ringbuf/ringbuf.h

/* SPDX-License-Identifier: MIT */

#pragma once

#ifndef rb_size_t
#define rb_size_t int
#endif

/** Signatures of allocators */
typedef void *(*ALLOC_T)(rb_size_t);

/** Signature of memcpy */
typedef void *(*MEMCPY_T)(void *, const void *, rb_size_t);

/**
 * @brief Ring buffer, also known as circular buffer.
 */
struct RingBuf {
  rb_size_t struct_size; /** Size of the struct */
  rb_size_t capacity;    /** The physical capacity of the entire ringbuf */
  rb_size_t count;       /** The number of elements in the buffer */
  void     *write_head;  /** Address of the write head */
  void     *read_head;   /** Address of the read head */
  void     *buffer;      /** The actual data */
  void     *buffer_end;  /** The end of the buffer */
} __attribute__((packed));

/*
 * Considerations: One hot encoding for the enum values 
 * (8 bit each with -fshort-enums)
 */

/** Result of a write */
enum WriteResult {
  WriteOk,          /** The write was successful */
  Full,             /** The buffer is full */
  InsufficientSpace /** There is not enough space to write */
};

/** Result of a read */
enum ReadResult {
  Empty,           /** The buffer is empty */
  ReadOk,          /** The read was successful */
  InsufficientData /** There is not enough data to read */
};

/**
 * @brief Initialize the ring buffer
 * @param rb The ring buffer to initialize
 * @param capacity The capacity of the ring buffer
 * @param alloc The allocator function
 * @param struct_size The size of the struct
 * @return void
 */
void rb_init(struct RingBuf *rb, rb_size_t capacity, ALLOC_T alloc,
             rb_size_t struct_size);

/**
 * @brief Clear the ring buffer
 * @details This function will reset the read and write heads to the beginning
 * of the buffer, and set the count to 0. It will not free the buffer.
 * @param rb The ring buffer
 */
void rb_clear(struct RingBuf *rb);

/**
 * @brief Insert data to the ring buffer
 * @param rb The ring buffer
 * @param item The item to insert
 * @param memcpy_fn The memcpy function
 * @return WriteResult
 */
enum WriteResult rb_push_back(struct RingBuf *rb, const void *item,
                              MEMCPY_T memcpy_fn);

/**
 * @brief Insert multiple data to the ring buffer
 *
 * @details This function is more efficient than calling rb_push_back multiple
 * times. It only advances the write head once, and attempts to write all the
 * memory in one go.
 *
 * If n is greater than the capacity, it will return Full.
 * If the full write will overflow, it will wrap around.
 *
 * If the buffer is full, it will return Full and not write
 * anything.
 *
 * @param rb The ring buffer
 * @param items The items to insert
 * @param memcpy_fn The memcpy function
 * @param n The number of items to insert
 * @return WriteResult
 */
enum WriteResult rb_push_many(struct RingBuf *rb, const void *items,
                              MEMCPY_T memcpy_fn, rb_size_t n);

/**
 * @brief Read data from the ring buffer
 * @param rb The ring buffer
 * @param item The item to read into
 * @return ReadResult
 */
enum ReadResult rb_pop_front(struct RingBuf *rb, void *item,
                             MEMCPY_T memcpy_fn);

/**
 * @brief Free the ring buffer
 * @param rb The ring buffer
 * @param free The free function
 */
void rb_destroy(struct RingBuf *rb, void(free)());