fix: compressor didn't chunkify big payload

lib/compress-stream.js

@@ -1,3 +1,11 @@
+/**
+ * As per the snappy framing format for streams, the size of any uncompressed chunk can be
+ * no longer than 65536 bytes.
+ *
+ * From: https://github.com/google/snappy/blob/main/framing_format.txt#L90:L92
+ */
+const UNCOMPRESSED_CHUNK_SIZE = 65536;
+
 var Transform = require('stream').Transform
   , util = require('util')
 
@@ -50,20 +58,39 @@ CompressStream.prototype._uncompressed = function (chunk) {
   )
 }
 
-CompressStream.prototype._transform = function (chunk, enc, callback) {
-  var self = this
-
-  snappy.compress(chunk, function (err, compressed) {
-    if (err)
-      return callback(err)
-
-    if (compressed.length < chunk.length)
-      self._compressed(chunk, compressed)
-    else
-      self._uncompressed(chunk)
-
-    callback()
-  })
+/**
+ * Some compression benchmarks : 
+ * 
+ *   i) Chunking in transform with snappy.compressSync (the new implementation)
+ *   ii) Chunking from outside with compressStream.write (using original snappy.compress)
+ *   iii) No chunking (Original)
+ * 
+ *  | Size              | in transform | compressStream.write | orginal (no chunking) |
+ *  |-------------------|--------------|----------------------|-----------------------|
+ *  | 10kb   (1 chunk)  | 0.0229 ms    | 0.0385 ms            | 0.0388 ms             |
+ *  | 100kb  (2 chunks) | 0.0562 ms    | 0.1051 ms            | 0.0844 ms             |
+ *  | 1000kb (16 chunks)| 0.382  ms    | 0.7971 ms            | 0.1998 ms             |
+ * 
+ */
+
+CompressStream.prototype._transform = function(chunk, enc, callback) {
+  new Promise(() => {
+    try {
+      for (let startFrom = 0; startFrom < chunk.length; startFrom += UNCOMPRESSED_CHUNK_SIZE) {
+        const endAt = startFrom + Math.min(chunk.length - startFrom, UNCOMPRESSED_CHUNK_SIZE);
+        const bytesChunk = chunk.slice(startFrom, endAt);
+        const compressed = snappy.compressSync(bytesChunk)
+        if (compressed.length < bytesChunk.length)
+          this._compressed(bytesChunk, compressed)
+        else
+          this._uncompressed(bytesChunk)
+
+      }
+      callback();
+    } catch (err) {
+      return callback(err);
+    }
+  }).catch(e => console.log(e))
 }
 
-module.exports = CompressStream
+module.exports = CompressStream

test/compress-test.js

@@ -1,10 +1,16 @@
 var spawn = require('child_process').spawn
-
   , createCompressStream = require('../').createCompressStream
   , test = require('tap').test
   , largerInput = require('fs').readFileSync(__filename)
   , largerInputString = largerInput.toString()
 
+const UNCOMPRESSED_CHUNK_SIZE = 65536
+let superLargeInput = largerInput;
+for (let i = largerInput.length; i <= UNCOMPRESSED_CHUNK_SIZE; i += largerInput.length) {
+  superLargeInput = Buffer.concat([superLargeInput, largerInput]);
+}
+const superLargeInputString = superLargeInput.toString();
+
 test('compress small string', function (t) {
   var child = spawn('python', [ '-m', 'snappy', '-d' ])
     , compressStream = createCompressStream()
@@ -48,3 +54,26 @@ test('compress large string', function (t) {
   compressStream.write(largerInputString)
   compressStream.end()
 })
+
+
+test('compress very very large string', function (t) {
+  var child = spawn('python', [ '-m', 'snappy', '-d' ])
+    , compressStream = createCompressStream()
+    , data = ''
+
+  child.stdout.on('data', function (chunk) {
+    data = data + chunk.toString()
+  })
+
+  child.stdout.on('end', function () {
+    t.equal(data, superLargeInputString)
+    t.end()
+  })
+
+  child.stderr.pipe(process.stderr)
+
+  compressStream.pipe(child.stdin)
+
+  compressStream.write(superLargeInputString)
+  compressStream.end()
+})