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
slip_unesc(unsigned char c,unsigned char * buf,int * pos,int * esc)15 static 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
slip_esc(unsigned char * s,unsigned char * d,int len)46 static 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
83 struct 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
slip_proto_init(struct slip_proto * slip)91 static 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
100 extern int slip_proto_read(int fd, void *buf, int len,
101 struct slip_proto *slip);
102 extern int slip_proto_write(int fd, void *buf, int len,
103 struct slip_proto *slip);
104
105 #endif
106