這是一個關於RenderScript如何使用 Struct 的文章，是學習RenderScript 一個必須要掌握的基礎知識點。
大綱
1. 如何定義Struct
2. 如何得到指針長度並循環為指針賦值
3. 整體DEMO代碼
如何定義Struct
RenderScript 裡面定義結構有兩種定義方法，參考如下：
1.
typedef struct tempArray
{
float2 position;
float size;
} Array_T;
Array_T *myArray;
2.
//定義一個struct
typedef struct __attribute__((packed, aligned(4))) tempArray {
int temp;
} Array_T;
Array_T *myArray;
RenderScript 定義Struct 成功後，會自動生成一個java文件，如上面的tempArray名稱的結構，會生產這個文件:ScriptField_tempArray,代碼如下：
/*
* 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
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* 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 */);
}
}
生成的代碼是提供給你做內存分配和操作類似數組的功能。
如何得到指針長度並循環為指針賦值
RenderScript 有兩個函數是專門用來獲取指針長度的：
rsGetAllocation： 返回一個己經分配過地址的指針
rsAllocationGetDimX ：獲取返回指針的長度
通過將這兩個函數做組合使用可以返回指針長度,代碼如下：
const int size = rsAllocationGetDimX(rsGetAllocation(myArray));
取得瞭長度即可以為指針內部變量賦值，代碼如下：
for(int i=0;i<size;i++){
array->temp=i; //循環賦值
rsDebug("current value is ====>", array->temp); //打印當前值
//指向下個指針
array++;
}
整體DEMO代碼
本DEMO沒有任何界面 ，隻是演示如何使用struct並打印出指針下標原素的值，如此簡單， 涉及的rs文件代碼如下：
#pragma version(1)
#pragma rs java_package_name(com.xuzhi.renderScriptArray)
#include "rs_graphics.rsh"
static int initialized = 0;
//定義一個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長度
//1.返回一個己經分配過地址的指針
//2.獲取返回指針的長度
const int size = rsAllocationGetDimX(rsGetAllocation(myArray));
for(int i=0;i<size;i++){
array->temp=i; //循環賦值
rsDebug("current value is ====>", array->temp); //打印當前值
//指向下個指針
array++;
}
}
int root(){
rsgClearColor(0.0f, 1.0f, 0.0f, 1.0f);
if(initialized==0){
initArray();
initialized=1;
}
return 16;
}
java 代碼如下：
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 並為其指定有多少個下標
array=new ScriptField_tempArray(mRS, 10,Allocation.USAGE_SCRIPT|Allocation.USAGE_GRAPHICS_VERTEX);
//實始化CcriptC
mScript=new ScriptC_array(mRS, resource, R.raw.array);
//綁定struct
mScript.bind_myArray(array);
//綁定腳本
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();
}
}
}
}
都加瞭註釋瞭，最主要的四段代碼標註瞭紅色，要註意。
運行結果：
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
摘自 Terry_龍
