Minor code cleanup and modernization

CHANGELOG.md

@@ -5,6 +5,23 @@ CHANGELOG
 ------------------
 
 * Java 17 or greater is now required.
+* Added support for MaxMind DB files larger than 2GB. The library now uses
+  an internal Buffer abstraction that can handle databases exceeding the
+  2GB ByteBuffer limit. Files under 2GB continue to use a single ByteBuffer
+  for optimal performance. Requested by nonetallt. GitHub #154. Fixed by
+  Silvano Cerza. GitHub #289.
+* `Metadata.getBuildDate()` has been replaced with `buildTime()`, which returns
+  `java.time.Instant` instead of `java.util.Date`. The instant represents the
+  database build time in UTC.
+* `DatabaseRecord`, `Metadata`, `Network`, and internal `DecodedValue` classes
+  have been converted to records. The following API changes were made:
+  * `DatabaseRecord.getData()` and `DatabaseRecord.getNetwork()` have been
+    replaced with record accessor methods `data()` and `network()`.
+  * Simple getter methods on `Metadata` (e.g., `getBinaryFormatMajorVersion()`,
+    `getDatabaseType()`, etc.) have been replaced with their corresponding record
+    accessor methods (e.g., `binaryFormatMajorVersion()`, `databaseType()`, etc.).
+  * `Network.getNetworkAddress()` and `Network.getPrefixLength()` have been
+    replaced with record accessor methods `networkAddress()` and `prefixLength()`.
 
 3.2.0 (2025-05-28)
 ------------------

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

@@ -1,7 +1,5 @@
 package com.maxmind.db;
 
-import java.io.IOException;
-import java.nio.channels.FileChannel;
 import java.nio.charset.CharacterCodingException;
 import java.nio.charset.CharsetDecoder;
 
@@ -12,8 +10,11 @@
  *
  * <p>This interface is designed to provide a long-based API while
  * remaining compatible with the limitations of underlying storage.
+ *
+ * <p>All underlying {@link java.nio.ByteBuffer}s are read-only to prevent
+ * accidental modification of shared data.
  */
-interface Buffer {
+sealed interface Buffer permits SingleBuffer, MultiBuffer {
     /**
      * Returns the total capacity of this buffer in bytes.
      *
@@ -96,16 +97,6 @@ interface Buffer {
      */
     Buffer duplicate();
 
-    /**
-     * Reads data from the given channel into this buffer starting at the
-     * current position.
-     *
-     * @param channel the file channel
-     * @return the number of bytes read
-     * @throws IOException if an I/O error occurs
-     */
-    long readFrom(FileChannel channel) throws IOException;
-
     /**
      * Decodes the buffer's content into a string using the given decoder.
      *

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

@@ -8,7 +8,6 @@
 import java.nio.ByteBuffer;
 import java.nio.channels.FileChannel;
 import java.util.ArrayList;
-import java.util.List;
 
 final class BufferHolder {
     // DO NOT PASS OUTSIDE THIS CLASS. Doing so will remove thread safety.
@@ -23,18 +22,48 @@ final class BufferHolder {
              FileChannel channel = file.getChannel()) {
             long size = channel.size();
             if (mode == FileMode.MEMORY) {
-                Buffer buf;
                 if (size <= chunkSize) {
-                    buf = new SingleBuffer(size);
+                    // Allocate, read, and make read-only
+                    ByteBuffer buffer = ByteBuffer.allocate((int) size);
+                    if (channel.read(buffer) != size) {
+                        throw new IOException("Unable to read "
+                                + database.getName()
+                                + " into memory. Unexpected end of stream.");
+                    }
+                    buffer.flip();
+                    this.buffer = new SingleBuffer(buffer);
                 } else {
-                    buf = new MultiBuffer(size);
-                }
-                if (buf.readFrom(channel) != buf.capacity()) {
-                    throw new IOException("Unable to read "
-                            + database.getName()
-                            + " into memory. Unexpected end of stream.");
+                    // Allocate chunks, read, and make read-only
+                    var fullChunks = (int) (size / chunkSize);
+                    var remainder = (int) (size % chunkSize);
+                    var totalChunks = fullChunks + (remainder > 0 ? 1 : 0);
+                    var buffers = new ByteBuffer[totalChunks];
+
+                    for (int i = 0; i < fullChunks; i++) {
+                        buffers[i] = ByteBuffer.allocate(chunkSize);
+                    }
+                    if (remainder > 0) {
+                        buffers[totalChunks - 1] = ByteBuffer.allocate(remainder);
+                    }
+
+                    var totalRead = 0L;
+                    for (var buffer : buffers) {
+                        var read = channel.read(buffer);
+                        if (read == -1) {
+                            break;
+                        }
+                        totalRead += read;
+                        buffer.flip();
+                    }
+
+                    if (totalRead != size) {
+                        throw new IOException("Unable to read "
+                                + database.getName()
+                                + " into memory. Unexpected end of stream.");
+                    }
+
+                    this.buffer = new MultiBuffer(buffers, chunkSize);
                 }
-                this.buffer = buf;
             } else {
                 if (size <= chunkSize) {
                     this.buffer = SingleBuffer.mapFromChannel(channel);
@@ -45,38 +74,27 @@ final class BufferHolder {
         }
     }
 
