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+#ifndef PA_RINGBUFFER_H
+#define PA_RINGBUFFER_H
+/*
+ * $Id$
+ * Portable Audio I/O Library
+ * Ring Buffer utility.
+ *
+ * Author: Phil Burk, http://www.softsynth.com
+ * modified for SMP safety on OS X by Bjorn Roche.
+ * also allowed for const where possible.
+ * modified for multiple-byte-sized data elements by Sven Fischer
+ *
+ * Note that this is safe only for a single-thread reader
+ * and a single-thread writer.
+ *
+ * This program is distributed with the PortAudio Portable Audio Library.
+ * For more information see: http://www.portaudio.com
+ * Copyright (c) 1999-2000 Ross Bencina and Phil Burk
+ *
+ * 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.
+ */
+
+/*
+ * The text above constitutes the entire PortAudio license; however,
+ * the PortAudio community also makes the following non-binding requests:
+ *
+ * Any person wishing to distribute modifications to the Software is
+ * requested to send the modifications to the original developer so that
+ * they can be incorporated into the canonical version. It is also
+ * requested that these non-binding requests be included along with the
+ * license above.
+ */
+
+/** @file
+ @ingroup common_src
+ @brief Single-reader single-writer lock-free ring buffer
+
+ PaUtilRingBuffer is a ring buffer used to transport samples between
+ different execution contexts (threads, OS callbacks, interrupt handlers)
+ without requiring the use of any locks. This only works when there is
+ a single reader and a single writer (ie. one thread or callback writes
+ to the ring buffer, another thread or callback reads from it).
+
+ The PaUtilRingBuffer structure manages a ring buffer containing N
+ elements, where N must be a power of two. An element may be any size
+ (specified in bytes).
+
+ The memory area used to store the buffer elements must be allocated by
+ the client prior to calling PaUtil_InitializeRingBuffer() and must outlive
+ the use of the ring buffer.
+
+ @note The ring buffer functions are not normally exposed in the PortAudio libraries.
+ If you want to call them then you will need to add pa_ringbuffer.c to your application source code.
+*/
+
+#if defined(__APPLE__)
+#include <sys/types.h>
+typedef int32_t ring_buffer_size_t;
+#elif defined( __GNUC__ )
+typedef long ring_buffer_size_t;
+#elif (_MSC_VER >= 1400)
+typedef long ring_buffer_size_t;
+#elif defined(_MSC_VER) || defined(__BORLANDC__)
+typedef long ring_buffer_size_t;
+#else
+typedef long ring_buffer_size_t;
+#endif
+
+
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif /* __cplusplus */
+
+typedef struct PaUtilRingBuffer
+{
+    ring_buffer_size_t  bufferSize; /**< Number of elements in FIFO. Power of 2. Set by PaUtil_InitRingBuffer. */
+    volatile ring_buffer_size_t  writeIndex; /**< Index of next writable element. Set by PaUtil_AdvanceRingBufferWriteIndex. */
+    volatile ring_buffer_size_t  readIndex;  /**< Index of next readable element. Set by PaUtil_AdvanceRingBufferReadIndex. */
+    ring_buffer_size_t  bigMask;    /**< Used for wrapping indices with extra bit to distinguish full/empty. */
+    ring_buffer_size_t  smallMask;  /**< Used for fitting indices to buffer. */
+    ring_buffer_size_t  elementSizeBytes; /**< Number of bytes per element. */
+    char  *buffer;    /**< Pointer to the buffer containing the actual data. */
+}PaUtilRingBuffer;
+
+/** Initialize Ring Buffer to empty state ready to have elements written to it.
+
+ @param rbuf The ring buffer.
+
+ @param elementSizeBytes The size of a single data element in bytes.
+
+ @param elementCount The number of elements in the buffer (must be a power of 2).
+
+ @param dataPtr A pointer to a previously allocated area where the data
+ will be maintained.  It must be elementCount*elementSizeBytes long.
+
+ @return -1 if elementCount is not a power of 2, otherwise 0.
+*/
+ring_buffer_size_t PaUtil_InitializeRingBuffer( PaUtilRingBuffer *rbuf, ring_buffer_size_t elementSizeBytes, ring_buffer_size_t elementCount, void *dataPtr );
+
+/** Reset buffer to empty. Should only be called when buffer is NOT being read or written.
