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project/fm_viewer/fav/ring.h

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+/******************************************************************************
+    QtAV:  Multimedia framework based on Qt and FFmpeg
+    Copyright (C) 2012-2016 Wang Bin <wbsecg1@gmail.com>
+
+*   This file is part of QtAV (from 2015)
+
+    This library is free software; you can redistribute it and/or
+    modify it under the terms of the GNU Lesser General Public
+    License as published by the Free Software Foundation; either
+    version 2.1 of the License, or (at your option) any later version.
+
+    This library is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+    Lesser General Public License for more details.
+
+    You should have received a copy of the GNU Lesser General Public
+    License along with this library; if not, write to the Free Software
+    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+******************************************************************************/
+
+#ifndef QTAV_RING_H
+#define QTAV_RING_H
+
+#include <cassert>
+#include <vector>
+
+namespace FAV {
+template<typename T, typename C>
+class ring_api {
+public:
+  ring_api() : m_0(0), m_1(0), m_s(0) {}
+  void push_back(const T &t);
+  void pop_front();
+  T &front() { return m_data[m_0]; }
+  const T &front() const { return m_data[m_0]; }
+  T &back() { return m_data[m_1]; }
+  const T &back() const { return m_data[m_1]; }
+  virtual size_t capacity() const = 0;
+  size_t size() const { return m_s;}
+  bool empty() const { return size() == 0;}
+  // need at() []?
+  const T &at(size_t i) const { assert(i < m_s); return m_data[index(m_0+i)];}
+  const T &operator[](size_t i) const { return at(i);}
+  T &operator[](size_t i) {assert(i < m_s); return m_data[index(m_0+i)];}
+protected:
+  size_t index(size_t i) const { return i < capacity() ? i : i - capacity();} // i always [0,capacity())
+  size_t m_0, m_1;
+  size_t m_s;
+  C m_data;
+};
+
+template<typename T>
+class ring : public ring_api<T, std::vector<T> > {
+  using ring_api<T, std::vector<T> >::m_data; // why need this?
+public:
+  ring(size_t capacity) : ring_api<T, std::vector<T> >() {
+      m_data.reserve(capacity);
+      m_data.resize(capacity);
+  }
+  size_t capacity() const {return m_data.size();}
+};
+template<typename T, int N>
+class static_ring : public ring_api<T, T[N]> {
+  using ring_api<T, T[N]>::m_data; // why need this?
+public:
+  static_ring() : ring_api<T, T[N]>() {}
+  size_t capacity() const {return N;}
+};
+
+template<typename T, typename C>
+void ring_api<T,C>::push_back(const T &t) {
+    if (m_s == capacity()) {
+        m_data[m_0] = t;
+        m_0 = index(++m_0);
+        m_1 = index(++m_1);
+    } else if (empty()) {
+        m_s = 1;
+        m_0 = m_1 = 0;
+        m_data[m_0] = t;
+    } else {
+      m_data[index(m_0 + m_s)] = t;
+      ++m_1;
+      ++m_s;
+    }
+}
+
+template<typename T, typename C>
+void ring_api<T,C>::pop_front() {
+    assert(!empty());
+    if (empty())
+      return;
+    m_data[m_0] = T(); //erase the old data
+    m_0 = index(++m_0);
+    --m_s;
+}
+} //namespace FAV
+#endif // QTAV_RING_H