java - 结构内部的 JNA 结构

Question

我对 JNA 编程很陌生。我有一个 native 代码如下

int Data(int Number, aaa *Data, int* error);

typedef struct {
    uint8 Storage;
    LStr path;
    int32 chart;
    int32 strt;
    LStr val;
    int32 timedata;
    } aaa;

typedef struct {
    int32   cnt;    /*num of bytes that follow*/    
    uChar   str[1]; 
} LStrval, *LStrPtr, **LStr;

如何使用 JNA 从 Java 调用此 native 函数。我尝试了几种选择，但没有得到结果。我尝试过的选项之一如下。

接口(interface)函数

public int SetStorage_Data(int num,Storage_Data.ByReference data, Pointer error);

 public class Storage_Data extends Structure{
        public static class ByReference extends Storage_Data implements Structure.ByReference {}

        public byte storage;
        public Stringtype.ByReference savepath;
        public int chart;
        public int strt;
        public Stringtype.ByReference val;
        public int timedata;

        @Override
        protected List getFieldOrder() {
            return Arrays.asList("storage", "savepath","chart",
                    "strt","val","timedata");
        }
    }



public class Stringtype extends Structure{
        public static class ByReference extends Stringtype implements Structure.ByReference {

            public ByReference(int buffersize) {
                super(buffersize);
                // TODO Auto-generated constructor stub
            }}

        public int count;
        public byte[] str;

        public Stringtype(int buffersize) {
            str = new byte[buffersize];
            count = str.length;
            allocateMemory();
        }

        @Override
        protected List getFieldOrder() {
            return Arrays.asList("count", "str");
        }
    }

以及 Java 调用

InjectionAnalyzerInterfaces.Storage_Data.ByReference storagedata = new InjectionAnalyzerInterfaces.Storage_Data.ByReference();

 int len= string.length;
 InjectionAnalyzerInterfaces.Stringtype.ByReference savepath = new InjectionAnalyzerInterfaces.Stringtype.ByReference(len);

            byte[] stringbyte = string.getBytes();
            System.arraycopy(stringbyte, 0, savepath.str, 0, bytes);
            storagedata.savepath = savepath;
            storagedata.chart = 1;
            storagedata.strt =1;
            String temp= "all";
            byte[] strtbyte = temp.getBytes();
            int dd = strtbyte.length;
            InjectionAnalyzerInterfaces.Stringtype.ByReference stra = new InjectionAnalyzerInterfaces.Stringtype.ByReference(dd);
            System.arraycopy(strtbyte, 0,  stra.str,0, dd);
            storagedata.strt = stra;


            storagedata.tdata = 0;

            Pointer error = new Memory(5);

            int status1 =  lib.Set_Config_Storage_Data(deviceNumber, storagedata, error);

请帮助我。预先感谢您

Answer 1

在定义 LStrVal 时，您需要初始化原始数组字段，以便 JNA 知道要分配多少内存(至少在开始时):

public byte str = new byte[1];

您需要重写 Structure.read() 来做正确的事情，并提供一个基于 Pointer 的构造函数以在从 native 内存初始化后读取:

public void read() {
    count = (int)readField("count");
    str = new byte[count];
    super.read();
}

public LStr(Pointer p) {
    super(p);
    read();
}

最后，您的包含结构具有 struct** 字段(不知道为什么)，您必须将其映射到 Pointer，并提供一个方便的函数来实际转换为您想要的结构:

public Pointer savepath;
public LStr getSavepath() {
    return savepath != null ? new LStr(savepath.getPointer(0)) : null;
}