| // Protocol Buffers - Google's data interchange format |
| // Copyright 2008 Google Inc. All rights reserved. |
| // https://developers.google.com/protocol-buffers/ |
| // |
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| // modification, are permitted provided that the following conditions are |
| // met: |
| // |
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| // notice, this list of conditions and the following disclaimer. |
| // * Redistributions in binary form must reproduce the above |
| // copyright notice, this list of conditions and the following disclaimer |
| // in the documentation and/or other materials provided with the |
| // distribution. |
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| // contributors may be used to endorse or promote products derived from |
| // this software without specific prior written permission. |
| // |
| // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
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| // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| |
| // This file provides alignment utilities for use in arenas. |
| // |
| // `ArenaAlign` contains a single `align` data member and provides |
| // the below functions which operate on the given alignment. |
| // |
| // Ceil(size_t n) - rounds `n` up to the nearest `align` boundary. |
| // Floor(size_t n) - rounds `n` down to the nearest `align` boundary. |
| // Ceil(T* P) - rounds `p` up to the nearest `align` boundary. |
| // IsAligned(size_t n) - returns true if `n` is aligned to `align` |
| // IsAligned(T* p) - returns true if `p` is aligned to `align` |
| // CheckAligned(T* p) - returns `p`. Checks alignment of `p` in debug. |
| // |
| // Additionally there is an optimized `CeilDefaultAligned(T*)` method which is |
| // equivalent to `Ceil(ArenaAlignDefault().CheckAlign(p))` but more efficiently |
| // implemented as a 'check only' for ArenaAlignDefault. |
| // |
| // These classes allow for generic arena logic using 'alignment policies'. |
| // |
| // For example: |
| // |
| // template <Align> |
| // void* NaiveAlloc(size_t n, Align align) { |
| // align.CheckAligned(n); |
| // uint8_t* ptr = align.CeilDefaultAligned(ptr_); |
| // ptr_ += n; |
| // return ptr; |
| // } |
| // |
| // void CallSites() { |
| // void *p1 = NaiveAlloc(n, ArenaAlignDefault()); |
| // void *p2 = NaiveAlloc(n, ArenaAlignAs(32)); |
| // } |
| // |
| #ifndef GOOGLE_PROTOBUF_ARENA_ALIGN_H__ |
| #define GOOGLE_PROTOBUF_ARENA_ALIGN_H__ |
| |
| #include <cstddef> |
| #include <cstdint> |
| |
| #include "google/protobuf/stubs/logging.h" |
| #include "google/protobuf/stubs/common.h" |
| #include "absl/numeric/bits.h" |
| |
| namespace google { |
| namespace protobuf { |
| namespace internal { |
| |
| struct ArenaAlignDefault { |
| static constexpr size_t align = 8; // NOLINT |
| |
| static constexpr bool IsAligned(size_t n) { return (n & (align - 1)) == 0; } |
| |
| template <typename T> |
| static bool IsAligned(T* ptr) { |
| return (reinterpret_cast<uintptr_t>(ptr) & (align - 1)) == 0; |
| } |
| |
| static constexpr size_t Ceil(size_t n) { return (n + align - 1) & -align; } |
| static constexpr size_t Floor(size_t n) { return (n & ~(align - 1)); } |
| |
| template <typename T> |
| T* Ceil(T* ptr) const { |
| uintptr_t intptr = reinterpret_cast<uintptr_t>(ptr); |
| return reinterpret_cast<T*>((intptr + align - 1) & -align); |
| } |
| |
| template <typename T> |
| T* CeilDefaultAligned(T* ptr) const { |
| return ArenaAlignDefault().CheckAligned(ptr); |
| } |
| |
| // Address sanitizer enabled alignment check |
| template <typename T> |
| static T* CheckAligned(T* ptr) { |
| GOOGLE_DCHECK(IsAligned(ptr)) << static_cast<void*>(ptr); |
| return ptr; |
| } |
| }; |
| |
| struct ArenaAlign { |
| static constexpr bool IsDefault() { return false; }; |
| |
| size_t align; |
| |
| constexpr bool IsAligned(size_t n) const { return (n & (align - 1)) == 0; } |
| |
| template <typename T> |
| bool IsAligned(T* ptr) const { |
| return (reinterpret_cast<uintptr_t>(ptr) & (align - 1)) == 0; |
| } |
| |
| constexpr size_t Ceil(size_t n) const { return (n + align - 1) & -align; } |
| constexpr size_t Floor(size_t n) const { return (n & ~(align - 1)); } |
| |
| template <typename T> |
| T* Ceil(T* ptr) const { |
| uintptr_t intptr = reinterpret_cast<uintptr_t>(ptr); |
| return reinterpret_cast<T*>((intptr + align - 1) & -align); |
| } |
| |
| template <typename T> |
| T* CeilDefaultAligned(T* ptr) const { |
| return Ceil(ArenaAlignDefault().CheckAligned(ptr)); |
| } |
| |
| // Address sanitizer enabled alignment check |
| template <typename T> |
| T* CheckAligned(T* ptr) const { |
| GOOGLE_DCHECK(IsAligned(ptr)) << static_cast<void*>(ptr); |
| return ptr; |
| } |
| }; |
| |
| inline ArenaAlign ArenaAlignAs(size_t align) { |
| // align must be a non zero power of 2 >= 8 |
| GOOGLE_DCHECK_NE(align, 0); |
| GOOGLE_DCHECK(absl::has_single_bit(align)) << "Invalid alignment " << align; |
| return ArenaAlign{align}; |
| } |
| |
| } // namespace internal |
| } // namespace protobuf |
| } // namespace google |
| |
| #endif // GOOGLE_PROTOBUF_ARENA_ALIGN_H__ |