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 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 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 91 #define SLIP_PROTO_INIT { \ 92 .ibuf = { '\0' }, \ 93 .obuf = { '\0' }, \ 94 .more = 0, \ 95 .pos = 0, \ 96 .esc = 0 \ 97 } 98 99 extern int slip_proto_read(int fd, void *buf, int len, 100 struct slip_proto *slip); 101 extern int slip_proto_write(int fd, void *buf, int len, 102 struct slip_proto *slip); 103 104 #endif 105