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68 lines
2.0 KiB
C++
68 lines
2.0 KiB
C++
// Copyright 2014 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef MOJO_PUBLIC_CPP_BINDINGS_LIB_FIXED_BUFFER_H_
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#define MOJO_PUBLIC_CPP_BINDINGS_LIB_FIXED_BUFFER_H_
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#include "mojo/public/cpp/bindings/lib/buffer.h"
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#include "mojo/public/cpp/system/macros.h"
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namespace mojo {
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namespace internal {
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// FixedBuffer provides a simple way to allocate objects within a fixed chunk
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// of memory. Objects are allocated by calling the |Allocate| method, which
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// extends the buffer accordingly. Objects allocated in this way are not freed
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// explicitly. Instead, they remain valid so long as the FixedBuffer remains
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// valid. The Leak method may be used to steal the underlying memory from the
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// FixedBuffer.
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//
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// Typical usage:
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//
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// {
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// FixedBuffer buf(8 + 8);
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//
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// int* a = static_cast<int*>(buf->Allocate(sizeof(int)));
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// *a = 2;
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//
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// double* b = static_cast<double*>(buf->Allocate(sizeof(double)));
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// *b = 3.14f;
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//
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// void* data = buf.Leak();
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// Process(data);
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//
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// free(data);
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// }
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//
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class FixedBuffer : public Buffer {
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public:
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explicit FixedBuffer(size_t size);
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~FixedBuffer() override;
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// Grows the buffer by |num_bytes| and returns a pointer to the start of the
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// addition. The resulting address is 8-byte aligned, and the content of the
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// memory is zero-filled.
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void* Allocate(size_t num_bytes) override;
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size_t size() const { return size_; }
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// Returns the internal memory owned by the Buffer to the caller. The Buffer
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// relinquishes its pointer, effectively resetting the state of the Buffer
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// and leaving the caller responsible for freeing the returned memory address
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// when no longer needed.
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void* Leak();
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private:
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char* ptr_;
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size_t cursor_;
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size_t size_;
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MOJO_DISALLOW_COPY_AND_ASSIGN(FixedBuffer);
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};
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} // namespace internal
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} // namespace mojo
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#endif // MOJO_PUBLIC_CPP_BINDINGS_LIB_FIXED_BUFFER_H_
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