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- // Copyright (c) 2011 The Chromium Authors. All rights reserved.
- // Use of this source code is governed by a BSD-style license that can be
- // found in the LICENSE file.
- #ifndef COURGETTE_MEMORY_ALLOCATOR_H_
- #define COURGETTE_MEMORY_ALLOCATOR_H_
- #include <stddef.h>
- #include <stdint.h>
- #include <stdlib.h>
- #include <string.h>
- #include "base/files/file.h"
- #include "base/logging.h"
- #include "base/memory/raw_ptr.h"
- #include "base/process/memory.h"
- #include "build/build_config.h"
- #ifndef NDEBUG
- // A helper class to track down call sites that are not handling error cases.
- template<class T>
- class CheckReturnValue {
- public:
- // Not marked explicit on purpose.
- CheckReturnValue(T value) : value_(value), checked_(false) { // NOLINT
- }
- CheckReturnValue(const CheckReturnValue& other)
- : value_(other.value_), checked_(other.checked_) {
- other.checked_ = true;
- }
- CheckReturnValue& operator=(const CheckReturnValue& other) {
- if (this != &other) {
- DCHECK(checked_);
- value_ = other.value_;
- checked_ = other.checked_;
- other.checked_ = true;
- }
- return *this;
- }
- ~CheckReturnValue() {
- DCHECK(checked_);
- }
- operator const T&() const {
- checked_ = true;
- return value_;
- }
- private:
- T value_;
- mutable bool checked_;
- };
- typedef CheckReturnValue<bool> CheckBool;
- #else
- typedef bool CheckBool;
- #endif
- namespace courgette {
- // Allocates memory for an instance of type T, instantiates an object in that
- // memory with arguments |args| (of type ArgTypes), and returns the constructed
- // instance. Returns null if allocation fails.
- template <class T, class... ArgTypes>
- T* UncheckedNew(ArgTypes... args) {
- void* ram = nullptr;
- return base::UncheckedMalloc(sizeof(T), &ram) ? new (ram) T(args...)
- : nullptr;
- }
- // Complement of UncheckedNew(): destructs |object| and releases its memory.
- template <class T>
- void UncheckedDelete(T* object) {
- if (object) {
- object->T::~T();
- free(object);
- }
- }
- // A deleter for std::unique_ptr that will delete the object via
- // UncheckedDelete().
- template <class T>
- struct UncheckedDeleter {
- inline void operator()(T* ptr) const { UncheckedDelete(ptr); }
- };
- #if BUILDFLAG(IS_WIN)
- // Manages a read/write virtual mapping of a physical file.
- class FileMapping {
- public:
- FileMapping();
- ~FileMapping();
- // Map a file from beginning to |size|.
- bool Create(HANDLE file, size_t size);
- void Close();
- // Returns true iff a mapping has been created.
- bool valid() const;
- // Returns a writable pointer to the beginning of the memory mapped file.
- // If Create has not been called successfully, return value is nullptr.
- void* view() const;
- protected:
- bool InitializeView(size_t size);
- HANDLE mapping_;
- raw_ptr<void> view_;
- };
- // Manages a temporary file and a memory mapping of the temporary file.
- // The memory that this class manages holds a pointer back to the TempMapping
- // object itself, so that given a memory pointer allocated by this class,
- // you can get a pointer to the TempMapping instance that owns that memory.
- class TempMapping {
- public:
- TempMapping();
- ~TempMapping();
- // Creates a temporary file of size |size| and maps it into the current
- // process's address space.
- bool Initialize(size_t size);
- // Returns a writable pointer to the reserved memory.
- void* memory() const;
- // Returns true if the mapping is valid and memory is available.
- bool valid() const;
- // Returns a pointer to the TempMapping instance that allocated the |mem|
- // block of memory. It's the callers responsibility to make sure that
- // the memory block was allocated by the TempMapping class.
- static TempMapping* GetMappingFromPtr(void* mem);
- protected:
- base::File file_;
- FileMapping mapping_;
- };
- // A memory allocator class that allocates memory either from the heap or via a
- // temporary file. The interface is STL inspired but the class does not throw
- // STL exceptions on allocation failure. Instead it returns nullptr.
- // A file allocation will be made if either the requested memory size exceeds
- // |kMaxHeapAllocationSize| or if a heap allocation fails.
- // Allocating the memory as a mapping of a temporary file solves the problem
- // that there might not be enough physical memory and pagefile to support the
- // allocation. This can happen because these resources are too small, or
- // already committed to other processes. Provided there is enough disk, the
- // temporary file acts like a pagefile that other processes can't access.
- template<class T>
- class MemoryAllocator {
- public:
- typedef T value_type;
- typedef value_type* pointer;
- typedef value_type& reference;
- typedef const value_type* const_pointer;
- typedef const value_type& const_reference;
- typedef size_t size_type;
- typedef ptrdiff_t difference_type;
- // Each allocation is tagged with a single byte so that we know how to
- // deallocate it.
