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Diffstat (limited to 'third_party/abseil_cpp/absl/base/casts.h')
| -rw-r--r-- | third_party/abseil_cpp/absl/base/casts.h | 184 |
1 files changed, 0 insertions, 184 deletions
diff --git a/third_party/abseil_cpp/absl/base/casts.h b/third_party/abseil_cpp/absl/base/casts.h deleted file mode 100644 index 322cc1d243..0000000000 --- a/third_party/abseil_cpp/absl/base/casts.h +++ /dev/null @@ -1,184 +0,0 @@ -// -// Copyright 2017 The Abseil Authors. -// -// Licensed under the Apache License, Version 2.0 (the "License"); -// you may not use this file except in compliance with the License. -// You may obtain a copy of the License at -// -// https://www.apache.org/licenses/LICENSE-2.0 -// -// Unless required by applicable law or agreed to in writing, software -// distributed under the License is distributed on an "AS IS" BASIS, -// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. -// See the License for the specific language governing permissions and -// limitations under the License. -// -// ----------------------------------------------------------------------------- -// File: casts.h -// ----------------------------------------------------------------------------- -// -// This header file defines casting templates to fit use cases not covered by -// the standard casts provided in the C++ standard. As with all cast operations, -// use these with caution and only if alternatives do not exist. - -#ifndef ABSL_BASE_CASTS_H_ -#define ABSL_BASE_CASTS_H_ - -#include <cstring> -#include <memory> -#include <type_traits> -#include <utility> - -#include "absl/base/internal/identity.h" -#include "absl/base/macros.h" -#include "absl/meta/type_traits.h" - -namespace absl { -ABSL_NAMESPACE_BEGIN - -namespace internal_casts { - -template <class Dest, class Source> -struct is_bitcastable - : std::integral_constant< - bool, - sizeof(Dest) == sizeof(Source) && - type_traits_internal::is_trivially_copyable<Source>::value && - type_traits_internal::is_trivially_copyable<Dest>::value && - std::is_default_constructible<Dest>::value> {}; - -} // namespace internal_casts - -// implicit_cast() -// -// Performs an implicit conversion between types following the language -// rules for implicit conversion; if an implicit conversion is otherwise -// allowed by the language in the given context, this function performs such an -// implicit conversion. -// -// Example: -// -// // If the context allows implicit conversion: -// From from; -// To to = from; -// -// // Such code can be replaced by: -// implicit_cast<To>(from); -// -// An `implicit_cast()` may also be used to annotate numeric type conversions -// that, although safe, may produce compiler warnings (such as `long` to `int`). -// Additionally, an `implicit_cast()` is also useful within return statements to -// indicate a specific implicit conversion is being undertaken. -// -// Example: -// -// return implicit_cast<double>(size_in_bytes) / capacity_; -// -// Annotating code with `implicit_cast()` allows you to explicitly select -// particular overloads and template instantiations, while providing a safer -// cast than `reinterpret_cast()` or `static_cast()`. -// -// Additionally, an `implicit_cast()` can be used to allow upcasting within a -// type hierarchy where incorrect use of `static_cast()` could accidentally -// allow downcasting. -// -// Finally, an `implicit_cast()` can be used to perform implicit conversions -// from unrelated types that otherwise couldn't be implicitly cast directly; -// C++ will normally only implicitly cast "one step" in such conversions. -// -// That is, if C is a type which can be implicitly converted to B, with B being -// a type that can be implicitly converted to A, an `implicit_cast()` can be -// used to convert C to B (which the compiler can then implicitly convert to A -// using language rules). -// -// Example: -// -// // Assume an object C is convertible to B, which is implicitly convertible -// // to A -// A a = implicit_cast<B>(C); -// -// Such implicit cast chaining may be useful within template logic. -template <typename To> -constexpr To implicit_cast(typename absl::internal::identity_t<To> to) { - return to; -} - -// bit_cast() -// -// Performs a bitwise cast on a type without changing the underlying bit -// representation of that type's value. The two types must be of the same size -// and both types must be trivially copyable. As with most casts, use with -// caution. A `bit_cast()` might be needed when you need to temporarily treat a -// type as some other type, such as in the following cases: -// -// * Serialization (casting temporarily to `char *` for those purposes is -// always allowed by the C++ standard) -// * Managing the individual bits of a type within mathematical operations -// that are not normally accessible through that type -// * Casting non-pointer types to pointer types (casting the other way is -// allowed by `reinterpret_cast()` but round-trips cannot occur the other -// way). -// -// Example: -// -// float f = 3.14159265358979; -// int i = bit_cast<int32_t>(f); -// // i = 0x40490fdb -// -// Casting non-pointer types to pointer types and then dereferencing them -// traditionally produces undefined behavior. -// -// Example: -// -// // WRONG -// float f = 3.14159265358979; // WRONG -// int i = * reinterpret_cast<int*>(&f); // WRONG -// -// The address-casting method produces undefined behavior according to the ISO -// C++ specification section [basic.lval]. Roughly, this section says: if an -// object in memory has one type, and a program accesses it with a different -// type, the result is undefined behavior for most values of "different type". -// -// Such casting results in type punning: holding an object in memory of one type -// and reading its bits back using a different type. A `bit_cast()` avoids this -// issue by implementing its casts using `memcpy()`, which avoids introducing -// this undefined behavior. -// -// NOTE: The requirements here are more strict than the bit_cast of standard -// proposal p0476 due to the need for workarounds and lack of intrinsics. -// Specifically, this implementation also requires `Dest` to be -// default-constructible. -template < - typename Dest, typename Source, - typename std::enable_if<internal_casts::is_bitcastable<Dest, Source>::value, - int>::type = 0> -inline Dest bit_cast(const Source& source) { - Dest dest; - memcpy(static_cast<void*>(std::addressof(dest)), - static_cast<const void*>(std::addressof(source)), sizeof(dest)); - return dest; -} - -// NOTE: This overload is only picked if the requirements of bit_cast are not -// met. It is therefore UB, but is provided temporarily as previous versions of -// this function template were unchecked. Do not use this in new code. -template < - typename Dest, typename Source, - typename std::enable_if< - !internal_casts::is_bitcastable<Dest, Source>::value, int>::type = 0> -ABSL_DEPRECATED( - "absl::bit_cast type requirements were violated. Update the types being " - "used such that they are the same size and are both TriviallyCopyable.") -inline Dest bit_cast(const Source& source) { - static_assert(sizeof(Dest) == sizeof(Source), - "Source and destination types should have equal sizes."); - - Dest dest; - memcpy(&dest, &source, sizeof(dest)); - return dest; -} - -ABSL_NAMESPACE_END -} // namespace absl - -#endif // ABSL_BASE_CASTS_H_ |