+
+ @param rbuf The ring buffer.
+*/
+void PaUtil_FlushRingBuffer( PaUtilRingBuffer *rbuf );
+
+/** Retrieve the number of elements available in the ring buffer for writing.
+
+ @param rbuf The ring buffer.
+
+ @return The number of elements available for writing.
+*/
+ring_buffer_size_t PaUtil_GetRingBufferWriteAvailable( const PaUtilRingBuffer *rbuf );
+
+/** Retrieve the number of elements available in the ring buffer for reading.
+
+ @param rbuf The ring buffer.
+
+ @return The number of elements available for reading.
+*/
+ring_buffer_size_t PaUtil_GetRingBufferReadAvailable( const PaUtilRingBuffer *rbuf );
+
+/** Write data to the ring buffer.
+
+ @param rbuf The ring buffer.
+
+ @param data The address of new data to write to the buffer.
+
+ @param elementCount The number of elements to be written.
+
+ @return The number of elements written.
+*/
+ring_buffer_size_t PaUtil_WriteRingBuffer( PaUtilRingBuffer *rbuf, const void *data, ring_buffer_size_t elementCount );
+
+/** Read data from the ring buffer.
+
+ @param rbuf The ring buffer.
+
+ @param data The address where the data should be stored.
+
+ @param elementCount The number of elements to be read.
+
+ @return The number of elements read.
+*/
+ring_buffer_size_t PaUtil_ReadRingBuffer( PaUtilRingBuffer *rbuf, void *data, ring_buffer_size_t elementCount );
+
+/** Get address of region(s) to which we can write data.
+
+ @param rbuf The ring buffer.
+
+ @param elementCount The number of elements desired.
+
+ @param dataPtr1 The address where the first (or only) region pointer will be
+ stored.
+
+ @param sizePtr1 The address where the first (or only) region length will be
+ stored.
+
+ @param dataPtr2 The address where the second region pointer will be stored if
+ the first region is too small to satisfy elementCount.
+
+ @param sizePtr2 The address where the second region length will be stored if
+ the first region is too small to satisfy elementCount.
+
+ @return The room available to be written or elementCount, whichever is smaller.
+*/
+ring_buffer_size_t PaUtil_GetRingBufferWriteRegions( PaUtilRingBuffer *rbuf, ring_buffer_size_t elementCount,
+                                       void **dataPtr1, ring_buffer_size_t *sizePtr1,
+                                       void **dataPtr2, ring_buffer_size_t *sizePtr2 );
+
+/** Advance the write index to the next location to be written.
+
+ @param rbuf The ring buffer.
+
+ @param elementCount The number of elements to advance.
+
+ @return The new position.
+*/
+ring_buffer_size_t PaUtil_AdvanceRingBufferWriteIndex( PaUtilRingBuffer *rbuf, ring_buffer_size_t elementCount );
+
+/** Get address of region(s) from which we can read data.
+
+ @param rbuf The ring buffer.
+
+ @param elementCount The number of elements desired.
+
+ @param dataPtr1 The address where the first (or only) region pointer will be
+ stored.
+
+ @param sizePtr1 The address where the first (or only) region length will be
+ stored.
+
+ @param dataPtr2 The address where the second region pointer will be stored if
+ the first region is too small to satisfy elementCount.
+
+ @param sizePtr2 The address where the second region length will be stored if
+ the first region is too small to satisfy elementCount.
+
+ @return The number of elements available for reading.
+*/
+ring_buffer_size_t PaUtil_GetRingBufferReadRegions( PaUtilRingBuffer *rbuf, ring_buffer_size_t elementCount,
+                                      void **dataPtr1, ring_buffer_size_t *sizePtr1,
+                                      void **dataPtr2, ring_buffer_size_t *sizePtr2 );
+
+/** Advance the read index to the next location to be read.
+
+ @param rbuf The ring buffer.
+
+ @param elementCount The number of elements to advance.
+
+ @return The new position.
+*/
+ring_buffer_size_t PaUtil_AdvanceRingBufferReadIndex( PaUtilRingBuffer *rbuf, ring_buffer_size_t elementCount );
+
+#ifdef __cplusplus
+}
+#endif /* __cplusplus */
+#endif /* PA_RINGBUFFER_H */