Initial file setup

edlin.asm

@@ -3,10 +3,55 @@ org 0x100
 
 ; FCB defines
 fcb_filename equ 1
+fcb_extension equ fcb_filename + 8
+fcb_record_size equ 14
+fcb_record_low equ 33
+fcb_record_high equ 35
 
 ; PSP defines
+psp_segment_size equ 0x0006
 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
+sys_set_dta equ 0x1a
+sys_block_read equ 0x27
+
+; Special instruction encodings
+%macro add_cx_ax 0
+	db 0x03, 0xC8 ; add cx, ax (direction swapped)
+%endmacro
+%macro add_di_cx 0
+	db 0x03, 0xF9 ; 023E add di, cx (direction swapped)
+%endmacro
+
+%macro or_al_al 0
+	db 0x0a, 0xc0 ; or al, al (direction swapped)
+%endmacro
+
+%macro xor_ax_ax 0
+	db 0x33, 0xc0 ; xor ax, ax (direction swapped)
+%endmacro
+
+%macro mov_ax_cx 0
+	db 0x8b, 0xc1 ; mov ax, cx (direction swapped)
+%endmacro
+%macro mov_dx_cx 0
+	db 0x8b, 0xD1 ; mov dx, cx (direction swapped)
+%endmacro
+%macro mov_di_dx 0
+	db 0x8B, 0xfa ; mov di, dx (direction swapped)
+%endmacro
+
+%macro cmp_byteaddr_bytext 2
+	db 0x82, 0x3e ; cmp byte […], byte +… (extended)
+	dw %1
+	db %2
+%endmacro
+
 jmp entrypoint
 
 __0102:
@@ -24,87 +69,116 @@ _trampoline_error_1:
 	jmp error
 
 entrypoint: ; 0181
-	mov byte [0x0a7f], 0
+	mov byte [__0a7f], 0
-	mov sp, 0x0d48
+	mov sp, stack.end
 
 ensure_file_argument:
-	db 0x82, 0x3e ; cmp byte […], byte +… (extended)
+	cmp_byteaddr_bytext psp_fcb_1 + fcb_filename, ' '
-	dw psp_fcb_1 + fcb_filename
-	db ' '
 	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
 
