include/ring.h

   1 /*
   2  * (C) Copyright 2014 Leo C. <erbl259-lmu@yahoo.de>
   3  *
   4  * SPDX-License-Identifier:     GPL-2.0+
   5  */
   6
   7 #ifndef RING_H
   8 #define RING_H
   9
  10 struct ring {
  11         uint8_t *data;
  12         uint_fast8_t mask;
  13         volatile uint_fast8_t begin;
  14         volatile uint_fast8_t end;
  15 };
  16
  17
  18 static inline
  19 void ring_init(struct ring *ring, uint8_t *buf, int size)
  20 {
  21         ring->data = buf;
  22         ring->mask = (size-1) & 0xff;
  23         ring->begin = 0;
  24         ring->end = 0;
  25 }
  26
  27 static inline
  28 int ring_write_ch(struct ring *ring, uint8_t ch)
  29 {
  30         uint_fast8_t ep = ring->end;
  31
  32         ring->data[ep] = ch;
  33         ep = (ep + 1) & ring->mask;
  34
  35         if ((ep) != ring->begin) {
  36                 ring->end = ep;
  37                 return 1;
  38         }
  39
  40         return -1;
  41 }
  42
  43 #if 0
  44 static inline
  45 int ring_write(struct ring *ring, uint8_t *data, int size)
  46 {
  47         int i;
  48
  49         for (i = 0; i < size; i++) {
  50                 if (ring_write_ch(ring, data[i]) < 0)
  51                         return -i;
  52         }
  53
  54         return i;
  55 }
  56 #endif
  57
  58 static inline
  59 int ring_read_ch(struct ring *ring)
  60 {
  61         int ret = -1;
  62         uint_fast8_t bp = ring->begin;
  63
  64         if (bp != ring->end) {
  65                 ret = ring->data[bp];
  66                 ring->begin = (bp + 1) & ring->mask;
  67         }
  68
  69         return ret;
  70 }
  71
  72
  73 static inline
  74 int_fast8_t ring_is_empty(struct ring *ring)
  75 {
  76         return ring->begin == ring->end;
  77 }
  78
  79 #endif /* RING_H */