1 // Copyright 2014 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #ifndef MOJO_PUBLIC_CPP_BINDINGS_LIB_FIXED_BUFFER_H_ 6 #define MOJO_PUBLIC_CPP_BINDINGS_LIB_FIXED_BUFFER_H_ 7 8 #include <stddef.h> 9 10 #include "base/macros.h" 11 #include "mojo/public/cpp/bindings/lib/buffer.h" 12 13 namespace mojo { 14 namespace internal { 15 16 // FixedBuffer provides a simple way to allocate objects within a fixed chunk 17 // of memory. Objects are allocated by calling the |Allocate| method, which 18 // extends the buffer accordingly. Objects allocated in this way are not freed 19 // explicitly. Instead, they remain valid so long as the FixedBuffer remains 20 // valid. The Leak method may be used to steal the underlying memory from the 21 // FixedBuffer. 22 // 23 // Typical usage: 24 // 25 // { 26 // FixedBuffer buf(8 + 8); 27 // 28 // int* a = static_cast<int*>(buf->Allocate(sizeof(int))); 29 // *a = 2; 30 // 31 // double* b = static_cast<double*>(buf->Allocate(sizeof(double))); 32 // *b = 3.14f; 33 // 34 // void* data = buf.Leak(); 35 // Process(data); 36 // 37 // free(data); 38 // } 39 40 class FixedBuffer : public Buffer { 41 public: 42 FixedBuffer(); 43 44 // |size| should be aligned using internal::Align. 45 void Initialize(void* memory, size_t size); 46 47 size_t size() const { return size_; } 48 49 // Grows the buffer by |num_bytes| and returns a pointer to the start of the 50 // addition. The resulting address is 8-byte aligned, and the content of the 51 // memory is zero-filled. 52 void* Allocate(size_t num_bytes) override; 53 54 protected: 55 char* ptr_; 56 size_t cursor_; 57 size_t size_; 58 59 DISALLOW_COPY_AND_ASSIGN(FixedBuffer); 60 }; 61 62 class FixedBufferForTesting : public FixedBuffer { 63 public: 64 explicit FixedBufferForTesting(size_t size); 65 ~FixedBufferForTesting() override; 66 67 // Returns the internal memory owned by the Buffer to the caller. The Buffer 68 // relinquishes its pointer, effectively resetting the state of the Buffer 69 // and leaving the caller responsible for freeing the returned memory address 70 // when no longer needed. 71 void* Leak(); 72 73 private: 74 DISALLOW_COPY_AND_ASSIGN(FixedBufferForTesting); 75 }; 76 77 } // namespace internal 78 } // namespace mojo 79 80 #endif // MOJO_PUBLIC_CPP_BINDINGS_LIB_FIXED_BUFFER_H_ 81
