zlib: Manage flush flags appropriately

If you call z.flush();z.write('foo'); then it would try to write 'foo'
before the flush was done, triggering an assertion in the zlib binding.

Closes #4950

1 files changed, 34 insertions, 13 deletions

diff --git a/lib/zlib.js b/lib/zlib.js
index dc0aeca304..c9263142de 100644
--- a/lib/zlib.js
+++ b/lib/zlib.js
@@ -226,8 +226,17 @@ function Zlib(opts, mode) {
 
   Transform.call(this, opts);
 
-  // means a different thing there.
-  this._readableState.chunkSize = null;
+  if (opts.flush) {
+    if (opts.flush !== binding.Z_NO_FLUSH &&
+        opts.flush !== binding.Z_PARTIAL_FLUSH &&
+        opts.flush !== binding.Z_SYNC_FLUSH &&
+        opts.flush !== binding.Z_FULL_FLUSH &&
+        opts.flush !== binding.Z_FINISH &&
+        opts.flush !== binding.Z_BLOCK) {
+      throw new Error('Invalid flush flag: ' + opts.flush);
+    }
+  }
+  this._flushFlag = opts.flush || binding.Z_NO_FLUSH;
 
   if (opts.chunkSize) {
     if (opts.chunkSize < exports.Z_MIN_CHUNK ||
@@ -308,22 +317,30 @@ Zlib.prototype.reset = function reset() {
   return this._binding.reset();
 };
 
+// This is the _flush function called by the transform class,
+// internally, when the last chunk has been written.
 Zlib.prototype._flush = function(callback) {
-  this._transform(null, '', callback);
+  this._transform(new Buffer(0), '', callback);
 };
 
 Zlib.prototype.flush = function(callback) {
   var ws = this._writableState;
-  var ts = this._transformState;
 
-  if (ws.writing) {
-    ws.needDrain = true;
+  if (ws.ended) {
+    if (callback)
+      process.nextTick(callback);
+  } else if (ws.ending) {
+    if (callback)
+      this.once('end', callback);
+  } else if (ws.needDrain) {
     var self = this;
     this.once('drain', function() {
-      self._flush(callback);
+      self.flush(callback);
     });
-  } else
-    this._flush(callback || function() {});
+  } else {
+    this._flushFlag = binding.Z_FULL_FLUSH;
+    this.write(new Buffer(0), '', callback);
+  }
 };
 
 Zlib.prototype.close = function(callback) {
@@ -358,10 +375,14 @@ Zlib.prototype._transform = function(chunk, encoding, cb) {
   // goodness.
   if (last)
     flushFlag = binding.Z_FINISH;
-  else if (chunk === null)
-    flushFlag = binding.Z_FULL_FLUSH;
-  else
-    flushFlag = binding.Z_NO_FLUSH;
+  else {
+    flushFlag = this._flushFlag;
+    // once we've flushed the last of the queue, stop flushing and
+    // go back to the normal behavior.
+    if (chunk.length >= ws.length) {
+      this._flushFlag = this._opts.flush || binding.Z_NO_FLUSH;
+    }
+  }
 
   var availInBefore = chunk && chunk.length;
   var availOutBefore = this._chunkSize - this._offset;