From 2ea66af742bca4b427f88de13254414730a33776 Mon Sep 17 00:00:00 2001
From: Lukas Stockner <lukas.stockner@freenet.de>
Date: Sat, 21 Aug 2021 03:15:31 +0200
Subject: Add support for Zstandard compression for .blend files

Compressing blendfiles can help save a lot of disk space, but the slowdown
while loading and saving is a major annoyance.
Currently Blender uses Zlib (aka gzip aka Deflate) for compression, but there
are now several more modern algorithms that outperform it in every way.

In this patch, I decided for Zstandard aka Zstd for several reasons:
- It is widely supported, both in other programs and libraries as well as in
  general-purpose compression utilities on Unix
- It is extremely flexible - spanning several orders of magnitude of
  compression speeds depending on the level setting.
- It is pretty much on the Pareto frontier for all of its configurations
  (meaning that no other algorithm is both faster and more efficient).

One downside of course is that older versions of Blender will not be able to
read these files, but one can always just re-save them without compression or
decompress the file manually with an external tool.

The implementation here saves additional metadata into the compressed file in
order to allow for efficient seeking when loading. This is standard-compliant
and will be ignored by other tools that support Zstd.
If the metadata is not present (e.g. because you manually compressed a .blend
file with another tool), Blender will fall back to sequential reading.

Saving is multithreaded to improve performance. Loading is currently not
multithreaded since it's not easy to predict the access patterns of the
loading code when seeking is supported.
In the future, we might want to look into making this more predictable or
disabling seeking for the main .blend file, which would then allow for
multiple background threads that decompress data ahead of time.

The compression level was chosen to get sizes comparable to previous versions
at much higher speeds. In the future, this could be exposed as an option.

Reviewed By: campbellbarton, brecht, mont29

Differential Revision: https://developer.blender.org/D5799
---
 build_files/cmake/Modules/FindZstd.cmake | 66 ++++++++++++++++++++++++++++++++
 1 file changed, 66 insertions(+)
 create mode 100644 build_files/cmake/Modules/FindZstd.cmake

(limited to 'build_files/cmake/Modules/FindZstd.cmake')

diff --git a/build_files/cmake/Modules/FindZstd.cmake b/build_files/cmake/Modules/FindZstd.cmake
new file mode 100644
index 00000000000..84606d01f44
--- /dev/null
+++ b/build_files/cmake/Modules/FindZstd.cmake
@@ -0,0 +1,66 @@
+# - Find Zstd library
+# Find the native Zstd includes and library
+# This module defines
+#  ZSTD_INCLUDE_DIRS, where to find zstd.h, Set when
+#                     ZSTD_INCLUDE_DIR is found.
+#  ZSTD_LIBRARIES, libraries to link against to use Zstd.
+#  ZSTD_ROOT_DIR, The base directory to search for Zstd.
+#                 This can also be an environment variable.
+#  ZSTD_FOUND, If false, do not try to use Zstd.
+#
+# also defined, but not for general use are
+#  ZSTD_LIBRARY, where to find the Zstd library.
+
+#=============================================================================
+# Copyright 2019 Blender Foundation.
+#
+# Distributed under the OSI-approved BSD License (the "License");
+# see accompanying file Copyright.txt for details.
+#
+# This software is distributed WITHOUT ANY WARRANTY; without even the
+# implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+# See the License for more information.
+#=============================================================================
+
+# If ZSTD_ROOT_DIR was defined in the environment, use it.
+IF(NOT ZSTD_ROOT_DIR AND NOT $ENV{ZSTD_ROOT_DIR} STREQUAL "")
+  SET(ZSTD_ROOT_DIR $ENV{ZSTD_ROOT_DIR})
+ENDIF()
+
+SET(_zstd_SEARCH_DIRS
+  ${ZSTD_ROOT_DIR}
+)
+
+FIND_PATH(ZSTD_INCLUDE_DIR
+  NAMES
+    zstd.h
+  HINTS
+    ${_zstd_SEARCH_DIRS}
+  PATH_SUFFIXES
+    include
+)
+
+FIND_LIBRARY(ZSTD_LIBRARY
+  NAMES
+    zstd
+  HINTS
+    ${_zstd_SEARCH_DIRS}
+  PATH_SUFFIXES
+    lib64 lib
+  )
+
+# handle the QUIETLY and REQUIRED arguments and set ZSTD_FOUND to TRUE if
+# all listed variables are TRUE
+INCLUDE(FindPackageHandleStandardArgs)
+FIND_PACKAGE_HANDLE_STANDARD_ARGS(Zstd DEFAULT_MSG
+    ZSTD_LIBRARY ZSTD_INCLUDE_DIR)
+
+IF(ZSTD_FOUND)
+  SET(ZSTD_LIBRARIES ${ZSTD_LIBRARY})
+  SET(ZSTD_INCLUDE_DIRS ${ZSTD_INCLUDE_DIR})
+ENDIF()
+
+MARK_AS_ADVANCED(
+  ZSTD_INCLUDE_DIR
+  ZSTD_LIBRARY
+)
-- 
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