Difference between revisions of "83Plus:BCALLs:42F7"

Latest revision as of 20:33, 24 September 2012

Synopsis

Official Name: InsertMem

BCALL Address: 42F7

Adds RAM space into an existing variable.

Inputs

• HL = amount of RAM to insert into the variable
• DE = the memory address where the RAM will be inserted

Outputs

• DE = the memory addressed where the RAM was inserted. Equivilant to the input.

Destroys

• All

Remarks

• This routine will not check to see if there is insufficient RAM. It is highly suggested to do that beforehand, using the bcall EnoughMem.
• The size field of the variable is not updated. The user must do this himself.
• DE cannot be the first byte of the variable's data or else the symbol entry's pointer to the data will become corrupt (the first byte being the size field?).

Example

 ld  hl,9
 B_CALL  EnoughMem
 jr  c,NotEnoughMem          ;make sure there is enough memory to insert the RAM
 
 ld  hl,ApplicationVariable
 rst  rMov9ToOP1
 B_CALL  ChkFindSym          ;find the application variable
 jr  c,AppVarNotFound
 
 inc  de
 inc  de          ;move past the size bytes
 
 ld  hl,9
 B_CALL  InsertMem          ;insert 9 bytes here
 
 ex  de,hl
 dec  hl
 ld  a,(hl)
 dec  hl
 push  hl
 ld  h,(hl)
 ld  l,a          ;ld hl,(de). Load the size of the AppVar in hl
 
 ld  de,9
 add  hl,de          ;add 9 to hl
 
 ex de,hl
 pop  hl
 ld  (hl),e
 inc  hl
 ld  (hl),d          ;Store the new size back into the AppVar
 
 ApplicationVariable:
  .db AppVarObj,"APPVAR",0