BMS/boot.asm at main · helmick43270/BMS · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
[BITS 16]
[ORG 0x7C00]

start:
	xor ax, ax
	mov ds, ax
	mov es, ax

main_loop:
	mov si, prompt
	call print_string
	mov di, 0x7E00
	mov cx, 0

read_loop:
	mov ah, 0x00
	int 0x16
	cmp al, 0x0D
	je parse_command
	cmp al, 0x08
	je handle_backspace
	cmp cx, 32
	je read_loop
	stosb
	inc cx
	mov ah, 0x0E
	int 0x10
	sti
	hlt
	jmp read_loop

handle_backspace:
	cmp cx, 0
	je read_loop
	dec di
	dec cx
	mov ah, 0x0E
	mov al, 0x08
	int 0x10
	mov al, ' '
	int 0x10
	mov al, 0x08
	int 0x10
	jmp read_loop

parse_command:
	mov al, 0
	stosb
	call print_newline

	cmp byte [0x7E00], 0
	je main_loop

	mov si, cmd_help
	mov di, 0x7E00
	call strcmp
	jc do_help

	mov si, cmd_cls
	mov di, 0x7E00
	call strcmp
	jc do_cls

	mov si, cmd_echo
	mov di, 0x7E00
	call strcmp
	jc do_echo

	mov si, msg_bad
	call print_string
	jmp main_loop

do_help:
	mov si, msg_help
	call print_string
	jmp main_loop

do_cls:
	mov ax, 0x0003
	int 0x10
	jmp main_loop

do_echo:
	mov si, 0x7E00 + 5
	call print_string
	call print_newline
	jmp main_loop

strcmp:
	push di
.loop:
	mov al, [si]
	cmp al, 0
	je .check_delimiter

	mov bl, [di]
	cmp al, bl
	jne .nomatch

	inc si
	inc di
	jmp .loop

.check_delimiter:
	mov bl, [di]
	cmp bl, ' '
	je .match
	cmp bl, 0
	je .match

.match:
	pop di
	stc
	ret

.nomatch:
	pop di
	clc
	ret

print_newline:
	mov ah, 0x0E
	mov al, 0x0D
	int 0x10

	mov al, 0x0A
	int 0x10
	ret

print_string:
	mov ah, 0x0E

.loop:
	lodsb
	cmp al, 0
	je .done

	int 0x10
	jmp .loop

.done:
	ret

prompt   db 'BMS> ', 0
cmd_help db 'help', 0
cmd_cls	 db 'cls', 0
cmd_echo db 'echo', 0
msg_help db 'Available Commands: help, cls, echo <text>', 13, 10, 0
msg_bad  db 'Unknown Command', 13, 10, 0

times 510-($-$$) db 0
dw 0xAA55