qdosmsq:vectors:achp

Differences

This shows you the differences between two versions of the page.

Link to this comparison view

Both sides previous revision Previous revision
qdosmsq:vectors:achp [2008/06/27 19:31]
norman
qdosmsq:vectors:achp [2010/10/25 16:42]
george.gwilt Change od to of in Example
Line 1: Line 1:
 +====== MM_ALCHP/MEM_ACHP - Vector $C0 ======
 +This vector allocates memory on the common heap. It should only be called in supervisor mode. The vector call is atomic.
 +
 +^Call Parameters^^Return Parameters^^
 +|D0.L|Unused|D0.L|Error code.|
 +|D1.L|Number of bytes required. |D1.L|Number of bytes allocated.|
 +|D2.L|Unused |D2.L|Corrupted.|
 +|D3.L|Unused |D3.L|Corrupted.|
 +|A0.L|Unused |A0.L|Address of allocated area.|
 +|A1.L|Unused |A1.L|Corrupted.|
 +|A2.L|Unused |A2.L|Corrupted.|
 +|A3.L|Unused |A3.L|Corrupted.|
 +|A6.L|System variables address |A6.L|Preserved.|
 +
 +===== Errors =====
 +|ERR_OM|Out of memory.|
 +
 +===== Notes =====
 +  * All registers not shown above are not used on entry and are preserved on exit.
 +  * **Must** be called in supervisor mode only.
 +  * Mainly used in device driver 'open' routines to allocate space for channel definition blocks and so on.
 +  * The area allocated is filled with $00. (Zeroised.)
 +  * This vector call is //atomic//.
 +
 +
 +===== Example =====
 +The example below shows the use of this vector to allocate an area of 16 bytes for use by the routine.
 +
 +<code>
 +Get_hp  move.w  MM_ALCHP,A2     ; MM_ALCHP vector address.
 +        moveq   #16,d1          ; Number of bytes required.
 +                                ; Assume A6 is correct already
 +        jsr     (a2)            ; Make the call
 +        bne.s   Error_handler   ; Oops!
 +
 +All_ok cmpi.b  #16,d1          ; Did we get 16 bytes?
 + bne.s   Error_handler   ; No, oops!
 +
 +Got_hp  ...                     ; Do something here.
 +</code>
  
  • qdosmsq/vectors/achp.txt
  • Last modified: 2010/10/25 16:42
  • by george.gwilt