From a8357047b283b16590b208375b0c603e12e139ae Mon Sep 17 00:00:00 2001
From: Wayne Warthen <wwarthen@gmail.com>
Date: Wed, 4 Mar 2020 13:00:35 -0800
Subject: [PATCH] Update hbios.asm

Adjusted used of DI/EI for PEEK and POKE to regain a bit of INTSTK space.  Added code so that HB_INVBNK can be used as a flag indicating if HBIOS is active, $FF is inactive, anything else means active.
---
 Source/HBIOS/hbios.asm | 80 ++++++++++++++++++++++++++----------------
 1 file changed, 49 insertions(+), 31 deletions(-)

diff --git a/Source/HBIOS/hbios.asm b/Source/HBIOS/hbios.asm
index bdeb6fe6..80376b43 100644
--- a/Source/HBIOS/hbios.asm
+++ b/Source/HBIOS/hbios.asm
@@ -269,10 +269,16 @@ HBX_IDENT:
 ; ACCOMMODATE FREERTOS.  HBX_BUF IS ONLY USED AS A BOUNCE BUFFER, SO IT'S
 ; USE WILL NEVER OVERLAP WITH BELOW.
 ;
+; HBX_INVOKE IS NOT RE-ENTRANT!  HB_INVBNK CAN BE USED GLOBALLY TO DETERMINE
+; IF HBIOS IS ALREADY ACTIVE.  HB_INVBNK WILL HAVE A VALUE != $FF WHEN HBIOS
+; IS ACTIVE.  ON RETURN, HB_INVBNK IS SET TO $FF TO INDICATE HBIOS IS NOT
+; ACTIVE.
+;
 HBX_INVOKE:
-	LD	(HBX_INVSP),SP		; SAVE ORIGINAL STACK FRAME
 	LD	A,(HB_CURBNK)		; GET CURRENT BANK
 	LD	(HB_INVBNK),A		; SAVE INVOCATION BANK
+	
+	LD	(HBX_INVSP),SP		; SAVE ORIGINAL STACK FRAME
 
 	LD	SP,HBX_BUF_END		; BORROW HBX_BUF FOR TEMP STACK
 	LD	A,BID_BIOS		; HBIOS BANK
@@ -290,6 +296,11 @@ HBX_INVOKE:
 	LD	SP,0			; RESTORE ORIGINAL STACK FRAME
 HBX_INVSP	.EQU	$ - 2
 
