/* Philip Thrasher's Crazy Awesome Ring Buffer Macros!
 *
 * Below you will find some naughty macros for easy owning and manipulating
 * generic ring buffers. Yes, they are slightly evil in readability, but they
 * are really fast, and they work great.
 *
 * Example usage:
 *
 * #include <stdio.h>
 *
 * // So we can use this in any method, this gives us a typedef
 * // named 'intBuffer'.
 * ringBuffer_typedef(int, intBuffer);
 *
 * int main() {
 *   // Declare vars.
 *   intBuffer myBuffer;
 *
 *   bufferInit(myBuffer,1024,int);
 *
 *   // We must have the pointer. All of the macros deal with the pointer.
 *   // (except for init.)
 *   intBuffer* myBuffer_ptr;
 *   myBuffer_ptr = &myBuffer;
 *
 *   // Write two values.
 *   bufferWrite(myBuffer_ptr,37);
 *   bufferWrite(myBuffer_ptr,72);
 *
 *   // Read a value into a local variable.
 *   int first;
 *   bufferRead(myBuffer_ptr,first);
 *   assert(first == 37); // true
 *
 *   int second;
 *   bufferRead(myBuffer_ptr,second);
 *   assert(second == 72); // true
 *
 *   return 0;
 * }
 *
 */


#ifndef _ringbuffer_h
#define _ringbuffer_h

int __mod(int a, int b)
{
    int r = a % b;
    return r < 0 ? r + b : r;
}

#define ringBuffer_typedef(T, NAME) \
  typedef struct { \
    int size; \
    int start; \
    int end; \
    T* elems; \
  } NAME

#define bufferInit(BUF, S, T) \
  BUF.size = S+1; \
  BUF.start = 0; \
  BUF.end = 0; \
  BUF.elems = (T*)calloc(BUF.size, sizeof(T))


#define bufferDestroy(BUF) free(BUF->elems)
#define nextStartIndex(BUF) ((BUF->start + 1) % BUF->size)
#define nextEndIndex(BUF) ((BUF->end + 1) % BUF->size)
#define isBufferEmpty(BUF) (BUF->end == BUF->start)
#define isBufferFull(BUF) (nextEndIndex(BUF) == BUF->start)
#define bufferGet(BUF, INDEX) (BUF->elems[__mod(BUF->end - INDEX, BUF->size)])

#define bufferWrite(BUF, ELEM) \
  BUF->elems[BUF->end] = ELEM; \
  BUF->end = (BUF->end + 1) % BUF->size; \
  if (isBufferEmpty(BUF)) { \
    BUF->start = nextStartIndex(BUF); \
  }

#define bufferRead(BUF, ELEM) \
    ELEM = BUF->elems[BUF->start]; \
    BUF->start = nextStartIndex(BUF);

#endif