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lmdb-safe
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Allow users to plug their own (de)serialization implementation 

* Move serialization-specific code into its own header
* Keep reflective-rapidjson-based implementation as example
This commit is contained in:
Martchus 2022-01-18 22:24:31 +01:00
parent b833bfef3b
commit d53687bdee
2 changed files with 43 additions and 29 deletions
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36
lmdb-reflective.hh Normal file
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@ -0,0 +1,36 @@
#pragma once
// Example for plugging a (de)serialization implementation using the binary
// (de)serializer provided by https://github.com/Martchus/reflective-rapidjson.
#include "lmdb-safe.hh"
#include <reflective-rapidjson/lib/binary/reflector.h>
#include <boost/iostreams/stream.hpp>
#include <boost/iostreams/stream_buffer.hpp>
#include <boost/iostreams/device/back_inserter.hpp>
namespace LMDBSafe {
template<typename T>
std::string serToString(const T& t)
{
auto ret = std::string();
auto inserter = boost::iostreams::back_insert_device<std::string>(ret);
auto stream = boost::iostreams::stream<boost::iostreams::back_insert_device<std::string>>(inserter);
auto deserializer = ReflectiveRapidJSON::BinaryReflector::BinarySerializer(&stream);
deserializer.write(t);
return ret;
}
template<typename T>
void serFromString(const string_view& str, T& ret)
{
auto source = boost::iostreams::array_source(str.data(), str.size());
auto stream = boost::iostreams::stream<boost::iostreams::array_source>(source);
auto serializer = ReflectiveRapidJSON::BinaryReflector::BinaryDeserializer(&stream);
ret = T();
serializer.read(ret);
}
}

36
lmdb-typed.hh
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@ -1,12 +1,6 @@
#pragma once
#include "lmdb-safe.hh"
#include <reflective-rapidjson/lib/binary/reflector.h>
#include <boost/iostreams/stream.hpp>
#include <boost/iostreams/stream_buffer.hpp>
#include <boost/iostreams/device/back_inserter.hpp>
namespace LMDBSafe {
/*
@ -20,38 +14,24 @@ namespace LMDBSafe {
make it more value "like" with unique_ptr
*/
/** Return the highest ID used in a database. Returns 0 for an empty DB.
This makes us start everything at ID=1, which might make it possible to
treat id 0 as special
*/
unsigned int MDBGetMaxID(MDBRWTransaction& txn, MDBDbi& dbi);
/** This is our serialization interface.
You can define your own serToString for your type if you know better
/** This is the serialization interface.
You need to define your these functions for the types you'd like to store.
*/
template<typename T>
std::string serToString(const T& t)
{
auto ret = std::string();
auto inserter = boost::iostreams::back_insert_device<std::string>(ret);
auto stream = boost::iostreams::stream<boost::iostreams::back_insert_device<std::string>>(inserter);
auto deserializer = ReflectiveRapidJSON::BinaryReflector::BinarySerializer(&stream);
deserializer.write(t);
return ret;
}
std::string serToString(const T& t);
template<typename T>
void serFromString(const string_view& str, T& ret)
{
auto source = boost::iostreams::array_source(str.data(), str.size());
auto stream = boost::iostreams::stream<boost::iostreams::array_source>(source);
auto serializer = ReflectiveRapidJSON::BinaryReflector::BinaryDeserializer(&stream);
ret = T();
serializer.read(ret);
}
void serFromString(const string_view& str, T& ret);
/** This is the serialization interface for keys.
You need to define your these functions for the types you'd like to use as keys.
*/
template <class T, class Enable>
inline std::string keyConv(const T& t);
@ -61,14 +41,12 @@ inline string_view keyConv(const T& t)
return string_view(reinterpret_cast<const char *>(&t), sizeof(t));
}
// this is how to override specific types.. it is ugly
template<class T, typename std::enable_if<std::is_same<T, std::string>::value,T>::type* = nullptr>
inline string_view keyConv(const T& t)
{
return t;
}
/** This is a struct that implements index operations, but
only the operations that are broadcast to all indexes.
Specifically, to deal with databases with less than the maximum