zlib: option for engine in convenience methods

Added option to expose engine to convenience methods

Refs: https://github.com/nodejs/node/issues/8874
PR-URL: https://github.com/nodejs/node/pull/13089
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>

doc/api/zlib.md

@@ -301,6 +301,7 @@ ignored by the decompression classes.
 * `strategy` {integer} (compression only)
 * `dictionary` {Buffer|TypedArray|DataView} (deflate/inflate only, empty dictionary by
   default)
+* `info` {boolean} (If `true`, returns an object with `buffer` and `engine`)
 
 See the description of `deflateInit2` and `inflateInit2` at
 <http://zlib.net/manual.html#Advanced> for more information on these.

lib/zlib.js

@@ -77,6 +77,13 @@ function isInvalidStrategy(strategy) {
   //         constants.Z_DEFAULT_STRATEGY (0)
 }
 
+function responseData(engine, buffer) {
+  if (engine._opts.info) {
+    return { buffer, engine };
+  }
+  return buffer;
+}
+
 function zlibBuffer(engine, buffer, callback) {
   // Streams do not support non-Buffer ArrayBufferViews yet. Convert it to a
   // Buffer without copying.
@@ -121,7 +128,7 @@ function zlibBuffer(engine, buffer, callback) {
 
     buffers = [];
     engine.close();
-    callback(err, buf);
+    callback(err, responseData(engine, buf));
   }
 }
 
@@ -134,7 +141,7 @@ function zlibBufferSync(engine, buffer) {
 
   var flushFlag = engine._finishFlushFlag;
 
-  return engine._processChunk(buffer, flushFlag);
+  return responseData(engine, engine._processChunk(buffer, flushFlag));
 }
 
 function zlibOnError(message, errno) {

test/parallel/test-zlib-convenience-methods.js

@@ -36,6 +36,10 @@ const opts = {
   chunkSize: 1024,
 };
 
+const optsInfo = {
+  info: true
+};
+
 for (const [type, expect] of [
   ['string', expectStr],
   ['Buffer', expectBuf],
@@ -44,10 +48,10 @@ for (const [type, expect] of [
   )
 ]) {
   for (const method of [
-    ['gzip', 'gunzip'],
-    ['gzip', 'unzip'],
-    ['deflate', 'inflate'],
-    ['deflateRaw', 'inflateRaw'],
+    ['gzip', 'gunzip', 'Gzip', 'Gunzip'],
+    ['gzip', 'unzip', 'Gzip', 'Unzip'],
+    ['deflate', 'inflate', 'Deflate', 'Inflate'],
+    ['deflateRaw', 'inflateRaw', 'DeflateRaw', 'InflateRaw'],
   ]) {
     zlib[method[0]](expect, opts, common.mustCall((err, result) => {
       zlib[method[1]](result, opts, common.mustCall((err, result) => {
@@ -65,6 +69,22 @@ for (const [type, expect] of [
       }));
     }));
 
+    zlib[method[0]](expect, optsInfo, common.mustCall((err, result) => {
+      assert.ok(result.engine instanceof zlib[method[2]],
+                `Should get engine ${method[2]} after ${method[0]} ` +
+                `${type} with info option.`);
+
+      const compressed = result.buffer;
+      zlib[method[1]](compressed, optsInfo, common.mustCall((err, result) => {
+        assert.strictEqual(result.buffer.toString(), expectStr,
+                           `Should get original string after ${method[0]}/` +
+                           `${method[1]} ${type} with info option.`);
+        assert.ok(result.engine instanceof zlib[method[3]],
+                  `Should get engine ${method[3]} after ${method[0]} ` +
+                  `${type} with info option.`);
+      }));
+    }));
+
     {
       const compressed = zlib[`${method[0]}Sync`](expect, opts);
       const decompressed = zlib[`${method[1]}Sync`](compressed, opts);
@@ -81,5 +101,21 @@ for (const [type, expect] of [
                          `Should get original string after ${method[0]}Sync/` +
                          `${method[1]}Sync ${type} without options.`);
     }
+
+
+    {
+      const compressed = zlib[`${method[0]}Sync`](expect, optsInfo);
+      assert.ok(compressed.engine instanceof zlib[method[2]],
+                `Should get engine ${method[2]} after ${method[0]} ` +
+                `${type} with info option.`);
+      const decompressed = zlib[`${method[1]}Sync`](compressed.buffer,
+                                                    optsInfo);
+      assert.strictEqual(decompressed.buffer.toString(), expectStr,
+                         `Should get original string after ${method[0]}Sync/` +
+                         `${method[1]}Sync ${type} without options.`);
+      assert.ok(decompressed.engine instanceof zlib[method[3]],
+                `Should get engine ${method[3]} after ${method[0]} ` +
+                `${type} with info option.`);
+    }
   }
 }