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155
CPM OPERATING SYSTEMS/CPM 68K/1.0X SOURCES/v102a/clib/channels.c
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155
CPM OPERATING SYSTEMS/CPM 68K/1.0X SOURCES/v102a/clib/channels.c
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/*****************************************************************************
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*
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* C H A N N E L A L L O C A T I N G R O U T I N E S
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* -----------------------------------------------------
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* Copyright 1984 by Digital Research Inc. All rights reserved.
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*
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* Herein are all the routines which deal with Channel Control Block
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* (CCB) allocation and initialization. These routines (documented
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* individually below) are:
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*
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* i = _allocc();
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* _freec(i);
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* _chinit();
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* __chinit(fd)
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* ccbptr = _chkc(ch);
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*
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*****************************************************************************/
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#include "portab.h" /* Include std definitions */
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#include "osif.h" /* Also CP/M ones */
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#include "osiferr.h" /* To set error vars */
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#include "errno.h" /* Error return vals */
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#ifdef MAXF5 /*--------------------------*/
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# define MAXCCBS 5 /* Maximum Num CCBs */
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maxfiles5() { ; } /* stubroutine for option.h */
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#else /*--------------------------*/
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#ifdef MAXF10 /*--------------------------*/
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# define MAXCCBS 10 /* Maximum Num CCBs */
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#else /*--------------------------*/
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# define MAXCCBS 16 /* Maximum Num CCBs */
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#endif /*--------------------------*/
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#endif /*--------------------------*/
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LONG _chvec ={0}; /* Allocate storage */
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FD _fds[MAXCCBS]; /* Allocate CCB storage */
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/*****************************************************************************
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* _ A L L O C C / _ F R E E C R O U T I N E S
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* -------------------------------------------------
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* Routines "_allocc" and "_freec" are used to allocate / deallocate a
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* channel number so that the user may do I/O directly without the OTS
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* getting in the way.
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* Note that this scheme preserves compatibility with OS's that really
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* truly use channels, and allows users to inform the C Run Time Library
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* routines that they are using the channel.
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* It's not important to use these routines under CP/M, since CP/M
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* allows you to have as many FCBs as you wish.
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*
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* Calling Sequence:
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* i = _allocc();
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* _freec(i);
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*****************************************************************************/
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WORD _allocc() /****************************/
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{ /* */
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REG WORD i; /* Define 2 temporaries */
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REG LONG j; /* */
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/* */
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j = 1; /* Start with channel 0 */
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for(i=0;i<MAXCCBS;i++) /* Look at the bits */
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{ /* */
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if((j & _chvec) == 0) /* If 0, then channel free */
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{ /* */
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_chvec |= j; /* set allocated bit */
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return(i); /* and return the channel # */
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} /* */
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j <<= 1; /* Up to next bit */
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} /* End FOR loop */
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RETERR(FAILURE,EMFILE); /* All channels in use! */
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} /****************************/
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WORD _freec(ch) /****************************/
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WORD ch; /* Channel number to free */
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{ /* */
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_chvec &= ~(1 << ch); /* Clear appropriate bit */
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return(SUCCESS); /* Return OK */
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} /****************************/
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/*****************************************************************************
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* C C B I N I T I A L I Z A T I O N
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* -----------------------------------
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* Routine "_chinit" is called from the run-time initialization to clear
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* out all the CCB storage.
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* Calling sequence:
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* _chinit();
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*
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* Routine "__chinit(fd)" is called from other low-level routines
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* for single channel initialization.
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* Calling sequence:
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* __chinit(fd)
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* where: fd = file descriptor #
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*****************************************************************************/
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_chinit() /****************************/
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{ /* */
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REG WORD i; /* Index */
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for(i=0;i<MAXCCBS;i++) /* For all channels */
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__chinit(i); /* Init fds(i); */
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} /****************************/
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/*****************************************************************************
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* The __chinit routine initializes only 1 channel.
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*****************************************************************************/
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__chinit(i)
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{ /****************************/
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REG FD *ch; /* -> CCB */
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REG BYTE *p; /* Byte pointer temporary */
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ch = _getccb(i); /* convert fd to CCB */
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ch -> chan = i; /* Load channel byte */
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ch -> flags = 0; /* clear flag word */
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ch -> user = 0; /* assume user 0 */
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ch -> sector = -1; /* Set no sector in buff */
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ch -> offset = 0; /* Clear file offset word */
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ch -> hiwater = 0; /* Init hiwater mark */
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ch -> fcb.drive = 0; /* Init drive field of fcb */
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p = &ch->fcb.fname[0]; /* Set to file var */
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while (p< &ch->fcb.ftype[3]) /* Init file name fields */
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*p++ = ' '; /* To spaces */
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while (p < &ch->fcb.record) /* Init rest of fcb */
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*p++ = 0; /* To zeros */
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} /****************************/
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/*****************************************************************************
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* C H A N N E L N U M B E R V A L I D A T I O N
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* -------------------------------------------------
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* This routine is used to validate a channel number and return the
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* pointer to the ccb area. The channel must be in range and open.
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*
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* Calling Sequence:
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*
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* Where:
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* ch Is the channel number
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* ccbptr Is the returned ccb address, NULLFD if error
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*****************************************************************************/
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FD *_chkc(ch) /****************************/
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REG UWORD ch; /* Facilitate error check */
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{ /* */
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REG FD *xcb; /* -> CCB */
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/****************************/
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if(ch >= MAXCCBS) /* Is channel in range? */
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RETERR(NULLFD,EBADF); /* No, quit now. */
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/* */
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xcb = _getccb(ch); /* xcb -> ccb for channel */
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if((xcb->flags & OPENED) == 0) /* Is channel OPEN? */
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RETERR(NULLFD,EBADF); /* Noooooooo!! */
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return(xcb); /* Else, return pointer */
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} /****************************/
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