linux/arch/um/drivers/slip_common.h
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   1#ifndef __UM_SLIP_COMMON_H
   2#define __UM_SLIP_COMMON_H
   3
   4#define BUF_SIZE 1500
   5 /* two bytes each for a (pathological) max packet of escaped chars +  *
   6  * terminating END char + initial END char                            */
   7#define ENC_BUF_SIZE (2 * BUF_SIZE + 2)
   8
   9/* SLIP protocol characters. */
  10#define SLIP_END             0300       /* indicates end of frame       */
  11#define SLIP_ESC             0333       /* indicates byte stuffing      */
  12#define SLIP_ESC_END         0334       /* ESC ESC_END means END 'data' */
  13#define SLIP_ESC_ESC         0335       /* ESC ESC_ESC means ESC 'data' */
  14
  15static inline int slip_unesc(unsigned char c, unsigned char *buf, int *pos,
  16                             int *esc)
  17{
  18        int ret;
  19
  20        switch(c){
  21        case SLIP_END:
  22                *esc = 0;
  23                ret=*pos;
  24                *pos=0;
  25                return(ret);
  26        case SLIP_ESC:
  27                *esc = 1;
  28                return(0);
  29        case SLIP_ESC_ESC:
  30                if(*esc){
  31                        *esc = 0;
  32                        c = SLIP_ESC;
  33                }
  34                break;
  35        case SLIP_ESC_END:
  36                if(*esc){
  37                        *esc = 0;
  38                        c = SLIP_END;
  39                }
  40                break;
  41        }
  42        buf[(*pos)++] = c;
  43        return(0);
  44}
  45
  46static inline int slip_esc(unsigned char *s, unsigned char *d, int len)
  47{
  48        unsigned char *ptr = d;
  49        unsigned char c;
  50
  51        /*
  52         * Send an initial END character to flush out any
  53         * data that may have accumulated in the receiver
  54         * due to line noise.
  55         */
  56
  57        *ptr++ = SLIP_END;
  58
  59        /*
  60         * For each byte in the packet, send the appropriate
  61         * character sequence, according to the SLIP protocol.
  62         */
  63
  64        while (len-- > 0) {
  65                switch(c = *s++) {
  66                case SLIP_END:
  67                        *ptr++ = SLIP_ESC;
  68                        *ptr++ = SLIP_ESC_END;
  69                        break;
  70                case SLIP_ESC:
  71                        *ptr++ = SLIP_ESC;
  72                        *ptr++ = SLIP_ESC_ESC;
  73                        break;
  74                default:
  75                        *ptr++ = c;
  76                        break;
  77                }
  78        }
  79        *ptr++ = SLIP_END;
  80        return (ptr - d);
  81}
  82
  83struct slip_proto {
  84        unsigned char ibuf[ENC_BUF_SIZE];
  85        unsigned char obuf[ENC_BUF_SIZE];
  86        int more; /* more data: do not read fd until ibuf has been drained */
  87        int pos;
  88        int esc;
  89};
  90
  91static inline void slip_proto_init(struct slip_proto * slip)
  92{
  93        memset(slip->ibuf, 0, sizeof(slip->ibuf));
  94        memset(slip->obuf, 0, sizeof(slip->obuf));
  95        slip->more = 0;
  96        slip->pos = 0;
  97        slip->esc = 0;
  98}
  99
 100extern int slip_proto_read(int fd, void *buf, int len,
 101                           struct slip_proto *slip);
 102extern int slip_proto_write(int fd, void *buf, int len,
 103                            struct slip_proto *slip);
 104
 105#endif
 106
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