| // 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 <memory> |
| |
| #include "base/basictypes.h" |
| #include "base/files/file.h" |
| #include "base/files/file_path.h" |
| #include "base/logging.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; |
| } |
| } |
| |
| ~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 { |
| |
| #if defined(OS_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 NULL. |
| void* view() const; |
| |
| protected: |
| bool InitializeView(size_t size); |
| |
| HANDLE mapping_; |
| 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 NULL. |
| // 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 { |
| HEAP_ALLOCATION, |
| FILE_ALLOCATION, |
| }; |
| |
| // 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() _THROW0() { |
| } |
| |
| // 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) _THROW0() { // NOLINT |
| } |
| |
| template<class OtherT> |
| MemoryAllocator(const MemoryAllocator<OtherT>& other) _THROW0() { // NOLINT |
| } |
| |
| ~MemoryAllocator() { |
| } |
| |
| void deallocate(pointer ptr, size_type size) { |
| uint8* mem = reinterpret_cast<uint8*>(ptr); |
| mem -= sizeof(T); |
| if (mem[0] == HEAP_ALLOCATION) { |
| delete [] mem; |
| } else { |
| DCHECK_EQ(static_cast<uint8>(FILE_ALLOCATION), mem[0]); |
| TempMapping* mapping = TempMapping::GetMappingFromPtr(mem); |
| delete mapping; |
| } |
| } |
| |
| 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 NULL; |
| |
| size_type bytes = count * sizeof(T); |
| uint8* mem = NULL; |
| |
| // First see if we can do this allocation on the heap. |
| if (count < kMaxHeapAllocationSize) |
| mem = new(std::nothrow) uint8[bytes]; |
| if (mem != NULL) { |
| mem[0] = static_cast<uint8>(HEAP_ALLOCATION); |
| } else { |
| // If either the heap allocation failed or the request exceeds the |
| // max heap allocation threshold, we back the allocation with a temp file. |
| TempMapping* mapping = new(std::nothrow) TempMapping(); |
| if (mapping && mapping->Initialize(bytes)) { |
| mem = reinterpret_cast<uint8*>(mapping->memory()); |
| mem[0] = static_cast<uint8>(FILE_ALLOCATION); |
| } |
| } |
| return mem ? reinterpret_cast<pointer>(mem + sizeof(T)) : NULL; |
| } |
| |
| 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 _THROW0() { |
| size_type count = static_cast<size_type>(-1) / sizeof(T); |
| return (0 < count ? count : 1); |
| } |
| }; |
| |
| #else // OS_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) { |
| delete [] ptr; |
| } |
| |
| pointer allocate(size_type count) { |
| if (count > max_size()) |
| return NULL; |
| return reinterpret_cast<pointer>( |
| new(std::nothrow) uint8[count * sizeof(T)]); |
| } |
| |
| 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 // OS_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_(NULL), size_(0), alloc_size_(0) { |
| } |
| |
| ~NoThrowBuffer() { |
| clear(); |
| } |
| |
| void clear() { |
| if (buffer_) { |
| alloc_.deallocate(buffer_, alloc_size_); |
| buffer_ = NULL; |
| size_ = 0; |
| alloc_size_ = 0; |
| } |
| } |
| |
| bool empty() const { |
| return size_ == 0; |
| } |
| |
| CheckBool reserve(size_t size) WARN_UNUSED_RESULT { |
| 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(); |
| } |
| |
| CheckBool append(const T* data, size_t size) WARN_UNUSED_RESULT { |
| if (failed()) |
| return false; |
| |
| if (size > alloc_.max_size() - size_) |
| return false; |
| |
| if (!size) |
| return true; |
| |
| 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; |
| } |
| |
| CheckBool resize(size_t size, const T& init_value) WARN_UNUSED_RESULT { |
| 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; |
| } |
| |
| CheckBool push_back(const T& item) WARN_UNUSED_RESULT { |
| 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 NULL; |
| return &buffer_[0]; |
| } |
| |
| T* begin() { |
| if (!size_) |
| return NULL; |
| return &buffer_[0]; |
| } |
| |
| const T* end() const { |
| if (!size_) |
| return NULL; |
| return &buffer_[size_ - 1]; |
| } |
| |
| T* end() { |
| if (!size_) |
| return NULL; |
| return &buffer_[size_ - 1]; |
| } |
| |
| 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_; |
| } |
| |
| 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: |
| 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_ |