From 21c6bb38e6cf0776dbdc37841280dffd6ca79990 Mon Sep 17 00:00:00 2001
From: Jan-Willem Blokland <Jan-Willem.Blokland@Shell.com>
Date: Wed, 14 Jul 2021 17:42:14 +0200
Subject: CMake: (feature) libaec (#703)

* CMake: (feature) libaec

Implemented better support for the compression library libaec.
Especially, for the new version 1.0.5:
- The CMake config files of this version 1.0.5 now set certain
  SZIP variables which can be used in the existing
  CMake structure.
- Both static and shared SZIP compatible libaec library contains
  all required objects such it can be easily used when building
  HDF5 from scratch.
- Introduced the USE_LIBAEC_STATIC option to make use of the static
  version of SZIP compatible libaec library.

* CMake: (fix) libaec

Implemented the fallback option for the case if version 1.0.5
of libaec could not be found.

* Docs: Added description about libaec implementation.

Added short description about the libaec improvement to the Bug Fixes
section in the Configuration sub-section.
---
 CMakeFilters.cmake       | 18 +++++++++++++++---
 release_docs/RELEASE.txt | 15 +++++++++++++++
 2 files changed, 30 insertions(+), 3 deletions(-)

diff --git a/CMakeFilters.cmake b/CMakeFilters.cmake
index d5f801e..51ac61c 100644
--- a/CMakeFilters.cmake
+++ b/CMakeFilters.cmake
@@ -10,6 +10,7 @@
 # help@hdfgroup.org.
 #
 option (USE_LIBAEC "Use AEC library as SZip Filter" OFF)
+option (USE_LIBAEC_STATIC "Use static AEC library " OFF)
 
 include (ExternalProject)
 include (FetchContent)
@@ -110,13 +111,24 @@ option (HDF5_ENABLE_SZIP_SUPPORT "Use SZip Filter" OFF)
 if (HDF5_ENABLE_SZIP_SUPPORT)
   option (HDF5_ENABLE_SZIP_ENCODING "Use SZip Encoding" OFF)
   if (NOT SZIP_USE_EXTERNAL)
-    find_package (SZIP NAMES ${SZIP_PACKAGE_NAME}${HDF_PACKAGE_EXT} COMPONENTS static shared)
-    if (NOT SZIP_FOUND)
-      find_package (SZIP) # Legacy find
+    set(SZIP_FOUND FALSE)
+    if (USE_LIBAEC)
+      set(libaec_USE_STATIC_LIBS ${USE_LIBAEC_STATIC})
+      find_package (libaec 1.0.5 CONFIG)
       if (SZIP_FOUND)
         set (LINK_COMP_LIBS ${LINK_COMP_LIBS} ${SZIP_LIBRARIES})
       endif ()
     endif ()
+
+    if (NOT SZIP_FOUND)
+      find_package (SZIP NAMES ${SZIP_PACKAGE_NAME}${HDF_PACKAGE_EXT} COMPONENTS static shared)
+      if (NOT SZIP_FOUND)
+        find_package (SZIP) # Legacy find
+        if (SZIP_FOUND)
+          set (LINK_COMP_LIBS ${LINK_COMP_LIBS} ${SZIP_LIBRARIES})
+        endif ()
+      endif ()
+    endif ()
   endif ()
   if (SZIP_FOUND)
     set (H5_HAVE_FILTER_SZIP 1)
diff --git a/release_docs/RELEASE.txt b/release_docs/RELEASE.txt
index 1e69f54..bd186d8 100644
--- a/release_docs/RELEASE.txt
+++ b/release_docs/RELEASE.txt
@@ -1060,6 +1060,21 @@ Bug Fixes since HDF5-1.12.0 release
 
     Configuration
     -------------
+    - Better support for libaec (open-source Szip library) in CMake
+ 
+      Implemented better support for libaec 1.0.5 (or later) library. This version 
+      of libaec contains improvements for better integration with HDF5. Furthermore,
+      the variable USE_LIBAEC_STATIC has been introduced to allow to make use of 
+      static version of libaec library. Use libaec_DIR or libaec_ROOT to set
+      the location in which libaec can be found.
+
+      Be aware, the Szip library of libaec 1.0.4 depends on another library within
+      libaec library. This dependency is not specified in the current CMake
+      configuration which means that one can not use the static Szip library of
+      libaec 1.0.4 when building HDF5. This has been resolved in libaec 1.0.5.
+
+      (JWSB - 2021/06/22)
+
     - Refactor CMake configure for Fortran
 
       The Fortran configure tests for KINDs reused a single output file that was
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