freebsd-dev/usr.sbin/ppp/pred.c
Brian Somers e979ce388b Make the man page a little more detailed.
Update the version number to 1.00.
Increase the predictor-1 buffer by 2 bytes.
1997-06-09 23:38:38 +00:00

219 lines
5.3 KiB
C

#include "fsm.h"
#include "hdlc.h"
#include "lcpproto.h"
#include "ccp.h"
/*
*
* $Id: pred.c,v 1.12 1997/06/09 03:27:35 brian Exp $
*
* pred.c -- Test program for Dave Rand's rendition of the
* predictor algorithm
* Updated by: iand@labtam.labtam.oz.au (Ian Donaldson)
* Updated by: Carsten Bormann <cabo@cs.tu-berlin.de>
* Original : Dave Rand <dlr@bungi.com>/<dave_rand@novell.com>
*/
/* The following hash code is the heart of the algorithm:
* It builds a sliding hash sum of the previous 3-and-a-bit characters
* which will be used to index the guess table.
* A better hash function would result in additional compression,
* at the expense of time.
*/
#define IHASH(x) do {iHash = (iHash << 4) ^ (x);} while(0)
#define OHASH(x) do {oHash = (oHash << 4) ^ (x);} while(0)
static unsigned short int iHash, oHash;
static unsigned char InputGuessTable[65536];
static unsigned char OutputGuessTable[65536];
static int
compress(source, dest, len)
unsigned char *source, *dest;
int len;
{
int i, bitmask;
unsigned char *flagdest, flags, *orgdest;
orgdest = dest;
while (len) {
flagdest = dest++; flags = 0; /* All guess wrong initially */
for (bitmask=1, i=0; i < 8 && len; i++, bitmask <<= 1) {
if (OutputGuessTable[oHash] == *source) {
flags |= bitmask; /* Guess was right - don't output */
} else {
OutputGuessTable[oHash] = *source;
*dest++ = *source; /* Guess wrong, output char */
}
OHASH(*source++);len--;
}
*flagdest = flags;
}
return(dest - orgdest);
}
static void
SyncTable(source, dest, len)
unsigned char *source, *dest;
int len;
{
while (len--) {
if (InputGuessTable[iHash] != *source) {
InputGuessTable[iHash] = *source;
}
IHASH(*dest++ = *source++);
}
}
static int
decompress(source, dest, len)
unsigned char *source, *dest;
int len;
{
int i, bitmask;
unsigned char flags, *orgdest;
orgdest = dest;
while (len) {
flags = *source++;
len--;
for (i=0, bitmask = 1; i < 8; i++, bitmask <<= 1) {
if (flags & bitmask) {
*dest = InputGuessTable[iHash]; /* Guess correct */
} else {
if (!len)
break; /* we seem to be really done -- cabo */
InputGuessTable[iHash] = *source; /* Guess wrong */
*dest = *source++; /* Read from source */
len--;
}
IHASH(*dest++);
}
}
return(dest - orgdest);
}
void
Pred1Init(direction)
int direction;
{
if (direction & 1) { /* Input part */
iHash = 0;
bzero(InputGuessTable, sizeof(InputGuessTable));
}
if (direction & 2) { /* Output part */
oHash = 0;
bzero(OutputGuessTable, sizeof(OutputGuessTable));
}
}
void
Pred1Output(int pri, u_short proto, struct mbuf *bp)
{
struct mbuf *mwp;
u_char *cp, *wp, *hp;
int orglen, len;
u_char bufp[MAX_MTU+2];
u_short fcs;
orglen = plength(bp) + 2; /* add count of proto */
mwp = mballoc((orglen+2)/8*9+12, MB_HDLCOUT);
hp = wp = MBUF_CTOP(mwp);
cp = bufp;
*wp++ = *cp++ = orglen >> 8;
*wp++ = *cp++ = orglen & 0377;
*cp++ = proto >> 8;
*cp++ = proto & 0377;
mbread(bp, cp, orglen-2);
fcs = HdlcFcs(INITFCS, bufp, 2+orglen);
fcs = ~fcs;
len = compress(bufp + 2, wp, orglen);
LogPrintf(LogDEBUG, "Pred1Output: orglen (%d) --> len (%d)\n", orglen, len);
CcpInfo.orgout += orglen;
if (len < orglen) {
*hp |= 0x80;
wp += len;
CcpInfo.compout += len;
} else {
bcopy(bufp+2, wp, orglen);
wp += orglen;
CcpInfo.compout += orglen;
}
*wp++ = fcs & 0377;
*wp++ = fcs >> 8;
mwp->cnt = wp - MBUF_CTOP(mwp);
HdlcOutput(PRI_NORMAL, PROTO_COMPD, mwp);
}
void
Pred1Input(bp)
struct mbuf *bp;
{
u_char *cp, *pp;
int len, olen, len1;
struct mbuf *wp;
u_char *bufp;
u_short fcs, proto;
wp = mballoc(MAX_MTU+2, MB_IPIN);
cp = MBUF_CTOP(bp);
olen = plength(bp);
pp = bufp = MBUF_CTOP(wp);
*pp++ = *cp & 0177;
len = *cp++ << 8;
*pp++ = *cp;
len += *cp++;
CcpInfo.orgin += len & 0x7fff;
if (len & 0x8000) {
len1 = decompress(cp, pp, olen - 4);
CcpInfo.compin += olen;
len &= 0x7fff;
if (len != len1) { /* Error is detected. Send reset request */
LogPrintf(LogLCP, "%s: Length Error\n", CcpFsm.name);
CcpSendResetReq(&CcpFsm);
pfree(bp);
pfree(wp);
return;
}
cp += olen - 4;
pp += len1;
} else {
CcpInfo.compin += len;
SyncTable(cp, pp, len);
cp += len;
pp += len;
}
*pp++ = *cp++; /* CRC */
*pp++ = *cp++;
fcs = HdlcFcs(INITFCS, bufp, wp->cnt = pp - bufp);
if (fcs != GOODFCS)
LogPrintf(LogDEBUG, "Pred1Input: fcs = 0x%04x (%s), len = 0x%x,"
" olen = 0x%x\n", fcs, (fcs == GOODFCS)? "good" : "bad",
len, olen);
if (fcs == GOODFCS) {
wp->offset += 2; /* skip length */
wp->cnt -= 4; /* skip length & CRC */
pp = MBUF_CTOP(wp);
proto = *pp++;
if (proto & 1) {
wp->offset++;
wp->cnt--;
} else {
wp->offset += 2;
wp->cnt -= 2;
proto = (proto << 8) | *pp++;
}
DecodePacket(proto, wp);
}
else
{
LogDumpBp(LogHDLC, "Bad FCS", wp);
CcpSendResetReq(&CcpFsm);
pfree(wp);
}
pfree(bp);
}