- enum AllocationType : uint8_t {
- HEAP_ALLOCATION = 0xF0, // Non-trivial constants to detect corruption.
- FILE_ALLOCATION = 0x0F,
- };
- // 5MB is the maximum heap allocation size that we'll attempt.
- // When applying a patch for Chrome 10.X we found that at this
- // threshold there were 17 allocations higher than this threshold
- // (largest at 136MB) 10 allocations just below the threshold and 6362
- // smaller allocations.
- static const size_t kMaxHeapAllocationSize = 1024 * 1024 * 5;
- template<class OtherT>
- struct rebind {
- // convert a MemoryAllocator<T> to a MemoryAllocator<OtherT>
- typedef MemoryAllocator<OtherT> other;
- };
- MemoryAllocator() {}
- // We can't use an explicit constructor here, as dictated by our style guide.
- // The implementation of basic_string in Visual Studio 2010 prevents this.
- MemoryAllocator(const MemoryAllocator<T>& other) { // NOLINT
- }
- template <class OtherT>
- MemoryAllocator(const MemoryAllocator<OtherT>& other) { // NOLINT
- }
- ~MemoryAllocator() {
- }
- void deallocate(pointer ptr, size_type size) {
- uint8_t* mem = reinterpret_cast<uint8_t*>(ptr);
- mem -= sizeof(T);
- if (mem[0] == HEAP_ALLOCATION)
- free(mem);
- else if (mem[0] == FILE_ALLOCATION)
- UncheckedDelete(TempMapping::GetMappingFromPtr(mem));
- else
- LOG(FATAL);
- }
- pointer allocate(size_type count) {
- // We use the first byte of each allocation to mark the allocation type.
- // However, so that the allocation is properly aligned, we allocate an
- // extra element and then use the first byte of the first element
- // to mark the allocation type.
- count++;
- if (count > max_size())
- return nullptr;
- size_type bytes = count * sizeof(T);
- uint8_t* mem = nullptr;
- // First see if we can do this allocation on the heap.
- if (count < kMaxHeapAllocationSize &&
- base::UncheckedMalloc(bytes, reinterpret_cast<void**>(&mem))) {
- mem[0] = static_cast<uint8_t>(HEAP_ALLOCATION);
- } else {
- // Back the allocation with a temp file if either the request exceeds the
- // max heap allocation threshold or the heap allocation failed.
- TempMapping* mapping = UncheckedNew<TempMapping>();
- if (mapping) {
- if (mapping->Initialize(bytes)) {
- mem = reinterpret_cast<uint8_t*>(mapping->memory());
- mem[0] = static_cast<uint8_t>(FILE_ALLOCATION);
- } else {
- UncheckedDelete(mapping);
- }
- }
- }
- // If the above fails (e.g. because we are in a sandbox), just try the heap.
- if (!mem && base::UncheckedMalloc(bytes, reinterpret_cast<void**>(&mem))) {
- mem[0] = static_cast<uint8_t>(HEAP_ALLOCATION);
- }
- return mem ? reinterpret_cast<pointer>(mem + sizeof(T)) : nullptr;
- }
- pointer allocate(size_type count, const void* hint) {
- return allocate(count);
- }
- void construct(pointer ptr, const T& value) {
- ::new(ptr) T(value);
- }
- void destroy(pointer ptr) {
- ptr->~T();
- }
- size_type max_size() const {
- size_type count = static_cast<size_type>(-1) / sizeof(T);
- return (0 < count ? count : 1);
- }
- };
- #else // BUILDFLAG(IS_WIN)
- // On Mac, Linux, we use a bare bones implementation that only does
- // heap allocations.
- template<class T>
- class MemoryAllocator {
- public:
- typedef T value_type;
- typedef value_type* pointer;
- typedef value_type& reference;
- typedef const value_type* const_pointer;
- typedef const value_type& const_reference;
- typedef size_t size_type;
- typedef ptrdiff_t difference_type;
- template<class OtherT>
- struct rebind {
- // convert a MemoryAllocator<T> to a MemoryAllocator<OtherT>
- typedef MemoryAllocator<OtherT> other;
- };
- MemoryAllocator() {
- }
- explicit MemoryAllocator(const MemoryAllocator<T>& other) {
- }
- template<class OtherT>
- explicit MemoryAllocator(const MemoryAllocator<OtherT>& other) {
- }
- ~MemoryAllocator() {
- }
- void deallocate(pointer ptr, size_type size) { free(ptr); }
- pointer allocate(size_type count) {
- if (count > max_size())
- return nullptr;
- pointer result = nullptr;
- return base::UncheckedMalloc(count * sizeof(T),
- reinterpret_cast<void**>(&result))
- ? result
- : nullptr;
- }
- pointer allocate(size_type count, const void* hint) {
- return allocate(count);
- }
- void construct(pointer ptr, const T& value) {
- ::new(ptr) T(value);
- }
- void destroy(pointer ptr) {
- ptr->~T();
- }
- size_type max_size() const {
- size_type count = static_cast<size_type>(-1) / sizeof(T);
- return (0 < count ? count : 1);
- }
- };
- #endif // BUILDFLAG(IS_WIN)
- // Manages a growable buffer. The buffer allocation is done by the
- // MemoryAllocator class. This class will not throw exceptions so call sites
- // must be prepared to handle memory allocation failures.
