12bc53e031
-- c99f979ad34f155fbeeea69b88bdc7458d89a21c by Derek Mauro <dmauro@google.com>: Remove a floating point division by zero test. This isn't testing behavior related to the library, and MSVC warns about it in opt mode. PiperOrigin-RevId: 285220804 -- 68b015491f0dbf1ab547994673281abd1f34cd4b by Gennadiy Rozental <rogeeff@google.com>: This CL introduces following changes to the class FlagImpl: * We eliminate the CommandLineFlagLocks struct. Instead callback guard and callback function are combined into a single CallbackData struct, while primary data lock is stored separately. * CallbackData member of class FlagImpl is initially set to be nullptr and is only allocated and initialized when a flag's callback is being set. For most flags we do not pay for the extra space and extra absl::Mutex now. * Primary data guard is stored in data_guard_ data member. This is a properly aligned character buffer of necessary size. During initialization of the flag we construct absl::Mutex in this space using placement new call. * We now avoid extra value copy after successful attempt to parse value out of string. Instead we swap flag's current value with tentative value we just produced. PiperOrigin-RevId: 285132636 -- ed45d118fb818969eb13094cf7827c885dfc562c by Tom Manshreck <shreck@google.com>: Change null-term* (and nul-term*) to NUL-term* in comments PiperOrigin-RevId: 285036610 -- 729619017944db895ce8d6d29c1995aa2e5628a5 by Derek Mauro <dmauro@google.com>: Use the Posix implementation of thread identity on MinGW. Some versions of MinGW suffer from thread_local bugs. PiperOrigin-RevId: 285022920 -- 39a25493503c76885bc3254c28f66a251c5b5bb0 by Greg Falcon <gfalcon@google.com>: Implementation detail change. Add further ABSL_NAMESPACE_BEGIN and _END annotation macros to files in Abseil. PiperOrigin-RevId: 285012012 GitOrigin-RevId: c99f979ad34f155fbeeea69b88bdc7458d89a21c Change-Id: I4c85d3704e45d11a9ac50d562f39640a6adbedc1
73 lines
2.6 KiB
C++
73 lines
2.6 KiB
C++
//
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// Copyright 2017 The Abseil Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// https://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//
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#ifndef ABSL_STRINGS_INTERNAL_RESIZE_UNINITIALIZED_H_
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#define ABSL_STRINGS_INTERNAL_RESIZE_UNINITIALIZED_H_
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#include <string>
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#include <type_traits>
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#include <utility>
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#include "absl/base/port.h"
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#include "absl/meta/type_traits.h" // for void_t
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namespace absl {
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ABSL_NAMESPACE_BEGIN
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namespace strings_internal {
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// Is a subclass of true_type or false_type, depending on whether or not
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// T has a __resize_default_init member.
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template <typename string_type, typename = void>
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struct ResizeUninitializedTraits {
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using HasMember = std::false_type;
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static void Resize(string_type* s, size_t new_size) { s->resize(new_size); }
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};
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// __resize_default_init is provided by libc++ >= 8.0
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template <typename string_type>
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struct ResizeUninitializedTraits<
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string_type, absl::void_t<decltype(std::declval<string_type&>()
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.__resize_default_init(237))> > {
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using HasMember = std::true_type;
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static void Resize(string_type* s, size_t new_size) {
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s->__resize_default_init(new_size);
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}
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};
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// Returns true if the std::string implementation supports a resize where
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// the new characters added to the std::string are left untouched.
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//
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// (A better name might be "STLStringSupportsUninitializedResize", alluding to
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// the previous function.)
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template <typename string_type>
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inline constexpr bool STLStringSupportsNontrashingResize(string_type*) {
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return ResizeUninitializedTraits<string_type>::HasMember::value;
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}
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// Like str->resize(new_size), except any new characters added to "*str" as a
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// result of resizing may be left uninitialized, rather than being filled with
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// '0' bytes. Typically used when code is then going to overwrite the backing
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// store of the std::string with known data.
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template <typename string_type, typename = void>
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inline void STLStringResizeUninitialized(string_type* s, size_t new_size) {
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ResizeUninitializedTraits<string_type>::Resize(s, new_size);
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}
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} // namespace strings_internal
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ABSL_NAMESPACE_END
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} // namespace absl
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#endif // ABSL_STRINGS_INTERNAL_RESIZE_UNINITIALIZED_H_
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