-db 0xBE, 0x3E, 0x09 ; 0197 mov si,0x93e
+	mov si, bak_extension
-db 0xBF, 0x65, 0x00 ; 019A mov di,0x65
+	mov di, psp_fcb_1 + fcb_filename + 8
-db 0xB9, 0x03, 0x00 ; 019D mov cx,0x3
+	mov cx, 3
-db 0xF3, 0xA6 ; 01A0 repe cmpsb
+	repe cmpsb
-db 0x74, 0x42 ; 01A2 jz 0x1e6
+	je print_bak_error
-db 0xB4, 0x0F ; 01A4 mov ah,0xf
+
-db 0xBA, 0x5C, 0x00 ; 01A6 mov dx,0x5c
+open_file:
-db 0xCD, 0x21 ; 01A9 int 0x21
+	mov ah, sys_open_file
-db 0xA2, 0x7E, 0x0A ; 01AB mov [0xa7e],al
+	mov dx, psp_fcb_1
-db 0x0A, 0xC0 ; 01AE or al,al
+	int 0x21
-db 0x74, 0x07 ; 01B0 jz 0x1b9
+
-db 0xBA, 0x03, 0x0A ; 01B2 mov dx,0xa03
+	mov [new_file_flag], al
-db 0xB4, 0x09 ; 01B5 mov ah,0x9
+	or_al_al
-db 0xCD, 0x21 ; 01B7 int 0x21
+	jz delete_old_bak
-db 0xBE, 0x5C, 0x00 ; 01B9 mov si,0x5c
+
-db 0xBF, 0x58, 0x0A ; 01BC mov di,0xa58
+	mov dx, new_file_str
-db 0xB9, 0x09, 0x00 ; 01BF mov cx,0x9
+	mov ah, sys_print_string
-db 0xF3, 0xA4 ; 01C2 rep movsb
+	int 0x21
-db 0xBE, 0x3E, 0x09 ; 01C4 mov si,0x93e
+
-db 0xA5 ; 01C7 movsw
+delete_old_bak: ; 01b9
-db 0xA4 ; 01C8 movsb
+	mov si, psp_fcb_1
-db 0xB4, 0x13 ; 01C9 mov ah,0x13
+	mov di, __0a58_fcb
-db 0xBA, 0x58, 0x0A ; 01CB mov dx,0xa58
+	mov cx, 9
-db 0xCD, 0x21 ; 01CE int 0x21
+	rep movsb
-db 0xB0, 0x24 ; 01D0 mov al,0x24
+
-db 0xBF, 0x61, 0x0A ; 01D2 mov di,0xa61
+	mov si, bak_extension
-db 0xAA ; 01D5 stosb
+	movsw
-db 0xAA ; 01D6 stosb
+	movsb
-db 0xAA ; 01D7 stosb
+
-db 0xB4, 0x16 ; 01D8 mov ah,0x16
+	mov ah, sys_delete_file
-db 0xCD, 0x21 ; 01DA int 0x21
+	mov dx, __0a58_fcb
-db 0x0A, 0xC0 ; 01DC or al,al
+	int 0x21
-db 0x74, 0x0C ; 01DE jz 0x1ec
+
-db 0xBA, 0x9B, 0x09 ; 01E0 mov dx,0x99b
+	; TODO: Why .$$$? What is this used for?
-db 0xE9, 0x96, 0x02 ; 01E3 jmp 0x47c
+	mov al, '$'
-db 0xBA, 0x78, 0x09 ; 01E6 mov dx,0x978
+	mov di, __0a58_fcb + fcb_extension
-db 0xE9, 0x90, 0x02 ; 01E9 jmp 0x47c
+	stosb
-db 0x33, 0xC0 ; 01EC xor ax,ax
+	stosb
-db 0xA3, 0x7D, 0x00 ; 01EE mov [0x7d],ax
+	stosb
-db 0xA3, 0x7F, 0x00 ; 01F1 mov [0x7f],ax
+
-db 0xA3, 0x79, 0x0A ; 01F4 mov [0xa79],ax
+	mov ah, sys_create_file
-db 0xA3, 0x7B, 0x0A ; 01F7 mov [0xa7b],ax
+	int 0x21
-db 0x40 ; 01FA inc ax
+	or_al_al
-db 0xA3, 0x6A, 0x00 ; 01FB mov [0x6a],ax
+	jz setup_file_parameters
-db 0xA3, 0x66, 0x0A ; 01FE mov [0xa66],ax
+
-db 0xBA, 0x49, 0x0D ; 0201 mov dx,0xd49
+	mov dx, directory_full_error
-db 0x8B, 0xFA ; 0204 mov di,dx
+	jmp error
-db 0xB4, 0x1A ; 0206 mov ah,0x1a
+
-db 0xCD, 0x21 ; 0208 int 0x21
+print_bak_error: ; 01e6
-db 0x8B, 0x0E, 0x06, 0x00 ; 020A mov cx,[0x6]
+	mov dx, bak_error
-db 0x49 ; 020E dec cx
+	jmp error
-db 0x89, 0x0E, 0x98, 0x0A ; 020F mov [0xa98],cx
+
-db 0xF6, 0x06, 0x7E, 0x0A, 0xFF ; 0213 test byte [0xa7e],0xff
