/* * Virtual tape driver - copyright 1998 Warren Toomey	wkt@cs.adfa.oz.au * * $Revision: 1.9 $ * $Date: 1998/02/01 00:49:15 $ */#include <sys/param.h>#include <sys/inode.h>#include "saio.h"/* Command sent to tape server */struct vtcmd {    char hdr1;			/* Header, 31 followed by 42 (decimal) */    char hdr2;    char cmd;			/* Command, one of VTC_XXX below */				/* Error comes back in top 4 bits */    char record;		/* Record we're accessing */    char blklo;			/* Block number, in lo/hi format */    char blkhi;    char sum0;			/* 16-bit checksum */    char sum1;};/* Header bytes */#define VT_HDR1		31#define VT_HDR2		42/* Commands available */#define VTC_QUICK	0	/* Quick read, no cksum sent */#define VTC_OPEN	1#define VTC_CLOSE	2#define VTC_READ	3	/* This file only uses READ and OPEN */#define VTC_WRITE	4/* Errors returned */#define VTE_NOREC	1	/* No such record available */#define VTE_OPEN	2	/* Can't open requested block */#define VTE_CLOSE	3	/* Can't close requested block */#define VTE_READ	4	/* Can't read requested block */#define VTE_WRITE	5	/* Can't write requested block */#define VTE_NOCMD       6       /* No such command */#define VTE_EOF         7       /* End of file: no blocks left to read */#define BLKSIZE         512/* Static things */struct vtcmd vtcmd;		/* Command buffer */struct vtcmd vtreply;		/* Reply from server */char *vtbuf;			/* Pointer to input buffer */unsigned int hitim, lotim;	/* Variables for delay loop */char oddeven=0;			/* Toggle status printing character */char *oddstr= ".*";char vtsendcmd();		/* Forward references */char vtgetc();/*** Standalone-dependent section *//* vtopen() is used to inform the server which record we'll be using */vtopen(io)register struct iob *io;{    register i;    vtcmd.record= io->i_boff; vtcmd.cmd= VTC_OPEN;    vtcmd.blklo=0; vtcmd.blkhi=0;    vtsendcmd();		/* Send the command to the server */}/* vtstrategy() must be called as a READ. We send a command * to the server, get a reply, and return the amount read * (even on EOF, which may be zero) or -1 on error. */vtstrategy(io, func)register struct iob *io;{    register error, i;    vtbuf= io->i_ma;    /* Assume record, blklo and blkhi are ok */    /* Assume i->i_cc is in multiples of BLKSIZE */    for (i=0; i<io->i_cc; i+=BLKSIZE, vtbuf+=BLKSIZE) {	vtcmd.cmd= VTC_READ;        error= vtsendcmd();		/* Send the command to the server */					/* Some programs rely on */					/* the buffer being cleared to */					/* indicate EOF, e.g cat */	if (error == VTE_EOF) { vtbuf[0]=0; return(i); }	if (error != 0) {	  printf("tape error %d", error);	  return(-1); 	}        			/* Increment block number for next time */	vtcmd.blklo++;	if (vtcmd.blklo==0) vtcmd.blkhi++;    }	return(io->i_cc);}/*** Protocol-specific stuff ***/char vtsendcmd(){    register i;    char error, cmd, sum0, sum1;			/* Build the checksum */    vtcmd.hdr1= VT_HDR1; vtcmd.hdr2= VT_HDR2;    vtcmd.sum0= VT_HDR1 ^ vtcmd.cmd ^ vtcmd.blklo;    vtcmd.sum1= VT_HDR2 ^ vtcmd.record ^ vtcmd.blkhi;			/* Send the command to the server */  sendcmd:    vtputc(vtcmd.hdr1);  vtputc(vtcmd.hdr2);    vtputc(vtcmd.cmd);   vtputc(vtcmd.record);    vtputc(vtcmd.blklo); vtputc(vtcmd.blkhi);    vtputc(vtcmd.sum0);  vtputc(vtcmd.sum1);  			/* Now get a valid reply from the server */  getreply:    vtreply.hdr1= vtgetc(); if (hitim==0) goto sendcmd;    if (vtreply.hdr1!=VT_HDR1) goto getreply;    vtreply.hdr2= vtgetc(); if (hitim==0) goto sendcmd;    if (vtreply.hdr2!=VT_HDR2) goto getreply;    vtreply.cmd= vtgetc(); if (hitim==0) goto sendcmd;    vtreply.record= vtgetc(); if (hitim==0) goto sendcmd;    vtreply.blklo= vtgetc(); if (hitim==0) goto sendcmd;    vtreply.blkhi= vtgetc(); if (hitim==0) goto sendcmd;			/* Calc. the cksum to date */    sum0= VT_HDR1 ^ vtreply.cmd ^ vtreply.blklo;    sum1= VT_HDR2 ^ vtreply.record ^ vtreply.blkhi;			/* Retrieve the block if no errs and a READ cmd */    if (vtreply.cmd==VTC_READ) {      for (i=0; i<BLKSIZE; i++) {	vtbuf[i]= vtgetc(); if (hitim==0) goto sendcmd;	sum0 ^= vtbuf[i]; i++;	vtbuf[i]= vtgetc(); if (hitim==0) goto sendcmd;	sum1 ^= vtbuf[i];      }    }			/* Get the checksum */    vtreply.sum0= vtgetc(); if (hitim==0) goto sendcmd;    vtreply.sum1= vtgetc(); if (hitim==0) goto sendcmd;			/* Try again on a bad checksum */    if ((sum0!=vtreply.sum0) || (sum1!=vtreply.sum1)) {	putchar('e'); goto sendcmd;    }    putchar(oddstr[oddeven]); oddeven= 1-oddeven;			/* Extract any error */    error= vtreply.cmd >> 4; return(error);}/*** Harware-specific stuff ***/struct  device  {        int     rcsr,rbuf;        int     tcsr,tbuf;};static struct  device *KL1= {0176500};		/* We use KL11 unit 1 *//* vtgetc() and vtputc(): A sort-of repeat of the getchar/putchar * code in prf.c, but without any console stuff *//* Get a character, or timeout and return with hitim zero */char vtgetc(){           register c;            KL1->rcsr = 1; hitim=3; lotim=65535;          while ((KL1->rcsr&0200)==0) {	   lotim--;	   if (lotim==0) hitim--;	   if (hitim==0) { putchar('t'); return(0); }	}        c = KL1->rbuf; return(c);}vtputc(c)register c;{        register s;        while((KL1->tcsr&0200) == 0) ;        s = KL1->tcsr;        KL1->tcsr = 0; KL1->tbuf = c; KL1->tcsr = s;}