Fix Issue #230: Error: Uncaught TypeError: undefined is not a function on <Buffer>.copy()

src/filesystem/implementation.js

@@ -56,6 +56,27 @@ function standard_check_result_cb(callback) {
   };
 }
 
+/**
+ * Coerce array-like data to Buffer so we can .copy(), etc.
+ * Allow null, a Buffer, or an object that can be dealt with
+ * by the Buffer constructor (e.g., Typed Array, Array, ...)
+ */
+function ensureBuffer(maybeBuffer) {
+  if(!maybeBuffer) {
+    return null;
+  }
+
+  if(Buffer.isBuffer(maybeBuffer)) {
+    return maybeBuffer;
+  }
+
+  try {
+    return new Buffer(maybeBuffer);
+  } catch(e) {
+    return null;
+  }
+}
+
 /**
  * Update node times. Only passed times are modified (undefined times are ignored)
  * and filesystem flags are examined in order to override update logic.
@@ -753,7 +774,10 @@ function write_data(context, ofd, buffer, offset, length, position, callback) {
     if(error) {
       callback(error);
     } else {
-      fileData = result;
+      fileData = ensureBuffer(result);
+      if(!fileData) {
+        return callback(new Errors.EIO('Expected Buffer'));
+      }
       var _position = (!(undefined === position || null === position)) ? position : ofd.position;
       var newSize = Math.max(fileData.length, _position + length);
       var newData = new Buffer(newSize);
@@ -793,7 +817,10 @@ function read_data(context, ofd, buffer, offset, length, position, callback) {
     if(error) {
       callback(error);
     } else {
-      fileData = result;
+      fileData = ensureBuffer(result);
+      if(!fileData) {
+        return callback(new Errors.EIO('Expected Buffer'));
+      }
       var _position = (!(undefined === position || null === position)) ? position : ofd.position;
       length = (_position + length > buffer.length) ? length - _position : length;
       fileData.copy(buffer, offset, _position, _position + length);
@@ -1180,6 +1207,10 @@ function truncate_file(context, path, length, callback) {
     if (error) {
       callback(error);
     } else {
+      fileData = ensureBuffer(fileData);
+      if(!fileData) {
+        return callback(new Errors.EIO('Expected Buffer'));
+      }
       var data = new Buffer(length);
       data.fill(0);
       if(fileData) {
@@ -1234,6 +1265,10 @@ function ftruncate_file(context, ofd, length, callback) {
       callback(error);
     } else {
       var data;
+      fileData = ensureBuffer(fileData);
+      if(!fileData) {
+        return callback(new Errors.EIO('Expected Buffer'));
+      }
       if(fileData) {
         data = fileData.slice(0, length);
       } else {