-    /**
-     * Construct a ThreadBuffer from the provided URL.
-     *
-     * @param stream the source of my bytes.
-     * @throws IOException          if unable to read from your source.
-     * @throws NullPointerException if you provide a NULL InputStream
-     */
-    BufferHolder(InputStream stream) throws IOException {
-        this(stream, MultiBuffer.DEFAULT_CHUNK_SIZE);
-    }
-
     BufferHolder(InputStream stream, int chunkSize) throws  IOException {
         if (null == stream) {
             throw new NullPointerException("Unable to use a NULL InputStream");
         }
-        List<ByteBuffer> chunks = new ArrayList<>();
-        long total = 0;
-        byte[] tmp = new byte[chunkSize];
+        var chunks = new ArrayList<ByteBuffer>();
+        var total = 0L;
+        var tmp = new byte[chunkSize];
         int read;
 
         while (-1 != (read = stream.read(tmp))) {
-            ByteBuffer chunk = ByteBuffer.allocate(read);
+            var chunk = ByteBuffer.allocate(read);
             chunk.put(tmp, 0, read);
             chunk.flip();
             chunks.add(chunk);
             total += read;
         }
 
         if (total <= chunkSize) {
-            byte[] data = new byte[(int) total];
-            int pos = 0;
-            for (ByteBuffer chunk : chunks) {
+            var data = new byte[(int) total];
+            var pos = 0;
+            for (var chunk : chunks) {
                 System.arraycopy(chunk.array(), 0, data, pos, chunk.capacity());
                 pos += chunk.capacity();
             }

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

@@ -37,7 +37,7 @@ public CHMCache(int capacity) {
 
     @Override
     public DecodedValue get(CacheKey<?> key, Loader loader) throws IOException {
-        DecodedValue value = cache.get(key);
+        var value = cache.get(key);
         if (value == null) {
             value = loader.load(key);
             if (!cacheFull) {

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

@@ -6,9 +6,6 @@
  * Signals that the underlying database has been closed.
  */
 public class ClosedDatabaseException extends IOException {
-
-    private static final long serialVersionUID = 1L;
-
     ClosedDatabaseException() {
         super("The MaxMind DB has been closed.");
     }

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

@@ -5,8 +5,6 @@
  * constructor in the class with the MaxMindDbConstructor annotation.
  */
 public class ConstructorNotFoundException extends RuntimeException {
-    private static final long serialVersionUID = 1L;
-
     ConstructorNotFoundException(String message) {
         super(message);
     }

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

@@ -7,11 +7,14 @@
  * lookup.
  *
  * @param <T> the type to deserialize the returned value to
+ * @param data the data for the record in the database. The record will be
+ *             {@code null} if there was no data for the address in the
+ *             database.
+ * @param network the network associated with the record in the database. This is
+ *                the largest network where all of the IPs in the network have the same
+ *                data.
  */
-public final class DatabaseRecord<T> {
-    private final T data;
-    private final Network network;
-
+public record DatabaseRecord<T>(T data, Network network) {
     /**
      * Create a new record.
      *
@@ -20,25 +23,6 @@ public final class DatabaseRecord<T> {
      * @param prefixLength the network prefix length associated with the record in the database.
      */
     public DatabaseRecord(T data, InetAddress ipAddress, int prefixLength) {
-        this.data = data;
-        this.network = new Network(ipAddress, prefixLength);
-    }
-
-    /**
-     * @return the data for the record in the database. The record will be
-     *         <code>null</code> if there was no data for the address in the
-     *         database.
-     */
-    public T getData() {
-        return data;
-    }
-
-    /**
-     * @return the network associated with the record in the database. This is
-     *         the largest network where all of the IPs in the network have the same
-     *         data.
-     */
-    public Network getNetwork() {
-        return network;
+        this(data, new Network(ipAddress, prefixLength));
     }
 }

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

@@ -3,15 +3,7 @@
 /**
  * {@code DecodedValue} is a wrapper for the decoded value and the number of bytes used
  * to decode it.
+ *
+ * @param value the decoded value
  */
-public final class DecodedValue {
-    final Object value;
-
-    DecodedValue(Object value) {
-        this.value = value;
-    }
-
-    Object getValue() {
-        return value;
-    }
-}
+record DecodedValue(Object value) {}