/* * 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 * Original : Dave Rand / * * $Id: pred.c,v 1.17 1997/11/22 03:37:44 brian Exp $ * */ #include #include #include #include #include #include "command.h" #include "mbuf.h" #include "log.h" #include "defs.h" #include "loadalias.h" #include "vars.h" #include "timer.h" #include "fsm.h" #include "hdlc.h" #include "lcpproto.h" #include "lcp.h" #include "ccp.h" #include "pred.h" /* 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) #define GUESS_TABLE_SIZE 65536 static unsigned short int iHash, oHash; static unsigned char *InputGuessTable; static unsigned char *OutputGuessTable; static int compress(u_char * source, u_char * 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(u_char * source, u_char * dest, int len) { while (len--) { if (InputGuessTable[iHash] != *source) { InputGuessTable[iHash] = *source; } IHASH(*dest++ = *source++); } } static int decompress(u_char * source, u_char * 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); } static void Pred1TermInput(void) { if (InputGuessTable != NULL) { free(InputGuessTable); InputGuessTable = NULL; } } static void Pred1TermOutput(void) { if (OutputGuessTable != NULL) { free(OutputGuessTable); OutputGuessTable = NULL; } } static void Pred1ResetInput(void) { iHash = 0; memset(InputGuessTable, '\0', GUESS_TABLE_SIZE); LogPrintf(LogCCP, "Predictor1: Input channel reset\n"); } static void Pred1ResetOutput(void) { oHash = 0; memset(OutputGuessTable, '\0', GUESS_TABLE_SIZE); LogPrintf(LogCCP, "Predictor1: Output channel reset\n"); } static int Pred1InitInput(void) { if (InputGuessTable == NULL) if ((InputGuessTable = malloc(GUESS_TABLE_SIZE)) == NULL) return 0; Pred1ResetInput(); return 1; } static int Pred1InitOutput(void) { if (OutputGuessTable == NULL) if ((OutputGuessTable = malloc(GUESS_TABLE_SIZE)) == NULL) return 0; Pred1ResetOutput(); return 1; } static int 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.uncompout += orglen; if (len < orglen) { *hp |= 0x80; wp += len; CcpInfo.compout += len; } else { memcpy(wp, bufp + 2, orglen); wp += orglen; CcpInfo.compout += orglen; } *wp++ = fcs & 0377; *wp++ = fcs >> 8; mwp->cnt = wp - MBUF_CTOP(mwp); HdlcOutput(PRI_NORMAL, PROTO_COMPD, mwp); return 1; } static struct mbuf * Pred1Input(u_short *proto, struct mbuf *bp) { u_char *cp, *pp; int len, olen, len1; struct mbuf *wp; u_char *bufp; u_short fcs; 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.uncompin += 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(LogCCP, "Pred1: Length error\n"); CcpSendResetReq(&CcpFsm); pfree(bp); pfree(wp); return NULL; } 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++; } return wp; } else { LogDumpBp(LogHDLC, "Bad FCS", wp); CcpSendResetReq(&CcpFsm); pfree(wp); } pfree(bp); return NULL; } static void Pred1DictSetup(u_short proto, struct mbuf * bp) { } static const char * Pred1DispOpts(struct lcp_opt *o) { return NULL; } static void Pred1GetOpts(struct lcp_opt *o) { o->id = TY_PRED1; o->len = 2; } static int Pred1SetOpts(struct lcp_opt *o) { if (o->id != TY_PRED1 || o->len != 2) { Pred1GetOpts(o); return MODE_NAK; } return MODE_ACK; } const struct ccp_algorithm Pred1Algorithm = { TY_PRED1, ConfPred1, Pred1DispOpts, { Pred1GetOpts, Pred1SetOpts, Pred1InitInput, Pred1TermInput, Pred1ResetInput, Pred1Input, Pred1DictSetup }, { Pred1GetOpts, Pred1SetOpts, Pred1InitOutput, Pred1TermOutput, Pred1ResetOutput, Pred1Output }, };