/****************************************************************
*                                                               *
*               CP/M-68K BDOS Disk Read/Write Module            *
*                                                               *
*       This module contains functions to perform sequential    *
*       or random access read or write to the disk for CP/M-68K *
*                                                               *
*       It includes the following external functions:           *
*                                                               *
*               bdosrw()    - sequential and random disk I/O    *
*                                                               *
*                                                               *
*       Compiled with Alcyon C on the VAX                       *
*                                                               *
****************************************************************/

#include "bdosinc.h"            /* Standard I/O declarations            */

#include "bdosdef.h"            /* Type and structure declarations for BDOS */


/* External function definitions */
EXTERN  UWORD   rdwrt();        /* disk read/write routine              */
EXTERN  WORD    getaloc();      /* allocate a block of disk space       */
EXTERN  WORD    swap();         /* assembly language byte swapper       */
EXTERN  UWORD   dirscan();      /* directory scanning routine           */
EXTERN  BOOLEAN openfile();     /* open file function passed to dirscan */
EXTERN  UWORD   close_fi();     /* close file function                  */
EXTERN  BOOLEAN create();       /* create file function passed to dirscan */
EXTERN  UWORD   ro_err();       /* read-only file error handler         */

/* External variable definitions */
EXTERN  UWORD   ro_dsk;         /* read-only disk vector                */


/**********************************************************/
/*  First, some utility functions used by seqio and ranio */
/**********************************************************/

/******************************
*  FCB block number routines  *
******************************/

WORD    blkindx(fcbp)
/*  return index into fcb disk map      */

REG struct fcb  *fcbp;                  /* pointer to fcb               */
{
    REG struct dpb *dparmp;             /* pointer to disk parameter block */
    REG WORD i;
    REG WORD blkshf;
    BSETUP

    dparmp = GBL.parmp;
    blkshf = dparmp->bsh;
    i = ((fcbp->extent) & dparmp->exm) << (7 - blkshf);
    return (i + (UBWORD(fcbp->cur_rec) >> blkshf) );
}


UWORD   blknum(fcbp, index, wrdfcb)
/* return block number in fcb indicated by index */

REG struct fcb  *fcbp;          /* pointer to fcb                       */
REG WORD        index;          /* index into disk map of fcb           */
WORD            wrdfcb;         /* boolean, fcb disk map of words       */
{
    if (wrdfcb)
        return( swap(fcbp->dskmap.big[index]) );
    else return( UBWORD(fcbp->dskmap.small[index]) );
}


setblk(fcbp, index, wrdfcb, block)
/* put block number into fcb */

REG struct fcb  *fcbp;          /* pointer to fcb                       */
REG WORD        index;          /* index into disk map of fcb           */
WORD            wrdfcb;         /* boolean, fcb disk map of words       */
REG UWORD       block;          /* block number                         */
{
    fcbp->s2 &= 0x7f;           /* set file write flag                  */
    if (wrdfcb)
        fcbp->dskmap.big[index] = swap(block);
    else fcbp->dskmap.small[index] = (UBYTE)block;
}


/***************************
*  disk read/write routine *
***************************/

UWORD do_io(block, rcrd, parm)

UWORD   block;          /* block number         */
UBYTE   rcrd;           /* record number        */
REG WORD parm;          /* write parameter      */
{
    REG LONG lsec;
    REG struct dpb *dparmp;
    BSETUP

    dparmp = GBL.parmp;                         /* init dpb pointer */
    lsec = ((LONG)block << (dparmp->bsh)) +
                (LONG)(rcrd & (dparmp->blm));
    return( rdwrt(lsec, GBL.dmaadr, parm) );
}


/*******************************************
*  routine for crossing extent boundaries  *
*******************************************/

WORD new_ext(fcbp, reading, ran)
/*  If sequential I/O, open the next extent                     */
/*  If random I/O, compute new extent from random record field  */

REG struct fcb  *fcbp;          /* pointer to fcb  */
BOOLEAN reading;                /* read/write flag */
WORD  ran;                      /* random I/O flag */
{
    REG UBYTE mod;              /* module number   */
    REG UBYTE ext;              /* extent number   */
    REG UBYTE t_mod;            /* temp mod number */
    REG UBYTE t_ext;            /* temp extent     */
    BSETUP

    if (ran)
    {
        mod = ( (fcbp->ran0) << 4) | ( (fcbp->ran1) >> 4);
        ext = ( ((fcbp->ran1) & 0x0f) << 1);
        if ((fcbp->ran2) & 0x80) ext |= 1;
                /* the calculation of ext was coded this way because of a */
                /* compiler bug from Alcyon */
    }
    else
    {
        mod = (fcbp->s2) & 0x3f;
        ext = (fcbp->extent) + 1;       /* for sequential, incr extent  */
    }
    if (ext >= 32)
    {
        ext = 0;
        mod += 1;
    }
    if (mod >= 64) return(6);           /* past maximum file size */
    if ( mod == ((fcbp->s2) & 0x3f) )
        if ( ! ((ext ^ (fcbp->extent)) & ~((GBL.parmp)->exm) & 0x1f) )
        {                               /* we're in same logical extent */
            fcbp->extent = ext;
            return(0);
        }
    /* Extent or Module numbers don't match     */
    /* Close the old extent and open a  one     */
    if ( close_fi(fcbp) >= 255 ) return(3);
                                        /* can't close old extent */
    t_mod = fcbp->s2;
    t_ext = fcbp->extent;
    fcbp->s2 = mod;
    fcbp->extent = ext;
    if ( dirscan(openfile, fcbp, 0) >= 255 )  /* open  extent */
    {
        if (reading)
        {                               /* reading unwritten extent */
            fcbp->s2 = t_mod;
            fcbp->extent = t_ext;
            return(4);
        }
        if ( dirscan(create, fcbp, 8) >= 255 )
            return(5);                  /* can't create new extent */
    }
    return(0);
}


