fix: fix isRead check on file descriptor

The argument flags must include one of the following access modes:
O_RDONLY, O_WRONLY, or O_RDWR.  These request opening the file read-
only, write-only, or read/write, respectively.
O_RDONLY is 0, O_WRONLY is 1, O_RDWR is 2, the flags use 2 bits for 3 states: 0 (0b00) / 1 (0b01) / 2 (0b10), the 2 bits will never be 3 (0b11).

closes #288

lib/descriptor.js

@@ -80,12 +80,7 @@ FileDescriptor.prototype.isCreate = function() {
  * @return {boolean} Opened for reading.
  */
 FileDescriptor.prototype.isRead = function() {
-  // special treatment because O_RDONLY is 0
-  return (
-    this._flags === constants.O_RDONLY ||
-    this._flags === (constants.O_RDONLY | constants.O_SYNC) ||
-    (this._flags & constants.O_RDWR) === constants.O_RDWR
-  );
+  return (this._flags & constants.O_WRONLY) !== constants.O_WRONLY;
 };
 
 /**

test/lib/descriptor.spec.js

@@ -1,5 +1,6 @@
 'use strict';
 
+const constants = require('constants');
 const FileDescriptor = require('../../lib/descriptor');
 const helper = require('../helper');
 
@@ -89,6 +90,11 @@ describe('FileDescriptor', function() {
       const fd = new FileDescriptor(flags('ax+'));
       assert.isTrue(fd.isAppend());
     });
+
+    it('not opened for appending (O_CREAT)', function() {
+      const fd = new FileDescriptor(constants.O_CREAT);
+      assert.isFalse(fd.isAppend());
+    });
   });
 
   describe('#isTruncate()', function() {
@@ -151,6 +157,11 @@ describe('FileDescriptor', function() {
       const fd = new FileDescriptor(flags('ax+'));
       assert.isFalse(fd.isTruncate());
     });
+
+    it('not opened for truncating (O_CREAT)', function() {
+      const fd = new FileDescriptor(constants.O_CREAT);
+      assert.isFalse(fd.isTruncate());
+    });
   });
 
   describe('#isCreate()', function() {
@@ -213,6 +224,11 @@ describe('FileDescriptor', function() {
       const fd = new FileDescriptor(flags('ax+'));
       assert.isTrue(fd.isCreate());
     });
+
+    it('opened for creation (O_CREAT)', function() {
+      const fd = new FileDescriptor(constants.O_CREAT);
+      assert.isTrue(fd.isCreate());
+    });
   });
 
   describe('#isRead()', function() {
@@ -275,6 +291,11 @@ describe('FileDescriptor', function() {
       const fd = new FileDescriptor(flags('ax+'));
       assert.isTrue(fd.isRead());
     });
+
+    it('opened for reading (O_CREAT)', function() {
+      const fd = new FileDescriptor(constants.O_CREAT);
+      assert.isTrue(fd.isRead());
+    });
   });
 
   describe('#isWrite()', function() {
@@ -337,6 +358,11 @@ describe('FileDescriptor', function() {
       const fd = new FileDescriptor(flags('ax+'));
       assert.isTrue(fd.isWrite());
     });
+
+    it('not opened for writing (O_CREAT)', function() {
+      const fd = new FileDescriptor(constants.O_CREAT);
+      assert.isFalse(fd.isWrite());
+    });
   });
 
   describe('#isExclusive()', function() {
@@ -399,5 +425,10 @@ describe('FileDescriptor', function() {
       const fd = new FileDescriptor(flags('ax+'));
       assert.isTrue(fd.isExclusive());
     });
+
+    it('not opened for exclusive (O_CREAT)', function() {
+      const fd = new FileDescriptor(constants.O_CREAT);
+      assert.isFalse(fd.isExclusive());
+    });
   });
 });