about summary refs log tree commit diff stats
path: root/subx/074print-int-decimal.subx
blob: 04dcd1a5ab1f8fa3f6766b2eb89ae673db586dc5 (plain) (blame)
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
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
# Helper to print an int32 in decimal.

== code
#   instruction                     effective address                                                   register    displacement    immediate
# . op          subop               mod             rm32          base        index         scale       r32
# . 1-3 bytes   3 bits              2 bits          3 bits        3 bits      3 bits        2 bits      2 bits      0/1/2/4 bytes   0/1/2/4 bytes

print-int32-decimal:  # out : (address stream), n : int32
    # works by generating characters from lowest to highest and pushing them
    # to the stack, before popping them one by one into the stream
    #
    # pseudocode:
    #   push sentinel
    #   EAX = abs(n)
    #   while true
    #     sign-extend EAX into EDX
    #     EAX, EDX = EAX/10, EAX%10
    #     EDX += '0'
    #     push EDX
    #     if (EAX == 0) break
    #   if n < 0
    #     push '-'
    #   w = out->write
    #   curr = &out->data[out->write]
    #   max = &out->data[out->length]
    #   while true
    #     pop into EAX
    #     if (EAX == sentinel) break
    #     if (curr >= max) abort
    #     *curr = AL
    #     ++curr
    #     ++w
    #   out->write = w
    # (based on K&R itoa: https://en.wikibooks.org/wiki/C_Programming/stdlib.h/itoa)
    # (this pseudocode contains registers because operations like division
    # require specific registers in x86)
    #
    # . prolog
    55/push-EBP
    89/copy                         3/mod/direct    5/rm32/EBP    .           .             .           4/r32/ESP   .               .                 # copy ESP to EBP
    # . save registers
    50/push-EAX
    51/push-ECX
    52/push-EDX
    53/push-EBX
    57/push-EDI
    # ten/ECX = 10
    b9/copy-to-ECX  0xa/imm32
    # push sentinel
    68/push  0/imm32/sentinel
    # EAX = abs(n)
    8b/copy                         1/mod/*+disp8   5/rm32/EBP    .           .             .           0/r32/EAX   0xc/disp8       .                 # copy *(EBP+12) to EAX
    3d/compare-EAX-with  0/imm32
    7d/jump-if-greater-or-equal  $print-int32-decimal:read-loop/disp8
$print-int32-decimal:negative:
    f7          3/subop/negate      3/mod/direct    0/rm32/EAX    .           .             .           .           .               .                 # negate EAX
$print-int32-decimal:read-loop:
    # EAX, EDX = EAX / 10, EAX % 10
    99/sign-extend-EAX-into-EDX
    f7          7/subop/idiv        3/mod/direct    1/rm32/ECX    .           .             .           .           .               .                 # divide EDX:EAX by ECX, storing quotient in EAX and remainder in EDX
    # EDX += '0'
    81          0/subop/add         3/mod/direct    2/rm32/EDX    .           .             .           .           .               0x30/imm32        # add to EDX
    # push EDX
    52/push-EDX
    # if (EAX == 0) break
    3d/compare-EAX-and  0/imm32
    7f/jump-if-greater  $print-int32-decimal:read-loop/disp8
$print-int32-decimal:read-break:
    # if (n < 0) push('-')
    81          7/subop/compare     1/mod/*+disp8   5/rm32/EBP    .           .             .           .           0xc/disp8       0/imm32           # compare *(EBP+12)
    7d/jump-if-greater-or-equal  $print-int32-decimal:write/disp8
$print-int32-decimal:push-negative:
    68/push  0x2d/imm32/-
$print-int32-decimal:write:
    # EDI = out
    8b/copy                         1/mod/*+disp8   5/rm32/EBP    .           .             .           7/r32/EDI   8/disp8         .                 # copy *(EBP+8) to EDI
    # w/EDX = out->write
    8b/copy                         0/mod/indirect  7/rm32/EDI    .           .             .           2/r32/EDX   .               .                 # copy *EDI to EDX
    # curr/ECX = &out->data[out->write]
    8d/copy-address                 1/mod/*+disp8   4/rm32/sib    7/base/EDI  2/index/EDX   .           1/r32/ECX   0xc/disp8       .                 # copy EBX+EDX+12 to ECX
    # max/EBX = &out->data[out->length]
    8b/copy                         1/mod/*+disp8   7/rm32/EDI    .           .             .           3/r32/EBX   8/disp8         .                 # copy *(EDI+8) to EBX
    8d/copy-address                 1/mod/*+disp8   4/rm32/sib    7/base/EDI  3/index/EBX   .           3/r32/EBX   0xc/disp8       .                 # copy EDI+EBX+12 to EBX
$print-int32-decimal:write-loop:
    # pop into EAX
    58/pop-to-EAX
    # if (EAX == sentinel) break
    3d/compare-EAX-and  0/imm32/sentinel
    74/jump-if-equal  $print-int32-decimal:write-break/disp8
    # if (curr >= max) abort
    39/compare                      3/mod/direct    1/rm32/ECX    .           .             .           3/r32/EBX   .               .                 # compare ECX with EBX
    7d/jump-if-greater-or-equal  $print-int32-decimal:abort/disp8
$print-int32-decimal:write-char:
    # *curr = AL
    88/copy-byte                    0/mod/indirect  1/rm32/ECX    .           .             .           0/r32/AL    .               .                 # copy AL to byte at *ECX
    # ++curr
    41/increment-ECX
    # ++w
    42/increment-EDX
    eb/jump  $print-int32-decimal:write-loop/disp8
$print-int32-decimal:write-break:
    # out->write = w
    89/copy                         0/mod/indirect  7/rm32/EDI    .           .             .           2/r32/EDX   .               .                 # copy EDX to *EDI
$print-int32-decimal:end:
    # . restore registers
    5f/pop-to-EDI
    5b/pop-to-EBX
    5a/pop-to-EDX
    59/pop-to-ECX
    58/pop-to-EAX
    # . epilog
    89/copy                         3/mod/direct    4/rm32/ESP    .           .             .           5/r32/EBP   .               .                 # copy EBP to ESP
    5d/pop-to-EBP
    c3/return

