1 files changed, 172 insertions, 0 deletions
diff --git a/CircBufferTimestamp.hpp b/CircBufferTimestamp.hpp
new file mode 100644
index 0000000..b6e0751
--- /dev/null
+++ b/CircBufferTimestamp.hpp
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+/*
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2018 Matthias P. Braendli
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#pragma once
+
+#include <vector>
+#include <mutex>
+#include <condition_variable>
+#include <cmath>
+
+template<class T>
+class CircularBuffer
+{
+    public:
+        CircularBuffer(size_t max_bufsize) :
+            m_maxbufsize(max_bufsize)
+        {
+        }
+
+        void set_ticks_per_sample(long long tps)
+        {
+            m_ticks_per_sample = tps;
+        }
+
+        /* Write num_elems from buf to the internal buffer, at the position
+         * given by timestamp
+         */
+        void write(const T *buf, size_t num_elems, long long timestamp)
+        {
+            std::unique_lock<std::mutex> lock(m_mutex);
+
+            if (m_timestamp_buf == 0 or timestamp < m_timestamp_buf) {
+                // First time we write to our buf, or jump back in time,
+                // we reset our buffer
+                resetbuf();
+                m_timestamp_buf = timestamp;
+            }
+
+            size_t sample_offset = (timestamp - m_timestamp_buf) /
+                                    m_ticks_per_sample;
+            size_t minsize = sample_offset + num_elems;
+
+            if (minsize > m_maxbufsize) {
+                truncatebuf();
+                if (minsize > m_maxbufsize) {
+                    resetbuf();
+                    m_timestamp_buf = timestamp;
+                    sample_offset = 0;
+                    minsize = num_elems;
+                }
+            }
+
+            if (m_buf.size() < minsize) {
+                m_buf.resize(minsize);
+            }
+            std::copy(buf, buf + num_elems, m_buf.begin() + sample_offset);
+
+            lock.unlock();
+            m_cv.notify_all();
+        }
+
+        /* Read num_elems elements from the internal buffer, starting
+         * from the end of the last read. Returns number of elements written */
+        size_t read(T *buf, size_t num_elems)
+        {
+            std::unique_lock<std::mutex> lock(m_mutex);
+
+            while (m_read_offset + num_elems > m_buf.size()) {
+                m_cv.wait(lock);
+            }
+
+            std::copy(m_buf.begin() + m_read_offset,
+                      m_buf.begin() + m_read_offset + num_elems,
+                      buf);
+
+            m_read_offset += num_elems;
+            return num_elems;
+        }
+
+        /* Read num_elems elements from the internal buffer at the
+         * position corresponding to the timestamp, which is also
+         * updated.
+         * Returns number of elements written.
+         */
+        size_t read(T *buf, size_t num_elems, long long *timestamp)
+        {
+            std::unique_lock<std::mutex> lock(m_mutex);
+
+            if (*timestamp < m_timestamp_buf) {
+                // Cannot give samples earlier than the timestamp
+                return 0;
+            }
+
+            const size_t sample_offset =
+                std::llrint(
+                        (double)(*timestamp - m_timestamp_buf) /
+                        (double)m_ticks_per_sample);
+            const size_t minsize = sample_offset + num_elems;
+
+            if (minsize > m_maxbufsize) {
+                // Too far in the future
+                return 0;
+            }
+
+            while (minsize > m_buf.size()) {
+                m_cv.wait(lock);
+            }
+
+            std::copy(m_buf.begin() + sample_offset,
+                      m_buf.begin() + sample_offset + num_elems,
+                      buf);
+
+            *timestamp = m_timestamp_buf + sample_offset * m_ticks_per_sample;
+            m_read_offset = sample_offset + num_elems;
+            return num_elems;
+        }
+
+    private:
+        void resetbuf()
+        {
+            m_buf.clear();
+            m_timestamp_buf = 0;
+            m_read_offset = 0;
+        }
+
+        void truncatebuf()
+        {
+            if (m_buf.size() < m_read_offset) {
+                throw std::logic_error("truncate " +
+                        std::to_string(m_buf.size()) + " " +
+                        std::to_string(m_read_offset));
+            }
+
+            for (size_t r = m_read_offset, w = 0;
+                    r < m_buf.size();
+                    r++, w++) {
+                m_buf[w] = m_buf[r];
+            }
+            m_read_offset = 0;
+            m_buf.resize(m_buf.size() - m_read_offset);
+        }
+
+        std::condition_variable m_cv;
+        std::mutex m_mutex;
+        std::vector<T> m_buf;
+        long long m_timestamp_buf = 0;
+        long long m_ticks_per_sample = 0;
+        size_t m_maxbufsize = 0;
+
+        size_t m_read_offset = 0;
+};