lib/circ_buf.c

   1 /* Author: Domen Puncer <domen@cba.si>.  License: WTFPL, see file LICENSE */
   2 #include <circ_buf.h>
   3 #include <string.h>
   4 #include <errno.h>
   5
   6 void circ_buf_init(struct circ_buf *cb, u8 *buf, unsigned size)
   7 {
   8         cb->data = buf;
   9         cb->size = size;
  10         cb->head = cb->tail = 0;
  11 }
  12
  13 unsigned circ_buf_len(struct circ_buf *cb)
  14 {
  15         unsigned tmp;
  16         tmp = cb->size + cb->head - cb->tail;
  17         if (tmp >= cb->size)
  18                 tmp -= cb->size;
  19         return tmp;
  20 }
  21
  22 unsigned circ_buf_free(struct circ_buf *cb)
  23 {
  24         unsigned tmp;
  25         tmp = cb->size + cb->tail - cb->head - 1;
  26         if (tmp >= cb->size)
  27                 tmp -= cb->size;
  28         return tmp;
  29 }
  30
  31 __inline static void memcpy_(u8 *dest, const u8 *src, int len)
  32 {
  33         while (len-- > 0)
  34                 *dest++ = *src++;
  35 }
  36
  37 unsigned circ_buf_put(struct circ_buf *cb, const u8 *data, unsigned len)
  38 {
  39         unsigned size;
  40         unsigned len_til_end;
  41
  42         size = circ_buf_free(cb);
  43         if (size == 0)
  44                 return -EAGAIN;
  45
  46         if (len > size)
  47                 len = size;
  48
  49         len_til_end = cb->size - cb->head;
  50         if (len_til_end > len)
  51                 len_til_end = len;
  52
  53         memcpy_(cb->data+cb->head, data, len_til_end);
  54         memcpy_(cb->data, data+len_til_end, len-len_til_end);
  55
  56         cb->head += len;
  57         if (cb->head >= cb->size)
  58                 cb->head -= cb->size;
  59         return len;
  60 }
  61
  62 unsigned circ_buf_get(struct circ_buf *cb, u8 *data, unsigned len)
  63 {
  64         unsigned size;
  65         unsigned len_til_end;
  66
  67         size = circ_buf_len(cb);
  68         if (size == 0)
  69                 return -EAGAIN;
  70
  71         if (len > size)
  72                 len = size;
  73
  74         len_til_end = cb->size - cb->tail;
  75         if (len_til_end > len)
  76                 len_til_end = len;
  77
  78         memcpy_(data, cb->data+cb->tail, len_til_end);
  79         memcpy_(data+len_til_end, cb->data, len-len_til_end);
  80
  81         cb->tail += len;
  82         if (cb->tail >= cb->size)
  83                 cb->tail -= cb->size;
  84         return len;
  85 }
  86
  87 /* for convenience */
  88 int circ_buf_put_one(struct circ_buf *cb, u8 data)
  89 {
  90         if (circ_buf_free(cb) == 0)
  91                 return -EAGAIN;
  92
  93         cb->data[cb->head++] = data;
  94         if (cb->head >= cb->size)
  95                 cb->head -= cb->size;
  96         return 0;
  97 }
  98
  99 int circ_buf_get_one(struct circ_buf *cb)
 100 {
 101         u8 data;
 102         if (circ_buf_len(cb) == 0)
 103                 return -EAGAIN;
 104
 105         data = cb->data[cb->tail++];
 106         if (cb->tail >= cb->size)
 107                 cb->tail -= cb->size;
 108         return data;
 109 }