fix https://github.com/maxmind/MaxMind-DB-Reader-java/issues/154

pom.xml

@@ -37,6 +37,11 @@
         </developer>
     </developers>
     <dependencies>
+        <dependency>
+            <groupId>it.unimi.dsi</groupId>
+            <artifactId>fastutil</artifactId>
+            <version>8.5.15</version>
+        </dependency>
         <dependency>
             <groupId>org.junit.jupiter</groupId>
             <artifactId>junit-jupiter</artifactId>

src/main/java/com/maxmind/db/BiInt2IntFunction.java

@@ -0,0 +1,15 @@
+package com.maxmind.db;
+
+import java.util.function.ToIntBiFunction;
+
+@FunctionalInterface
+interface BiInt2IntFunction extends ToIntBiFunction<Integer, Integer> {
+
+    @Override
+    default int applyAsInt(Integer integer, Integer integer2) {
+        return apply(integer, integer);
+    }
+
+    int apply(int integer0, int integer1);
+
+}

src/main/java/com/maxmind/db/BigByteBuffer.java

@@ -0,0 +1,298 @@
+package com.maxmind.db;
+
+import it.unimi.dsi.fastutil.bytes.ByteBigList;
+import it.unimi.dsi.fastutil.ints.Int2IntFunction;
+import it.unimi.dsi.fastutil.longs.Long2LongFunction;
+import java.nio.BufferUnderflowException;
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
+import java.util.Objects;
+
+/**
+ * This provides minimal functionality from {@link ByteBuffer} that is required for this library,
+ * but it is modified to work with files larger than Java's normal memory mapped file size limit.
+ */
+final class BigByteBuffer {
+
+    public static final boolean NATIVE_IS_BIG_ENDIAN =
+        ByteOrder.nativeOrder() == ByteOrder.BIG_ENDIAN;
+
+    public static BigByteBuffer wrap(ByteBigList bytes) {
+        return new BigByteBuffer(bytes, 0, bytes.size64(), bytes.size64());
+    }
+
+    // copied from Unsafe.java
+    private static long toUnsignedLong(byte n) {
+        return n & 0xffL;
+    }
+
+    // copied from Unsafe.java
+    private static int toUnsignedInt(byte n) {
+        return n & 0xff; 
+    }
+
+    private static final BiInt2IntFunction PICK_POS =
+        NATIVE_IS_BIG_ENDIAN
+            ? (int top, int pos) -> top - pos
+            : (int top, int pos) -> pos;
+
+    private static final Int2IntFunction CONV_ENDIAN_INT =
+        NATIVE_IS_BIG_ENDIAN
+            ? Int2IntFunction.identity()
+            : Integer::reverseBytes;
+
+    private static final Long2LongFunction CONV_ENDIAN_LONG =
+        NATIVE_IS_BIG_ENDIAN
+            ? Long2LongFunction.identity()
+            : Long::reverseBytes;
+
+    final ByteBigList bytes;
+    final long capacity;
+    long position;
+    long limit;
+
+    private BigByteBuffer(
+        ByteBigList bytes,
+        long position,
+        long limit,
+        long capacity
+    ) {
+        this.bytes = bytes;
+        this.capacity = capacity;
+        this.limit = limit;
+        this.position = position;
+    }
+
+    /**
+     * {@link ByteBuffer#get()}
+     */
+    public byte get() {
+        return bytes.getByte(nextGetIndex(1));
+    }
+
+    /**
+     * {@link ByteBuffer#get(int)}
+     */
+    public byte get(long index) {
+        return bytes.getByte(checkIndex(index));
+    }
+
+    /**
+     * {@link ByteBuffer#get(byte[])}
+     */
+    public BigByteBuffer get(byte[] dst) {
+        return get(dst, 0, dst.length);
+    }
+
+    /**
+     * {@link ByteBuffer#get(byte[], int, int)} )}
+     */
+    public BigByteBuffer get(byte[] dst, int offset, int length) {
+        Objects.checkFromIndexSize(offset, length, dst.length);
+        long pos = position();
+        if (length > limit() - pos) {
+            throw new BufferUnderflowException();
+        }
+
+        this.bytes.getElements(pos, dst, offset, length);
+
+        position(pos + length);
+        return this;
+    }
+
+    public long getLong() {
+        long index = nextGetIndex(8);
+        byte i0 = get(index);
+        byte i1 = get(++index);
+        byte i2 = get(++index);
+        byte i3 = get(++index);
+        byte i4 = get(++index);
+        byte i5 = get(++index);
+        byte i6 = get(++index);
+        byte i7 = get(++index);
+        return CONV_ENDIAN_LONG.applyAsLong(((toUnsignedLong(i0) << PICK_POS.apply(56, 0))
+            | (toUnsignedLong(i1) << PICK_POS.apply(56, 8))
+            | (toUnsignedLong(i2) << PICK_POS.apply(56, 16))
+            | (toUnsignedLong(i3) << PICK_POS.apply(56, 24))
+            | (toUnsignedLong(i4) << PICK_POS.apply(56, 32))
+            | (toUnsignedLong(i5) << PICK_POS.apply(56, 40))
+            | (toUnsignedLong(i6) << PICK_POS.apply(56, 48))
+            | (toUnsignedLong(i7) << PICK_POS.apply(56, 56))));
+    }
+
+    public int getInt() {
+        long index = nextGetIndex(4);
+        byte i0 = get(index);
+        byte i1 = get(++index);
+        byte i2 = get(++index);
+        byte i3 = get(++index);
+        return CONV_ENDIAN_INT.applyAsInt(((toUnsignedInt(i0) << PICK_POS.apply(24, 0))
