commit 74a57221dfb310d7802fec1d99ee083d065d4471
author Herb Derby <herb@google.com> Tue Nov 15 17:50:03 2022 -0500
committer SkCQ <skcq-be@skia-corp.google.com.iam.gserviceaccount.com> Wed Nov 16 16:25:39 2022 +0000
tree 8997f86d7d6b2bedfa1559557003ee9cd8c749f3
parent d7c177a69e16be3ba97289e636fb853d3e8b2336

Move data pointer for move operator=

The original implementation just moved each element over to
the destination Array. It maybe that it was discovered that
moving the pointer didn't pay off. I don't know if this was
tested or not.

Move the pointer from that to this if possible. Otherwise,
move the elements one-by-one.

Change-Id: I8c1dae1a79e46bb230c8eb84be723e0c05ba7459
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/605718
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Herb Derby <herb@google.com>
Reviewed-by: John Stiles <johnstiles@google.com>

include/private/SkTArray.h

diff --git a/include/private/SkTArray.h b/include/private/SkTArray.h
index 9af1e2f..0e935a2 100644
--- a/include/private/SkTArray.h
+++ b/include/private/SkTArray.h
@@ -59,15 +59,14 @@
 
     SkTArray(SkTArray&& that) {
         if (that.fOwnMemory) {
-            fData = that.fData;
-            fSize = that.fSize;
-            fCapacity = that.fCapacity;
-            fOwnMemory = true;
+            fData = std::exchange(that.fData, nullptr);
+            fSize = std::exchange(that.fSize, 0);
 
-            that.fData = nullptr;
-            that.fSize = 0;
+            // exchange does not work for bit fields.
+            fCapacity = that.fCapacity;
             that.fCapacity = 0;
-            that.fOwnMemory = true;
+
+            fOwnMemory = true;
         } else {
             this->init(that.fSize);
             that.move(fData);
@@ -103,10 +102,25 @@
     SkTArray& operator=(SkTArray&& that) {
         if (this != &that) {
             this->clear();
-            this->checkRealloc(that.size(), kExactFit);
-            fSize = that.fSize;
-            that.move(fData);
-            that.fSize = 0;
+            if (that.fOwnMemory) {
+                // The storage is on the heap, so move the data pointer.
+                if (fOwnMemory) {
+                    sk_free(fData);
+                }
+
+                fData = std::exchange(that.fData, nullptr);
+
+                // Can't use exchange with bitfields.
+                fCapacity = that.fCapacity;
+                that.fCapacity = 0;
+
+                fOwnMemory = true;
+            } else {
+                // The data is stored inline in that, so move it element-by-element.
+                this->checkRealloc(that.size(), kExactFit);
+                that.move(fData);
+            }
+            fSize = std::exchange(that.fSize, 0);
         }
         return *this;
     }