1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef __UM_SLIP_COMMON_H
3 #define __UM_SLIP_COMMON_H
4
5 #define BUF_SIZE 1500
6 /* two bytes each for a (pathological) max packet of escaped chars + *
7 * terminating END char + initial END char */
8 #define ENC_BUF_SIZE (2 * BUF_SIZE + 2)
9
10 /* SLIP protocol characters. */
11 #define SLIP_END 0300 /* indicates end of frame */
12 #define SLIP_ESC 0333 /* indicates byte stuffing */
13 #define SLIP_ESC_END 0334 /* ESC ESC_END means END 'data' */
14 #define SLIP_ESC_ESC 0335 /* ESC ESC_ESC means ESC 'data' */
15
16 static inline int slip_unesc(unsigned char c, unsigned char *buf, int *pos,
17 int *esc)
18 {
19 int ret;
20
21 switch(c){
22 case SLIP_END:
23 *esc = 0;
24 ret=*pos;
25 *pos=0;
26 return(ret);
27 case SLIP_ESC:
28 *esc = 1;
29 return(0);
30 case SLIP_ESC_ESC:
31 if(*esc){
32 *esc = 0;
33 c = SLIP_ESC;
34 }
35 break;
36 case SLIP_ESC_END:
37 if(*esc){
38 *esc = 0;
39 c = SLIP_END;
40 }
41 break;
42 }
43 buf[(*pos)++] = c;
44 return(0);
45 }
46
47 static inline int slip_esc(unsigned char *s, unsigned char *d, int len)
48 {
49 unsigned char *ptr = d;
50 unsigned char c;
51
52 /*
53 * Send an initial END character to flush out any
54 * data that may have accumulated in the receiver
55 * due to line noise.
56 */
57
58 *ptr++ = SLIP_END;
59
60 /*
61 * For each byte in the packet, send the appropriate
62 * character sequence, according to the SLIP protocol.
63 */
64
65 while (len-- > 0) {
66 switch(c = *s++) {
67 case SLIP_END:
68 *ptr++ = SLIP_ESC;
69 *ptr++ = SLIP_ESC_END;
70 break;
71 case SLIP_ESC:
72 *ptr++ = SLIP_ESC;
73 *ptr++ = SLIP_ESC_ESC;
74 break;
75 default:
76 *ptr++ = c;
77 break;
78 }
79 }
80 *ptr++ = SLIP_END;
81 return (ptr - d);
82 }
83
84 struct slip_proto {
85 unsigned char ibuf[ENC_BUF_SIZE];
86 unsigned char obuf[ENC_BUF_SIZE];
87 int more; /* more data: do not read fd until ibuf has been drained */
88 int pos;
89 int esc;
90 };
91
92 static inline void slip_proto_init(struct slip_proto * slip)
93 {
94 memset(slip->ibuf, 0, sizeof(slip->ibuf));
95 memset(slip->obuf, 0, sizeof(slip->obuf));
96 slip->more = 0;
97 slip->pos = 0;
98 slip->esc = 0;
99 }
100
101 extern int slip_proto_read(int fd, void *buf, int len,
102 struct slip_proto *slip);
103 extern int slip_proto_write(int fd, void *buf, int len,
104 struct slip_proto *slip);
105
106 #endif
107
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