Pascal III: Accessing the extra memory (2 of 5)

.PROC Allocate,4
FindSeg .EQU 41

SegBase .EQU Temp1
Bank .EQU Temp2
SegNum .EQU Temp3
NumPages .EQU Temp4

EnterProc RetAddr

PULL SegBase
PULL Bank
PULL SegNum
PULL NumPages

P_A_Word NumPages,Pages

SOSCall Find_Seg,Param
BEQ $1 ; If it worked,great
SOSCall Find_Seg,Param ; Else try again!
$1 BEQ $2
LDA #0 ; 2 failures ==> return 0 pages
STA Pages
STA Pages+1

$2 LDA SPage ; Send back starting address
LDY #1 ; in high byte!!
STA (SegBase),Y
DEY
TYA
STA (SegBase),Y

A_P_Word Pages,NumPages
A_P_Byte SBank,Bank
A_P_Byte Seg, SegNum

Return RetAddr

Param .BYTE 06
SrchMde .BYTE 02 ; Can cross more than one boundary
SegId .BYTE 30 ; First user segment?
Pages .WORD
SBank .BYTE
SPage .BYTE
.WORD
Seg .BYTE

RetAddr .WORD

.PROC DeAllocate,1
; PROCEDURE DeAllocate(SegNum:INTEGER); EXTERNAL;
Release_Seg .EQU 45
EnterProc RetAddr
PULL SegNum

LDA SegNum
BEQ Ret ; Don't release all segs!

SOSCALL Release_Seg,Param
Ret Return RetAddr

Param .BYTE 1
SegNum .WORD ; Only first byte used by SOS, but PULL
; needs 2
RetAddr .WORD

.END

================================================================
; This file contains an assembly language procedure which moves
; bytes from one bank to another. Use this from Pascal to get
; access to the rest of the bank space in larger machines.
; This can allow you to do SOS Request-Seg calls and use
; that area for data storage for later use or to pass to an
; assembly procedure. This procedure does two slightly difficult
; things :
;
; 1. it avoids holes in bank memory map, and
; 2. it switches banks on both source and destination at the
; right times.
;
; Pascal declaration is:
; PROCEDURE FetchBytes(SrcBank:INTEGER; Source:INTEGER;
; DstBank:INTEGER; Dest:INTEGER;
; PageCount:INTEGER; Count:INTEGER
; ); EXTERNAL;
;
; The procedure will copy 256*PageCount+Count bytes from
; Source (a bank pointer to bank pair starting with SrcBank) to
; Dest (a bank pointer to bank pair starting with DstBank);
; A SrcBank or DstBank of -1 means "in Pascal's bank pair"
; Thus FetchBytes(-1,Atsign(S),-1,Atsign(D),0,C) ==
; MoveLeft(S,D,C)
;
; RESTRICTIONS:
; 1. Equivalent to a moveleft (ascending transfer)
; 2. Cannot reach top and bottom (system) banks,
; and "real" addresses must be offset
; by $2000 to render bank addresses
;
; ALGORITHM:
; 1. If we're moving X*65535 +Y*256 + Z bytes, then
; 2. First move Y pages to clear middle byte of Count
; 3. Then use middle byte to move X*256 pages,
; 4. Finally, move Z bytes in last page.
; ==============================================================
; MACRO Defs
.MACRO PULL
PLA
STA %1
PLA
STA %1+1
.ENDM

.MACRO PUSH
LDA %1+1
PHA
LDA %1
PHA
.ENDM