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diff --git a/src/pa_ringbuffer.c b/src/pa_ringbuffer.c
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+/*
+ * $Id$
+ * Portable Audio I/O Library
+ * Ring Buffer utility.
+ *
+ * Author: Phil Burk, http://www.softsynth.com
+ * modified for SMP safety on Mac OS X by Bjorn Roche
+ * modified for SMP safety on Linux by Leland Lucius
+ * 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 uses 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
+*/
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+#include "pa_ringbuffer.h"
+#include <string.h>
+#include "pa_memorybarrier.h"
+
+/***************************************************************************
+ * Initialize FIFO.
+ * elementCount must be power of 2, returns -1 if not.
+ */
+ring_buffer_size_t PaUtil_InitializeRingBuffer( PaUtilRingBuffer *rbuf, ring_buffer_size_t elementSizeBytes, ring_buffer_size_t elementCount, void *dataPtr )
+{
+    if( ((elementCount-1) & elementCount) != 0) return -1; /* Not Power of two. */
+    rbuf->bufferSize = elementCount;
+    rbuf->buffer = (char *)dataPtr;
+    PaUtil_FlushRingBuffer( rbuf );
+    rbuf->bigMask = (elementCount*2)-1;
+    rbuf->smallMask = (elementCount)-1;
+    rbuf->elementSizeBytes = elementSizeBytes;
+    return 0;
+}
+
+/***************************************************************************
+** Return number of elements available for reading. */
+ring_buffer_size_t PaUtil_GetRingBufferReadAvailable( const PaUtilRingBuffer *rbuf )
+{
+    return ( (rbuf->writeIndex - rbuf->readIndex) & rbuf->bigMask );
+}
+/***************************************************************************
+** Return number of elements available for writing. */
+ring_buffer_size_t PaUtil_GetRingBufferWriteAvailable( const PaUtilRingBuffer *rbuf )
+{
+    return ( rbuf->bufferSize - PaUtil_GetRingBufferReadAvailable(rbuf));
+}
+
+/***************************************************************************
+** Clear buffer. Should only be called when buffer is NOT being read or written. */
+void PaUtil_FlushRingBuffer( PaUtilRingBuffer *rbuf )
+{
+    rbuf->writeIndex = rbuf->readIndex = 0;
+}
+
+/***************************************************************************
+** Get address of region(s) to which we can write data.
+** If the region is contiguous, size2 will be zero.
+** If non-contiguous, size2 will be the size of second region.
+** Returns 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 )
+{
+    ring_buffer_size_t   index;
+    ring_buffer_size_t   available = PaUtil_GetRingBufferWriteAvailable( rbuf );
+    if( elementCount > available ) elementCount = available;
+    /* Check to see if write is not contiguous. */
+    index = rbuf->writeIndex & rbuf->smallMask;
+    if( (index + elementCount) > rbuf->bufferSize )
+    {
+        /* Write data in two blocks that wrap the buffer. */
+        ring_buffer_size_t   firstHalf = rbuf->bufferSize - index;
+        *dataPtr1 = &rbuf->buffer[index*rbuf->elementSizeBytes];
+        *sizePtr1 = firstHalf;
+        *dataPtr2 = &rbuf->buffer[0];
+        *sizePtr2 = elementCount - firstHalf;
+    }
+    else
+    {
+        *dataPtr1 = &rbuf->buffer[index*rbuf->elementSizeBytes];
+        *sizePtr1 = elementCount;
+        *dataPtr2 = NULL;
+        *sizePtr2 = 0;
+    }
+
+    if( available )
+        PaUtil_FullMemoryBarrier(); /* (write-after-read) => full barrier */
+
+    return elementCount;
+}
+
+
+/***************************************************************************
+*/
+ring_buffer_size_t PaUtil_AdvanceRingBufferWriteIndex( PaUtilRingBuffer *rbuf, ring_buffer_size_t elementCount )
+{
+    /* ensure that previous writes are seen before we update the write index
+       (write after write)
+    */
+    PaUtil_WriteMemoryBarrier();
+    return rbuf->writeIndex = (rbuf->writeIndex + elementCount) & rbuf->bigMask;
+}
+
+/***************************************************************************
+** Get address of region(s) from which we can read data.
