Initial read stream implementation

lib/fs.js

@@ -376,6 +376,96 @@ exports.realpath = function(path, callback) {
   });
 }
 
+exports.fileReadStream = function(path, options) {
+  return new FileReadStream(path, options);
+};
+
+var FileReadStream = exports.FileReadStream = function(path, options) {
+  this.path = path;
+  this.fd = null;
+  this.readable = true;
+  this.paused = false;
+
+  this.flags = 'r';
+  this.encoding = 'binary';
+  this.mode = 0666;
+  this.bufferSize = 4 * 1024;
+
+  process.mixin(this, options || {});
+
+  var
+    self = this,
+    buffer = [];
+
+  function read() {
+    if (!self.readable || self.paused) {
+      return;
+    }
+
+    fs.read(self.fd, self.bufferSize, undefined, self.encoding, function(err, data, bytesRead) {
+      if (bytesRead === 0) {
+        self.emit('end');
+        self.close();
+        return;
+      }
+
+      // do not emit events if the stream is paused
+      if (self.paused) {
+        buffer.push(data);
+        return;
+      }
+
+      self.emit('data', data);
+      read();
+    });
+  }
+
+  fs.open(this.path, this.flags, this.mode, function(err, fd) {
+    if (err) {
+      self.emit('error', err);
+      return;
+    }
+
+    self.fd = fd;
+    self.emit('open', fd);
+    read();
+  });
+
+  this.close = function() {
+    this.readable = false;
+    fs.close(this.fd, function(err) {
+      if (err) {
+        self.emit('error', err);
+        return;
+      }
+
+      self.emit('close');
+    });
+  };
+
+  this.pause = function() {
+    this.paused = true;
+  };
+
+  this.resume = function() {
+    this.paused = false;
+
+    // emit any buffered read events before continuing
+    var data;
+    while (!this.paused) {
+      data = buffer.shift();
+      if (data === undefined) {
+        break;
+      }
+
+      self.emit('data', data);
+    }
+
+    read();
+  };
+};
+FileReadStream.prototype.__proto__ = process.EventEmitter.prototype;
+
 exports.fileWriteStream = function(path, options) {
   return new FileWriteStream(path, options);
 };

test/simple/test-file-read-stream.js

@@ -0,0 +1,54 @@
+process.mixin(require('../common'));
+
+var
+  fn = path.join(fixturesDir, 'multipart.js'),
+  file = fs.fileReadStream(fn),
+
+  callbacks = {
+    open: -1,
+    end: -1,
+    close: -1
+  },
+
+  paused = false,
+
+  fileContent = '';
+
+file
+  .addListener('open', function(fd) {
+    callbacks.open++;
+    assert.equal('number', typeof fd);
+    assert.ok(file.readable);
+  })
+  .addListener('error', function(err) {
+    throw err;
+  })
+  .addListener('data', function(data) {
+    assert.ok(!paused);
+    fileContent += data;
+    
+    paused = true;
+    file.pause();
+    assert.ok(file.paused);
+
+    setTimeout(function() {
+      paused = false;
+      file.resume();
+      assert.ok(!file.paused);
+    }, 10);
+  })
+  .addListener('end', function(chunk) {
+    callbacks.end++;
+  })
+  .addListener('close', function() {
+    callbacks.close++;
+    assert.ok(!file.readable);
+
+    assert.equal(fs.readFileSync(fn), fileContent);
+  });
+
+process.addListener('exit', function() {
+  for (var k in callbacks) {
+    assert.equal(0, callbacks[k], k+' count off by '+callbacks[k]);
+  }
+});