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Add scope_exit utilities

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This commit is contained in:
Howard Hinnant
2021-05-06 14:58:47 -04:00
committed by manojsdoshi
parent 2c559116fb
commit f1a9e8840f
3 changed files with 385 additions and 0 deletions
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1
Builds/CMake/RippledCore.cmake
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@@ -712,6 +712,7 @@ target_sources (rippled PRIVATE
src/test/basics/KeyCache_test.cpp
src/test/basics/PerfLog_test.cpp
src/test/basics/RangeSet_test.cpp
src/test/basics/scope_test.cpp
src/test/basics/Slice_test.cpp
src/test/basics/StringUtilities_test.cpp
src/test/basics/TaggedCache_test.cpp

191
src/ripple/basics/scope.h Normal file
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@@ -0,0 +1,191 @@
//------------------------------------------------------------------------------
/*
This file is part of rippled: https://github.com/ripple/rippled
Copyright (c) 2021 Ripple Inc.
Permission to use, copy, modify, and/or distribute this software for any
purpose with or without fee is hereby granted, provided that the above
copyright notice and this permission notice appear in all copies.
THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
ANY SPECIAL , DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
//==============================================================================
#ifndef RIPPLE_BASICS_SCOPE_H_INCLUDED
#define RIPPLE_BASICS_SCOPE_H_INCLUDED
#include <exception>
#include <type_traits>
#include <utility>
namespace ripple {
// RAII scope helpers. As specified in Library Fundamental, Version 3
// Basic design of idea: https://www.youtube.com/watch?v=WjTrfoiB0MQ
// Specification:
// http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2020/n4873.html#scopeguard
// This implementation deviates from the spec slightly:
// The scope_exit and scope_fail constructors taking a functor are not
// permitted to throw an exception. This was done because some compilers
// did not like the superfluous try/catch in the common instantiations
// where the construction was noexcept. Instead a static_assert is used
// to enforce this restriction.
template <class EF>
class scope_exit
{
EF exit_function_;
bool execute_on_destruction_{true};
public:
~scope_exit()
{
if (execute_on_destruction_)
exit_function_();
}
scope_exit(scope_exit&& rhs) noexcept(
std::is_nothrow_move_constructible_v<EF> ||
std::is_nothrow_copy_constructible_v<EF>)
: exit_function_{std::forward<EF>(rhs.exit_function_)}
, execute_on_destruction_{rhs.execute_on_destruction_}
{
rhs.release();
}
scope_exit&
operator=(scope_exit&&) = delete;
template <class EFP>
explicit scope_exit(
EFP&& f,
std::enable_if_t<
!std::is_same_v<std::remove_cv_t<EFP>, scope_exit> &&
std::is_constructible_v<EF, EFP>>* = 0) noexcept
: exit_function_{std::forward<EFP>(f)}
{
static_assert(
std::
is_nothrow_constructible_v<EF, decltype(std::forward<EFP>(f))>);
}
void
release() noexcept
{
execute_on_destruction_ = false;
}
};
template <class EF>
scope_exit(EF) -> scope_exit<EF>;
template <class EF>
class scope_fail
{
EF exit_function_;
bool execute_on_destruction_{true};
int uncaught_on_creation_{std::uncaught_exceptions()};
public:
~scope_fail()
{
if (execute_on_destruction_ &&
std::uncaught_exceptions() > uncaught_on_creation_)
exit_function_();
}
scope_fail(scope_fail&& rhs) noexcept(
std::is_nothrow_move_constructible_v<EF> ||
std::is_nothrow_copy_constructible_v<EF>)
: exit_function_{std::forward<EF>(rhs.exit_function_)}
, execute_on_destruction_{rhs.execute_on_destruction_}
, uncaught_on_creation_{rhs.uncaught_on_creation_}
{
rhs.release();
}
scope_fail&
operator=(scope_fail&&) = delete;
template <class EFP>
explicit scope_fail(
EFP&& f,
std::enable_if_t<
!std::is_same_v<std::remove_cv_t<EFP>, scope_fail> &&
std::is_constructible_v<EF, EFP>>* = 0) noexcept
: exit_function_{std::forward<EFP>(f)}
{
static_assert(
std::
is_nothrow_constructible_v<EF, decltype(std::forward<EFP>(f))>);
}
void
release() noexcept
{
execute_on_destruction_ = false;
}
};
template <class EF>
scope_fail(EF) -> scope_fail<EF>;
template <class EF>
class scope_success
{
EF exit_function_;
bool execute_on_destruction_{true};
int uncaught_on_creation_{std::uncaught_exceptions()};
public:
~scope_success() noexcept(noexcept(exit_function_()))
{
if (execute_on_destruction_ &&
std::uncaught_exceptions() <= uncaught_on_creation_)
exit_function_();
}
scope_success(scope_success&& rhs) noexcept(
std::is_nothrow_move_constructible_v<EF> ||
std::is_nothrow_copy_constructible_v<EF>)
: exit_function_{std::forward<EF>(rhs.exit_function_)}
, execute_on_destruction_{rhs.execute_on_destruction_}
, uncaught_on_creation_{rhs.uncaught_on_creation_}
{
rhs.release();
}
scope_success&
operator=(scope_success&&) = delete;
template <class EFP>
explicit scope_success(
EFP&& f,
std::enable_if_t<
!std::is_same_v<std::remove_cv_t<EFP>, scope_success> &&
std::is_constructible_v<EF, EFP>>* =
0) noexcept(std::is_nothrow_constructible_v<EF, EFP> || std::is_nothrow_constructible_v<EF, EFP&>)
: exit_function_{std::forward<EFP>(f)}
{
}
void
release() noexcept
{
execute_on_destruction_ = false;
}
};
template <class EF>
scope_success(EF) -> scope_success<EF>;
} // namespace ripple
#endif

