From a9a047c0e3b9ec69284a96af0c1d04e5314d8fce Mon Sep 17 00:00:00 2001
From: Jacques Lucke <jacques@blender.org>
Date: Thu, 20 Jun 2024 14:09:29 +0200
Subject: [PATCH] Core: use implicit sharing for PackedFile data

Found this bottleneck when checking #122281. With this patch, `ED_undo_pop` in
the provided file speeds up from `132 ms` to `18 ms`.

Pull Request: https://projects.blender.org/blender/blender/pulls/123243
---
 source/blender/blenkernel/intern/image.cc      |  6 ++----
 source/blender/blenkernel/intern/packedFile.cc | 18 ++++++++++++------
 source/blender/makesdna/DNA_packedFile_types.h | 10 +++++++++-
 3 files changed, 23 insertions(+), 11 deletions(-)

diff --git a/source/blender/blenkernel/intern/image.cc b/source/blender/blenkernel/intern/image.cc
index 6aa7144d262..43d67be1a44 100644
--- a/source/blender/blenkernel/intern/image.cc
+++ b/source/blender/blenkernel/intern/image.cc
@@ -1363,10 +1363,8 @@ static bool image_memorypack_imbuf(
   }
 
   ImagePackedFile *imapf;
-  PackedFile *pf = MEM_cnew<PackedFile>("PackedFile");
-
-  pf->size = ibuf->encoded_size;
-  pf->data = IMB_steal_encoded_buffer(ibuf);
+  PackedFile *pf = BKE_packedfile_new_from_memory(IMB_steal_encoded_buffer(ibuf),
+                                                  ibuf->encoded_size);
 
   imapf = static_cast<ImagePackedFile *>(MEM_mallocN(sizeof(ImagePackedFile), "Image PackedFile"));
   STRNCPY(imapf->filepath, filepath);
diff --git a/source/blender/blenkernel/intern/packedFile.cc b/source/blender/blenkernel/intern/packedFile.cc
index 90c4a2c2140..f1a49e4c80f 100644
--- a/source/blender/blenkernel/intern/packedFile.cc
+++ b/source/blender/blenkernel/intern/packedFile.cc
@@ -87,7 +87,7 @@ int BKE_packedfile_read(PackedFile *pf, void *data, int size)
     }
 
     if (size > 0) {
-      memcpy(data, ((char *)pf->data) + pf->seek, size);
+      memcpy(data, ((const char *)pf->data) + pf->seek, size);
     }
     else {
       size = 0;
@@ -148,8 +148,9 @@ void BKE_packedfile_free(PackedFile *pf)
 {
   if (pf) {
     BLI_assert(pf->data != nullptr);
+    BLI_assert(pf->sharing_info != nullptr);
 
-    MEM_SAFE_FREE(pf->data);
+    pf->sharing_info->remove_user_and_delete_if_last();
     MEM_freeN(pf);
   }
   else {
@@ -165,7 +166,7 @@ PackedFile *BKE_packedfile_duplicate(const PackedFile *pf_src)
   PackedFile *pf_dst;
 
   pf_dst = static_cast<PackedFile *>(MEM_dupallocN(pf_src));
-  pf_dst->data = MEM_dupallocN(pf_src->data);
+  pf_dst->sharing_info->add_user();
 
   return pf_dst;
 }
@@ -177,6 +178,7 @@ PackedFile *BKE_packedfile_new_from_memory(void *mem, int memlen)
   PackedFile *pf = static_cast<PackedFile *>(MEM_callocN(sizeof(*pf), "PackedFile"));
   pf->data = mem;
   pf->size = memlen;
+  pf->sharing_info = blender::implicit_sharing::info_for_mem_free(mem);
 
   return pf;
 }
@@ -891,7 +893,9 @@ void BKE_packedfile_blend_write(BlendWriter *writer, const PackedFile *pf)
     return;
   }
   BLO_write_struct(writer, PackedFile, pf);
-  BLO_write_raw(writer, pf->size, pf->data);
+  BLO_write_shared(writer, pf->data, pf->size, pf->sharing_info, [&]() {
+    BLO_write_raw(writer, pf->size, pf->data);
+  });
 }
 
 void BKE_packedfile_blend_read(BlendDataReader *reader, PackedFile **pf_p)
@@ -901,8 +905,10 @@ void BKE_packedfile_blend_read(BlendDataReader *reader, PackedFile **pf_p)
   if (pf == nullptr) {
     return;
   }
-
-  BLO_read_data_address(reader, &pf->data);
+  pf->sharing_info = BLO_read_shared(reader, &pf->data, [&]() {
+    BLO_read_data_address(reader, &pf->data);
+    return blender::implicit_sharing::info_for_mem_free(const_cast<void *>(pf->data));
+  });
   if (pf->data == nullptr) {
     /* We cannot allow a PackedFile with a nullptr data field,
      * the whole code assumes this is not possible. See #70315. */
diff --git a/source/blender/makesdna/DNA_packedFile_types.h b/source/blender/makesdna/DNA_packedFile_types.h
index b5730d51698..cb9ca36dd34 100644
--- a/source/blender/makesdna/DNA_packedFile_types.h
+++ b/source/blender/makesdna/DNA_packedFile_types.h
@@ -8,8 +8,16 @@
 
 #pragma once
 
+#include "BLI_implicit_sharing.h"
+
 typedef struct PackedFile {
   int size;
   int seek;
-  void *data;
+  /**
+   * Raw data from the shared file. This data is const because it uses implicit sharing and may be
+   * shared with e.g. the undo system.
+   */
+  const void *data;
+  /** Sharing info corresponding to the data above. This is run-time data. */
+  const ImplicitSharingInfoHandle *sharing_info;
 } PackedFile;