1 # Helper to print an int32 in decimal.
  2 
  3 == code
  4 #   instruction                     effective address                                                   register    displacement    immediate
  5 # . op          subop               mod             rm32          base        index         scale       r32
  6 # . 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
  7 
  8 write-int32-decimal:  # out: (addr stream byte), n: int
  9     # works by generating characters from lowest to highest and pushing them
 10     # to the stack, before popping them one by one into the stream
 11     #
 12     # pseudocode:
 13     #   push sentinel
 14     #   eax = abs(n)
 15     #   while true
 16     #     sign-extend eax into edx
 17     #     eax, edx = eax/10, eax%10
 18     #     edx += '0'
 19     #     push edx
 20     #     if (eax == 0) break
 21     #   if n < 0
 22     #     push '-'
 23     #   w = out->write
 24     #   curr = &out->data[out->write]
 25     #   max = &out->data[out->size]
 26     #   while true
 27     #     pop into eax
 28     #     if (eax == sentinel) break
 29     #     if (curr >= max) abort
 30     #     *curr = AL
 31     #     ++curr
 32     #     ++w
 33     #   out->write = w
 34     # (based on K&R itoa: https://en.wikibooks.org/wiki/C_Programming/stdlib.h/itoa)
 35     # (this pseudocode contains registers because operations like division
 36     # require specific registers in x86)
 37     #
 38     # . prologue
 39     55/push-ebp
 40     89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
 41     # . save registers
 42     50/push-eax
 43     51/push-ecx
 44     52/push-edx
 45     53/push-ebx
 46     57/push-edi
 47     # const ten/ecx = 10
 48     b9/copy-to-ecx  0xa/imm32
 49     # push sentinel
 50     68/push  0/imm32/sentinel
 51     # var eax: int = abs(n)
 52     8b/copy                         1/mod/*+disp8   5/rm32/ebp    .           .             .           0/r32/eax   0xc/disp8       .                 # copy *(ebp+12) to eax
 53     3d/compare-eax-with  0/imm32
 54     7d/jump-if->=  $write-int32-decimal:read-loop/disp8
 55 $write-int32-decimal:negative:
 56     f7          3/subop/negate      3/mod/direct    0/rm32/eax    .           .             .           .           .               .                 # negate eax
 57 $write-int32-decimal:read-loop:
 58     # eax, edx = eax / 10, eax % 10
 59     99/sign-extend-eax-into-edx
 60     f7          7/subop/idiv        3/mod/direct    1/rm32/ecx    .           .             .           .           .               .                 # divide edx:eax by ecx, storing quotient in eax and remainder in edx
 61     # edx += '0'
 62     81          0/subop/add         3/mod/direct    2/rm32/edx    .           .             .           .           .               0x30/imm32        # add to edx
 63     # push edx
 64     52/push-edx
 65     # if (eax == 0) break
 66     3d/compare-eax-and  0/imm32
 67     7f/jump-if->  $write-int32-decimal:read-loop/disp8
 68 $write-int32-decimal:read-break:
 69     # if (n < 0) push('-')
 70     81          7/subop/compare     1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0xc/disp8       0/imm32           # compare *(ebp+12)
 71     7d/jump-if->=  $write-int32-decimal:write/disp8
 72 $write-int32-decimal:push-negative:
 73     68/push  0x2d/imm32/-
 74 $write-int32-decimal:write:
 75     # edi = out
 76     8b/copy                         1/mod/*+disp8   5/rm32/ebp    .           .             .           7/r32/edi   8/disp8         .                 # copy *(ebp+8) to edi
 77     # var w/edx: int = out->write
 78     8b/copy                         0/mod/indirect  7/rm32/edi    .           .             .           2/r32/edx   .               .                 # copy *edi to edx
 79     # var curr/ecx: (addr byte) = &out->data[out->write]
 80     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
 81     # var max/ebx: (addr byte) = &out->data[out->size]
 82     8b/copy                         1/mod/*+disp8   7/rm32/edi    .           .             .           3/r32/ebx   8/disp8         .                 # copy *(edi+8) to ebx