193
src/test/basics/scope_test.cpp Normal file
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@@ -0,0 +1,193 @@
//------------------------------------------------------------------------------
/*
This file is part of rippled: https://github0.com/ripple/rippled
Copyright (c) 2021 Ripple Inc.
Permission to use, copy, modify, and/or distribute this software for any
purpose with or without fee is hereby granted, provided that the above
copyright notice and this permission notice appear in all copies.
THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
ANY SPECIAL , DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
//==============================================================================
#include <ripple/basics/scope.h>
#include <ripple/beast/unit_test.h>
namespace ripple {
namespace test {
struct scope_test : beast::unit_test::suite
{
void
test_scope_exit()
{
// scope_exit always executes the functor on destruction,
// unless release() is called
int i = 0;
{
scope_exit x{[&i]() { i = 1; }};
}
BEAST_EXPECT(i == 1);
{
scope_exit x{[&i]() { i = 2; }};
x.release();
}
BEAST_EXPECT(i == 1);
{
scope_exit x{[&i]() { i += 2; }};
auto x2 = std::move(x);
}
BEAST_EXPECT(i == 3);
{
scope_exit x{[&i]() { i = 4; }};
x.release();
auto x2 = std::move(x);
}
BEAST_EXPECT(i == 3);
{
try
{
scope_exit x{[&i]() { i = 5; }};
throw 1;
}
catch (...)
{
}
}
BEAST_EXPECT(i == 5);
{
try
{
scope_exit x{[&i]() { i = 6; }};
x.release();
throw 1;
}
catch (...)
{
}
}
BEAST_EXPECT(i == 5);
}
void
test_scope_fail()
{
// scope_fail executes the functor on destruction only
// if an exception is unwinding, unless release() is called
int i = 0;
{
scope_fail x{[&i]() { i = 1; }};
}
BEAST_EXPECT(i == 0);
{
scope_fail x{[&i]() { i = 2; }};
x.release();
}
BEAST_EXPECT(i == 0);
{
scope_fail x{[&i]() { i = 3; }};
auto x2 = std::move(x);
}
BEAST_EXPECT(i == 0);
{
scope_fail x{[&i]() { i = 4; }};
x.release();
auto x2 = std::move(x);
}
BEAST_EXPECT(i == 0);
{
try
{
scope_fail x{[&i]() { i = 5; }};
throw 1;
}
catch (...)
{
}
}
BEAST_EXPECT(i == 5);
{
try
{
scope_fail x{[&i]() { i = 6; }};
x.release();
throw 1;
}
catch (...)
{
}
}
BEAST_EXPECT(i == 5);
}
void
test_scope_success()
{
// scope_success executes the functor on destruction only
// if an exception is not unwinding, unless release() is called
int i = 0;
{
scope_success x{[&i]() { i = 1; }};
}
BEAST_EXPECT(i == 1);
{
scope_success x{[&i]() { i = 2; }};
x.release();
}
BEAST_EXPECT(i == 1);
{
scope_success x{[&i]() { i += 2; }};
auto x2 = std::move(x);
}
BEAST_EXPECT(i == 3);
{
scope_success x{[&i]() { i = 4; }};
x.release();
auto x2 = std::move(x);
}
BEAST_EXPECT(i == 3);
{
try
{
scope_success x{[&i]() { i = 5; }};
throw 1;
}
catch (...)
{
}
}
BEAST_EXPECT(i == 3);
{
try
{
scope_success x{[&i]() { i = 6; }};
x.release();
throw 1;
}
catch (...)
{
}
}
BEAST_EXPECT(i == 3);
}
void
run() override
{
test_scope_exit();
test_scope_fail();
test_scope_success();
}
};
BEAST_DEFINE_TESTSUITE(scope, ripple_basics, ripple);
} // namespace test
} // namespace ripple