count */);
mIOBuffer.reset(index * Item.sizeof);
copyToArrayLocal(i, mIOBuffer);
}
public synchronized void set(Item i,
int index,
boolean copyNow) {
if (mItemArray ==
null) mItemArray =
new Item[getType().getX()
/* count */];
mItemArray[index] = i;
if (copyNow) {
copyToArray(i, index);
FieldPacker fp =
new FieldPacker(Item.sizeof);
copyToArrayLocal(i, fp);
mAllocation.setFromFieldPacker(index, fp);
}
}
public synchronized Item get(
int index) {
if (mItemArray ==
null)
return null;
return mItemArray[index];
}
public synchronized void set_temp(
int index,
int v,
boolean copyNow) {
if (mIOBuffer ==
null) mIOBuffer =
new FieldPacker(Item.sizeof * getType().getX()
/* count */);
if (mItemArray ==
null) mItemArray =
new Item[getType().getX()
/* count */];
if (mItemArray[index] ==
null) mItemArray[index] =
new Item();
mItemArray[index].temp = v;
if (copyNow) {
mIOBuffer.reset(index * Item.sizeof);
mIOBuffer.addI32(v);
FieldPacker fp =
new FieldPacker(4);
fp.addI32(v);
mAllocation.setFromFieldPacker(index, 0, fp);
}
}
public synchronized int get_temp(
int index) {
if (mItemArray ==
null)
return 0;
return mItemArray[index].temp;
}
public synchronized void copyAll() {
for (
int ct = 0; ct < mItemArray.length; ct++) copyToArray(mItemArray[ct], ct);
mAllocation.setFromFieldPacker(0, mIOBuffer);
}
public synchronized void resize(
int newSize) {
if (mItemArray !=
null) {
int oldSize = mItemArray.length;
int copySize = Math.min(oldSize, newSize);
if (newSize == oldSize)
return;
Item ni[] =
new Item[newSize];
System.arraycopy(mItemArray, 0, ni, 0, copySize);
mItemArray = ni;
}
mAllocation.resize(newSize);
if (mIOBuffer !=
null) mIOBuffer =
new FieldPacker(Item.sizeof * getType().getX()
/* count */);
}
}
生成的代码是提供给你做内存分配和操作类似数组的功能。
如何得到指针长度并循环为指针赋值
RenderScript 有两个函数是专门用来获取指针长度的：
rsGetAllocation： 返回一个己经分配过地址的指针
rsAllocationGetDimX ：获取返回指针的长度
通过将这两个函数做组合使用可以返回指针长度,代码如下：
const int size = rsAllocationGetDimX(rsGetAllocation(myArray));
取得了长度即可以为指针内部变量赋值，代码如下：
for(int i=0
;i
array->temp=i; //循环赋值
rsDebug("current value is ====>", array->temp); //打印当前值
//指向下个指针
array++;
}
整体DEMO代码
本DEMO没有任何界面 ，只是演示如何使用struct并打印出指针下标原素的值，如此简单， 涉及的rs文件代码如下：
#pragma version(1)
#pragma rs java_package_name(com.xuzhi.renderScriptArray)
#include "rs_graphics.rsh"
static int initialized = 0
;
//定义一个struct
typedef struct __attribute__((packed, aligned(4))) tempArray {
int temp
;
} Array_T
;
Array_T *myArray
;
static void initArray(){
Array_T *array=myArray
;
//得到struct长度
//1.返回一个己经分配过地址的指针
//2.获取返回指针的长度
const int size = rsAllocationGetDimX(rsGetAllocation(myArray));
for(int i=0
;i
array->temp=i; //循环赋值
rsDebug("current value is ====>", array->temp); //打印当前值
//指向下个指针
array++;
}
}
int root(){
rsgClearColor(0.0f, 1.0f, 0.0f, 1.0f);
if(initialized==0){
initArray();
initialized=1;
}
return 16;
}
java 代码如下：
package com.xuzhi.renderScriptArray;
import android.app.Activity;
import android.content.Context;
import android.content.res.Resources;
import android.os.Bundle;
import android.renderscript.Allocation;
import android.renderscript.RSSurfaceView;
import android.renderscript.RenderScriptGL;
public class RenderScriptsArrayActivity
extends Activity {
/** Called when the activity is first created. */@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(
new renderScriptView(
this));
}
public class renderScriptRS {
private ScriptC_array mScript;
private ScriptField_tempArray array;
RenderScriptGL mRS;
public renderScriptRS(RenderScriptGL rs,Resources resource) {
// TODO Auto-generated constructor stub
mRS=rs;
//初始化struct 并为其指定有多少个下标
array=new ScriptField_tempArray(mRS, 10,Allocation.USAGE_SCRIPT|Allocation.USAGE_GRAPHICS_VERTEX);//实始化CcriptC
mScript=new ScriptC_array(mRS, resource, R.raw.array);//绑定struct
mScript.bind_myArray(array);//绑定脚本
mRS.bindRootScript(mScript);}
}
public class renderScriptView
extends RSSurfaceView {
private RenderScriptGL mRS;
private renderScriptRS mRender;
public renderScriptView(Context context) {
super(context);
// TODO Auto-generated constructor stub
}
@Override
protected void onAttachedToWindow() {
super.onAttachedToWindow();
android.util.Log.e("rs", "onAttachedToWindow");
if (mRS ==
null) {
RenderScriptGL.SurfaceConfig sc =
new RenderScriptGL.SurfaceConfig();
mRS = createRenderScriptGL(sc);
mRender =
new renderScriptRS(mRS, getResources());
}
}
@Override
protected void onDetachedFromWindow() {
super.onDetachedFromWindow();
if (mRS !=
null) {
mRS =
null;
destroyRenderScriptGL();
}
}
}
}
都加了注释了，最主要的四段代码标注了红色，要注意。
运行结果：
03-09 15:47:50.492: D/RenderScript(2298): current value is ====> 0 0x0
03-09 15:47:50.507: D/RenderScript(2298): current value is ====> 1 0x1
03-09 15:47:50.507: D/RenderScript(2298): current value is ====> 2 0x2
03-09 15:47:50.507: D/RenderScript(2298): current value is ====> 3 0x3
03-09 15:47:50.507: D/RenderScript(2298): current value is ====> 4 0x4
03-09 15:47:50.507: D/RenderScript(2298): current value is ====> 5 0x5
03-09 15:47:50.507: D/RenderScript(2298): current value is ====> 6 0x6
03-09 15:47:50.507: D/RenderScript(2298): current value is ====> 7 0x7
03-09 15:47:50.507: D/RenderScript(2298): current value is ====> 8 0x8
03-09 15:47:50.507: D/RenderScript(2298): current value is ====> 9 0x9