 83     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
 84 $write-int32-decimal:write-loop:
 85     # pop into eax
 86     58/pop-to-eax
 87     # if (eax == sentinel) break
 88     3d/compare-eax-and  0/imm32/sentinel
 89     74/jump-if-=  $write-int32-decimal:write-break/disp8
 90     # if (curr >= max) abort
 91     39/compare                      3/mod/direct    1/rm32/ecx    .           .             .           3/r32/ebx   .               .                 # compare ecx with ebx
 92     73/jump-if-addr>=  $write-int32-decimal:abort/disp8
 93 $write-int32-decimal:write-char:
 94     # *curr = AL
 95     88/copy-byte                    0/mod/indirect  1/rm32/ecx    .           .             .           0/r32/AL    .               .                 # copy AL to byte at *ecx
 96     # ++curr
 97     41/increment-ecx
 98     # ++w
 99     42/increment-edx
100     eb/jump  $write-int32-decimal:write-loop/disp8
101 $write-int32-decimal:write-break:
102     # out->write = w
103     89/copy                         0/mod/indirect  7/rm32/edi    .           .             .           2/r32/edx   .               .                 # copy edx to *edi
104 $write-int32-decimal:end:
105     # . restore registers
106     5f/pop-to-edi
107     5b/pop-to-ebx
108     5a/pop-to-edx
109     59/pop-to-ecx
110     58/pop-to-eax
111     # . epilogue
112     89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
113     5d/pop-to-ebp
114     c3/return
115 
116 $write-int32-decimal:abort:
117     (abort "write-int32-decimal: stream out of space")
118     # never gets here
119 
120 test-write-int32-decimal:
121     # - check that a single-digit number converts correctly
122     # setup
123     # . clear-stream(_test-stream)
124     # . . push args
125     68/push  _test-stream/imm32
126     # . . call
127     e8/call  clear-stream/disp32
128     # . . discard args
129     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
130     # write-int32-decimal(_test-stream, 9)
131     # . . push args
132     68/push  9/imm32
133     68/push  _test-stream/imm32
134     # . . call
135     e8/call  write-int32-decimal/disp32
136     # . . discard args
137     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
138     # check-stream-equal(_test-stream, "9", msg)
139     # . . push args
140     68/push  "F - test-write-int32-decimal"/imm32
141     68/push  "9"/imm32
142     68/push  _test-stream/imm32
143     # . . call
144     e8/call  check-stream-equal/disp32
145     # . . discard args
146     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
147     # . end
148     c3/return
149 
150 test-write-int32-decimal-zero:
151     # - check that 0 converts correctly
152     # setup
153     # . clear-stream(_test-stream)
154     # . . push args
155     68/push  _test-stream/imm32
156     # . . call
157     e8/call  clear-stream/disp32
158     # . . discard args
159     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
160     # write-int32-decimal(_test-stream, 0)
161     # . . push args
162     68/push  0/imm32
163     68/push  _test-stream/imm32
164     # . . call
165     e8/call  write-int32-decimal/disp32
166     # . . discard args
167     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
168     # check-stream-equal(_test-stream, "0", msg)
169     # . . push args
170     68/push  "F - test-write-int32-decimal-zero"/imm32
171     68/push  "0"/imm32
172     68/push  _test-stream/imm32
173     # . . call
174     e8/call  check-stream-equal/disp32
175     # . . discard args
176     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
177     # . end
178     c3/return
179 
180 test-write-int32-decimal-multiple-digits:
181     # - check that a multi-digit number converts correctly
182     # setup
183     # . clear-stream(_test-stream)
184     # . . push args
185     68/push  _test-stream/imm32
186     # . . call
187     e8/call  clear-stream/disp32
188     # . . discard args
189     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
190     # write-int32-decimal(_test-stream, 10)
191     # . . push args
192     68/push  0xa/imm32
193     68/push  _test-stream/imm32
