#ifndef UC_RINGBUG_H_
#define UC_RINGBUG_H_
#include <stdint.h>
#ifdef __cplusplus
extern "C" {
#endif

typedef struct UCRingBuf UCRingBuf;
struct UCRingBuf {
    char *base;
    uint32_t sz;
    uint32_t read_idx;
    uint32_t write_idx;
};

/**
 * Creates a new ringbuffer of at least @sz length.
 * The length will be rounded up to the neares page size
 *
 * The ringbuffer is implementd by mapping the same physical memory
 * twice into virtual memory adjacent to eachother, avoiding
 * a splitting up read/writes when the ringbuffer wraps around.
 *
 * This means accessing rb.base[rb.len] up to rb.base[rb.len * 2 - 1]
 * is accessing the same memory as rb.base[0] up to rb.base[rb.len -1]
 *
 * @param rb UCRingBuf to initialize
 * @param sz minimum length of the ring buffer
 * @returns 0 on success
 */
int uc_ringbuf_init(UCRingBuf *rb, uint32_t sz);

/** Free resources used by the ring buffer.
 *
 * @return 0 on success
 */
int uc_ringbuf_destroy(UCRingBuf *rb);

/**
 * Write data to the ringbuffer. The number of bytes to write must fit
 * in the free space of the ringbuffer
 *
 * @param rb UCRingBuf to write to.
 * @param data data to write
 * @param sz number of bytes to write from data
 * @return 0 on success
 */
int uc_ringbuf_write(UCRingBuf *rb, const void *restrict data, uint32_t sz);

/** Read data from the ringbuffer
 *
 * @param rb UCRingBuf to write to.
 * @param data buffer to copy data into
 * @param sz number of bytes to read, must not exceed available data
 *            in the buffer
 * @return 0 on success
 */
int uc_ringbuf_read(UCRingBuf *rb, void *restrict data, uint32_t sz);


/** Inspect how much free space is available for writing to the ring buffer
 *
 * @param rb UCRingBuf to inspect
 * @returns number of free bytes
 */
uint32_t uc_ringbuf_available(const UCRingBuf *rb);

/**
 * Length of available data in the ringbuffer
 *
 * @param rb UCRingBuf get length of
 *
 * @return length of data available to read
 */
static inline uint32_t uc_ringbuf_len(const UCRingBuf *rb)
{
    return rb->write_idx - rb->read_idx;
}

/**
 *  Get a pointer to the first unread byte
 *  Caller is responsible for reading no more than the available
 *  data
 *
 * @param rb UCRingBuf to peek into
 *
 * @returns pointer to first unread byte
*/
static inline void *uc_ringbuf_peek(const UCRingBuf *rb)
{
    return &rb->base[rb->read_idx];
}

#ifdef __cplusplus
}
#endif

#endif