/************************************
* Routine to calculate the maximum  *
* extent number of an FCB in a      *
* extent-folded environment         *
************************************/

UWORD calcext(fcbp)

REG struct fcb *fcbp;

{
    REG UWORD i;
    REG BYTE *p;
    BSETUP

    i = 15;
    p = &(fcbp->dskmap.small[16]);
    do
    {
        if (*--p) break;
        i -= 1;
    } while (i);
/* Now i contains the index of the last non-zero block in the FCB */
    if ((GBL.parmp)->dsm > 255) i >>= 1;
    i >>= 7 - ((GBL.parmp)->bsh);
    return ( (fcbp->extent) & ~((GBL.parmp)->exm) & 0x1f | i );
}


/*********************************
* Routine to get the actual      *
* record count of the currently  *
* active logical extent of a FCB *
*********************************/

UWORD get_rc(fcbp)

REG struct fcb *fcbp;

{
    REG UWORD ext;

    ext = calcext(fcbp);        /* find last active extent in fcb */
    if (ext == fcbp->extent) return(UBWORD(fcbp->rcdcnt));
                        /* if this is the last active fcb, return fcb's rc */
    else if (ext > fcbp->extent) return(128);
                        /* if the fcb has more extents past this one, then */
                        /* the current one is logically full    */
    else return (0);
                        /* if we seeked past the last active extent, rc = 0 */
}


/************************
*  bdosrw entry point   *
************************/

UWORD bdosrw(fcbp, reading, random)

REG struct fcb *fcbp;           /* fcbp is a pointer to a fcb */
REG BOOLEAN reading;            /* boolean to tell whether to read or write */
WORD random;                    /* 0 = sequential, 1 = random (normal),  */
                                /* 2 = random with zero fill    */
{
    REG UWORD   block;          /* block number from fcb        */
    REG WORD    index;          /* index into disk map of fcb   */
    REG BYTE    *old_dma;       /* temp holding spot for dmaadr */
    REG WORD    parm;           /* parameter to do-io           */
    REG WORD    bigfile;        /* file system is in word mode  */
    REG UWORD   rtn;            /* return parameter             */
    REG UBYTE   rc;             /* temp storage for rcdcnt      */
    BSETUP

    bigfile = ((GBL.parmp)->dsm) & ~0xff;
    if ( ( ! reading) && (fcbp->ftype[robit] & 0x80) )
                 ro_err(fcbp,((GBL.dpbp)->dpbp)->drm);
                                /* check for read-only file */
    if (random)
    {
        if ( rtn = new_ext(fcbp, reading, TRUE) ) return(rtn);
                        /* open new extent if necessary, return if error */
        fcbp->cur_rec = (fcbp->ran2) & 0x7f;
    }
    else                /* sequential */
        if (fcbp->cur_rec == 128)
        {                       /* time to try next extent */
            if ( new_ext(fcbp, reading, FALSE) )
                return(1);      /* if can't open new extent, error */
            fcbp->cur_rec = 0;  /* opened new extent, zero cur_rec */
        }

    /* record is now in active fcb */
    rc = fcbp->rcdcnt;
    if ( UBWORD(fcbp->cur_rec) >= get_rc(fcbp) )
    {
        if (reading) return(1);         /* reading unwritten data */
        fcbp->s2 &= 0x7f;               /* set file write flag */
        rc = fcbp->cur_rec + 1;
    }
    index = blkindx(fcbp);              /* get index into fcb disk map */
    block = blknum(fcbp, index, bigfile);
    if (block) parm = (reading ? 0 : 1);
    else                /* if allocated block, parm is just read or write */
    {                                   /* unallocated block    */
        if (reading) return(1);         /* reading unwritten data */

        /* Writing to new block */
        /* The parm passed to getaloc is the previously allocated block */
        /*      or 0, if the previous block is not allocated            */

        block = getaloc(blknum(fcbp, (index ? (index - 1) : 0), bigfile));
        if (block == ~0) return(2);     /* out of space */
        setblk(fcbp, index, bigfile, block);
        parm = 3;
        if (random == 2)
        {                               /* Write random with zero fill  */
            old_dma = GBL.dmaadr;
            GBL.dmaadr = GBL.dirbufp;   /* Do DMA from dir_buf */
            index = SECLEN;
            do GBL.dmaadr[--index] = 0;
                while (index);          /* zero the dma buffer */
            for (index = 0; index <= ((GBL.parmp)->blm); index++)
            {
                do_io(block, (UBYTE)index, parm);
                                        /* write zeros to the block */
                parm = 1;               /* next write is not to new block */
            }
            GBL.dmaadr = old_dma;       /* restore dma address  */
        }
    }
    rtn = do_io(block, fcbp->cur_rec, parm);
    if ( rtn == 0 )
    {
        fcbp->rcdcnt = rc;
        if ( ! random ) fcbp->cur_rec += 1;
    }
    return(rtn);
}

bp->rcdcnt = rc;
        if ( ! random ) fcbp->cur_rec += 1;
    }
    return(rtn);
}

bp->rcdcnt = rc;
        if ( ! random ) fcbp->cur_rec += 1;
    }
    return(rtn);
}

bp->rcdcnt = rc;
        if ( ! random ) fcbp->cur_rec += 1;
    }
    return(rtn);
}