+            | (toUnsignedInt(i1) << PICK_POS.apply(24, 8))
+            | (toUnsignedInt(i2) << PICK_POS.apply(24, 16))
+            | (toUnsignedInt(i3) << PICK_POS.apply(24, 24))));
+    }
+
+    /**
+     * {@link ByteBuffer#getDouble()}
+     */
+    public double getDouble() {
+        return Double.longBitsToDouble(getLong());
+    }
+
+    /**
+     * {@link ByteBuffer#getFloat()}
+     */
+    public float getFloat() {
+        return Float.intBitsToFloat(getInt());
+    }
+
+    /**
+     * {@link ByteBuffer#position()}
+     */
+    public long position() {
+        return position;
+    }
+
+    // copied from Buffer.java
+    /**
+     * {@link ByteBuffer#position(int)}
+     */
+    public BigByteBuffer position(final long newPosition) {
+        if (newPosition > limit | newPosition < 0) {
+            throw createPositionException(newPosition);
+        }
+        position = newPosition;
+        return this;
+    }
+
+    /**
+     * {@link ByteBuffer#limit()}
+     */
+    public long limit() {
+        return limit;
+    }
+
+    /**
+     * {@link ByteBuffer#limit(int)}
+     */
+    public BigByteBuffer limit(final long newLimit) {
+        if (newLimit > capacity | newLimit < 0) {
+            throw createLimitException(newLimit);
+        }
+        limit = newLimit;
+        if (position > newLimit) {
+            position = newLimit;
+        }
+        return this;
+    }
+
+    /**
+     * {@link ByteBuffer#capacity()}
+     */
+    long capacity() {
+        return capacity;
+    }
+
+    // copied from Buffer.java
+    /**
+     * Verify that {@code 0 < newPosition <= limit}
+     *
+     * @param newPosition
+     *        The new position value
+     *
+     * @throws IllegalArgumentException
+     *         If the specified position is out of bounds.
+     */
+    private IllegalArgumentException createPositionException(long newPosition) {
+        String msg = null;
+
+        if (newPosition > limit) {
+            msg = "newPosition > limit: (" + newPosition + " > " + limit + ")";
+        } else { // assume negative
+            assert newPosition < 0 : "newPosition expected to be negative";
+            msg = "newPosition < 0: (" + newPosition + " < 0)";
+        }
+
+        return new IllegalArgumentException(msg);
+    }
+
+    // copied from Buffer.java
+    /**
+     * Verify that {@code 0 < newLimit <= capacity}
+     *
+     * @param newLimit
+     *        The new limit value
+     *
+     * @throws IllegalArgumentException
+     *         If the specified limit is out of bounds.
+     */
+    private IllegalArgumentException createLimitException(long newLimit) {
+        String msg = null;
+
+        if (newLimit > capacity) {
+            msg = "newLimit > capacity: (" + newLimit + " > " + capacity + ")";
+        } else { // assume negative
+            assert newLimit < 0 : "newLimit expected to be negative";
+            msg = "newLimit < 0: (" + newLimit + " < 0)";
+        }
+
+        return new IllegalArgumentException(msg);
+    }
+
+    // copied from Buffer.java
+    /**
+     * {@link ByteBuffer#nextGetIndex(int)}
+     */
+    long nextGetIndex(long nb) {                    // package-private
+        long p = position;
+        if (limit - p < nb) {
+            throw new BufferUnderflowException();
+        }
+        position = p + nb;
+        return p;
+    }
+
+    // copied from Buffer.java
+    /**
+     * Checks the given index against the limit, throwing an {@link
+     * IndexOutOfBoundsException} if it is not smaller than the limit
+     * or is smaller than zero.
+     */
+    long checkIndex(long i) {                       // package-private
+        if ((i < 0) || (i >= limit)) {
+            throw new IndexOutOfBoundsException();
+        }
+        return i;
+    }
+
+    /**
+     * Get a {@link ByteBuffer} for the current buffer's position. {@link #position()}
+     * is forwarded by the number of bytes.
+     *
+     * @param limit is the number of bytes from {@link #position()} to put into the
+     *              {@link ByteBuffer}.
+     * @throws BufferUnderflowException if there aren't enough bytes remaining
+     */
+    public ByteBuffer getByteBuffer(int limit) {
+        /*
+        A more optimal solution might be to create a ByteBuffer implementation that
+        is backed by bytes.subList(position, limit).
+         */
+        final long position = nextGetIndex(limit);
+        final byte[] bufferBytes = new byte[limit];
+        bytes.getElements(position, bufferBytes, 0, limit);
+        return ByteBuffer.wrap(bufferBytes);
+    }
+
+    /**
+     * {@link ByteBuffer#duplicate()}
+     */
+    public BigByteBuffer duplicate() {
+        return new BigByteBuffer(
+            bytes,
+            position(),
+            limit(),
+            capacity());
+    }
+
+}