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/* Part of SWI-Prolog
Author: Jan Wielemaker and Peter Ludemann
E-mail: J.Wielemaker@vu.nl
WWW: http://www.swi-prolog.org
Copyright (c) 2000-2023, University of Amsterdam
VU University Amsterdam
SWI-Prolog Solutions b.v.
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in
the documentation and/or other materials provided with the
distribution.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE.
*/
#ifndef _SWI_CPP2_ATOMMAP_H
#define _SWI_CPP2_ATOMMAP_H
#include <map>
#include <mutex>
#include <shared_mutex>
#include "SWI-cpp2.h"
// The AtomMap class is a wrapper around a std::map, mapping alias
// names to blobs. The blobs are of type PlAtom or PlTerm, so this is
// actually an atom->atom or atom->term map.
// The entries are protected by a mutex, so the operations are thread-safe.
// The operations do appropriate calls to register and unregister the atoms/blobs.
//
// When defining an AtomMap, you specify the value type and how it is stored.
// The supported values are:
// PlAtom,PlAtom
// PlTerm,PlRecord
// The API automatically converts between the value and stored value types.
//
// The operations are:
// PlAtom find(PlAtom name) - look up, returning PlAtom::null if not found
// void insert(PlAtom name, PlAtom symbol) - insert, throwing a
// PlPermissionError if it's already there
// void erase(PlAtom name) - remove the entry (no error if it's already been removed)
template <typename ValueType, typename StoredValueType>
class AtomMap
{
public:
explicit AtomMap() = delete;
// On error, the message is something like
// No permission to <insert_op> <insert_type> `<key>'
// using PlPermissionError(insert_op_, insert_type_, key)
explicit AtomMap(const std::string& insert_op, const std::string& insert_type)
: insert_op_(insert_op), insert_type_(insert_type)
{ }
AtomMap(const AtomMap&) = delete;
AtomMap(const AtomMap&&) = delete;
AtomMap& operator =(const AtomMap&) = delete;
AtomMap& operator =(const AtomMap&&) = delete;
~AtomMap()
{ std::scoped_lock lock__(lock_);
auto lookup = entries_.begin();
while ( lookup != entries_.end() )
lookup = erase_inside_lock(lookup);
}
void
insert(PlAtom key, ValueType value)
{ std::scoped_lock lock__(lock_);
insert_inside_lock(key, value);
}
[[nodiscard]]
ValueType
find(PlAtom key)
{ std::shared_lock lock__(lock_);
return find_inside_lock(key);
}
void
erase(PlAtom key)
{ std::scoped_lock lock__(lock_);
erase_inside_lock(key);
}
size_t
size()
{ std::shared_lock lock__(lock_);
return size_inside_lock();
}
private:
typedef std::map<atom_t, StoredValueType> map_t;
[[nodiscard]]
ValueType
find_inside_lock(PlAtom key)
{ const auto lookup = entries_.find(key.unwrap());
if ( lookup == entries_.end() )
return ValueType(ValueType::null);
else
return ValueType(lookup->second);
}
void
insert_inside_lock(PlAtom key, ValueType value)
{ const auto lookup = find_inside_lock(key);
if ( lookup.is_null() )
{ StoredValueType stored_value(StoredValueType::null);
register_value(value, &stored_value);
key.register_ref();
entries_.insert(std::make_pair(key.unwrap(), stored_value));
} else if ( lookup != value )
{ throw PlPermissionError(insert_op_, insert_type_, PlTerm_atom(key));
}
}
void
erase_inside_lock(PlAtom key)
{ auto lookup = entries_.find(key.unwrap());
if ( lookup == entries_.end() )
return;
// TODO: As an alternative to removing the entry, leave it in place
// (with db==nullptr showing that it's been closed; or with
// the value as PlAtom::null), so that rocks_close/1 can
// distinguish an alias lookup that should throw a
// PlExistenceError because it's never been opened.
erase_inside_lock(lookup);
}
auto erase_inside_lock(typename map_t::iterator lookup)
{ PlAtom(lookup->first).unregister_ref();
unregister_stored_value(&lookup->second);
return entries_.erase(lookup);
}
size_t
size_inside_lock() const
{ return entries_.size();
}
// Implementation for map<PlAtom,PlAtom>
static void
register_value(const PlAtom &value, PlAtom *stored_value)
{ *stored_value = value;
stored_value->register_ref();
}
static void
unregister_stored_value(PlAtom *stored_value)
{ stored_value->unregister_ref();
}
// Implementation for map<PlAtom,PlRecord> (external: PlAtom,PlTerm>)
static void
register_value(const PlTerm &value, PlRecord *stored_value)
{ *stored_value = value.record();
}
static void
unregister_stored_value(PlRecord *stored_value)
{ stored_value->erase();
}
// Data: mutex + map
std::shared_mutex lock_;
// TODO: Define the necessary operators for PlAtom, so that it can be
// the key instead of atom_t.
map_t entries_;
std::string insert_op_; // for PlPermissionError
std::string insert_type_; // for PlPermissionError
};
#endif /*_SWI_CPP2_ATOMMAP_H*/
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