guard.hpp

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#pragma once
 
extern "C" {
#include <setjmp.h>
}
 
#include <iostream>
#include <utility>
 
#include "error.hpp"
#include "exception.hpp"
#include "utils/function_traits.hpp"
 
namespace cppgres {
 
template <typename Func> struct ffi_guard {
  Func func;
 
  ffi_guard(Func f) : func(std::move(f)) {}
 
  template <typename... Args>
  auto operator()(Args &&...args) -> decltype(func(std::forward<Args>(args)...)) {
    int state;
    sigjmp_buf *pbuf;
    ::ErrorContextCallback *cb;
    sigjmp_buf buf;
    ::MemoryContext mcxt = ::CurrentMemoryContext;
 
    pbuf = ::PG_exception_stack;
    cb = ::error_context_stack;
    ::PG_exception_stack = &buf;
 
    // restore state upon exit
    std::shared_ptr<void> defer(nullptr, [&](...) {
      ::error_context_stack = cb;
      ::PG_exception_stack = pbuf;
    });
 
    state = sigsetjmp(buf, 1);
 
    if (state == 0) {
      return func(std::forward<Args>(args)...);
    } else if (state == 1) {
      throw pg_exception(mcxt);
    }
    __builtin_unreachable();
  }
};
 
template <typename Func> auto ffi_guarded(Func f) { return ffi_guard<Func>{f}; }
 
} // namespace cppgres