From 678f5ceb99bc62a2639476527694a655cfc053e5 Mon Sep 17 00:00:00 2001
From: Tobias Hienzsch <post@tobias-hienzsch.de>
Date: Wed, 25 Sep 2024 02:20:40 +0200
Subject: [PATCH] [cpp] Cleanup HDF5 reader & writer

---
 src/cpp/main.cpp                 |  2 +-
 src/cpp/pffdtd/hdf.hpp           | 21 +++++++++++++--------
 src/cpp/pffdtd/simulation_2d.cpp |  2 +-
 src/cpp/pffdtd/simulation_3d.cpp | 30 +++++-------------------------
 4 files changed, 20 insertions(+), 35 deletions(-)

diff --git a/src/cpp/main.cpp b/src/cpp/main.cpp
index c28b7f0..2f40b95 100644
--- a/src/cpp/main.cpp
+++ b/src/cpp/main.cpp
@@ -114,7 +114,7 @@ auto main(int argc, char** argv) -> int {
     auto const sim    = pffdtd::loadSimulation2D(simDir);
     auto const out    = engine(sim);
 
-    auto results = pffdtd::H5FWriter{simDir / args.sim2d.out};
+    auto results = pffdtd::HDF5Writer{simDir / args.sim2d.out};
     results.write("out", out);
 
     auto const stop = pffdtd::getTime();
diff --git a/src/cpp/pffdtd/hdf.hpp b/src/cpp/pffdtd/hdf.hpp
index caaeb55..9811e14 100644
--- a/src/cpp/pffdtd/hdf.hpp
+++ b/src/cpp/pffdtd/hdf.hpp
@@ -32,11 +32,16 @@ inline constexpr auto isStdVector = false;
 template<typename T>
 inline constexpr auto isStdVector<std::vector<T>> = true;
 
-struct H5FReader {
-  explicit H5FReader(std::filesystem::path const& path)
-      : _handle{H5Fopen(path.string().c_str(), H5F_ACC_RDONLY, H5P_DEFAULT)} {}
+struct HDF5Reader {
+  explicit HDF5Reader(std::filesystem::path const& path)
+      : _handle{[&] {
+        if (not std::filesystem::exists(path)) {
+          raisef<std::invalid_argument>("file '{}' does not exist", path.string());
+        }
+        return H5Fopen(path.string().c_str(), H5F_ACC_RDONLY, H5P_DEFAULT);
+      }()} {}
 
-  ~H5FReader() { H5Fclose(_handle); }
+  ~HDF5Reader() { H5Fclose(_handle); }
 
   [[nodiscard]] auto handle() const noexcept -> hid_t { return _handle; }
 
@@ -131,11 +136,11 @@ struct H5FReader {
   hid_t _handle;
 };
 
-struct H5FWriter {
-  explicit H5FWriter(std::filesystem::path const& path)
+struct HDF5Writer {
+  explicit HDF5Writer(std::filesystem::path const& path)
       : _handle{H5Fcreate(path.string().c_str(), H5F_ACC_TRUNC, H5P_DEFAULT, H5P_DEFAULT)} {}
 
-  ~H5FWriter() { H5Fclose(_handle); }
+  ~HDF5Writer() { H5Fclose(_handle); }
 
   auto write(char const* name, stdex::mdspan<double const, stdex::dextents<size_t, 2>> buf) -> void {
     hsize_t dims[2]{
@@ -170,7 +175,7 @@ struct H5FWriter {
 };
 
 template<typename T>
-[[nodiscard]] auto read(H5FReader& reader, char const* dset_str, int ndims, hsize_t* dims) -> std::unique_ptr<T[]> {
+[[nodiscard]] auto read(HDF5Reader& reader, char const* dset_str, int ndims, hsize_t* dims) -> std::unique_ptr<T[]> {
   auto dset   = H5Dopen(reader.handle(), dset_str, H5P_DEFAULT);
   auto dspace = H5Dget_space(dset);
   PFFDTD_ASSERT(H5Sget_simple_extent_ndims(dspace) == ndims);
diff --git a/src/cpp/pffdtd/simulation_2d.cpp b/src/cpp/pffdtd/simulation_2d.cpp
index 1953c0e..f9a19a7 100644
--- a/src/cpp/pffdtd/simulation_2d.cpp
+++ b/src/cpp/pffdtd/simulation_2d.cpp
@@ -10,7 +10,7 @@
 namespace pffdtd {
 
 auto loadSimulation2D(std::filesystem::path const& dir) -> Simulation2D {
-  auto sim = H5FReader{dir / "sim.h5"};
+  auto sim = HDF5Reader{dir / "sim.h5"};
 
   auto const Nx = sim.read<int64_t>("Nx");
   auto const Ny = sim.read<int64_t>("Ny");
diff --git a/src/cpp/pffdtd/simulation_3d.cpp b/src/cpp/pffdtd/simulation_3d.cpp
index 241b4b0..b739320 100644
--- a/src/cpp/pffdtd/simulation_3d.cpp
+++ b/src/cpp/pffdtd/simulation_3d.cpp
@@ -90,12 +90,7 @@ template<typename Real>
   ////////////////////////////////////////////////////////////////////////
   // Read constants HDF5 dataset
   ////////////////////////////////////////////////////////////////////////
-  auto filename = simDir / "constants.h5";
-  if (not std::filesystem::exists(filename)) {
-    raisef<std::invalid_argument>("file '{}' does not exist", filename.string());
-  }
-
-  auto constants = H5FReader{filename};
+  auto constants = HDF5Reader{simDir / "constants.h5"};
 
   //////////////////
   // constants
@@ -147,12 +142,7 @@ template<typename Real>
   ////////////////////////////////////////////////////////////////////////
   // Read vox HDF5 dataset
   ////////////////////////////////////////////////////////////////////////
-  filename = simDir / "vox_out.h5";
-  if (not std::filesystem::exists(filename)) {
-    raisef<std::invalid_argument>("file '{}' does not exist", filename.string());
-  }
-
-  auto vox_out = H5FReader{filename};
+  auto vox_out = HDF5Reader{simDir / "vox_out.h5"};
 
   //////////////////
   // integers
@@ -206,12 +196,7 @@ template<typename Real>
   ////////////////////////////////////////////////////////////////////////
   // Read signals HDF5 dataset
   ////////////////////////////////////////////////////////////////////////
-  filename = simDir / "signals.h5";
-  if (not std::filesystem::exists(filename)) {
-    raisef<std::invalid_argument>("file '{}' does not exist", filename.string());
-  }
-
-  auto signals = H5FReader{filename};
+  auto signals = HDF5Reader{simDir / "signals.h5"};
 
   //////////////////
   // integers
@@ -254,12 +239,7 @@ template<typename Real>
   ////////////////////////////////////////////////////////////////////////
   // Read materials HDF5 dataset
   ////////////////////////////////////////////////////////////////////////
-  filename = simDir / "materials.h5";
-  if (not std::filesystem::exists(filename)) {
-    raisef<std::invalid_argument>("file '{}' does not exist", filename.string());
-  }
-
-  auto materials = H5FReader{filename};
+  auto materials = HDF5Reader{simDir / "materials.h5"};
 
   //////////////////
   // integers
@@ -539,7 +519,7 @@ void writeOutputs_impl(Simulation3D<Real> const& sim, std::filesystem::path cons
     }
   }
 
-  auto writer = H5FWriter{simDir / "sim_outs.h5"};
+  auto writer = HDF5Writer{simDir / "sim_outs.h5"};
   writer.write("u_out", u_out);
   std::puts("wrote output dataset");
 }