!include once #1027304 // Eclipse Collections

import java.nio.*;
import java.nio.channels.*;

// read-only, so far. should be thread-safe
final sclass BufferedDiskByteMemory64 implements IByteMemory64, AutoCloseable {
  File file;
  long size; // file size in ints
  RandomAccessFile raf;
  bool bigEndian = true;
  bool writable = false;
  bool debug;

  // byte buffers
  int byteBufferShift = 30; // each buffer is 1 GB
  int byteBufferSize = 1 << byteBufferShift;
  MappedByteBuffer[] byteBuffers;
  
  *(File *file) {
    this(file, false);
  }
  
  *(File *file, bool *writable) {
    load(file, writable);
  }
  
  void load(File file, bool writable default false) ctex {
    this.file = file;
    this.writable = writable;
    size = fileSize(file);
    raf = newRandomAccessFile(file, writable ? "rw" : "r");
    
    byteBuffers = new MappedByteBuffer[toInt(rightShift_ceil(size, byteBufferShift))];
    FileChannel channel = raf.getChannel();
    for i over byteBuffers: {
      long pos = (long) i << byteBufferShift;
      int len = toInt(min(1 << byteBufferShift, size-pos));
      //print("Mapping bytes " + longToHex(pos) + "-" + longToHex(pos+len));
      byteBuffers[i] = channel.map(FileChannel.MapMode.READ_ONLY, pos, len);
      byteBuffers[i].order(bigEndian ? ByteOrder.BIG_ENDIAN : ByteOrder.LITTLE_ENDIAN);
    }
  }
  
  public void close {
    dispose raf;
  }
  
  public byte getByte(long idx) {
    rangeCheck(idx, size);
    ret byteBuffers[(int) (idx >> byteBufferShift)].get(((int) idx) & (byteBufferSize-1));
  }
  
  public int getInt(long idx) {
    int ofs = ((int) idx) & (byteBufferSize-1);
    // check if we are crossing a buffer boundary
    if (ofs > byteBufferSize-4)
      ret getInt_manual(idx);
    try {
      ret byteBuffers[(int) (idx >> byteBufferShift)].getInt(ofs);
    } on fail {
      print(+idx);
    }
  }
  
  public int getInt_manual(long idx) {
    assertTrue(+bigEndian);
    ret ubyteToInt(getByte(idx)) << 24 |
      ubyteToInt(getByte(idx+1)) << 16 |
      ubyteToInt(getByte(idx+2)) << 8 |
      ubyteToInt(getByte(idx+3));
  }
  
  public void set(long idx, int val) {
    checkWritable();
    fail("todo");
  }
  
  void checkWritable {
    if (!writable) fail("read-only");
  }
  
  public long size() {
    ret size;
  }
  
  public void ensureSize(int size) {
    this.size = max(this.size, size);
  }
}

Began life as a copy of #1029446