+setup_file_parameters: ; 01ec
-db 0x75, 0x26 ; 0218 jnz 0x240
+	xor_ax_ax
-db 0x81, 0xE9, 0x49, 0x0D ; 021A sub cx,0xd49
+	mov [psp_fcb_1 + fcb_record_low], ax
-db 0xD1, 0xE9 ; 021E shr cx,1
+	mov [psp_fcb_1 + fcb_record_high], ax
-db 0x8B, 0xC1 ; 0220 mov ax,cx
+	mov [__0a58_fcb + fcb_record_low], ax
-db 0xD1, 0xE9 ; 0222 shr cx,1
+	mov [__0a58_fcb + fcb_record_high], ax
-db 0x89, 0x0E, 0x94, 0x0A ; 0224 mov [0xa94],cx
+
-db 0x03, 0xC8 ; 0228 add cx,ax
+	inc ax
-db 0x8B, 0xD1 ; 022A mov dx,cx
+	mov [psp_fcb_1 + fcb_record_size], ax
-db 0x81, 0xC2, 0x49, 0x0D ; 022C add dx,0xd49
+	mov [__0a58_fcb + fcb_record_size], ax
-db 0x89, 0x16, 0x96, 0x0A ; 0230 mov [0xa96],dx
+
-db 0xBA, 0x5C, 0x00 ; 0234 mov dx,0x5c
+	mov dx, disk_transfer_area
-db 0xB4, 0x27 ; 0237 mov ah,0x27
+	mov_di_dx
-db 0xCD, 0x21 ; 0239 int 0x21
+	mov ah, sys_set_dta
-db 0xE8, 0x20, 0x01 ; 023B call 0x35e
+	int 0x21
-db 0x03, 0xF9 ; 023E add di,cx
+
+	mov cx, [psp_segment_size]
+	dec cx
+	mov [__0a98], cx
+
+	test byte [new_file_flag], 0xff
+	jnz __0240
+
+	sub cx, disk_transfer_area
+	; cx is now the amount of memory available starting at disk_transfer_area
+
+	; __0a94 = ¼ available memory
+	shr cx, 1
+	mov_ax_cx
+	shr cx, 1
+	mov [__0a94], cx
+	; __0a94 = ¾ available memory
+	add_cx_ax
+
+	mov_dx_cx
+	add dx, disk_transfer_area
+	mov [__0a96], dx
+
+read_file:
+	mov dx, psp_fcb_1
+	mov ah, sys_block_read
+	int 0x21
+	call __035e
+	add_di_cx
+
+__0240:
 db 0xFC ; 0240 cld
 db 0xC6, 0x05, 0x1A ; 0241 mov byte [di],0x1a
 db 0x89, 0x3E, 0x9A, 0x0A ; 0244 mov [0xa9a],di
@@ -224,7 +298,11 @@ db 0x05, 0x27, 0x06 ; 0355 add ax,0x627
 db 0x70, 0x03 ; 0358 jo 0x35d
 db 0x17 ; 035A pop ss
 db 0x04, 0xA6 ; 035B add al,0xa6
-db 0x08, 0x57, 0x51 ; 035D or [bx+0x51],dl
+db 0x08 ; 035D db 0x08
+
+__035e:
+db 0x57 ; 035E push di
+db 0x51 ; 035F push cx
 db 0xB0, 0x1A ; 0360 mov al,0x1a
 db 0xF2, 0xAE ; 0362 repne scasb
 db 0x8B, 0xF9 ; 0364 mov di,cx
@@ -341,7 +419,7 @@ 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
 
@@ -853,18 +931,43 @@ 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$"
+bak_error db "Cannot edit .BAK file--rename file$" ; 0978
-__099b db "No room in directory for file$"
+directory_full_error db "No room in directory for file$" ; 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.? $"
 __0a21 db "Line too long", 13, 10, '$'
 __0a31 db "End of input file", 13, 10, '$'
 __0a45 db "Abort edit (Y/N)? $"
+
+; 0a58
+section .bss
+__0a58_fcb: resb 37 ; 0a58 … 0a7c
+
+; 0a7d
+resb 1
+
+new_file_flag: resb 1 ; 0a7e
+__0a7f: resb 1
+
+resb 20
+
+__0a94: resw 1
+__0a96: resw 1
+__0a98: resw 1
+
+resb 430
+
+stack: resb 256 ; 0c48
+.end: ; 0d48
+
+resb 1
+
+disk_transfer_area: ; 0d49