From ad8918f3262c5bee869b785239c03fa08faf4114 Mon Sep 17 00:00:00 2001
From: "Dr. Chat" <arkolbed@gmail.com>
Date: Tue, 2 Jun 2015 10:11:59 -0500
Subject: [PATCH] RingBuffer util class

---
 src/xenia/base/ring_buffer.cpp | 56 ++++++++++++++++++++++++++++++++++
 src/xenia/base/ring_buffer.h   | 38 +++++++++++++++++++++++
 2 files changed, 94 insertions(+)
 create mode 100644 src/xenia/base/ring_buffer.cpp
 create mode 100644 src/xenia/base/ring_buffer.h

diff --git a/src/xenia/base/ring_buffer.cpp b/src/xenia/base/ring_buffer.cpp
new file mode 100644
index 000000000..48953f745
--- /dev/null
+++ b/src/xenia/base/ring_buffer.cpp
@@ -0,0 +1,56 @@
+/**
+******************************************************************************
+* Xenia : Xbox 360 Emulator Research Project                                 *
+******************************************************************************
+* Copyright 2015 Ben Vanik. All rights reserved.                             *
+* Released under the BSD license - see LICENSE in the root for more details. *
+******************************************************************************
+*/
+
+#include "xenia/base/ring_buffer.h"
+
+namespace xe {
+
+RingBuffer::RingBuffer(uint8_t *raw_buffer, size_t size, size_t write_offset)
+    : raw_buffer_(raw_buffer),
+      size_(size),
+      write_offset_(write_offset) {}
+
+int RingBuffer::Write(uint8_t *buffer, size_t num_bytes) {
+  size_t bytes_written = 0;
+  size_t input_offset = 0;
+  size_t bytes_to_write = 0;
+
+  // write offset -> end
+  bytes_to_write =
+        num_bytes < size_ - write_offset_ ? num_bytes : size_ - write_offset_;
+
+  std::memcpy(raw_buffer_ + write_offset_, buffer, bytes_to_write);
+  input_offset = bytes_to_write;
+  write_offset_ += bytes_to_write;
+
+  // Wraparound (begin -> num_bytes)
+  if (input_offset < num_bytes) {
+    bytes_to_write = num_bytes - input_offset;
+
+    std::memcpy(raw_buffer_, buffer + input_offset, bytes_to_write);
+    write_offset_ = bytes_to_write;
+  }
+
+  return 0;
+}
+
+size_t RingBuffer::DistanceToOffset(size_t offset) {
+  if (offset < size_ && offset >= write_offset_) {
+    // Doesn't wraparound.
+    return offset - write_offset_;
+  } else {
+    // Wraparound.
+    size_t dist = size_ - write_offset_;
+    dist += offset;
+
+    return dist;
+  }
+}
+
+} // namespace xe
\ No newline at end of file
diff --git a/src/xenia/base/ring_buffer.h b/src/xenia/base/ring_buffer.h
new file mode 100644
index 000000000..44c6b6f49
--- /dev/null
+++ b/src/xenia/base/ring_buffer.h
@@ -0,0 +1,38 @@
+/**
+******************************************************************************
+* Xenia : Xbox 360 Emulator Research Project                                 *
+******************************************************************************
+* Copyright 2015 Ben Vanik. All rights reserved.                             *
+* Released under the BSD license - see LICENSE in the root for more details. *
+******************************************************************************
+*/
+
+#ifndef XENIA_BASE_RING_BUFFER_H_
+#define XENIA_BASE_RING_BUFFER_H_
+
+#include <cstdint>
+#include <string>
+#include <vector>
+
+namespace xe {
+
+class RingBuffer {
+  public:
+    RingBuffer(uint8_t *raw_buffer, size_t size, size_t write_offset = 0);
+
+    int Write(uint8_t *buffer, size_t num_bytes);
+
+    size_t DistanceToOffset(size_t offset);
+
+    void SetWriteOffset(size_t write_offset) { write_offset_ = write_offset; }
+    size_t GetWriteOffset() { return write_offset_; }
+
+  private:
+    uint8_t *raw_buffer_;
+    size_t size_;
+    size_t write_offset_;
+};
+
+} // namespace xe
+
+#endif // XENIA_BASE_RING_BUFFER_H_
\ No newline at end of file