Repo created

TMessagesProj/jni/voip/webrtc/base/profiler/stack_buffer.h

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+// Copyright 2019 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 BASE_PROFILER_STACK_BUFFER_H_
+#define BASE_PROFILER_STACK_BUFFER_H_
+
+#include <stddef.h>
+#include <stdint.h>
+#include <memory>
+
+#include "base/base_export.h"
+#include "base/macros.h"
+
+namespace base {
+
+// This class contains a buffer for stack copies that can be shared across
+// multiple instances of StackSampler.
+class BASE_EXPORT StackBuffer {
+ public:
+  // The expected alignment of the stack on the current platform. Windows and
+  // System V AMD64 ABIs on x86, x64, and ARM require the stack to be aligned
+  // to twice the pointer size. Excepted from this requirement is code setting
+  // up the stack during function calls (between pushing the return address
+  // and the end of the function prologue). The profiler will sometimes
+  // encounter this exceptional case for leaf frames.
+  static constexpr size_t kPlatformStackAlignment = 2 * sizeof(uintptr_t);
+
+  StackBuffer(size_t buffer_size);
+  ~StackBuffer();
+
+  // Returns a kPlatformStackAlignment-aligned pointer to the stack buffer.
+  uintptr_t* buffer() const {
+    // Return the first address in the buffer aligned to
+    // kPlatformStackAlignment. The buffer is guaranteed to have enough space
+    // for size() bytes beyond this value.
+    return reinterpret_cast<uintptr_t*>(
+        (reinterpret_cast<uintptr_t>(buffer_.get()) + kPlatformStackAlignment -
+         1) &
+        ~(kPlatformStackAlignment - 1));
+  }
+
+  // Size in bytes.
+  size_t size() const { return size_; }
+
+ private:
+  // The buffer to store the stack.
+  const std::unique_ptr<uint8_t[]> buffer_;
+
+  // The size in bytes of the requested buffer allocation. The actual allocation
+  // is larger to accommodate alignment requirements.
+  const size_t size_;
+
+  DISALLOW_COPY_AND_ASSIGN(StackBuffer);
+};
+
+}  // namespace base
+
+#endif  // BASE_PROFILER_STACK_BUFFER_H_