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package jdk.internal.foreign;

import jdk.internal.access.foreign.UnmapperProxy;
import jdk.internal.misc.ScopedMemoryAccess;

import java.nio.ByteBuffer;

/**
 * Implementation for a mapped memory segments. A mapped memory segment is a native memory segment, which
 * additionally features an {@link UnmapperProxy} object. This object provides detailed information about the
 * memory mapped segment, such as the file descriptor associated with the mapping. This information is crucial
 * in order to correctly reconstruct a byte buffer object from the segment (see {@link #makeByteBuffer()}).
 */
public final class MappedMemorySegmentImpl extends NativeMemorySegmentImpl {

    private final UnmapperProxy unmapper;

    static final ScopedMemoryAccess SCOPED_MEMORY_ACCESS = ScopedMemoryAccess.getScopedMemoryAccess();

    public MappedMemorySegmentImpl(long min, UnmapperProxy unmapper, long length, boolean readOnly, MemorySessionImpl scope) {
        super(min, length, readOnly, scope);
        this.unmapper = unmapper;
    }

    @Override
    ByteBuffer makeByteBuffer() {
        return NIO_ACCESS.newMappedByteBuffer(unmapper, min, (int)length, null, this);
    }

    @Override
    MappedMemorySegmentImpl dup(long offset, long size, boolean readOnly, MemorySessionImpl scope) {
        return new MappedMemorySegmentImpl(min + offset, unmapper, size, readOnly, scope);
    }

    // mapped segment methods

    @Override
    public MappedMemorySegmentImpl asSlice(long offset, long newSize) {
        return (MappedMemorySegmentImpl)super.asSlice(offset, newSize);
    }

    @Override
    public boolean isMapped() {
        return true;
    }

    // support for mapped segments

    public void load() {
        if (unmapper != null) {
            SCOPED_MEMORY_ACCESS.load(sessionImpl(), NIO_ACCESS.mappedMemoryUtils(),
                    min, unmapper.isSync(), length);
        }
    }

    public void unload() {
        if (unmapper != null) {
            SCOPED_MEMORY_ACCESS.unload(sessionImpl(), NIO_ACCESS.mappedMemoryUtils(),
                    min, unmapper.isSync(), length);
        }
    }

    public boolean isLoaded() {
        return unmapper == null ||
                SCOPED_MEMORY_ACCESS.isLoaded(sessionImpl(),
                        NIO_ACCESS.mappedMemoryUtils(), min, unmapper.isSync(), length);
    }

    public void force() {
        if (unmapper != null) {
            SCOPED_MEMORY_ACCESS.force(sessionImpl(), NIO_ACCESS.mappedMemoryUtils(),
                    unmapper.fileDescriptor(), min, unmapper.isSync(), 0, length);
        }
    }

}