winamp/Src/replicant/nu/LockFreeRingBuffer.cpp

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2024-09-24 12:54:57 +00:00
/*
* LockFreeRingBuffer.cpp
* Lock-free ring buffer data structure.
* One thread can be consumer and one can be producer
*
* Created by Ben Allison on 11/10/07.
* Copyright 2007 Nullsoft, Inc. All rights reserved.
*
*/
#include "LockFreeRingBuffer.h"
#include "foundation/types.h"
#include "foundation/atomics.h"
#include "foundation/error.h"
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#define MIN(a,b) ((a<b)?(a):(b))
LockFreeRingBuffer::LockFreeRingBuffer()
{
ringBuffer=0;
ringBufferSize=0;
ringBufferUsed=0;
ringWritePosition=0;
ringReadPosition=0;
}
LockFreeRingBuffer::~LockFreeRingBuffer()
{
free(ringBuffer);
ringBuffer=0;
}
void LockFreeRingBuffer::Reset()
{
free(ringBuffer);
ringBuffer=0;
}
bool LockFreeRingBuffer::reserve(size_t bytes)
{
void *new_ring_buffer = realloc(ringBuffer, bytes);
if (!new_ring_buffer)
return false;
ringBufferSize=bytes;
ringBuffer = (char *)new_ring_buffer;
clear();
return true;
}
int LockFreeRingBuffer::expand(size_t bytes)
{
if (bytes > ringBufferSize)
{
char *new_buffer = (char *)realloc(ringBuffer, bytes);
if (!new_buffer)
return NErr_OutOfMemory;
size_t write_offset = ringReadPosition-ringBuffer;
size_t read_offset = ringWritePosition-ringBuffer;
/* update write pointer for the new buffer */
ringWritePosition = new_buffer + write_offset;
if (write_offset > read_offset || !ringBufferUsed) /* ringBufferUsed will resolve the ambiguity when ringWritePosition == ringReadPosition */
{
/* the ring buffer looks like [ RXXXW ], so we don't need to move anything.
Just update the read pointer */
ringReadPosition = new_buffer + write_offset;
}
else
{
/* [XXW RXX] needs to become [XXW RXX] */
size_t end_bytes = ringBufferSize-write_offset; // number of bytes that we need to relocate (the RXX portion)
char *new_read_pointer = &new_buffer[bytes - end_bytes];
memmove(new_read_pointer, ringReadPosition, end_bytes);
ringReadPosition = new_read_pointer; /* update read pointer */
}
ringBufferSize=bytes;
ringBuffer = new_buffer;
#if defined(__ARM_ARCH_7A__)
__asm__ __volatile__ ("dmb" : : : "memory");
#endif
return NErr_Success;
}
else
return NErr_NoAction;
}
bool LockFreeRingBuffer::empty() const
{
return (ringBufferUsed==0);
}
size_t LockFreeRingBuffer::read(void *dest, size_t len)
{
int8_t *out = (int8_t *)dest; // lets us do pointer math easier
size_t toCopy=ringBufferUsed;
if (toCopy > len) toCopy = len;
size_t copied=0;
len-=toCopy;
// read to the end of the ring buffer
size_t end = ringBufferSize-(ringReadPosition-ringBuffer);
size_t read1 = MIN(end, toCopy);
memcpy(out, ringReadPosition, read1);
#if defined(__ARM_ARCH_7A__)
__asm__ __volatile__ ("dmb" : : : "memory");
#endif
copied+=read1;
ringReadPosition+=read1;
if (ringReadPosition == ringBuffer + ringBufferSize)
ringReadPosition=ringBuffer;
// update positions
nx_atomic_sub(read1, &ringBufferUsed);
toCopy-=read1;
out = (int8_t *)out+read1;
// see if we still have more to read after wrapping around
if (toCopy)
{
memcpy(out, ringReadPosition, toCopy);
#if defined(__ARM_ARCH_7A__)
__asm__ __volatile__ ("dmb" : : : "memory");
#endif
copied+=toCopy;
ringReadPosition+=toCopy;
