fixup! zlib: do not coalesce multiple .flush() calls

addaleax · addaleax · commit 21db4226cfe1 · 2019-07-12T00:18:47.000+02:00
diff --git a/lib/zlib.js b/lib/zlib.js
@@ -316,15 +316,28 @@ ZlibBase.prototype._flush = function(callback) {
 //     Z_SYNC_FLUSH < Z_FULL_FLUSH < Z_FINISH
 const flushiness = [];
 let i = 0;
-for (const flushFlag of [Z_NO_FLUSH, Z_BLOCK, Z_PARTIAL_FLUSH,
-                         Z_SYNC_FLUSH, Z_FULL_FLUSH, Z_FINISH]) {
+const kFlushFlagList = [Z_NO_FLUSH, Z_BLOCK, Z_PARTIAL_FLUSH,
+                        Z_SYNC_FLUSH, Z_FULL_FLUSH, Z_FINISH];
+for (const flushFlag of kFlushFlagList) {
   flushiness[flushFlag] = i++;
 }
 
 function maxFlush(a, b) {
   return flushiness[a] > flushiness[b] ? a : b;
 }
 
+// Set up a list of 'special' buffers that can be written using .write()
+// from the .flush() code as a way of introducing flushing operations into the
+// write sequence.
+const kFlushBuffers = [];
+{
+  const dummyArrayBuffer = new ArrayBuffer();
+  for (const flushFlag of kFlushFlagList) {
+    kFlushBuffers[flushFlag] = Buffer.from(dummyArrayBuffer);
+    kFlushBuffers[flushFlag][kFlushFlag] = flushFlag;
+  }
+}
+
 ZlibBase.prototype.flush = function(kind, callback) {
   const ws = this._writableState;
 
@@ -340,9 +353,7 @@ ZlibBase.prototype.flush = function(kind, callback) {
     if (callback)
       this.once('end', callback);
   } else {
-    const flushBuffer = Buffer.alloc(0);
-    flushBuffer[kFlushFlag] = kind;
-    this.write(flushBuffer, '', callback);
+    this.write(kFlushBuffers[kind], '', callback);
   }
 };
 
diff --git a/test/parallel/test-zlib-flush-write-sync-interleaved.js b/test/parallel/test-zlib-flush-write-sync-interleaved.js
@@ -13,14 +13,31 @@ const decompress = createGunzip();
 decompress.setEncoding('utf8');
 
 const events = [];
+const compressedChunks = [];
 
 for (const chunk of ['abc', 'def', 'ghi']) {
   compress.write(chunk, common.mustCall(() => events.push({ written: chunk })));
   compress.flush(Z_PARTIAL_FLUSH, common.mustCall(() => {
     events.push('flushed');
-    decompress.write(compress.read(), common.mustCall(() => {
-      events.push({ read: decompress.read() });
-    }));
+    const chunk = compress.read();
+    if (chunk !== null)
+      compressedChunks.push(chunk);
+  }));
+}
+
+compress.end(common.mustCall(() => {
+  events.push('compress end');
+  writeToDecompress();
+}));
+
+function writeToDecompress() {
+  // Write the compressed chunks to a decompressor, one by one, in order to
+  // verify that the flushes actually worked.
+  const chunk = compressedChunks.shift();
+  if (chunk === undefined) return decompress.end();
+  decompress.write(chunk, common.mustCall(() => {
+    events.push({ read: decompress.read() });
+    writeToDecompress();
   }));
 }
 
@@ -29,11 +46,12 @@ process.on('exit', () => {
     { written: 'abc' },
     'flushed',
     { written: 'def' },
-    { read: 'abc' },
     'flushed',
     { written: 'ghi' },
-    { read: 'def' },
     'flushed',
+    'compress end',
+    { read: 'abc' },
+    { read: 'def' },
     { read: 'ghi' }
   ]);
 });
