initial changes

src/io/file.js

@@ -0,0 +1,67 @@
+import * as ops from '../ops';
+
+let next_thread_id = 1;
+
+export default class file {
+  constructor(conn, handle, remote_path) {
+    this.conn = conn;
+    this.handle = handle;
+    this.remote_path = remote_path;
+    this.thread_id = next_thread_id++;
+  }
+
+  conn;
+  handle = null;
+  thread_id;
+  remote_path;
+
+  async close() {
+    if (this.handle !== null) {
+      const result = await ops.close_file(this.conn, this.remote_path,
+                                          this.handle, this.thread_id);
+      if (result === 0) {
+        this.handle = null;
+      }
+      return result;
+    }
+
+    return 0;
+  }
+
+  async get_size() {
+    if (this.handle === null) {
+      return Promise.reject(new Error('\'get_size()\' failed: invalid handle'));
+    }
+
+    const attrs = await ops.get_file_attributes(
+        this.conn, this.handle, this.remote_path, this.thread_id);
+    return attrs.size;
+  }
+
+  async read(offset, length) {
+    if (this.handle === null) {
+      return Promise.reject(new Error('\'read()\' failed: invalid handle'));
+    }
+
+    return ops.read_file(this.conn, this.handle, this.remote_path, offset,
+                         length, this.thread_id);
+  }
+
+  async truncate(length) {
+    if (this.handle === null) {
+      return Promise.reject(new Error('\'truncate()\' failed: invalid handle'));
+    }
+
+    return ops.truncate_file(this.conn, this.handle, this.remote_path, length,
+                             this.thread_id);
+  }
+
+  async write(offset, buffer) {
+    if (this.handle === null) {
+      return Promise.reject(new Error('\'write()\' failed: invalid handle'));
+    }
+
+    return ops.write_file(this.conn, this.handle, this.remote_path, offset,
+                          buffer, this.thread_id);
+  }
+}