nx_atomic_sub(toCopy, &ringBufferUsed);
if (ringReadPosition == ringBuffer + ringBufferSize)
ringReadPosition=ringBuffer;
}
return copied;
}
size_t LockFreeRingBuffer::advance_to(size_t position)
{
intptr_t bytes_to_flush = (intptr_t)(position - (size_t)ringReadPosition);
if (bytes_to_flush < 0)
bytes_to_flush += ringBufferSize;
return advance(bytes_to_flush);
}
size_t LockFreeRingBuffer::at(size_t offset, void *dest, size_t len) const
{
size_t toCopy=ringBufferUsed;
// make a local copy of this so we don't blow the original
char *ringReadPosition = this->ringReadPosition;
/* --- do a "dummy read" to deal with the offset request --- */
size_t dummy_end = ringBufferSize-(ringReadPosition-ringBuffer);
offset = MIN(toCopy, offset);
size_t read0 = MIN(dummy_end, offset);
ringReadPosition+=read0;
if (ringReadPosition == ringBuffer + ringBufferSize)
ringReadPosition=ringBuffer;
// update positions
toCopy-=read0;
offset-=read0;
// do second-half read (wraparound)
if (offset)
{
ringReadPosition+=offset;
toCopy-=offset;
}
// dummy read done
/* --- set up destination buffer and copy size --- */
int8_t *out = (int8_t *)dest; // lets us do pointer math easier
if (toCopy > len) toCopy=len;
size_t copied=0;
/* --- read to the end of the ring buffer --- */
size_t end = ringBufferSize-(ringReadPosition-ringBuffer);
size_t read1 = MIN(end, toCopy);
memcpy(out, ringReadPosition, read1);
copied+=read1;
ringReadPosition+=read1;
if (ringReadPosition == ringBuffer + ringBufferSize)
ringReadPosition=ringBuffer;
// update positions
toCopy-=read1;
out = (int8_t *)out+read1;
/* --- see if we still have more to read after wrapping around --- */
if (toCopy)
{
memcpy(out, ringReadPosition, toCopy);
copied+=toCopy;
ringReadPosition+=toCopy;
}
return copied;
}
size_t LockFreeRingBuffer::peek(void *dest, size_t len) const
{
int8_t *out = (int8_t *)dest; // lets us do pointer math easier
size_t toCopy=ringBufferUsed;
if (toCopy > len) toCopy=len;
size_t copied=0;
// make a local copy of this so we don't blow the original
char *ringReadPosition = this->ringReadPosition;
// read to the end of the ring buffer
size_t end = ringBufferSize-(ringReadPosition-ringBuffer);
size_t read1 = MIN(end, toCopy);
memcpy(out, ringReadPosition, read1);
copied+=read1;
ringReadPosition+=read1;
if (ringReadPosition == ringBuffer + ringBufferSize)
ringReadPosition=ringBuffer;
// update positions
toCopy-=read1;
out = (int8_t *)out+read1;
// see if we still have more to read after wrapping around
if (toCopy)
{
memcpy(out, ringReadPosition, toCopy);
copied+=toCopy;
ringReadPosition+=toCopy;
}
return copied;
}
size_t LockFreeRingBuffer::advance(size_t len)
{
#if defined(__ARM_ARCH_7A__)
__asm__ __volatile__ ("dmb" : : : "memory");
#endif
size_t toCopy=ringBufferUsed;
if (toCopy>len) toCopy=len;
size_t copied=0;
len-=toCopy;
// read to the end of the ring buffer
size_t end = ringBufferSize-(ringReadPosition-ringBuffer);
size_t read1 = MIN(end, toCopy);
copied+=read1;
ringReadPosition+=read1;
if (ringReadPosition == ringBuffer + ringBufferSize)
ringReadPosition=ringBuffer;
// update positions
toCopy-=read1;
nx_atomic_sub(read1, &ringBufferUsed);
// see if we still have more to read after wrapping around
if (toCopy)
{
copied+=toCopy;
ringReadPosition+=toCopy;
