Add support for setting the locking behavior when opening file

doc/developer_guide.md

@@ -206,7 +206,7 @@ is a sensible thing to do. We assume similar about `bool` and
 Anything `H5Easy` related goes in files with the appropriate name.
 
 #### Everything Else
-What's left goes in `tests/unit/test_high_five_base.cpp`. This covers opening
+What's left goes in `tests/unit/tests_high_five_base.cpp`. This covers opening
 files, groups, dataset or attributes; checking certain pathological edge cases;
 etc.
 

include/highfive/H5PropertyList.hpp

@@ -714,6 +714,27 @@ class AttributePhaseChange {
     unsigned _min_dense;
 };
 
+///
+/// \brief Set locking FileAccessProps
+///
+/// Since HDF5 in version 1.10.0, `single-writer / multiple-readers` support was added.
+/// To achieve this, locks were added when accessing the file.
+/// They can be disabled with the `HDF5_USE_FILE_LOCKING` environment variable.
+/// However, if it's known at access time that one will never have another process writing the file,
+/// the locks can be avoided.
+///
+/// See more in https://support.hdfgroup.org/documentation/hdf5/latest/_file_lock.html
+///
+class FileLocking {
+  public:
+    explicit FileLocking(bool use_file_locking, bool ignore_when_disabled);
+    void apply(const hid_t list) const;
+  private:
+    friend FileAccessProps;
+    bool _use_file_locking;
+    bool _ignore_when_disabled;
+};
+
 /// @}
 
 }  // namespace HighFive

include/highfive/bits/H5PropertyList_misc.hpp

@@ -501,5 +501,12 @@ inline void AttributePhaseChange::apply(hid_t hid) const {
     detail::h5p_set_attr_phase_change(hid, _max_compact, _min_dense);
 }
 
+inline FileLocking::FileLocking(bool use_file_locking, bool ignore_when_disabled)
+    : _use_file_locking(use_file_locking)
+    , _ignore_when_disabled(ignore_when_disabled) { }
+
+inline void FileLocking::apply(hid_t hid) const {
+    detail::h5p_set_file_locking(hid, _use_file_locking, _ignore_when_disabled);
+}
 
 }  // namespace HighFive

include/highfive/bits/h5p_wrapper.hpp

@@ -371,6 +371,14 @@ inline herr_t h5p_set_attr_phase_change(hid_t plist_id, unsigned max_compact, un
     return err;
 }
 
+inline herr_t h5p_set_file_locking(hid_t plist_id, bool use_file_locking, bool ignore_when_disabled) {
+    herr_t err = H5Pset_file_locking(plist_id, use_file_locking, ignore_when_disabled);
+    if (err < 0) {
+        HDF5ErrMapper::ToException<PropertyException>("Unable to set locking");
+    }
+    return err;
+}
+
 
 }  // namespace detail
 }  // namespace HighFive

tests/unit/tests_high_five_base.cpp

@@ -1273,6 +1273,17 @@ TEST_CASE("AttributePhaseChange") {
     }
 }
 
+TEST_CASE("Locking") {
+    auto fapl = HighFive::FileAccessProps::Default();
+    fapl.add(HighFive::FileLocking(true, false));
+    std::string path = "openmodes.h5";
+    HighFive::File file(path, HighFive::File::ReadOnly, fapl);
+
+    // can't open the same file twice with different locking
+    CHECK_THROWS_AS(HighFive::File(path), FileException);
+}
+
+
 TEST_CASE("datasetOffset") {
     std::string filename = "datasetOffset.h5";
     std::string dsetname = "dset";