/* * $Id: ringbuffer.c 90 2002-01-22 00:51:49Z phil $ * ringbuffer.c * Ring Buffer utility.. * * Author: Phil Burk, http://www.softsynth.com * modified for SMP safety on Mac OS X by Bjorn Roche * also, alowed for const where possible * 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.audiomulch.com/portaudio/ * 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. * * 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. * * 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. * */#include <stdio.h>#include <stdlib.h>#include <math.h>#include "ringbuffer.h"#include <string.h>/* * We can undefine this, to turn off memory barriers, but that * is only useful if we know we don't need to be MP safe or * we are interested in doing some kind of tests. */#define MPSAFE/**************** * First, we'll define some memory barrier primitives based on the system. * right now only OS X and FreeBSD are supported. In addition to providing * memory barriers, these functions should ensure that data cached in registers * is written out to cache where it can be snooped by other CPUs. (ie, the volatile * keyword should not be required) * * the primitives that must be defined are: * * FullMemoryBarrier() * ReadMemoryBarrier() * WriteMemoryBarrier() * ****************/#if defined(__APPLE__) || defined(__FreeBSD__)#   include <libkern/OSAtomic.h>    /* Here are the memory barrier functions. Mac OS X and FreeBSD only provide       full memory barriers, so the three types of barriers are the same.       The asm volatile may be redundant with the memory barrier, but       until I have proof of that, I'm leaving it. */#   define FullMemoryBarrier()  do{ asm volatile("":::"memory"); OSMemoryBarrier(); }while(false)#   define ReadMemoryBarrier()  do{ asm volatile("":::"memory"); OSMemoryBarrier(); }while(false)#   define WriteMemoryBarrier() do{ asm volatile("":::"memory"); OSMemoryBarrier(); }while(false)#else#   error Memory Barriers not defined on this system or system unknown#endif/*************************************************************************** * Initialize FIFO. * numBytes must be power of 2, returns -1 if not. */long RingBuffer_Init( RingBuffer *rbuf, long numBytes, void *dataPtr ){    if( ((numBytes-1) & numBytes) != 0) return -1; /* Not Power of two. */    rbuf->bufferSize = numBytes;    rbuf->buffer = (char *)dataPtr;    RingBuffer_Flush( rbuf );    rbuf->bigMask = (numBytes*2)-1;    rbuf->smallMask = (numBytes)-1;    return 0;}/***************************************************************************** Return number of bytes available for reading. */long RingBuffer_GetReadAvailable( RingBuffer *rbuf ){#ifdef MPSAFE    ReadMemoryBarrier();#endif    return ( (rbuf->writeIndex - rbuf->readIndex) & rbuf->bigMask );}/***************************************************************************** Return number of bytes available for writing. */long RingBuffer_GetWriteAvailable( RingBuffer *rbuf ){    /* Since we are calling RingBuffer_GetReadAvailable, we don't need an aditional MB */    return ( rbuf->bufferSize - RingBuffer_GetReadAvailable(rbuf));}/***************************************************************************** Clear buffer. Should only be called when buffer is NOT being read. */void RingBuffer_Flush( RingBuffer *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 numBytes, whichever is smaller.*/long RingBuffer_GetWriteRegions( RingBuffer *rbuf, long numBytes,                                 void **dataPtr1, long *sizePtr1,                                 void **dataPtr2, long *sizePtr2 ){    long   index;    long   available = RingBuffer_GetWriteAvailable( rbuf );    if( numBytes > available ) numBytes = available;    /* Check to see if write is not contiguous. */    index = rbuf->writeIndex & rbuf->smallMask;    if( (index + numBytes) > rbuf->bufferSize )    {        /* Write data in two blocks that wrap the buffer. */        long   firstHalf = rbuf->bufferSize - index;        *dataPtr1 = &rbuf->buffer[index];        *sizePtr1 = firstHalf;        *dataPtr2 = &rbuf->buffer[0];        *sizePtr2 = numBytes - firstHalf;    }    else    {        *dataPtr1 = &rbuf->buffer[index];        *sizePtr1 = numBytes;        *dataPtr2 = NULL;        *sizePtr2 = 0;    }    return numBytes;}/****************************************************************************/long RingBuffer_AdvanceWriteIndex( RingBuffer *rbuf, long numBytes ){#ifdef MPSAFE    /* we need to ensure that previous writes are seen before we update the write index */    WriteMemoryBarrier();    return rbuf->writeIndex = (rbuf->writeIndex + numBytes) & rbuf->bigMask;#else    return rbuf->writeIndex = (rbuf->writeIndex + numBytes) & rbuf->bigMask;#endif}/***************************************************************************** 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 written or numBytes, whichever is smaller.*/long RingBuffer_GetReadRegions( RingBuffer *rbuf, long numBytes,                                void **dataPtr1, long *sizePtr1,                                void **dataPtr2, long *sizePtr2 ){    long   index;    long   available = RingBuffer_GetReadAvailable( rbuf );    if( numBytes > available ) numBytes = available;    /* Check to see if read is not contiguous. */    index = rbuf->readIndex & rbuf->smallMask;    if( (index + numBytes) > rbuf->bufferSize )    {        /* Write data in two blocks that wrap the buffer. */        long firstHalf = rbuf->bufferSize - index;        *dataPtr1 = &rbuf->buffer[index];        *sizePtr1 = firstHalf;        *dataPtr2 = &rbuf->buffer[0];        *sizePtr2 = numBytes - firstHalf;    }    else    {        *dataPtr1 = &rbuf->buffer[index];        *sizePtr1 = numBytes;        *dataPtr2 = NULL;        *sizePtr2 = 0;    }    return numBytes;}/****************************************************************************/long RingBuffer_AdvanceReadIndex( RingBuffer *rbuf, long numBytes ){#ifdef MPSAFE    /* we need to ensure that previous writes are always seen before updating the index. */    WriteMemoryBarrier();    return rbuf->readIndex = (rbuf->readIndex + numBytes) & rbuf->bigMask;#else    return rbuf->readIndex = (rbuf->readIndex + numBytes) & rbuf->bigMask;#endif}/***************************************************************************** Return bytes written. */long RingBuffer_Write( RingBuffer *rbuf, const void *data, long numBytes ){    long size1, size2, numWritten;    void *data1, *data2;    numWritten = RingBuffer_GetWriteRegions( rbuf, numBytes, &data1, &size1, &data2, &size2 );    if( size2 > 0 )    {        memcpy( data1, data, size1 );        data = ((char *)data) + size1;        memcpy( data2, data, size2 );    }    else    {        memcpy( data1, data, size1 );    }    RingBuffer_AdvanceWriteIndex( rbuf, numWritten );    return numWritten;}/***************************************************************************** Return bytes read. */long RingBuffer_Read( RingBuffer *rbuf, void *data, long numBytes ){    long size1, size2, numRead;    void *data1, *data2;    numRead = RingBuffer_GetReadRegions( rbuf, numBytes, &data1, &size1, &data2, &size2 );    if( size2 > 0 )    {        memcpy( data, data1, size1 );        data = ((char *)data) + size1;        memcpy( data, data2, size2 );    }    else    {        memcpy( data, data1, size1 );    }    RingBuffer_AdvanceReadIndex( rbuf, numRead );    return numRead;}