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#include "../include/al/ring_buffer.h"
#include "../include/al/atomic.h"
#include "../include/al/macros.h"
// https://github.com/MusicPlayerDaemon/MPD/blob/master/src/util/RingBuffer.hxx
// This is no longer an implementation of a "contiguous" ring buffer but I used this as reference.
// Wrapping is handled in read() and write().
// https://andrea.lattuada.me/blog/2019/the-design-and-implementation-of-a-lock-free-ring-buffer-with-contiguous-reservations.html
void al_ring_buffer_init(struct al_ring_buffer *buf, u8 *data, ptrdiff_t length)
{
buf->start = data;
buf->end = data + length;
al_ring_buffer_reset(buf);
}
static inline u8 *previous(struct al_ring_buffer *buf, u8 *ptr)
{
if (ptr == buf->start) ptr = buf->end;
return --ptr;
}
static inline void add(struct al_ring_buffer *buf, u8 **v, u8 *ptr, ptrdiff_t n)
{
ptr += n;
al_assert(ptr <= buf->end);
if (ptr == buf->end) ptr = buf->start;
atomic_store(void)(v, ptr, AL_ATOMIC_RELEASE);
}
ptrdiff_t al_ring_buffer_space(struct al_ring_buffer *buf)
{
u8 *wp = (u8 *)atomic_load(void)(&buf->write, AL_ATOMIC_RELAXED);
u8 *rp = previous(buf, (u8 *)atomic_load(void)(&buf->read, AL_ATOMIC_RELAXED));
return (wp <= rp) ? rp - wp : (buf->end - wp) + (rp - buf->start);
}
u8 *al_ring_buffer_write_chunk(struct al_ring_buffer *buf, ptrdiff_t *size)
{
u8 *wp = (u8 *)atomic_load(void)(&buf->write, AL_ATOMIC_ACQUIRE);
u8 *rp = previous(buf, (u8 *)atomic_load(void)(&buf->read, AL_ATOMIC_RELAXED));
*size = ((wp <= rp) ? rp : buf->end) - wp;
return wp;
}
void al_ring_buffer_append(struct al_ring_buffer *buf, u8 *ptr, ptrdiff_t n)
{
add(buf, &buf->write, ptr, n);
}
ptrdiff_t al_ring_buffer_occupied(struct al_ring_buffer *buf)
{
u8 *rp = (u8 *)atomic_load(void)(&buf->read, AL_ATOMIC_RELAXED);
u8 *wp = (u8 *)atomic_load(void)(&buf->write, AL_ATOMIC_RELAXED);
return (rp <= wp) ? wp - rp : (buf->end - rp) + (wp - buf->start);
}
u8 *al_ring_buffer_read_chunk(struct al_ring_buffer *buf, ptrdiff_t *size)
{
u8 *rp = (u8 *)atomic_load(void)(&buf->read, AL_ATOMIC_ACQUIRE);
u8 *wp = (u8 *)atomic_load(void)(&buf->write, AL_ATOMIC_RELAXED);
*size = ((rp <= wp) ? wp : buf->end) - rp;
return rp;
}
void al_ring_buffer_consume(struct al_ring_buffer *buf, u8 *ptr, ptrdiff_t n)
{
add(buf, &buf->read, ptr, n);
}
ptrdiff_t al_ring_buffer_write(struct al_ring_buffer *buf, u8 *data, ptrdiff_t n)
{
u8 *wp = (u8 *)atomic_load(void)(&buf->write, AL_ATOMIC_ACQUIRE);
u8 *rp = previous(buf, (u8 *)atomic_load(void)(&buf->read, AL_ATOMIC_RELAXED));
ptrdiff_t size = MIN(((wp <= rp) ? rp : buf->end) - wp, n);
al_memcpy(wp, data, (size_t)size);
wp += size;
if (wp >= buf->end) {
ptrdiff_t wrap = MIN(rp - buf->start, n - size);
al_memcpy(buf->start, data + size, (size_t)wrap);
wp = buf->start + wrap;
size += wrap;
}
atomic_store(void)(&buf->write, wp, AL_ATOMIC_RELEASE);
return size;
}
ptrdiff_t al_ring_buffer_read(struct al_ring_buffer *buf, u8 *ptr, ptrdiff_t n)
{
u8 *rp = (u8 *)atomic_load(void)(&buf->read, AL_ATOMIC_ACQUIRE);
u8 *wp = (u8 *)atomic_load(void)(&buf->write, AL_ATOMIC_RELAXED);
ptrdiff_t size = MIN(((rp <= wp) ? wp : buf->end) - rp, n);
al_memcpy(ptr, rp, (size_t)size);
rp += size;
if (rp >= buf->end) {
ptrdiff_t wrap = MIN(wp - buf->start, n - size);
al_memcpy(ptr + size, buf->start, (size_t)wrap);
rp = buf->start + wrap;
size += wrap;
}
atomic_store(void)(&buf->read, rp, AL_ATOMIC_RELEASE);
return size;
}
ptrdiff_t al_ring_buffer_peek(struct al_ring_buffer *buf, u8 *ptr, ptrdiff_t offset, ptrdiff_t n)
{
u8 *rp = (u8 *)atomic_load(void)(&buf->read, AL_ATOMIC_RELAXED);
u8 *wp = (u8 *)atomic_load(void)(&buf->write, AL_ATOMIC_RELAXED);
ptrdiff_t size;
if (rp <= wp) {
rp += offset;
size = MIN(wp - rp, n);
if (size < 0) return 0;
al_memcpy(ptr, rp, (size_t)size);
} else {
rp += offset;
size = MIN(buf->end - rp, n);
if (size > 0) {
al_memcpy(ptr, rp, (size_t)size);
n -= size;
rp = buf->start;
} else {
rp = buf->start - size;
size = 0;
}
ptrdiff_t wrap = MIN(wp - rp, n);
if (wrap > 0) {
al_memcpy(ptr + size, rp, (size_t)wrap);
size += wrap;
}
}
return size;
}
ptrdiff_t al_ring_buffer_discard(struct al_ring_buffer *buf, ptrdiff_t n)
{
u8 *rp = (u8 *)atomic_load(void)(&buf->read, AL_ATOMIC_ACQUIRE);
u8 *wp = (u8 *)atomic_load(void)(&buf->write, AL_ATOMIC_RELAXED);
ptrdiff_t discard = MIN(((rp <= wp) ? wp : buf->end) - rp, n);
rp += discard;
if (rp >= buf->end) {
ptrdiff_t wrap = MIN(wp - buf->start, n - discard);
rp = buf->start + wrap;
discard += wrap;
}
atomic_store(void)(&buf->read, rp, AL_ATOMIC_RELEASE);
return discard;
}
// Not thread-safe.
void al_ring_buffer_reset(struct al_ring_buffer *buf)
{
atomic_store(void)(&buf->read, buf->start, AL_ATOMIC_RELAXED);
atomic_store(void)(&buf->write, buf->start, AL_ATOMIC_RELAXED);
}
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