194     # . . call
195     e8/call  write-int32-decimal/disp32
196     # . . discard args
197     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
198     # check-stream-equal(_test-stream, "10", msg)
199     # . . push args
200     68/push  "F - test-write-int32-decimal-multiple-digits"/imm32
201     68/push  "10"/imm32
202     68/push  _test-stream/imm32
203     # . . call
204     e8/call  check-stream-equal/disp32
205     # . . discard args
206     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
207     # . end
208     c3/return
209 
210 test-write-int32-decimal-negative:
211     # - check that a negative single-digit number converts correctly
212     # setup
213     # . clear-stream(_test-stream)
214     # . . push args
215     68/push  _test-stream/imm32
216     # . . call
217     e8/call  clear-stream/disp32
218     # . . discard args
219     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
220     # write-int32-decimal(_test-stream, -9)
221     # . . push args
222     68/push  -9/imm32
223     68/push  _test-stream/imm32
224     # . . call
225     e8/call  write-int32-decimal/disp32
226     # . . discard args
227     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
228 +-- 26 lines: #?     # dump _test-stream -----------------------------------------------------------------------------------------------------------------------------------
254     # check-stream-equal(_test-stream, "-9", msg)
255     # . . push args
256     68/push  "F - test-write-int32-decimal-negative"/imm32
257     68/push  "-9"/imm32
258     68/push  _test-stream/imm32
259     # . . call
260     e8/call  check-stream-equal/disp32
261     # . . discard args
262     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
263     # . end
264     c3/return
265 
266 # There's a special bit pattern that corresponds to no 2's complement integer.
267 # There doesn't seem to be a widespread convention for representing it.
268 test-write-int32-decimal-indefinite-integer:
269     # setup
270     # . clear-stream(_test-stream)
271     # . . push args
272     68/push  _test-stream/imm32
273     # . . call
274     e8/call  clear-stream/disp32
275     # . . discard args
276     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
277     # write-int32-decimal(_test-stream, 0x80000000)
278     # . . push args
279     68/push  0x80000000/imm32
280     68/push  _test-stream/imm32
281     # . . call
282     e8/call  write-int32-decimal/disp32
283     # . . discard args
284     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
285     # check-stream-equal(_test-stream, "-(", msg)
286     # . . push args
287     68/push  "F - test-write-int32-decimal-indefinite-integer"/imm32
288     68/push  "-("/imm32
289     68/push  _test-stream/imm32
290     # . . call
291     e8/call  check-stream-equal/disp32
292     # . . discard args
293     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
294     # . end
295     c3/return
296 
297 test-write-int32-decimal-negative-multiple-digits:
298     # - check that a multi-digit number converts correctly
299     # setup
300     # . clear-stream(_test-stream)
301     # . . push args
302     68/push  _test-stream/imm32
303     # . . call
304     e8/call  clear-stream/disp32
305     # . . discard args
306     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
307     # write-int32-decimal(_test-stream, -10)
308     # . . push args
309     68/push  -0xa/imm32
310     68/push  _test-stream/imm32
311     # . . call
312     e8/call  write-int32-decimal/disp32
313     # . . discard args
314     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
315     # check-stream-equal(_test-stream, "-10", msg)
316     # . . push args
317     68/push  "F - test-write-int32-decimal-negative-multiple-digits"/imm32
318     68/push  "-10"/imm32
319     68/push  _test-stream/imm32
320     # . . call
321     e8/call  check-stream-equal/disp32
322     # . . discard args
323     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
324     # . end
325     c3/return
326 
327 decimal-digit?:  # c: grapheme -> result/eax: boolean
328     # . prologue
329     55/push-ebp
