loopy unpacking and multi packing

Current implementation of persistency configures a packer and unpacker for each location. This MR changes this to:

• one packer per object type
• each unpacker for a given location also unpacks all linked locations if they are not unpacked already. This will allow to request a location to be unpacked individually.
• Packing and unpacking configurations are simplified. PersistRecoConf is removed as most of it's functionality is not needed anymore.

Part of set !3750 (merged) DaVinci!747 (merged) MooreAnalysis!92 (merged) Analysis!918 (merged) Moore!1638 (merged)

Event/EventPacker/include/Event/PackedDataBuffer.h

@@ -272,6 +272,8 @@ namespace LHCb::Hlt::PackedData {
     bool compress( Compression compression, int level, ByteBuffer::buffer_type& output ) const {
       return m_buffer.compress( compression, level, output );
     }
+    std::uint32_t key() { return m_key; }
+
     /// Reserve size for the buffer
     void reserve( std::size_t size ) { m_buffer.reserve( size ); }
     /// Function called by serializable objects' save method.
@@ -302,9 +304,16 @@ namespace LHCb::Hlt::PackedData {
       m_buffer.write( x, pos );
     }
     /// Add byte buffer of a packed data buffer to another one
-    void addBuffer( PackedDataOutBuffer const& x ) { m_buffer.writeBuffer( x.m_buffer ); }
-    /// Add a byte buffer to a packed data buffer
-    void addBuffer( ByteBuffer const& x ) { m_buffer.writeBuffer( x ); }
+    void addBuffer( PackedDataOutBuffer const& x ) {
+      // if empty, inherit value from x. If not empty, require to be the same
+      if ( x.m_key != m_key ) {
+        if ( m_key != 0 || m_buffer.size() != 0 || m_buffer.pos() != 0 ) {
+          throw std::runtime_error( "PackedDataInBuffer: merging buffers with distinct keys" );
+        }
+        m_key = x.m_key;
+      }
+      m_buffer.writeBuffer( x.m_buffer );
+    }
     /// Save a size integer.
     std::pair<std::size_t, std::size_t> saveSize( std::size_t x ) { return save<uint32_t>( x ); }
     /// Save a vector of scalars.
@@ -339,7 +348,8 @@ namespace LHCb::Hlt::PackedData {
     }
 
   private:
-    ByteBuffer m_buffer; ///< Internal byte buffer
+    std::uint32_t m_key = 0u; ///< key used to encode, and thus required, to decode stored strings
+    ByteBuffer    m_buffer;   ///< Internal byte buffer
   };
 
   /** @class PackedDataInBuffer PackedDataBuffer.h
@@ -350,19 +360,10 @@ namespace LHCb::Hlt::PackedData {
    */
   class PackedDataInBuffer {
   public:
-    /// Return whether the end of buffer was reached.
-    bool eof() const { return m_buffer.eof(); }
-    /// Skip a number of bytes from the buffer.
-    void skip( std::size_t n ) { m_buffer.readNull( n ); }
-    /// Initialize from an existing byte buffer.
-    bool init( ByteBuffer::buffer_view data, bool compressed = false ) {
-      return m_buffer.init( data, compressed );
-    }
-    bool init( const ByteBuffer& buffer, bool compressed = false ) {
-      return m_buffer.init( buffer.buffer(), compressed );
-    }
+    PackedDataInBuffer( std::uint32_t key = 0 ) : m_key{key} {}
     /// Initialize from an existing header and byte buffer.
-    void init( const ObjectHeader header, ByteBuffer::buffer_view data ) {
+    PackedDataInBuffer( const ObjectHeader header, ByteBuffer::buffer_view data, std::uint32_t key ) {
+      m_key = key;
       m_buffer.clear();
       m_buffer.write( header.classID );
       m_buffer.write( header.locationID );
@@ -371,6 +372,22 @@ namespace LHCb::Hlt::PackedData {
       for ( auto d : data ) m_buffer.write( d );
       m_buffer.reset();
     }
+    /// init a byte buffer from a subset of another packed data buffer
+    PackedDataInBuffer( PackedDataInBuffer const& x, std::size_t pos, std::size_t size = -1 ) {
+      m_key = x.m_key;
+      m_buffer.assign(
+          x.m_buffer.subspan( pos, size == static_cast<std::size_t>( -1 ) ? x.m_buffer.pos() - pos : size ) );
+    }
+    /// Return whether the end of buffer was reached.
+    bool eof() const { return m_buffer.eof(); }
+    /// Skip a number of bytes from the buffer.
+    void skip( std::size_t n ) { m_buffer.readNull( n ); }
+    /// Initialize from an existing byte buffer.
+    bool init( ByteBuffer::buffer_view data, bool compressed = false ) { return m_buffer.init( data, compressed ); }
+    bool init( const ByteBuffer& buffer, bool compressed = false ) {
+      return m_buffer.init( buffer.buffer(), compressed );
+    }
+    std::uint32_t key() const { return m_key; }
     /// Return a reference to the internal buffer.
     const ByteBuffer& buffer() const { return m_buffer; }
     /// Clear the internal byte buffer.
@@ -419,12 +436,6 @@ namespace LHCb::Hlt::PackedData {
       return x;
     }
 
-    /// Add a byte buffer of a packed data buffer to another one at a given position
-    void addBuffer( PackedDataInBuffer const& x, std::uint32_t p ) {
-      return m_buffer.assign( x.m_buffer.subspan( p, x.m_buffer.pos() - p ) );
-    }
-    /// Add a byte buffer of a packed data buffer to another one at a given position
-    void addBuffer( ByteBuffer const& x, std::uint32_t p ) { return m_buffer.assign( x.subspan( p, x.pos() - p ) ); }
     /// Load a scalar from a given position and return it.
     template <typename T>
     T loadAt( std::size_t i ) const {
@@ -469,7 +480,8 @@ namespace LHCb::Hlt::PackedData {
     }
 
   private:
-    ByteBuffer m_buffer; ///< Internal byte buffer
+    std::uint32_t m_key = 0; ///< key used to encode, and thus required to decode stored strings
+    ByteBuffer    m_buffer;  ///< Internal byte buffer
   };
 
 } // namespace LHCb::Hlt::PackedData