summaryrefslogtreecommitdiff
path: root/04/guessing_game
blob: 5c85252f91ca114b71124a7a0bc679c1ecc5337a (plain)
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
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
global exit_code
exit_code = main()
exit(exit_code)

function main
	local secret_number
	local guess
	global 32 input_line
	local p_line
	p_line = &input_line
	secret_number = getrand(100)
	puts(.str_intro)
	
	:guess_loop
		puts(.str_guess)
		syscall(0, 0, p_line, 30)
		guess = stoi(p_line)
		if guess < secret_number goto too_low
		if guess > secret_number goto too_high
		puts(.str_got_it)
		return 0
		:too_low
			puts(.str_too_low)
			goto guess_loop
		:too_high
			puts(.str_too_high)
			goto guess_loop

:str_intro
	string I'm thinking of a number.
	byte 10
	byte 0

:str_guess
	string Guess what it is:
	byte 32
	byte 0

:str_got_it
	string You got it!
	byte 10
	byte 0

:str_too_low
	string Too low!
	byte 10
	byte 0

:str_too_high
	string Too high!
	byte 10
	byte 0

; get a "random" number from 0 to x using the system clock
function getrand
	argument x
	global 16 getrand_time
	local ptime
	local n
	
	ptime = &getrand_time
	syscall(228, 0, ptime) ; clock_gettime(CLOCK_REALTIME, ptime)
	ptime += 8 ; nanoseconds at offset 8 in struct timespec
	n = *4ptime
	n %= x
	return n

; returns a pointer to a null-terminated string containing the number given
function itos
	global 32 itos_string
	argument x
	local c
	local p
	p = &itos_string
	p += 30
	:itos_loop
		c = x % 10
		c += '0
		*1p = c
		x /= 10
		if x == 0 goto itos_loop_end
		p -= 1
		goto itos_loop
	:itos_loop_end
	return p


; returns the number at the start of the given string
function stoi
	argument s
	local p
	local n
	local c
	n = 0
	p = s
	:stoi_loop
		c = *1p
		if c < '0 goto stoi_loop_end
		if c > '9 goto stoi_loop_end
		n *= 10
		n += c - '0
		p += 1
		goto stoi_loop
	:stoi_loop_end
	return n


function strlen
	argument s
	local p
	p = s
	:strlen_loop
		if *1p == 0 goto strlen_loop_end
		p += 1
		goto strlen_loop
	:strlen_loop_end
	return p - s

function fputs
	argument fd
	argument s
	local length
	length = strlen(s)
	syscall(1, fd, s, length)
	return

function puts
	argument s
	fputs(1, s)
	return

function fputn
	argument fd
	argument n
	local s
	s = itos(n)
	fputs(fd, s)
	return

function exit
	argument status_code
	syscall(0x3c, status_code)

function syscall
	; I've done some testing, and this should be okay even if
	; rbp-56 goes beyond the end of the stack.
	; mov rax, [rbp-16]
	byte 0x48
	byte 0x8b
	byte 0x85
	byte 0xf0
	byte 0xff
	byte 0xff
	byte 0xff
	; mov rdi, rax
	byte 0x48
	byte 0x89
	byte 0xc7
	
	; mov rax, [rbp-24]
	byte 0x48
	byte 0x8b
	byte 0x85
	byte 0xe8
	byte 0xff
	byte 0xff
	byte 0xff
	; mov rsi, rax
	byte 0x48
	byte 0x89
	byte 0xc6
	
	; mov rax, [rbp-32]
	byte 0x48
	byte 0x8b
	byte 0x85
	byte 0xe0
	byte 0xff
	byte 0xff
	byte 0xff
	; mov rdx, rax
	byte 0x48
	byte 0x89
	byte 0xc2
	
	; mov rax, [rbp-40]
	byte 0x48
	byte 0x8b
	byte 0x85
	byte 0xd8
	byte 0xff
	byte 0xff
	byte 0xff
	; mov r10, rax
	byte 0x49
	byte 0x89
	byte 0xc2
	
	; mov rax, [rbp-48]
	byte 0x48
	byte 0x8b
	byte 0x85
	byte 0xd0
	byte 0xff
	byte 0xff
	byte 0xff
	; mov r8, rax
	byte 0x49
	byte 0x89
	byte 0xc0
	
	; mov rax, [rbp-56]
	byte 0x48
	byte 0x8b
	byte 0x85
	byte 0xc8
	byte 0xff
	byte 0xff
	byte 0xff
	; mov r9, rax
	byte 0x49
	byte 0x89
	byte 0xc1
	
	; mov rax, [rbp-8]
	byte 0x48
	byte 0x8b
	byte 0x85
	byte 0xf8
	byte 0xff
	byte 0xff
	byte 0xff
	
	; syscall
	byte 0x0f
	byte 0x05
	
	return