| // Copyright 2013 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 MOJO_PUBLIC_BINDINGS_LIB_BUFFER_H_ |
| #define MOJO_PUBLIC_BINDINGS_LIB_BUFFER_H_ |
| |
| #include <stddef.h> |
| |
| #include <deque> |
| |
| #include "mojo/public/system/macros.h" |
| |
| namespace mojo { |
| |
| // Buffer provides a way to allocate memory. Allocations are 8-byte aligned and |
| // zero-initialized. Allocations remain valid for the lifetime of the Buffer. |
| class Buffer { |
| public: |
| typedef void (*Destructor)(void* address); |
| |
| Buffer(); |
| virtual ~Buffer(); |
| |
| virtual void* Allocate(size_t num_bytes, Destructor func = NULL) = 0; |
| |
| static Buffer* current(); |
| |
| private: |
| Buffer* previous_; |
| }; |
| |
| namespace internal { |
| |
| // The following class is designed to be allocated on the stack. If necessary, |
| // it will failover to allocating objects on the heap. |
| class ScratchBuffer : public Buffer { |
| public: |
| ScratchBuffer(); |
| virtual ~ScratchBuffer(); |
| |
| virtual void* Allocate(size_t num_bytes, Destructor func = NULL) |
| MOJO_OVERRIDE; |
| |
| private: |
| enum { kMinSegmentSize = 512 }; |
| |
| struct Segment { |
| Segment* next; |
| char* cursor; |
| char* end; |
| }; |
| |
| void* AllocateInSegment(Segment* segment, size_t num_bytes); |
| void AddOverflowSegment(size_t delta); |
| |
| char fixed_data_[kMinSegmentSize]; |
| Segment fixed_; |
| Segment* overflow_; |
| |
| struct PendingDestructor { |
| Destructor func; |
| void* address; |
| }; |
| std::deque<PendingDestructor> pending_dtors_; |
| |
| MOJO_DISALLOW_COPY_AND_ASSIGN(ScratchBuffer); |
| }; |
| |
| // FixedBuffer provides a simple way to allocate objects within a fixed chunk |
| // of memory. Objects are allocated by calling the |Allocate| method, which |
| // extends the buffer accordingly. Objects allocated in this way are not freed |
| // explicitly. Instead, they remain valid so long as the FixedBuffer remains |
| // valid. The Leak method may be used to steal the underlying memory from the |
| // FixedBuffer. |
| // |
| // Typical usage: |
| // |
| // { |
| // FixedBuffer buf(8 + 8); |
| // |
| // int* a = static_cast<int*>(buf->Allocate(sizeof(int))); |
| // *a = 2; |
| // |
| // double* b = static_cast<double*>(buf->Allocate(sizeof(double))); |
| // *b = 3.14f; |
| // |
| // void* data = buf.Leak(); |
| // Process(data); |
| // |
| // free(data); |
| // } |
| // |
| class FixedBuffer : public Buffer { |
| public: |
| explicit FixedBuffer(size_t size); |
| virtual ~FixedBuffer(); |
| |
| // Grows the buffer by |num_bytes| and returns a pointer to the start of the |
| // addition. The resulting address is 8-byte aligned, and the content of the |
| // memory is zero-filled. |
| virtual void* Allocate(size_t num_bytes, Destructor func = NULL) |
| MOJO_OVERRIDE; |
| |
| size_t size() const { return size_; } |
| |
| // Returns the internal memory owned by the Buffer to the caller. The Buffer |
| // relinquishes its pointer, effectively resetting the state of the Buffer |
| // and leaving the caller responsible for freeing the returned memory address |
| // when no longer needed. |
| void* Leak(); |
| |
| private: |
| char* ptr_; |
| size_t cursor_; |
| size_t size_; |
| |
| MOJO_DISALLOW_COPY_AND_ASSIGN(FixedBuffer); |
| }; |
| |
| } // namespace internal |
| |
| class AllocationScope { |
| public: |
| AllocationScope() {} |
| ~AllocationScope() {} |
| |
| Buffer* buffer() { return &buffer_; } |
| |
| private: |
| internal::ScratchBuffer buffer_; |
| |
| MOJO_DISALLOW_COPY_AND_ASSIGN(AllocationScope); |
| }; |
| |
| } // namespace mojo |
| |
| #endif // MOJO_PUBLIC_BINDINGS_LIB_BUFFER_H_ |