feat(REST): add support for REST command

Allows the client to resume a transfer at the specified bytes

src/commands/registration/rest.js

@@ -0,0 +1,16 @@
+const _ = require('lodash');
+
+module.exports = {
+  directive: 'REST',
+  handler: function ({command} = {}) {
+    const arg = _.get(command, 'arg');
+    const byteCount = parseInt(arg, 10);
+
+    if (isNaN(byteCount) || byteCount < 0) return this.reply(501, 'Byte count must be 0 or greater');
+
+    this.restByteCount = byteCount;
+    return this.reply(350, `Resarting next transfer at ${byteCount}`);
+  },
+  syntax: '{{cmd}} <byte-count>',
+  description: 'Restart transfer from the specified point. Resets after any STORE or RETRIEVE'
+};

src/commands/registration/retr.js

@@ -12,8 +12,9 @@ module.exports = {
       this.commandSocket.pause();
       dataSocket = socket;
     })
-    .then(() => when.try(this.fs.read.bind(this.fs), command.arg))
+    .then(() => when.try(this.fs.read.bind(this.fs), command.arg, {start: this.restByteCount}))
     .then(stream => {
+      this.restByteCount = 0;
       return when.promise((resolve, reject) => {
         dataSocket.on('error', err => stream.emit('error', err));
 

src/commands/registration/stor.js

@@ -15,8 +15,9 @@ module.exports = {
       this.commandSocket.pause();
       dataSocket = socket;
     })
-    .then(() => when.try(this.fs.write.bind(this.fs), fileName, {append}))
+    .then(() => when.try(this.fs.write.bind(this.fs), fileName, {append, start: this.restByteCount}))
     .then(stream => {
+      this.restByteCount = 0;
       return when.promise((resolve, reject) => {
         stream.once('error', err => dataSocket.emit('error', err));
         stream.once('finish', () => resolve(this.reply(226, fileName)));

src/commands/registration/type.js

@@ -2,7 +2,6 @@
 module.exports = {
   directive: 'TYPE',
   handler: function ({command} = {}) {
-
     if (/^A[0-9]?$/i.test(command.arg)) {
       this.transferType = 'ascii';
     } else if (/^L[0-9]?$/i.test(command.arg) || /^I$/i.test(command.arg)) {

src/commands/registry.js

@@ -21,6 +21,7 @@ const commands = [
   require('./registration/port'),
   require('./registration/pwd'),
   require('./registration/quit'),
+  require('./registration/rest'),
   require('./registration/retr'),
   require('./registration/rmd'),
   require('./registration/rnfr'),

src/connection.js

@@ -18,7 +18,7 @@ class FtpConnection {
     this.transferType = 'binary';
     this.encoding = 'utf8';
     this.bufferSize = false;
-    this.restByteCount = 0;
+    this._restByteCount = 0;
     this._secure = false;
 
     this.connector = new BaseConnector(this);
@@ -50,6 +50,13 @@ class FtpConnection {
     }
   }
 
+  get restByteCount() {
+    return this._restByteCount > 0 ? this._restByteCount : undefined;
+  }
+  set restByteCount(rbc) {
+    this._restByteCount = rbc;
+  }
+
   get secure() {
     return this.server.isTLS || this._secure;
   }
@@ -68,7 +75,7 @@ class FtpConnection {
     return when.try(() => {
       const loginListeners = this.server.listeners('login');
       if (!loginListeners || !loginListeners.length) {
-        if (!this.server.options.anoymous) throw new errors.GeneralError('No "login" listener setup', 500);
+        if (!this.server.options.anonymous) throw new errors.GeneralError('No "login" listener setup', 500);
       } else {
         return this.server.emitPromise('login', {connection: this, username, password});
       }

src/fs.js

@@ -65,22 +65,22 @@ class FileSystem {
     });
   }
 
-  write(fileName, {append = false} = {}) {
+  write(fileName, {append = false, start = undefined} = {}) {
     const {fsPath} = this._resolvePath(fileName);
-    const stream = syncFs.createWriteStream(fsPath, {flags: !append ? 'w+' : 'a+'});
+    const stream = syncFs.createWriteStream(fsPath, {flags: !append ? 'w+' : 'a+', start});
     stream.once('error', () => fs.unlink(fsPath));
     stream.once('close', () => stream.end());
     return stream;
   }
 
-  read(fileName) {
+  read(fileName, {start = undefined} = {}) {
     const {fsPath} = this._resolvePath(fileName);
     return fs.stat(fsPath)
     .tap(stat => {
       if (stat.isDirectory()) throw new errors.FileSystemError('Cannot read a directory');
     })
     .then(() => {
-      const stream = syncFs.createReadStream(fsPath, {flags: 'r'});
+      const stream = syncFs.createReadStream(fsPath, {flags: 'r', start});
       return stream;
     });
   }