Move file transfer API to the code library

This is useful for emulators, which might want to emulate the event.

projects/core/src/main/java/dan200/computercraft/core/apis/transfer/TransferredFile.java

@@ -0,0 +1,48 @@
+// SPDX-FileCopyrightText: 2022 The CC: Tweaked Developers
+//
+// SPDX-License-Identifier: MPL-2.0
+
+package dan200.computercraft.core.apis.transfer;
+
+import dan200.computercraft.api.lua.LuaFunction;
+import dan200.computercraft.core.apis.handles.BinaryReadableHandle;
+import dan200.computercraft.core.apis.handles.ByteBufferChannel;
+import dan200.computercraft.core.methods.ObjectSource;
+
+import java.nio.ByteBuffer;
+import java.util.Collections;
+import java.util.Optional;
+
+/**
+ * A binary file handle that has been transferred to this computer.
+ * <p>
+ * This inherits all methods of {@link BinaryReadableHandle binary file handles}, meaning you can use the standard
+ * {@link BinaryReadableHandle#read(Optional) read functions} to access the contents of the file.
+ *
+ * @cc.module [kind=event] file_transfer.TransferredFile
+ * @see BinaryReadableHandle
+ */
+public class TransferredFile implements ObjectSource {
+    private final String name;
+    private final BinaryReadableHandle handle;
+
+    public TransferredFile(String name, ByteBuffer contents) {
+        this.name = name;
+        handle = BinaryReadableHandle.of(new ByteBufferChannel(contents));
+    }
+
+    /**
+     * Get the name of this file being transferred.
+     *
+     * @return The file's name.
+     */
+    @LuaFunction
+    public final String getName() {
+        return name;
+    }
+
+    @Override
+    public Iterable<Object> getExtra() {
+        return Collections.singleton(handle);
+    }
+}

projects/core/src/main/java/dan200/computercraft/core/apis/transfer/TransferredFiles.java

@@ -0,0 +1,45 @@
+// SPDX-FileCopyrightText: 2022 The CC: Tweaked Developers
+//
+// SPDX-License-Identifier: MPL-2.0
+
+package dan200.computercraft.core.apis.transfer;
+
+import dan200.computercraft.api.lua.LuaFunction;
+
+import java.util.List;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+/**
+ * A list of files that have been transferred to this computer.
+ *
+ * @cc.module [kind=event] file_transfer.TransferredFiles
+ */
+public class TransferredFiles {
+    public static final String EVENT = "file_transfer";
+
+    private final AtomicBoolean consumed = new AtomicBoolean(false);
+    private final Runnable onConsumed;
+
+    private final List<TransferredFile> files;
+
+    public TransferredFiles(List<TransferredFile> files, Runnable onConsumed) {
+        this.files = files;
+        this.onConsumed = onConsumed;
+    }
+
+    /**
+     * All the files that are being transferred to this computer.
+     *
+     * @return The list of files.
+     */
+    @LuaFunction
+    public final List<TransferredFile> getFiles() {
+        consumed();
+        return files;
+    }
+
+    private void consumed() {
+        if (consumed.getAndSet(true)) return;
+        onConsumed.run();
+    }
+}