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Unified Diff: content/common/partial_circular_buffer.h

Issue 13473005: Adding partially circular memory buffer wrapper. (Closed) Base URL: svn://svn.chromium.org/chrome/trunk/src
Patch Set: Rebase Created 7 years, 8 months ago
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Index: content/common/partial_circular_buffer.h
diff --git a/content/common/partial_circular_buffer.h b/content/common/partial_circular_buffer.h
new file mode 100644
index 0000000000000000000000000000000000000000..b692ac5ff39ce818cd9b70ed6870c17136a9523c
--- /dev/null
+++ b/content/common/partial_circular_buffer.h
@@ -0,0 +1,70 @@
+// Copyright (c) 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 CONTENT_COMMON_PARTIAL_CIRCULAR_BUFFER_H_
+#define CONTENT_COMMON_PARTIAL_CIRCULAR_BUFFER_H_
+
+#include "base/basictypes.h"
+#include "base/gtest_prod_util.h"
+#include "content/common/content_export.h"
+
+namespace content {
+
+// A wrapper around a memory buffer that allows circular read and write with a
+// selectable wrapping position. Buffer layout (after wrap; H is header):
+// -----------------------------------------------------------
+// | H | Beginning | End | Middle |
+// -----------------------------------------------------------
+// ^---- Non-wrapping -----^ ^--------- Wrapping ----------^
+// The non-wrapping part is never overwritten. The wrapping part will be
+// circular. The very first part is the header (see the BufferData struct
+// below). It consists of the following information:
+// - Length written to the buffer (not including header).
+// - Wrapping position.
+// - End position of buffer. (If the last byte is at x, this will be x + 1.)
+// Users of wrappers around the same underlying buffer must ensure that writing
+// is finished before reading is started.
+class CONTENT_EXPORT PartialCircularBuffer {
+ public:
+ // Use for reading. |buffer_size| is in bytes and must be larger than the
+ // header size (see above).
+ PartialCircularBuffer(void* buffer, uint32 buffer_size);
+
+ // Use for writing. |buffer_size| is in bytes and must be larger than the
+ // header size (see above).
+ PartialCircularBuffer(void* buffer,
+ uint32 buffer_size,
+ uint32 wrap_position);
+
+ uint32 Read(void* buffer, uint32 buffer_size);
+ void Write(const void* buffer, uint32 buffer_size);
+
+ private:
+ friend class PartialCircularBufferTest;
+
+#pragma pack(push)
+#pragma pack(4)
+ struct BufferData {
+ uint32 total_written;
+ uint32 wrap_position;
+ uint32 end_position;
+ uint8 data[1];
+ };
+#pragma pack(pop)
+
+ void DoWrite(void* dest, const void* src, uint32 num);
+
+ // Used for reading and writing.
+ BufferData* buffer_data_;
+ uint32 memory_buffer_size_;
+ uint32 data_size_;
+ uint32 position_;
+
+ // Used for reading.
+ uint32 total_read_;
+};
+
+} // namespace content
+
+#endif // CONTENT_COMMON_PARTIAL_CIRCULAR_BUFFER_H_
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