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Reorganized user-defined function proxy, and used a provenance fence
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,124 @@ | ||
| #pragma once | ||
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| #include <sqlite3.h> | ||
| #include <new> // std::launder | ||
| #include <string> // std::string | ||
| #include <functional> // std::function | ||
| #include <utility> // std::move | ||
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| #include "error_code.h" | ||
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| namespace sqlite_orm { | ||
| namespace internal { | ||
| /* | ||
| * Stores type-erased information in relation to a user-defined scalar or aggregate function object: | ||
| * - name and argument count | ||
| * - function pointers for construction/destruction | ||
| * - function dispatch | ||
| * - allocated memory and location | ||
| * | ||
| * As such, it also serves as a context for aggregation operations instead of using `sqlite3_aggregate_context()`. | ||
| */ | ||
| struct udf_proxy { | ||
| using func_call_fn_t = void (*)(void* udfHandle, | ||
| sqlite3_context* context, | ||
| int argsCount, | ||
| sqlite3_value** values); | ||
| using final_call_fn_t = void (*)(void* udfHandle, sqlite3_context* context); | ||
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| struct destruct_only_deleter { | ||
| template<class F> | ||
| void operator()(F* f) const noexcept { | ||
| f->~F(); | ||
| } | ||
| }; | ||
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| std::string name; | ||
| int argumentsCount; | ||
| std::function<void*(void* location)> constructAt; | ||
| xdestroy_fn_t destroy; | ||
| func_call_fn_t func; | ||
| final_call_fn_t finalAggregateCall; | ||
| // flag whether the UDF has been constructed at `udfHandle`; | ||
| // necessary for aggregation operations | ||
| bool constructed; | ||
| // pointer to memory for UDF in derived proxy veneer | ||
| void* const udfHandle; | ||
| }; | ||
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| /* | ||
| * A veneer to `udf_proxy` that provides memory space for a user-defined function object. | ||
| * | ||
| * Note: it must be a veneer, i.e. w/o any non-trivially destructible member variables. | ||
| */ | ||
| template<class UDF> | ||
| struct udf_proxy_veneer : udf_proxy { | ||
| // allocated memory for user-defined function | ||
| alignas(UDF) char storage[sizeof(UDF)]; | ||
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| udf_proxy_veneer(std::string name, | ||
| int argumentsCount, | ||
| std::function<void*(void* location)> constructAt, | ||
| xdestroy_fn_t destroy, | ||
| func_call_fn_t run) : | ||
| udf_proxy { | ||
| std::move(name), argumentsCount, std::move(constructAt), destroy, run, nullptr, false, | ||
| #if __cpp_lib_launder >= 201606L | ||
| std::launder((UDF*)this->storage) | ||
| #else | ||
| storage | ||
| #endif | ||
| } | ||
| {} | ||
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| udf_proxy_veneer(std::string name, | ||
| int argumentsCount, | ||
| std::function<void*(void* location)> constructAt, | ||
| xdestroy_fn_t destroy, | ||
| func_call_fn_t step, | ||
| final_call_fn_t finalCall) : | ||
| udf_proxy { | ||
| std::move(name), argumentsCount, std::move(constructAt), destroy, step, finalCall, false, | ||
| #if __cpp_lib_launder >= 201606L | ||
| std::launder((UDF*)this->storage) | ||
| #else | ||
| storage | ||
| #endif | ||
| } | ||
| {} | ||
| }; | ||
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| inline void scalar_function_callback(sqlite3_context* context, int argsCount, sqlite3_value** values) { | ||
| udf_proxy* proxy = static_cast<udf_proxy*>(sqlite3_user_data(context)); | ||
| if(proxy->argumentsCount != -1 && proxy->argumentsCount != argsCount) { | ||
| throw std::system_error{orm_error_code::arguments_count_does_not_match}; | ||
| } | ||
| const std::unique_ptr<void, xdestroy_fn_t> udfHandle{proxy->constructAt(proxy->udfHandle), proxy->destroy}; | ||
| proxy->func(udfHandle.get(), context, argsCount, values); | ||
| } | ||
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| inline void aggregate_function_step_callback(sqlite3_context* context, int argsCount, sqlite3_value** values) { | ||
| udf_proxy* proxy = static_cast<udf_proxy*>(sqlite3_user_data(context)); | ||
| if(!proxy->constructed) { | ||
| if(proxy->argumentsCount != -1 && proxy->argumentsCount != argsCount) { | ||
| throw std::system_error{orm_error_code::arguments_count_does_not_match}; | ||
| } | ||
| proxy->constructAt(proxy->udfHandle); | ||
| proxy->constructed = true; | ||
| } | ||
| proxy->func(proxy->udfHandle, context, argsCount, values); | ||
| } | ||
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| inline void aggregate_function_final_callback(sqlite3_context* context) { | ||
| udf_proxy* proxy = static_cast<udf_proxy*>(sqlite3_user_data(context)); | ||
| // note: it is possible that the 'step' function was never called | ||
| if(!proxy->constructed) { | ||
| proxy->constructAt(proxy->udfHandle); | ||
| proxy->constructed = true; | ||
| } | ||
| proxy->finalAggregateCall(proxy->udfHandle, context); | ||
| proxy->destroy(proxy->udfHandle); | ||
| proxy->constructed = false; | ||
| } | ||
| } | ||
| } |
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