pipewire/spa/include/spa/ringbuffer.h

/* Simple Plugin API
 * Copyright (C) 2016 Wim Taymans <wim.taymans@gmail.com>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
 * Boston, MA 02110-1301, USA.
 */

#ifndef __SPA_RINGBUFFER_H__
#define __SPA_RINGBUFFER_H__

#ifdef __cplusplus
extern "C" {
#endif

struct spa_ringbuffer;
#define SPA_TYPE__RingBuffer           SPA_TYPE_INTERFACE_BASE "RingBuffer"
#define SPA_TYPE_RINGBUFFER_BASE       SPA_TYPE__RingBuffer ":"

#include <string.h>

#include <spa/defs.h>

/**
 * spa_ringbuffer:
 * @readindex: the current read index
 * @writeindex: the current write index
 * @size: the size of the ringbuffer must be power of 2
 * @mask: mask as @size - 1
 */
struct spa_ringbuffer {
  uint32_t     readindex;
  uint32_t     writeindex;
  uint32_t     size;
  uint32_t     mask;
};

/**
 * spa_ringbuffer_init:
 * @rbuf: a #struct spa_ringbuffer
 * @data: pointer to an array
 * @size: the number of elements in @data
 *
 * Initialize a #struct spa_ringbuffer with @data and @size.
 * Size must be a power of 2.
 *
 * Returns: %SPA_RESULT_OK, unless size is not a power of 2.
 */
static inline int
spa_ringbuffer_init (struct spa_ringbuffer *rbuf,
                     uint32_t size)
{
  if (SPA_UNLIKELY ((size & (size - 1)) != 0))
    return SPA_RESULT_ERROR;

  rbuf->size = size;
  rbuf->mask = size - 1;
  rbuf->readindex = 0;
  rbuf->writeindex = 0;

  return SPA_RESULT_OK;
}

/**
 * spa_ringbuffer_clear:
 * @rbuf: a #struct spa_ringbuffer
 *
 * Clear @rbuf
 */
static inline void
spa_ringbuffer_clear (struct spa_ringbuffer *rbuf)
{
  rbuf->readindex = 0;
  rbuf->writeindex = 0;
}

/**
 * spa_ringbuffer_get_read_index:
 * @rbuf: a #struct spa_ringbuffer
 * @index: the value of readindex, should be masked to get the
 *         offset in the ringbuffer memory
 *
 * Returns: number of available bytes to read. values < 0 mean
 *          there was an underrun. values > rbuf->size means there
 *          was an overrun.
 */
static inline int32_t
spa_ringbuffer_get_read_index (struct spa_ringbuffer *rbuf,
                               uint32_t              *index)
{
  int32_t avail;

  *index = __atomic_load_n (&rbuf->readindex, __ATOMIC_RELAXED);
  avail = (int32_t) (__atomic_load_n (&rbuf->writeindex, __ATOMIC_ACQUIRE) - *index);

  return avail;
}

/**
 * spa_ringbuffer_read_data:
 * @rbuf: a #struct spa_ringbuffer
 * @buffer: memory to read from
 * @offset: offset in @buffer to read from
 * @data: destination memory
 * @len: number of bytes to read
 *
 * Read @len bytes from @rbuf starting @offset. @offset must be masked
 * with the size of @rbuf and len should be smaller than the size.
 */
static inline void
spa_ringbuffer_read_data (struct spa_ringbuffer *rbuf,
                          void                  *buffer,
                          uint32_t               offset,
                          void                  *data,
                          uint32_t               len)
{
  uint32_t first = SPA_MIN (len, rbuf->size - offset);
  memcpy (data, buffer + offset, first);
  if (SPA_UNLIKELY (len > first)) {
    memcpy (data + first, buffer, len - first);
  }
}

/**
 * spa_ringbuffer_read_update:
 * @rbuf: a #struct spa_ringbuffer
 * @index: new index
 *
 * Update the read pointer to @index
 */
static inline void
spa_ringbuffer_read_update (struct spa_ringbuffer *rbuf,
                            int32_t                index)
{
  __atomic_store_n (&rbuf->readindex, index, __ATOMIC_RELEASE);
}

/**
 * spa_ringbuffer_get_write_index:
 * @rbuf: a #struct spa_ringbuffer
 * @index: the value of writeindex, should be masked to get the
 *         offset in the ringbuffer memory
 *
 * Returns: the fill level of @rbuf. values < 0 mean
 *          there was an underrun. values > rbuf->size means there
 *          was an overrun. Subtract from the buffer size to get
 *          the number of bytes available for writing.
 */
static inline int32_t
spa_ringbuffer_get_write_index (struct spa_ringbuffer *rbuf,
                                uint32_t              *index)
{
  int32_t filled;

  *index = __atomic_load_n (&rbuf->writeindex, __ATOMIC_RELAXED);
  filled = (int32_t) (*index - __atomic_load_n (&rbuf->readindex, __ATOMIC_ACQUIRE));

  return filled;
}

static inline void
spa_ringbuffer_write_data (struct spa_ringbuffer *rbuf,
                           void                  *buffer,
                           uint32_t               offset,
                           void                  *data,
                           uint32_t               len)
{
  uint32_t first = SPA_MIN (len, rbuf->size - offset);
  memcpy (buffer + offset, data, first);
  if (SPA_UNLIKELY (len > first)) {
    memcpy (buffer, data + first, len - first);
  }
}

/**
 * spa_ringbuffer_write_update:
 * @rbuf: a #struct spa_ringbuffer
 * @index: new index
 *
 * Update the write pointer to @index
 *
 */
static inline void
spa_ringbuffer_write_update (struct spa_ringbuffer *rbuf,
                             int32_t                index)
{
  __atomic_store_n (&rbuf->writeindex, index, __ATOMIC_RELEASE);
}


#ifdef __cplusplus
}  /* extern "C" */
#endif

#endif /* __SPA_RINGBUFFER_H__ */