From 6fa68e1fc11ee72d858f9a79e6178d82a13d3460 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juhani=20Krekel=C3=A4?= <juhani@krekelä.fi>
Date: Fri, 30 Jul 2021 13:20:59 +0300
Subject: [PATCH] More symbolicity

---
 edlin.asm | 48 ++++++++++++++++++++++++++++++++++++------------
 1 file changed, 36 insertions(+), 12 deletions(-)

diff --git a/edlin.asm b/edlin.asm
index 1d764b8..5fad037 100644
--- a/edlin.asm
+++ b/edlin.asm
@@ -3,10 +3,28 @@ org 0x100
 
 ; FCB defines
 fcb_filename equ 1
+fcb_extension equ fcb_filename + 8
 
 ; PSP defines
 psp_fcb_1 equ 0x005c
 
+; Syscall defined
+sys_print_string equ 9
+sys_open_file equ 0xf
+sys_delete_file equ 0x13
+sys_create_file equ 0x16
+
+; Special instruction encodings
+%macro or_al_al 0
+	db 0x0a, 0xc0 ; or al, al (longer encoding)
+%endmacro
+
+%macro cmp_byteaddr_bytext 2
+	db 0x82, 0x3e ; cmp byte […], byte +… (extended)
+	dw %1
+	db %2
+%endmacro
+
 jmp entrypoint
 
 __0102:
@@ -28,16 +46,15 @@ entrypoint: ; 0181
 	mov sp, stack_end
 
 ensure_file_argument:
-	db 0x82, 0x3e ; cmp byte […], byte +… (extended)
-	dw psp_fcb_1 + fcb_filename
-	db ' '
+	cmp_byteaddr_bytext psp_fcb_1 + fcb_filename, ' '
 	je print_filename_missing_error
 
-	db 0x0a, 0xc0 ; or al, al (longer encoding)
+	; AL at program start a flag of whether drive specifier in first parameter valid
+	or_al_al
 	mov dx, invalid_name_error
 	jnz _trampoline_error_1
 
-	mov si, __093e
+	mov si, bak_extension
 	mov di, psp_fcb_1 + fcb_filename + 8
 	mov cx, 3
 	repe cmpsb
@@ -343,7 +360,7 @@ db 0xCD, 0x21 ; 0477 int 0x21
 db 0xBA, 0xB9, 0x09 ; 0479 mov dx,0x9b9
 
 error: ; 047c
-	mov ah, 9
+	mov ah, sys_print_string
 	int 0x21
 	int 0x20
 
@@ -855,16 +872,16 @@ db 0xBC, 0x48, 0x0D ; 0935 mov sp,0xd48
 db 0xE8, 0xE2, 0xFF ; 0938 call 0x91d
 db 0xE9, 0x35, 0xF9 ; 093B jmp 0x273
 
-__093e db "BAK"
+bak_extension db "BAK" ; 093e
 
 invalid_name_error db "Invalid drive or file name$" ; 0941
 filename_missing_error db "File name must be specified$" ; 095c
-__0978 db "Cannot edit .BAK file--rename file$"
-__099b db "No room in directory for file$"
+bak_error db "Cannot edit .BAK file--rename file$" ; 0978
+directory_full_error db "No room in directory for file$" ; 099b
 __09b9 db "Disk full--file write not completed$"
 __09dd db 13, 10, "Insufficient memory", 13, 10, '$'
 __09f5 db "Entry error", 13, 10, '$'
-__0a03 db "New file", 13, 10, '$'
+new_file_str db "New file", 13, 10, '$' ; 0a03
 __0a0e db "Not found", 13, 10, '$'
 __0a1a db "O.K.? $"
 __0a21 db "Line too long", 13, 10, '$'
@@ -872,7 +889,14 @@ __0a31 db "End of input file", 13, 10, '$'
 __0a45 db "Abort edit (Y/N)? $"
 
 ; 0a58
+section .bss
+__0a58:
 
-__0a7f equ 0x0a7f
+resb 38
 
-stack_end equ 0x0d48
+__0a7e: resb 1
+__0a7f: resb 1
+
+resb 712
+
+stack_end: ; 0d48