如何在Java中将int []转换为ByteBuffer？

Question

正如标题所说,我需要在Java中将int []转换为ByteBuffer.有推荐的方法吗？

我想通过JNI将ByteBuffer传递给C++.在这种情况下,对于任何特定的字节序转换,我需要注意什么？

编辑:对不起,我错误地写了ByteArray,但意味着类型ByteBuffer.

编辑:示例代码:

我剥掉了不必要的部分.我从c ++调用JNI上的Java函数来加载资源并将其作为bytebuffer传递回c ++.它适用于各种其他资源.现在我有一个"int []",并想知道是否有一种优雅的方式将其转换为bytebuffer,或者我必须采用旧式方式并将其填入for循环中.

ByteBuffer  resource= null;
resource = ByteBuffer.allocateDirect((x*y+2)*4).order(ByteOrder.nativeOrder());
.
.
ByteBuffer GetResourcePNG(String text)
{
    .
    .
    int []  pix;
    map.getPixels(pix,0,x,0,0,x,y);

    return resource;
}

Answer 1

你必须使用ByteBuffer.allocateDirect,如果你希望能够使用JNI的GetDirectBufferAddress.

使用ByteBuffer.order(ByteOrder.nativeOrder())调整ByteBuffer实例的字节顺序来匹配当前平台.

ByteBuffer正确配置了字节顺序后,使用ByteBuffer.asIntBuffer()它将其视图作为a java.nio.IntBuffer并用数据填充它.

完整示例:

import java.nio.ByteBuffer; import java.nio.ByteOrder; import java.nio.IntBuffer;

public class Test {
    static final int bytes_per_datum = 4;

    public static void main(String args[]) {
        main2("Native Endian", ByteOrder.nativeOrder());
        main2("Big Endian", ByteOrder.BIG_ENDIAN);
        main2("Little Endian", ByteOrder.LITTLE_ENDIAN);
    }

    static void main2(String comment, ByteOrder endian) {
        int[] data = { 1, 0xF, 0xFF, 0xFFF, 0xFFFF, 0xFFFFF, 0xFFFFFF, 0xFFFFFFF, 0xFFFFFFFF };
        ByteBuffer bb = ByteBuffer.allocateDirect(data.length * bytes_per_datum);
        bb.order(endian); // endian must be set before putting ints into the buffer
        put_ints(bb, data);

        System.out.println(comment + ": ");
        print(bb);
    }

    static void put_ints(ByteBuffer bb, int[] data) {
        IntBuffer b = bb.asIntBuffer(); // created IntBuffer starts only from the ByteBuffer's relative position
                                        // if you plan to reuse this IntBuffer, be mindful of its position
        b.put(data); // position of this IntBuffer changes by +data.length;
    } // this IntBuffer goes out of scope

    static void print(ByteBuffer bb) { // prints from start to limit
        ByteBuffer bb_2 = bb.duplicate(); // shares backing content, but has its own capacity/limit/position/mark (equivalent to original buffer at initialization)
        bb_2.rewind();
        for (int x = 0, xx = bb_2.limit(); x < xx; ++x) {
            System.out.print((bb_2.get() & 0xFF) + " "); // 0xFF for display, since java bytes are signed
            if ((x + 1) % bytes_per_datum == 0) {
                System.out.print(System.lineSeparator());
            }
        }
    }
}