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89 lines
3.3 KiB
C
89 lines
3.3 KiB
C
/****************************************************************************/
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/* */
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/* _ b l k i o F u n c t i o n */
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/* ----------------------------- */
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/* Copyright 1982 by Digital Research Inc. All rights reserved. */
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/* */
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/* The _blkio function is used to read / write a set of contiguous */
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/* sectors in an open file. */
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/* Note: it will use CP/M function 44 (Set Multi-Sector Count) if */
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/* MAXSXFR > 1. This is for BDOS version 3.0 or greater. */
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/* */
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/* Calling Sequence: */
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/* */
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/* ret = _blkio(ccb,sector,buffer,count,bdosfunc); */
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/* */
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/* Where: */
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/* ret = sectors actually read/written */
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/* ccb -> the open file channel control block */
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/* sector = The desired starting sector number */
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/* buffer = The memory address to begin transfer */
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/* count = the number of sectors to read/write */
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/* bdosfunc= The BDOS function number (B_READ / B_WRITE) */
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/* */
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/* */
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/****************************************************************************/
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#include <portab.h>
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#include <cpm.h>
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LONG
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_blkio(ccb,sector,buffer,count,bdosfunc)
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/****************************/
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REG FD *ccb; /* open file pointer */
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REG LONG sector; /* Sector number */
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REG BYTE *buffer; /* User's buffer area */
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REG LONG count; /* # of sectors to do */
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REG int bdosfunc; /* BDOS function to use */
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/****************************/
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{ /****************************/
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REG WORD nsecs; /* # secs to xfer each time */
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REG LONG seccnt; /* # sectors processed */
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REG WORD xuser; /* old user number */
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/****************************/
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seccnt = 0; /* Zero count initally */
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xuser = __BDOS(USER,0xFFL); /* Get current user # */
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if(xuser != ccb->user) /* File have a different 1? */
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__BDOS(USER,(LONG)ccb->user); /* Yes, set to that */
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/* */
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while (count > 0) /* Until all sectors xferred*/
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{ /* */
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__BDOS(SETDMA,buffer); /* Set new DMA address */
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ccb->fcb.record = sector; /* Set new record number */
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#if _MAXSXFR > 1 /* Can we xfer multi-secs? */
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nsecs = min(_MAXSXFR,count); /* Ifso, xfer many */
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__BDOS(SETMSC,nsecs); /* Always set before r/w */
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#else /* if possible */
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nsecs = 1; /* o.w. xfer singly */
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#endif /* */
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if(__BDOS(bdosfunc,&(ccb->fcb)) /* do the read */
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!= 0) /* Check for errors */
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{ /****************************/
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/*** WE SHOULD CHECK FOR SPARSE FILES HERE... ***/
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if(nsecs>1) /* were we trying multi-sec?*/
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nsecs = __cpmrv >>_MAXSHFT; /* adjust nsecs read ifso */
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else nsecs=0; /* ow. assume 0 secs read */
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return(seccnt+nsecs); /* Return nfg */
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} /****************************/
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/* */
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sector += nsecs; /* Increment sector number */
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count -= nsecs; /* Down count */
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seccnt += nsecs; /* Bump sector count */
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buffer += nsecs*SECSIZ; /* Increment address */
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} /****************************/
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if(ccb->user != xuser) /* Different user #'s?? */
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__BDOS(USER,(LONG)xuser); /* Yes, reset to original */
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return(seccnt); /* All is OK */
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} /****************************/
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