$print-int32-decimal:abort:
    # . _write(2/stderr, error)
    # . . push args
    68/push  "print-int32-decimal: out of space"/imm32
    68/push  2/imm32/stderr
    # . . call
    e8/call  _write/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
    # . syscall(exit, 1)
    bb/copy-to-EBX  1/imm32
    b8/copy-to-EAX  1/imm32/exit
    cd/syscall  0x80/imm8
    # never gets here

test-print-int32-decimal:
    # - check that a single-digit number converts correctly
    # setup
    # . clear-stream(_test-stream)
    # . . push args
    68/push  _test-stream/imm32
    # . . call
    e8/call  clear-stream/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add to ESP
    # print-int32-decimal(_test-stream, 9)
    # . . push args
    68/push  9/imm32
    68/push  _test-stream/imm32
    # . . call
    e8/call  print-int32-decimal/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
    # check-stream-equal(_test-stream, "9", msg)
    # . . push args
    68/push  "F - test-print-int32-decimal"/imm32
    68/push  "9"/imm32
    68/push  _test-stream/imm32
    # . . call
    e8/call  check-stream-equal/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               0xc/imm32         # add to ESP
    # . end
    c3/return

test-print-int32-decimal-zero:
    # - check that 0 converts correctly
    # setup
    # . clear-stream(_test-stream)
    # . . push args
    68/push  _test-stream/imm32
    # . . call
    e8/call  clear-stream/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add to ESP
    # print-int32-decimal(_test-stream, 0)
    # . . push args
    68/push  0/imm32
    68/push  _test-stream/imm32
    # . . call
    e8/call  print-int32-decimal/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
    # check-stream-equal(_test-stream, "0", msg)
    # . . push args
    68/push  "F - test-print-int32-decimal-zero"/imm32
    68/push  "0"/imm32
    68/push  _test-stream/imm32
    # . . call
    e8/call  check-stream-equal/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               0xc/imm32         # add to ESP
    # . end
    c3/return

test-print-int32-decimal-multiple-digits:
    # - check that a multi-digit number converts correctly
    # setup
    # . clear-stream(_test-stream)
    # . . push args
    68/push  _test-stream/imm32
    # . . call
    e8/call  clear-stream/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add to ESP
    # print-int32-decimal(_test-stream, 10)
    # . . push args
    68/push  0xa/imm32
    68/push  _test-stream/imm32
    # . . call
    e8/call  print-int32-decimal/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
    # check-stream-equal(_test-stream, "10", msg)
    # . . push args
    68/push  "F - test-print-int32-decimal-multiple-digits"/imm32
    68/push  "10"/imm32
    68/push  _test-stream/imm32
    # . . call
    e8/call  check-stream-equal/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               0xc/imm32         # add to ESP
    # . end
    c3/return

test-print-int32-decimal-negative:
    # - check that a negative single-digit number converts correctly
    # setup
    # . clear-stream(_test-stream)
    # . . push args
    68/push  _test-stream/imm32
    # . . call
    e8/call  clear-stream/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add to ESP
    # print-int32-decimal(_test-stream, -9)
    # . . push args
    68/push  -9/imm32
    68/push  _test-stream/imm32
    # . . call
    e8/call  print-int32-decimal/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
#?     # dump _test-stream {{{
#?     # . write(2/stderr, "^")
#?     # . . push args
#?     68/push  "^"/imm32
#?     68/push  2/imm32/stderr
#?     # . . call
#?     e8/call  write/disp32
#?     # . . discard args
#?     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
#?     # . write-stream(2/stderr, _test-stream)
#?     # . . push args
#?     68/push  _test-stream/imm32
#?     68/push  2/imm32/stderr
#?     # . . call
#?     e8/call  write-stream/disp32
#?     # . . discard args
#?     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
#?     # . write(2/stderr, "$\n")
#?     # . . push args
#?     68/push  "$\n"/imm32
#?     68/push  2/imm32/stderr
#?     # . . call
#?     e8/call  write/disp32
#?     # . . discard args
#?     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
#?     # }}}
    # check-stream-equal(_test-stream, "-9", msg)
    # . . push args
    68/push  "F - test-print-int32-decimal-negative"/imm32
    68/push  "-9"/imm32
    68/push  _test-stream/imm32
    # . . call
    e8/call  check-stream-equal/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               0xc/imm32         # add to ESP
    # . end
    c3/return

test-print-int32-decimal-negative-multiple-digits:
    # - check that a multi-digit number converts correctly
    # setup
    # . clear-stream(_test-stream)
    # . . push args
    68/push  _test-stream/imm32
    # . . call
    e8/call  clear-stream/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add to ESP
    # print-int32-decimal(_test-stream, -10)
    # . . push args
    68/push  -0xa/imm32
    68/push  _test-stream/imm32
    # . . call
    e8/call  print-int32-decimal/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
    # check-stream-equal(_test-stream, "-10", msg)
    # . . push args
    68/push  "F - test-print-int32-decimal-negative-multiple-digits"/imm32
    68/push  "-10"/imm32
    68/push  _test-stream/imm32
    # . . call
    e8/call  check-stream-equal/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               0xc/imm32         # add to ESP
    # . end
    c3/return

# . . vim:nowrap:textwidth=0