+	PUSH	AF			; SAVE AF
+	OR	$FF			; CLEAR INVBNK TO INACTIVE VALUE
+	LD	(HB_INVBNK),A		; SAVE IT
+	POP	AF			; RESTORE AF
+
 	RET				; RETURN TO CALLER
 ;
 ;;::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
@@ -482,14 +493,11 @@ HBX_TGTADR	.EQU	$ + 1
 ;
 ; PEEK & POKE ROUTINES
 ;   ADDRESS IN HL, BANK IN D, VALUE IN/OUT IN E, A IS TRASHED
-;   IM1/IM2 INTERRUPTS ARE DISABLED DURING HBX_PEEK & HBX_POKE.
+;   THESE ROUTINES ARE NOT INTENDED TO BE CALLED DIRECTLY -- THEY ARE
+;   HELPERS FOR THE HBIOS API AND ARE CALLED BY HBIOS BANK CODE.  THE
+;   HBIOS BANK CODE BRACKETS THE USE OF THESE ROUTINES WITH DI/EI.
 ;
 HBX_PEEK:
-#IF (INTMODE > 0)
-	LD	A,I
-	DI
-	PUSH	AF
-#ENDIF
 	LD	(HBX_PPSP),SP		; SAVE ORIGINAL STACK FRAME
 	LD	SP,HBX_TMPSTK		; USE SMALL TEMP STACK FRAME IN HI MEM
 	LD	A,(HB_CURBNK)
@@ -500,11 +508,6 @@ HBX_PEEK:
 	JR	HBX_PPRET
 ;
 HBX_POKE:
-#IF (INTMODE > 0)
-	LD	A,I
-	DI
-	PUSH	AF
-#ENDIF
 	LD	(HBX_PPSP),SP		; SAVE ORIGINAL STACK FRAME
 	LD	SP,HBX_TMPSTK		; USE SMALL TEMP STACK FRAME IN HI MEM
 	LD	A,(HB_CURBNK)
@@ -518,11 +521,6 @@ HBX_PPRET:
 	CALL	HBX_BNKSEL
 	LD	SP,0			; RESTORE ORIGINAL STACK FRAME
 HBX_PPSP	.EQU	$ - 2
-#IF (INTMODE > 0)
-	POP	AF
-	JP	PO,$+4
-	EI
-#ENDIF
 	RET
 ;
 ; PRIVATE STACK AT END OF HBIOS CODE
@@ -671,23 +669,23 @@ HBX_BUF_END	.EQU	$
 ; HBIOS PROXY MGMT BLOCK (TOP 32 BYTES)
 ;
 #IFDEF ROMBOOT
-	.DB	BID_BOOT		; CURRENTLY ACTIVE LOW MEMORY BANK ID
+	.DB	BID_BOOT		; HB_CURBNK: CURRENTLY ACTIVE LOW MEMORY BANK ID
 #ELSE
-	.DB	BID_USR			; CURRENTLY ACTIVE LOW MEMORY BANK ID
-#ENDIF
-	.DB	0			; BANK ACTIVE AT TIME OF HBIOS CALL INVOCATION
-	.DW	0			; BNKCPY SOURCE ADDRESS
-	.DB	BID_USR			; BNKCPY SOURCE BANK ID
-	.DW	0			; BNKCPY DESTINATION ADDRESS
-	.DB	BID_USR			; BNKCPY DESTINATION BANK ID
-	.DW	0			; BNKCPY LENGTH
+	.DB	BID_USR			; HB_CURBNK: CURRENTLY ACTIVE LOW MEMORY BANK ID
+#ENDIF
+	.DB	$FF			; HB_INVBNK: BANK ACTIVE AT TIME OF HBIOS CALL INVOCATION
+	.DW	0			; HB_SRCADR: BNKCPY SOURCE ADDRESS
+	.DB	BID_USR			; HB_SRCBNK: BNKCPY SOURCE BANK ID
+	.DW	0			; HB_DSTADR: BNKCPY DESTINATION ADDRESS
+	.DB	BID_USR			; HB_DSTBNK: BNKCPY DESTINATION BANK ID
+	.DW	0			; HB_CPYLEN: BNKCPY LENGTH
 	.FILL	6,0			; FILLER, RESERVED FOR FUTURE HBIOS USE
-	JP	HBX_INVOKE		; FIXED ADR ENTRY FOR HBX_INVOKE (ALT FOR RST 08)
-	JP	HBX_BNKSEL		; FIXED ADR ENTRY FOR HBX_BNKSEL
-	JP	HBX_BNKCPY		; FIXED ADR ENTRY FOR HBX_BNKCPY
-	JP	HBX_BNKCALL		; FIXED ADR ENTRY FOR HBX_BNKCALL
+	JP	HBX_INVOKE		; HB_INVOKE: FIXED ADR ENTRY FOR HBX_INVOKE (ALT FOR RST 08)
+	JP	HBX_BNKSEL		; HB_BNKSEL: FIXED ADR ENTRY FOR HBX_BNKSEL
+	JP	HBX_BNKCPY		; HB_BNKCPY: FIXED ADR ENTRY FOR HBX_BNKCPY
+	JP	HBX_BNKCALL		; HB_BNKCALL: FIXED ADR ENTRY FOR HBX_BNKCALL
 	.DW	HBX_IDENT		; ADDRESS OF HBIOS PROXY START (DEPRECATED)
-	.DW	HBX_IDENT		; ADDRESS OF HBIOS IDENT INFO DATA BLOCK
+	.DW	HBX_IDENT		; HB_IDENT: ADDRESS OF HBIOS IDENT INFO DATA BLOCK
 ;
 	.FILL	MEMTOP - $		; FILL TO END OF MEMORY (AS NEEDED)
 	.ORG	HBX_IMG + HBX_SIZ	; RESET ORG
@@ -2455,7 +2453,17 @@ SYS_SETSECS:
 ; RETURN: E=BYTE VALUE
 ;
 SYS_PEEK:
+#IF (INTMODE > 0)
+	LD	A,I
+	DI
+	PUSH	AF
+#ENDIF
 	CALL	HBX_PEEK		; IMPLEMENTED IN PROXY
+#IF (INTMODE > 0)
+	POP	AF
+	JP	PO,$+4
+	EI
+#ENDIF
 	XOR	A
 	RET
 ;
@@ -2463,7 +2471,17 @@ SYS_PEEK:
 ; ENTRY: D=BANK ID, HL=ADDRESS IN HBIOS BANK, E=BYTE VALUE
 ;
 SYS_POKE:
+#IF (INTMODE > 0)
+	LD	A,I
+	DI
+	PUSH	AF
+#ENDIF
 	CALL	HBX_POKE		; IMPLEMENTED IN PROXY
+#IF (INTMODE > 0)
+	POP	AF
+	JP	PO,$+4
+	EI
+#ENDIF
 	XOR	A
 	RET
 ;