- // The interface is STL inspired to avoid having to make too many changes
- // to code that previously was using STL.
- template<typename T, class Allocator = MemoryAllocator<T> >
- class NoThrowBuffer {
- public:
- typedef T value_type;
- static const size_t kAllocationFailure = 0xffffffff;
- static const size_t kStartSize = sizeof(T) > 0x100 ? 1 : 0x100 / sizeof(T);
- NoThrowBuffer() : buffer_(nullptr), size_(0), alloc_size_(0) {}
- ~NoThrowBuffer() {
- clear();
- }
- void clear() {
- if (buffer_) {
- alloc_.deallocate(buffer_, alloc_size_);
- buffer_ = nullptr;
- size_ = 0;
- alloc_size_ = 0;
- }
- }
- bool empty() const {
- return size_ == 0;
- }
- [[nodiscard]] CheckBool reserve(size_t size) {
- if (failed())
- return false;
- if (size <= alloc_size_)
- return true;
- if (size < kStartSize)
- size = kStartSize;
- T* new_buffer = alloc_.allocate(size);
- if (!new_buffer) {
- clear();
- alloc_size_ = kAllocationFailure;
- } else {
- if (buffer_) {
- memcpy(new_buffer, buffer_, size_ * sizeof(T));
- alloc_.deallocate(buffer_, alloc_size_);
- }
- buffer_ = new_buffer;
- alloc_size_ = size;
- }
- return !failed();
- }
- [[nodiscard]] CheckBool append(const T* data, size_t size) {
- if (failed())
- return false;
- if (size > alloc_.max_size() - size_)
- return false;
- if (!size)
- return true;
- // Disallow source range from overlapping with buffer_, since in this case
- // reallocation would cause use-after-free.
- DCHECK(data + size <= buffer_ || data >= buffer_ + alloc_size_);
- if ((alloc_size_ - size_) < size) {
- const size_t max_size = alloc_.max_size();
- size_t new_size = alloc_size_ ? alloc_size_ : kStartSize;
- while (new_size < size_ + size) {
- if (new_size < max_size - new_size) {
- new_size *= 2;
- } else {
- new_size = max_size;
- }
- }
- if (!reserve(new_size))
- return false;
- }
- memcpy(buffer_ + size_, data, size * sizeof(T));
- size_ += size;
- return true;
- }
- [[nodiscard]] CheckBool resize(size_t size, const T& init_value) {
- if (size > size_) {
- if (!reserve(size))
- return false;
- for (size_t i = size_; i < size; ++i)
- buffer_[i] = init_value;
- } else if (size < size_) {
- // TODO(tommi): Should we allocate a new, smaller buffer?
- // It might be faster for us to simply change the size.
- }
- size_ = size;
- return true;
- }
- [[nodiscard]] CheckBool push_back(const T& item) { return append(&item, 1); }
- const T& back() const {
- return buffer_[size_ - 1];
- }
- T& back() {
- return buffer_[size_ - 1];
- }
- const T* begin() const {
- if (!size_)
- return nullptr;
- return buffer_;
- }
- T* begin() {
- if (!size_)
- return nullptr;
- return buffer_;
- }
- const T* end() const {
- if (!size_)
- return nullptr;
- return buffer_ + size_;
- }
- T* end() {
- if (!size_)
- return nullptr;
- return buffer_ + size_;
- }
- const T& operator[](size_t index) const {
- DCHECK(index < size_);
- return buffer_[index];
- }
- T& operator[](size_t index) {
- DCHECK(index < size_);
- return buffer_[index];
- }
- size_t size() const {
- return size_;
- }
- size_t capacity() const {
- return alloc_size_;
- }
- T* data() const {
- return buffer_;
- }
- // Returns true if an allocation failure has ever occurred for this object.
- bool failed() const {
- return alloc_size_ == kAllocationFailure;
- }
- protected:
- raw_ptr<T> buffer_;
- size_t size_; // how much of the buffer we're using.
- size_t alloc_size_; // how much space we have allocated.
- Allocator alloc_;
- };
- } // namespace courgette
- #endif // COURGETTE_MEMORY_ALLOCATOR_H_
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