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Android RenderScript 使用 Struct 及其下标的赋值

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
1. 如何定义Struct
2. 如何得到指针长度并循环为指针赋值
3. 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
 *
 *      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);
 &

补充:移动开发 , Android ,
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