avr/ring.h

   1 #ifndef RING_H
   2 #define RING_H
   3
   4 struct ring {
   5         uint8_t *data;
   6         uint_fast8_t mask;
   7         volatile uint_fast8_t begin;
   8         volatile uint_fast8_t end;
   9 };
  10
  11
  12 static inline
  13 void ring_init(struct ring *ring, uint8_t *buf, int size)
  14 {
  15         ring->data = buf;
  16         ring->mask = (size-1) & 0xff;
  17         ring->begin = 0;
  18         ring->end = 0;
  19 }
  20
  21 static inline
  22 int ring_write_ch(struct ring *ring, uint8_t ch)
  23 {
  24         uint_fast8_t ep = ring->end;
  25
  26         ring->data[ep] = ch;
  27         ep = (ep + 1) & ring->mask;
  28
  29         if ((ep) != ring->begin) {
  30                 ring->end = ep;
  31                 return 1;
  32         }
  33
  34         return -1;
  35 }
  36
  37 #if 0
  38 static inline
  39 int ring_write(struct ring *ring, uint8_t *data, int size)
  40 {
  41         int i;
  42
  43         for (i = 0; i < size; i++) {
  44                 if (ring_write_ch(ring, data[i]) < 0)
  45                         return -i;
  46         }
  47
  48         return i;
  49 }
  50 #endif
  51
  52 static inline
  53 int ring_read_ch(struct ring *ring)
  54 {
  55         int ret = -1;
  56         uint_fast8_t bp = ring->begin;
  57
  58         if (bp != ring->end) {
  59                 ret = ring->data[bp];
  60                 ring->begin = (bp + 1) & ring->mask;
  61         }
  62
  63         return ret;
  64 }
  65
  66
  67 static inline
  68 int_fast8_t ring_is_empty(struct ring *ring)
  69 {
  70         return ring->begin == ring->end;
  71 }
  72
  73 #endif /* RING_H */
  74