Add promise support for fs.readv (#970)

lib/fs/__tests__/multi-param.test.js

@@ -149,6 +149,70 @@ describe('fs.write()', () => {
   })
 })
 
+describe('fs.readv()', () => {
+  let TEST_FILE
+  let TEST_DATA
+  let TEST_FD
+
+  beforeEach(() => {
+    TEST_FILE = path.join(os.tmpdir(), 'fs-extra', 'readv-test-file')
+    TEST_DATA = crypto.randomBytes(SIZE)
+    fs.writeFileSync(TEST_FILE, TEST_DATA)
+    TEST_FD = fs.openSync(TEST_FILE, 'r')
+  })
+
+  afterEach(() => {
+    return fs.close(TEST_FD)
+      .then(() => fs.remove(TEST_FILE))
+  })
+
+  describe('with promises', () => {
+    it('returns an object', () => {
+      const bufferArray = [Buffer.alloc(SIZE / 2), Buffer.alloc(SIZE / 2)]
+      return fs.readv(TEST_FD, bufferArray, 0)
+        .then(({ bytesRead, buffers }) => {
+          assert.strictEqual(bytesRead, SIZE, 'bytesRead is correct')
+          assert.deepStrictEqual(buffers, bufferArray, 'returned data matches mutated input param')
+          assert.deepStrictEqual(Buffer.concat(buffers), TEST_DATA, 'data is correct')
+        })
+    })
+
+    it('returns an object when minimal arguments are passed', () => {
+      const bufferArray = [Buffer.alloc(SIZE / 2), Buffer.alloc(SIZE / 2)]
+      return fs.readv(TEST_FD, bufferArray)
+        .then(({ bytesRead, buffers }) => {
+          assert.strictEqual(bytesRead, SIZE, 'bytesRead is correct')
+          assert.deepStrictEqual(buffers, bufferArray, 'returned data matches mutated input param')
+          assert.deepStrictEqual(Buffer.concat(buffers), TEST_DATA, 'data is correct')
+        })
+    })
+  })
+
+  describe('with callbacks', () => {
+    it('works', done => {
+      const bufferArray = [Buffer.alloc(SIZE / 2), Buffer.alloc(SIZE / 2)]
+      fs.readv(TEST_FD, bufferArray, 0, (err, bytesRead, buffers) => {
+        assert.ifError(err)
+        assert.strictEqual(bytesRead, SIZE, 'bytesRead is correct')
+        assert.deepStrictEqual(buffers, bufferArray, 'returned data matches mutated input param')
+        assert.deepStrictEqual(Buffer.concat(buffers), TEST_DATA, 'data is correct')
+        done()
+      })
+    })
+
+    it('works when minimal arguments are passed', done => {
+      const bufferArray = [Buffer.alloc(SIZE / 2), Buffer.alloc(SIZE / 2)]
+      fs.readv(TEST_FD, bufferArray, (err, bytesRead, buffers) => {
+        assert.ifError(err)
+        assert.strictEqual(bytesRead, SIZE, 'bytesRead is correct')
+        assert.deepStrictEqual(buffers, bufferArray, 'returned data matches mutated input param')
+        assert.deepStrictEqual(Buffer.concat(buffers), TEST_DATA, 'data is correct')
+        done()
+      })
+    })
+  })
+})
+
 describe('fs.writev()', () => {
   let TEST_FILE
   let TEST_DATA

lib/fs/index.js

@@ -65,7 +65,7 @@ exports.exists = function (filename, callback) {
   })
 }
 
-// fs.read(), fs.write(), & fs.writev() need special treatment due to multiple callback args
+// fs.read(), fs.write(), fs.readv(), & fs.writev() need special treatment due to multiple callback args
 
 exports.read = function (fd, buffer, offset, length, position, callback) {
   if (typeof callback === 'function') {
@@ -97,6 +97,22 @@ exports.write = function (fd, buffer, ...args) {
   })
 }
 
+// Function signature is
+// s.readv(fd, buffers[, position], callback)
+// We need to handle the optional arg, so we use ...args
+exports.readv = function (fd, buffers, ...args) {
+  if (typeof args[args.length - 1] === 'function') {
+    return fs.readv(fd, buffers, ...args)
+  }
+
+  return new Promise((resolve, reject) => {
+    fs.readv(fd, buffers, ...args, (err, bytesRead, buffers) => {
+      if (err) return reject(err)
+      resolve({ bytesRead, buffers })
+    })
+  })
+}
+
 // Function signature is
 // s.writev(fd, buffers[, position], callback)
 // We need to handle the optional arg, so we use ...args