ringbuffer.h

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/* Simple Plugin API */
/* SPDX-FileCopyrightText: Copyright © 2018 Wim Taymans */
/* SPDX-License-Identifier: MIT */
 
#ifndef SPA_RINGBUFFER_H
#define SPA_RINGBUFFER_H
 
#ifdef __cplusplus
extern "C" {
#endif


 
struct spa_ringbuffer;
 
#include <string.h>
 
#include <spa/utils/defs.h>
 
#ifndef SPA_API_RINGBUFFER
 #ifdef SPA_API_IMPL
  #define SPA_API_RINGBUFFER SPA_API_IMPL
 #else
  #define SPA_API_RINGBUFFER static inline
 #endif
#endif

struct spa_ringbuffer {
        uint32_t readindex;    /*< the current read index */
        uint32_t writeindex;  /*< the current write index */
};
 
#define SPA_RINGBUFFER_INIT()   ((struct spa_ringbuffer) { 0, 0 })

 * Initialize a spa_ringbuffer with \a size.
 *
 * \param rbuf a spa_ringbuffer
 */
SPA_API_RINGBUFFER void spa_ringbuffer_init(struct spa_ringbuffer *rbuf)
{
        *rbuf = SPA_RINGBUFFER_INIT();
}

 * \param size the target size of \a rbuf
 */
SPA_API_RINGBUFFER void spa_ringbuffer_set_avail(struct spa_ringbuffer *rbuf, uint32_t size)
{
        rbuf->readindex = 0;
        rbuf->writeindex = size;
}

 * \param rbuf a  spa_ringbuffer
 * \param index the value of readindex, should be taken modulo the size of the
 *         ringbuffer memory to get the offset in the ringbuffer memory
 * \return number of available bytes to read. values < 0 mean
 *         there was an underrun. values > rbuf->size means there
 *         was an overrun.
 */
SPA_API_RINGBUFFER int32_t spa_ringbuffer_get_read_index(struct spa_ringbuffer *rbuf, uint32_t *index)
{
        *index = __atomic_load_n(&rbuf->readindex, __ATOMIC_RELAXED);
        return (int32_t) (__atomic_load_n(&rbuf->writeindex, __ATOMIC_ACQUIRE) - *index);
}

 *
 * \param rbuf a struct \ref spa_ringbuffer
 * \param buffer memory to read from
 * \param size the size of \a buffer
 * \param offset offset in \a buffer to read from
 * \param data destination memory
 * \param len number of bytes to read
 */
SPA_API_RINGBUFFER void
spa_ringbuffer_read_data(struct spa_ringbuffer *rbuf SPA_UNUSED,
                         const void *buffer, uint32_t size,
                         uint32_t offset, void *data, uint32_t len)
{
        uint32_t l0 = SPA_MIN(len, size - offset), l1 = len - l0;
        spa_memcpy(data, SPA_PTROFF(buffer, offset, void), l0);
        if (SPA_UNLIKELY(l1 > 0))
                spa_memcpy(SPA_PTROFF(data, l0, void), buffer, l1);
}

SPA_API_RINGBUFFER void spa_ringbuffer_read_update(struct spa_ringbuffer *rbuf, int32_t index)
{
        __atomic_store_n(&rbuf->readindex, index, __ATOMIC_RELEASE);
}

 * \param index the value of writeindex, should be taken modulo the size of the
 *         ringbuffer memory to get the offset in the ringbuffer memory
 * \return the fill level of \a 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.
 */
SPA_API_RINGBUFFER int32_t spa_ringbuffer_get_write_index(struct spa_ringbuffer *rbuf, uint32_t *index)
{
        *index = __atomic_load_n(&rbuf->writeindex, __ATOMIC_RELAXED);
        return (int32_t) (*index - __atomic_load_n(&rbuf->readindex, __ATOMIC_ACQUIRE));
}

 *
 * \param rbuf a spa_ringbuffer
 * \param buffer memory to write to
 * \param size the size of \a buffer
 * \param offset offset in \a buffer to write to
 * \param data source memory
 * \param len number of bytes to write
 */
SPA_API_RINGBUFFER void
spa_ringbuffer_write_data(struct spa_ringbuffer *rbuf SPA_UNUSED,
                          void *buffer, uint32_t size,
                          uint32_t offset, const void *data, uint32_t len)
{
        uint32_t l0 = SPA_MIN(len, size - offset), l1 = len - l0;
        spa_memcpy(SPA_PTROFF(buffer, offset, void), data, l0);
        if (SPA_UNLIKELY(l1 > 0))
                spa_memcpy(buffer, SPA_PTROFF(data, l0, void), l1);
}

SPA_API_RINGBUFFER 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 */