+** If the region is contiguous, size2 will be zero.
+** If non-contiguous, size2 will be the size of second region.
+** Returns room available to be read or elementCount, whichever is smaller.
+*/
+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 )
+{
+    ring_buffer_size_t   index;
+    ring_buffer_size_t   available = PaUtil_GetRingBufferReadAvailable( rbuf ); /* doesn't use memory barrier */
+    if( elementCount > available ) elementCount = available;
+    /* Check to see if read is not contiguous. */
+    index = rbuf->readIndex & rbuf->smallMask;
+    if( (index + elementCount) > rbuf->bufferSize )
+    {
+        /* Write data in two blocks that wrap the buffer. */
+        ring_buffer_size_t firstHalf = rbuf->bufferSize - index;
+        *dataPtr1 = &rbuf->buffer[index*rbuf->elementSizeBytes];
+        *sizePtr1 = firstHalf;
+        *dataPtr2 = &rbuf->buffer[0];
+        *sizePtr2 = elementCount - firstHalf;
+    }
+    else
+    {
+        *dataPtr1 = &rbuf->buffer[index*rbuf->elementSizeBytes];
+        *sizePtr1 = elementCount;
+        *dataPtr2 = NULL;
+        *sizePtr2 = 0;
+    }
+
+    if( available )
+        PaUtil_ReadMemoryBarrier(); /* (read-after-read) => read barrier */
+
+    return elementCount;
+}
+/***************************************************************************
+*/
+ring_buffer_size_t PaUtil_AdvanceRingBufferReadIndex( PaUtilRingBuffer *rbuf, ring_buffer_size_t elementCount )
+{
+    /* ensure that previous reads (copies out of the ring buffer) are always completed before updating (writing) the read index.
+       (write-after-read) => full barrier
+    */
+    PaUtil_FullMemoryBarrier();
+    return rbuf->readIndex = (rbuf->readIndex + elementCount) & rbuf->bigMask;
+}
+
+/***************************************************************************
+** Return elements written. */
+ring_buffer_size_t PaUtil_WriteRingBuffer( PaUtilRingBuffer *rbuf, const void *data, ring_buffer_size_t elementCount )
+{
+    ring_buffer_size_t size1, size2, numWritten;
+    void *data1, *data2;
+    numWritten = PaUtil_GetRingBufferWriteRegions( rbuf, elementCount, &data1, &size1, &data2, &size2 );
+    if( size2 > 0 )
+    {
+
+        memcpy( data1, data, size1*rbuf->elementSizeBytes );
+        data = ((char *)data) + size1*rbuf->elementSizeBytes;
+        memcpy( data2, data, size2*rbuf->elementSizeBytes );
+    }
+    else
+    {
+        memcpy( data1, data, size1*rbuf->elementSizeBytes );
+    }
+    PaUtil_AdvanceRingBufferWriteIndex( rbuf, numWritten );
+    return numWritten;
+}
+
+/***************************************************************************
+** Return elements read. */
+ring_buffer_size_t PaUtil_ReadRingBuffer( PaUtilRingBuffer *rbuf, void *data, ring_buffer_size_t elementCount )
+{
+    ring_buffer_size_t size1, size2, numRead;
+    void *data1, *data2;
+    numRead = PaUtil_GetRingBufferReadRegions( rbuf, elementCount, &data1, &size1, &data2, &size2 );
+    if( size2 > 0 )
+    {
+        memcpy( data, data1, size1*rbuf->elementSizeBytes );
+        data = ((char *)data) + size1*rbuf->elementSizeBytes;
+        memcpy( data, data2, size2*rbuf->elementSizeBytes );
+    }
+    else
+    {
+        memcpy( data, data1, size1*rbuf->elementSizeBytes );
+    }
+    PaUtil_AdvanceRingBufferReadIndex( rbuf, numRead );
+    return numRead;
+}