slip_common.h
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#ifndef __UM_SLIP_COMMON_H
#define __UM_SLIP_COMMON_H
#define BUF_SIZE 1500
/* two bytes each for a (pathological) max packet of escaped chars + *
* terminating END char + initial END char */
#define ENC_BUF_SIZE (2 * BUF_SIZE + 2)
/* SLIP protocol characters. */
#define SLIP_END 0300 /* indicates end of frame */
#define SLIP_ESC 0333 /* indicates byte stuffing */
#define SLIP_ESC_END 0334 /* ESC ESC_END means END 'data' */
#define SLIP_ESC_ESC 0335 /* ESC ESC_ESC means ESC 'data' */
static inline int slip_unesc(unsigned char c, unsigned char *buf, int *pos,
int *esc)
{
int ret;
switch(c){
case SLIP_END:
*esc = 0;
ret=*pos;
*pos=0;
return(ret);
case SLIP_ESC:
*esc = 1;
return(0);
case SLIP_ESC_ESC:
if(*esc){
*esc = 0;
c = SLIP_ESC;
}
break;
case SLIP_ESC_END:
if(*esc){
*esc = 0;
c = SLIP_END;
}
break;
}
buf[(*pos)++] = c;
return(0);
}
static inline int slip_esc(unsigned char *s, unsigned char *d, int len)
{
unsigned char *ptr = d;
unsigned char c;
/*
* Send an initial END character to flush out any
* data that may have accumulated in the receiver
* due to line noise.
*/
*ptr++ = SLIP_END;
/*
* For each byte in the packet, send the appropriate
* character sequence, according to the SLIP protocol.
*/
while (len-- > 0) {
switch(c = *s++) {
case SLIP_END:
*ptr++ = SLIP_ESC;
*ptr++ = SLIP_ESC_END;
break;
case SLIP_ESC:
*ptr++ = SLIP_ESC;
*ptr++ = SLIP_ESC_ESC;
break;
default:
*ptr++ = c;
break;
}
}
*ptr++ = SLIP_END;
return (ptr - d);
}
struct slip_proto {
unsigned char ibuf[ENC_BUF_SIZE];
unsigned char obuf[ENC_BUF_SIZE];
int more; /* more data: do not read fd until ibuf has been drained */
int pos;
int esc;
};
static inline void slip_proto_init(struct slip_proto * slip)
{
memset(slip->ibuf, 0, sizeof(slip->ibuf));
memset(slip->obuf, 0, sizeof(slip->obuf));
slip->more = 0;
slip->pos = 0;
slip->esc = 0;
}
extern int slip_proto_read(int fd, void *buf, int len,
struct slip_proto *slip);
extern int slip_proto_write(int fd, void *buf, int len,
struct slip_proto *slip);
#endif