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90 lines
2.9 KiB
Plaintext
90 lines
2.9 KiB
Plaintext
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;==========================================================================
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;
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; File: QueueUtils.a
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;
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; Contains: CEnqueueHead routine (should probably be in Queue.a)
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;
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; Written by: Paul Wolf
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;
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; Copyright: © 1992-1993 by Apple Computer, Inc., All rights reserved.
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;
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; This file initializes all the files that comprise the New SCSI Manager
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;
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; Change History (most recent first):
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;
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; <SM8> 10/14/93 pdw <MC> roll-in.
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; <SM7> 9/12/93 pdw Changed name of EnqueueHead to CEnqueueHead to avoid conflict
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; with newly added ROM OS routine.
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; <SM5> 6/29/93 pdw Changed headers included.
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; <SM4> 5/5/93 PW Converted names to meanies-friendly names. Updated with latest
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; from Ludwig stuff.
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; <SM3> 3/20/93 PW Removed some of the PDMDebug stuff that's not needed.
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; <SM2> 1/31/93 PW Update from the latest of Ludwig. Also changes required for PDM
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; (will update Ludwig with these as needed myself).
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;
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;==========================================================================
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MACHINE MC68020 ; '020-level
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BLANKS ON ; assembler accepts spaces & tabs in operand field
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STRING ASIS ; generate string as specified
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PRINT OFF ; do not send subsequent lines to the listing file
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; don't print includes
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CASE OBJECT ; preserve case in object file
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;--------------------------------------------------------------------------
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LOAD 'StandardEqu.d' ; from StandardEqu.a and for building ROMs
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INCLUDE 'Debug.a' ; for NAME macro
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;***********************************************************************
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; CEnqueueHead -- add a queue element to the head of a queue.
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;-----------------------------------------------------------------------
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;
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; Entry:
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; A0 - points to the queue element
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; A1 - points to the queue header
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; All registers are preserved; there are no error conditions.
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;
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; The element is inserted at the beginning of the list.
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;
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;-----------------------------------------------------------------------
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;
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CEnqueueHead PROC EXPORT
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move.l 4(sp), A0 ; get ptr to Q element
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move.l 8(sp), A1 ; get ptr to Q header
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MOVE SR, -(SP) ;preserve status
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ADDQ #2, A1 ;point to QHead
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ORI #$0700, SR ;disable interrupts for exclusion
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TST.L (A1)+ ;anything in the queue? (QHead)
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BNE.S DOQINSERT ;if so, skip ahead
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;
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; the queue is empty so make the head and tail point to the new element
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;
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MOVE.L A0, (A1) ;QTail
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MOVE.L A0, -(A1) ;QHead
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CLR.L QLINK(A0) ;clear the link of the element
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BRA.S ENQDONE
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;
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; insert the element at the head of the list
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;
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DOQINSERT MOVE.L A2, -(SP) ;preserve A2
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MOVE.L -(A1), A2 ;get ptr to old QHead
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MOVE.L A2, QLINK(A0) ;update new link to old head
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MOVE.L A0, (A1) ;update QHead
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MOVE.L (SP)+, A2 ;restore A2
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;
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ENQDONE SUBQ #2, A1 ;restore A1
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MOVE (SP)+, SR ;restore status and go home
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RTS
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NAME 'CEnqueueHead'
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ENDP
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END
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