nx_atomic_sub(toCopy, &ringBufferUsed);
if (ringReadPosition == ringBuffer + ringBufferSize)
ringReadPosition=ringBuffer;
}
return copied;
}
size_t LockFreeRingBuffer::avail() const
{
return ringBufferSize - ringBufferUsed;
}
size_t LockFreeRingBuffer::write(const void *buffer, size_t bytes)
{
size_t used=ringBufferUsed;
size_t avail = ringBufferSize - used;
bytes = MIN(avail, bytes);
// write to the end of the ring buffer
size_t end = ringBufferSize-(ringWritePosition-ringBuffer);
size_t copied=0;
size_t write1 = MIN(end, bytes);
memcpy(ringWritePosition, buffer, write1);
#if defined(__ARM_ARCH_7A__)
__asm__ __volatile__ ("dmb" : : : "memory");
#endif
copied+=write1;
ringWritePosition+=write1;
if (ringWritePosition == ringBuffer + ringBufferSize)
ringWritePosition=ringBuffer;
// update positions
nx_atomic_add(write1, &ringBufferUsed);
bytes-=write1;
buffer = (const int8_t *)buffer+write1;
// see if we still have more to write after wrapping around
if (bytes)
{
memcpy(ringWritePosition, buffer, bytes);
#if defined(__ARM_ARCH_7A__)
__asm__ __volatile__ ("dmb" : : : "memory");
#endif
copied+=bytes;
ringWritePosition+=bytes;
nx_atomic_add(bytes, &ringBufferUsed);
if (ringWritePosition == ringBuffer + ringBufferSize)
ringWritePosition=ringBuffer;
}
return copied;
}
size_t LockFreeRingBuffer::update(size_t bytes)
{
size_t used=ringBufferUsed;
size_t avail = ringBufferSize - used;
bytes = MIN(avail, bytes);
// write to the end of the ring buffer
size_t end = ringBufferSize-(ringWritePosition-ringBuffer);
size_t copied=0;
size_t write1 = MIN(end, bytes);
#if defined(__ARM_ARCH_7A__)
__asm__ __volatile__ ("dmb" : : : "memory");
#endif
copied+=write1;
ringWritePosition+=write1;
if (ringWritePosition == ringBuffer + ringBufferSize)
ringWritePosition=ringBuffer;
// update positions
nx_atomic_add(write1, &ringBufferUsed);
bytes-=write1;
// see if we still have more to write after wrapping around
if (bytes)
{
/* no need for memory barrier here, we havn't written anything in the interim */
copied+=bytes;
ringWritePosition+=bytes;
nx_atomic_add(bytes, &ringBufferUsed);
if (ringWritePosition == ringBuffer + ringBufferSize)
ringWritePosition=ringBuffer;
}
return copied;
}
void LockFreeRingBuffer::get_write_buffer(size_t bytes, void **buffer, size_t *bytes_available)
{
size_t used=ringBufferUsed;
size_t avail = ringBufferSize - used;
bytes = MIN(avail, bytes);
// can only write to the end of the ring buffer
size_t end = ringBufferSize-(ringWritePosition-ringBuffer);
*bytes_available = MIN(end, bytes);
*buffer = ringWritePosition;
}
void LockFreeRingBuffer::get_read_buffer(size_t bytes, const void **buffer, size_t *bytes_available)
{
size_t toCopy=ringBufferUsed;
if (toCopy > bytes) toCopy=bytes;
// read to the end of the ring buffer
size_t end = ringBufferSize-(ringReadPosition-ringBuffer);
*bytes_available = MIN(end, toCopy);
*buffer = ringReadPosition;
}
size_t LockFreeRingBuffer::size() const
{
return ringBufferUsed;
}
void LockFreeRingBuffer::clear()
{
nx_atomic_write(0, &ringBufferUsed);
ringWritePosition=ringBuffer;
ringReadPosition=ringBuffer;
}
size_t LockFreeRingBuffer::write_position() const
{
return (size_t)ringWritePosition;
}
size_t LockFreeRingBuffer::read_position() const
{
return (size_t)ringReadPosition;
}