javaandroidandroid-studiotensorflow-litemappedbytebuffer

MappedByteBuffer(in Android Studio) constructor is broken(super constructor broken)


I have a byte array and it has to be converted to MappedByteBuffer.

But when I try creating MappedByteBuffer, an error occurs.

error: cannot find symbol method MappedByteBuffer(int,int,int,int,byte[],int)

MappedByteBuffer.java

package java.nio;

import java.io.FileDescriptor;
import sun.misc.Unsafe;

public abstract class MappedByteBuffer
    extends ByteBuffer
{

   ...

// Android-added: Additional constructor for use by Android's DirectByteBuffer.
    MappedByteBuffer(int mark, int pos, int lim, int cap, byte[] buf, int offset) {
        super(mark, pos, lim, cap, buf, offset);  // <- when I hover mouse here, ByteBuffer() in ByteBuffer cannot be applied to message appears with a red underline.
        this.fd = null;
    }

   ...

}

ByteBuffer.java

package java.nio;
import libcore.io.Memory;
import dalvik.annotation.codegen.CovariantReturnType;

public abstract class ByteBuffer
    extends Buffer
    implements Comparable<ByteBuffer>
{

    // These fields are declared here rather than in Heap-X-Buffer in order to
    // reduce the number of virtual method invocations needed to access these
    // values, which is especially costly when coding small buffers.
    //
    final byte[] hb;                  // Non-null only for heap buffers
    final int offset;
    boolean isReadOnly;                 // Valid only for heap buffers

    // Creates a new buffer with the given mark, position, limit, capacity,
    // backing array, and array offset
    //
    ByteBuffer(int mark, int pos, int lim, int cap,   // package-private
                 byte[] hb, int offset)
    {
        // Android-added: elementSizeShift parameter (log2 of element size).
        super(mark, pos, lim, cap, 0 /* elementSizeShift */);
        this.hb = hb;
        this.offset = offset;
    }

    ...

}

What I think strange is when goto definition of extends ByteBuffer in MappedByteBuffer.java, it shows ByteBuffer.annotated.java, not ByteBuffer.java

ByteBuffer.annotated.java


// -- This file was mechanically generated: Do not edit! -- //


package java.nio;


@SuppressWarnings({"unchecked", "deprecation", "all"})
public abstract class ByteBuffer extends java.nio.Buffer implements java.lang.Comparable<java.nio.ByteBuffer> {

ByteBuffer(int mark, int pos, int lim, int cap) { super(0, 0, 0, 0, 0); throw new RuntimeException("Stub!"); }

I don't know what {classname}.annotated.java does, so it might not be an error, but I pasted because I think it's odd.

So how can I create MappedByteBuffer from byte array? There is only 1 constructor, but it's broken.


Solution

  • There is only 1 constructor, but it's broken

    That constructor isn't public (it's package-private), so you can't call it.

    So how can I create MappedByteBuffer from byte array?

    You can't, not without writing it to a file first. From the docs:

    A direct byte buffer whose content is a memory-mapped region of a file.

    If you do need to create a MappedByteBuffer specifically and not just a ByteBuffer from a byte array, you need to write it to a file and use FileChannel.map. If you just need a ByteBuffer, you can use ByteBuffer.wrap