DYdel.opl

DYdel:(dp%,sz%)
rem delete a diary record at dp%, length sz%
local mc%(7),tmp%,start%
rem local da%

rem da%=peekw($2004) rem diary address
rem print"diary: $";hex$(da%)
rem sz%=peekb(da%+dp%) rem read size of record at diary pointer dp%

rem * OS al$shrink to delete record from diary cell
rem * shrink diary cell by sz% bytes at dp%

rem utw_s0 <- dp%, store dp% at utw_s0
rem D loaded by OPL usr(), with dp%
mc%(1)=$DD41 rem STD $41 store D in $41 $42 (utw_s0) offset location dp%

rem D <- sz%
mc%(2)=$01CC rem NOP :LDD #
mc%(3)=sz% rem sz%

rem X <- diary cell, call al$shrink to shrink by sz% at dp%
mc%(4)=$01CE rem NOP LDX #
mc%(5)=$2004 rem $2004 diary tag
mc%(6)=$3F04 rem OS al$shrink, X=diary tag, D=sz%, location utw_s0=dp%
mc%(7)=$3901 rem RTS :NOP
rem utw_s0-3 trashed by OS call, (D=value in addr(X), X=$2040)
rem on exit X=$2040, contents of X in D, $2040 is pointer to end of allocator area, end of last cell
rem so nothing particularly useful is returned by al$shrink in X or D

start%=addr(mc%())
rem print"c:$";hex$(start%),"D:$";hex$(dp%); :get rem ** for debug
rem print"r" rem to indicate run

tmp%=usr(start%,dp%) rem usr(x%,y%) y% into D, call mc at x%, return X
rem tmp%=$2040, pointer to end of allocator cells
return