Specifiy more precisely when to re-read attributes

include/openPMD/Series.hpp

@@ -364,9 +364,6 @@ class SeriesImpl : public AttributableImpl
      * Note on re-parsing of a Series:
      * If init == false, the parsing process will seek for new
      * Iterations/Records/Record Components etc.
-     * Re-parsing of objects that have already been parsed is not implemented
-     * as of yet. Such a facility will be required upon implementing things such
-     * as resizable datasets.
      */
     void readGorVBased( bool init = true );
     void readBase();

include/openPMD/backend/Attributable.hpp

@@ -215,7 +215,24 @@ class AttributableImpl
     std::vector< std::string > myPath() const;
 
     void flushAttributes();
-    void readAttributes( bool reread = false );
+    enum ReadMode {
+        /**
+         * Don't read an attribute from the backend if it has been previously
+         * read.
+         */
+        IgnoreExisting,
+        /**
+         * Read all the attributes that the backend has to offer and override
+         * if it has been read previously.
+         */
+        OverrideExisting,
+        /**
+         * Remove all attributes that have been read previously and read
+         * everything that the backend currently has to offer.
+         */
+        FullyReread
+    };
+    void readAttributes( ReadMode );
 
     /** Retrieve the value of a floating point Attribute of user-defined precision with ensured type-safety.
      *

src/Iteration.cpp

@@ -445,7 +445,7 @@ void Iteration::read_impl( std::string const & groupPath )
         pOpen.path = s->meshesPath();
         IOHandler()->enqueue(IOTask(&meshes, pOpen));
 
-        meshes.readAttributes();
+        meshes.readAttributes( ReadMode::FullyReread );
 
         auto map = meshes.eraseStaleEntries();
 
@@ -510,7 +510,7 @@ void Iteration::read_impl( std::string const & groupPath )
         pOpen.path = s->particlesPath();
         IOHandler()->enqueue(IOTask(&particles, pOpen));
 
-        particles.readAttributes();
+        particles.readAttributes( ReadMode::FullyReread );
 
         /* obtain all particle species */
         pList.paths->clear();
@@ -532,7 +532,7 @@ void Iteration::read_impl( std::string const & groupPath )
         particles.dirty() = false;
     }
 
-    readAttributes();
+    readAttributes( ReadMode::FullyReread );
 }
 
 AdvanceStatus

src/Mesh.cpp

@@ -379,7 +379,7 @@ Mesh::read()
 
     readBase();
 
-    readAttributes();
+    readAttributes( ReadMode::FullyReread );
 }
 } // openPMD
 

src/ParticleSpecies.cpp

@@ -123,7 +123,7 @@ ParticleSpecies::read()
         }
     }
 
-    readAttributes();
+    readAttributes( ReadMode::FullyReread );
 }
 
 namespace

src/Record.cpp

@@ -136,7 +136,7 @@ Record::read()
 
     readBase();
 
-    readAttributes();
+    readAttributes( ReadMode::FullyReread );
 }
 
 template <>

src/RecordComponent.cpp

@@ -370,7 +370,7 @@ RecordComponent::readBase()
     else
         throw std::runtime_error("Unexpected Attribute datatype for 'unitSI'");
 
-    readAttributes();
+    readAttributes( ReadMode::FullyReread );
 }
 
 bool

src/Series.cpp

@@ -948,8 +948,8 @@ void SeriesImpl::readOneIterationFileBased( std::string const & filePath )
         throw std::runtime_error("Unknown openPMD version - " + version);
     IOHandler()->enqueue(IOTask(&series.iterations, pOpen));
 
-    readAttributes();
-    series.iterations.readAttributes();
+    readAttributes( ReadMode::IgnoreExisting );
+    series.iterations.readAttributes(ReadMode::OverrideExisting );
 }
 
 void
@@ -1017,11 +1017,11 @@ SeriesImpl::readGorVBased( bool do_init )
         throw std::runtime_error("Unknown openPMD version - " + version);
     IOHandler()->enqueue(IOTask(&series.iterations, pOpen));
 
-    readAttributes();
+    readAttributes( ReadMode::IgnoreExisting );
     /*
      * __step__ changes over steps, so reread that.
      */
-    series.iterations.readAttributes( /* reread = */ true );
+    series.iterations.readAttributes( ReadMode::OverrideExisting );
     /* obtain all paths inside the basepath (i.e. all iterations) */
     Parameter< Operation::LIST_PATHS > pList;
     IOHandler()->enqueue(IOTask(&series.iterations, pList));

src/backend/Attributable.cpp

@@ -186,30 +186,39 @@ AttributableImpl::flushAttributes()
 }
 
 void
-AttributableImpl::readAttributes( bool reread )
+AttributableImpl::readAttributes( ReadMode mode )
 {
+    auto & attri = get();
     Parameter< Operation::LIST_ATTS > aList;
     IOHandler()->enqueue(IOTask(this, aList));
     IOHandler()->flush();
     std::vector< std::string > written_attributes = attributes();
 
+    /* std::set_difference requires sorted ranges */
+    std::sort(aList.attributes->begin(), aList.attributes->end());
+    std::sort(written_attributes.begin(), written_attributes.end());
+
     std::set< std::string > tmpAttributes;
-    if( reread )
-    {
-        tmpAttributes = std::set< std::string >(
-            aList.attributes->begin(),
-            aList.attributes->end() );
-    }
-    else
+    switch( mode )
     {
-        /* std::set_difference requires sorted ranges */
-        std::sort(aList.attributes->begin(), aList.attributes->end());
-        std::sort(written_attributes.begin(), written_attributes.end());
-
+    case ReadMode::IgnoreExisting:
+        // reread: aList - written_attributes
         std::set_difference(
             aList.attributes->begin(), aList.attributes->end(),
             written_attributes.begin(), written_attributes.end(),
             std::inserter(tmpAttributes, tmpAttributes.begin()));
+        break;
+    case ReadMode::OverrideExisting:
+        tmpAttributes = std::set< std::string >(
+            aList.attributes->begin(),
+            aList.attributes->end() );
+        break;
+    case ReadMode::FullyReread:
+        attri.m_attributes.clear();
+        tmpAttributes = std::set< std::string >(
+            aList.attributes->begin(),
+            aList.attributes->end() );
+        break;
     }
 
     using DT = Datatype;

src/backend/PatchRecordComponent.cpp

@@ -115,7 +115,7 @@ PatchRecordComponent::read()
     else
         throw std::runtime_error("Unexpected Attribute datatype for 'unitSI'");
 
-    readAttributes(); // this will set dirty() = false
+    readAttributes( ReadMode::FullyReread ); // this will set dirty() = false
 }
 
 bool