#ifndef RINGBUFFER_H
#define RINGBUFFER_H

#include <stddef.h>

#include <atomic>
#include <memory>
#include <utility>

#include "almalloc.h"


/* NOTE: This lockless ringbuffer implementation is copied from JACK, extended
 * to include an element size. Consequently, parameters and return values for a
 * size or count is in 'elements', not bytes. Additionally, it only supports
 * single-consumer/single-provider operation.
 */
struct ll_ringbuffer {
    std::atomic<size_t> write_ptr{0u};
    std::atomic<size_t> read_ptr{0u};
    size_t size{0u};
    size_t size_mask{0u};
    size_t elem_size{0u};

    alignas(16) char buf[];

    DEF_PLACE_NEWDEL()
};


struct ll_ringbuffer_data {
    char *buf;
    size_t len;
};
using ll_ringbuffer_data_pair = std::pair<ll_ringbuffer_data,ll_ringbuffer_data>;


/**
 * Create a new ringbuffer to hold at least `sz' elements of `elem_sz' bytes.
 * The number of elements is rounded up to the next power of two (even if it is
 * already a power of two, to ensure the requested amount can be written).
 */
ll_ringbuffer *ll_ringbuffer_create(size_t sz, size_t elem_sz, int limit_writes);
/** Reset the read and write pointers to zero. This is not thread safe. */
void ll_ringbuffer_reset(ll_ringbuffer *rb);

/**
 * The non-copying data reader. Returns two ringbuffer data pointers that hold
 * the current readable data at `rb'. If the readable data is in one segment
 * the second segment has zero length.
 */
ll_ringbuffer_data_pair ll_ringbuffer_get_read_vector(const ll_ringbuffer *rb);
/**
 * The non-copying data writer. Returns two ringbuffer data pointers that hold
 * the current writeable data at `rb'. If the writeable data is in one segment
 * the second segment has zero length.
 */
ll_ringbuffer_data_pair ll_ringbuffer_get_write_vector(const ll_ringbuffer *rb);

/**
 * Return the number of elements available for reading. This is the number of
 * elements in front of the read pointer and behind the write pointer.
 */
size_t ll_ringbuffer_read_space(const ll_ringbuffer *rb);
/**
 * The copying data reader. Copy at most `cnt' elements from `rb' to `dest'.
 * Returns the actual number of elements copied.
 */
size_t ll_ringbuffer_read(ll_ringbuffer *rb, void *dest, size_t cnt);
/**
 * The copying data reader w/o read pointer advance. Copy at most `cnt'
 * elements from `rb' to `dest'. Returns the actual number of elements copied.
 */
size_t ll_ringbuffer_peek(ll_ringbuffer *rb, void *dest, size_t cnt);
/** Advance the read pointer `cnt' places. */
void ll_ringbuffer_read_advance(ll_ringbuffer *rb, size_t cnt);

/**
 * Return the number of elements available for writing. This is the number of
 * elements in front of the write pointer and behind the read pointer.
 */
size_t ll_ringbuffer_write_space(const ll_ringbuffer *rb);
/**
 * The copying data writer. Copy at most `cnt' elements to `rb' from `src'.
 * Returns the actual number of elements copied.
 */
size_t ll_ringbuffer_write(ll_ringbuffer *rb, const void *src, size_t cnt);
/** Advance the write pointer `cnt' places. */
void ll_ringbuffer_write_advance(ll_ringbuffer *rb, size_t cnt);


using RingBufferPtr = std::unique_ptr<ll_ringbuffer>;

#endif /* RINGBUFFER_H */