zlib: use `.bytesWritten` instead of `.bytesRead`

The introduction of `.bytesRead` to zlib streams was unfortunate,
because other streams in Node.js core use the exact opposite naming
of `.bytesRead` and `.bytesWritten`.

While one could see how the original naming makes sense in
a `Transform` stream context, we should try to work towards more
consistent APIs in core for these things.

This introduces `zlib.bytesWritten` and documentation-only deprecates
`zlib.bytesRead`.

PR-URL: https://github.com/nodejs/node/pull/19414
Refs: https://github.com/nodejs/node/issues/8874
Refs: https://github.com/nodejs/node/pull/13088
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Сковорода Никита Андреевич <chalkerx@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

1 files changed, 19 insertions, 4 deletions

diff --git a/lib/zlib.js b/lib/zlib.js
index 01a2ebe933..a39e9c20ee 100644
--- a/lib/zlib.js
+++ b/lib/zlib.js
@@ -288,7 +288,7 @@ function Zlib(opts, mode) {
     }
   }
   Transform.call(this, opts);
-  this.bytesRead = 0;
+  this.bytesWritten = 0;
   this._handle = new binding.Zlib(mode);
   this._handle.jsref = this; // Used by processCallback() and zlibOnError()
   this._handle.onerror = zlibOnError;
@@ -327,6 +327,21 @@ Object.defineProperty(Zlib.prototype, '_closed', {
   }
 });
 
+// `bytesRead` made sense as a name when looking from the zlib engine's
+// perspective, but it is inconsistent with all other streams exposed by Node.js
+// that have this concept, where it stands for the number of bytes read
+// *from* the stream (that is, net.Socket/tls.Socket & file system streams).
+Object.defineProperty(Zlib.prototype, 'bytesRead', {
+  configurable: true,
+  enumerable: true,
+  get() {
+    return this.bytesWritten;
+  },
+  set(value) {
+    this.bytesWritten = value;
+  }
+});
+
 Zlib.prototype.params = function params(level, strategy, callback) {
   checkRangesOrGetDefault(level, 'level', Z_MIN_LEVEL, Z_MAX_LEVEL);
   checkRangesOrGetDefault(strategy, 'strategy', Z_DEFAULT_STRATEGY, Z_FIXED);
@@ -501,7 +516,7 @@ function processChunkSync(self, chunk, flushFlag) {
     }
   }
 
-  self.bytesRead = inputRead;
+  self.bytesWritten = inputRead;
 
   if (nread >= kMaxLength) {
     _close(self);
@@ -558,8 +573,8 @@ function processCallback() {
   var availOutAfter = state[0];
   var availInAfter = state[1];
 
-  var inDelta = (handle.availInBefore - availInAfter);
-  self.bytesRead += inDelta;
+  const inDelta = handle.availInBefore - availInAfter;
+  self.bytesWritten += inDelta;
 
   var have = handle.availOutBefore - availOutAfter;
   if (have > 0) {