330     89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
331     # . save registers
332     51/push-ecx
333     # ecx = c
334     8b/copy                         1/mod/*+disp8   5/rm32/ebp    .           .             .           1/r32/ecx   8/disp8         .                 # copy *(ebp+8) to ecx
335     # result = false
336     b8/copy-to-eax  0/imm32/false
337     # return false if c < '0'
338     81          7/subop/compare     3/mod/direct    1/rm32/ecx    .           .             .           .           .               0x30/imm32        # compare ecx
339     7c/jump-if-<  $decimal-digit?:end/disp8
340     # return (c <= '9')
341     81          7/subop/compare     3/mod/direct    1/rm32/ecx    .           .             .           .           .               0x39/imm32        # compare ecx
342     7f/jump-if->  $decimal-digit?:end/disp8
343 $decimal-digit?:true:
344     b8/copy-to-eax  1/imm32/true
345 $decimal-digit?:end:
346     # . restore registers
347     59/pop-to-ecx
348     # . epilogue
349     89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
350     5d/pop-to-ebp
351     c3/return
352 
353 test-decimal-digit-below-0:
354     # eax = decimal-digit?(0x2f)
355     # . . push args
356     68/push  0x2f/imm32
357     # . . call
358     e8/call  decimal-digit?/disp32
359     # . . discard args
360     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
361     # check-ints-equal(eax, 0, msg)
362     # . . push args
363     68/push  "F - test-decimal-digit-below-0"/imm32
364     68/push  0/imm32/false
365     50/push-eax
366     # . . call
367     e8/call  check-ints-equal/disp32
368     # . . discard args
369     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
370     c3/return
371 
372 test-decimal-digit-0-to-9:
373     # eax = decimal-digit?(0x30)
374     # . . push args
375     68/push  0x30/imm32
376     # . . call
377     e8/call  decimal-digit?/disp32
378     # . . discard args
379     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
380     # check-ints-equal(eax, 1, msg)
381     # . . push args
382     68/push  "F - test-decimal-digit-at-0"/imm32
383     68/push  1/imm32/true
384     50/push-eax
385     # . . call
386     e8/call  check-ints-equal/disp32
387     # . . discard args
388     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
389     # eax = decimal-digit?(0x39)
390     # . . push args
391     68/push  0x39/imm32
392     # . . call
393     e8/call  decimal-digit?/disp32
394     # . . discard args
395     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
396     # check-ints-equal(eax, 1, msg)
397     # . . push args
398     68/push  "F - test-decimal-digit-at-9"/imm32
399     68/push  1/imm32/true
400     50/push-eax
401     # . . call
402     e8/call  check-ints-equal/disp32
403     # . . discard args
404     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
405     c3/return
406 
407 test-decimal-digit-above-9:
408     # eax = decimal-digit?(0x3a)
409     # . . push args
410     68/push  0x3a/imm32
411     # . . call
412     e8/call  decimal-digit?/disp32
413     # . . discard args
414     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
415     # check-ints-equal(eax, 0, msg)
416     # . . push args
417     68/push  "F - test-decimal-digit-above-9"/imm32
418     68/push  0/imm32/false
419     50/push-eax
420     # . . call
421     e8/call  check-ints-equal/disp32
422     # . . discard args
423     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
424     c3/return
425 
426 to-decimal-digit:  # in: grapheme -> out/eax: int
427     # . prologue
428     55/push-ebp
429     89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
430     # eax = in
431     8b/copy                         1/mod/*+disp8   5/rm32/ebp    .           .             .           0/r32/eax   8/disp8         .                 # copy *(ebp+8) to eax
432 $to-decimal-digit:check0:
433     # if (eax < '0') goto abort
434     3d/compare-eax-with  0x30/imm32/0
435     7c/jump-if-<  $to-decimal-digit:abort/disp8
436 $to-decimal-digit:check1:
437     # if (eax > '9') goto abort
438     3d/compare-eax-with  0x39/imm32/f
439     7f/jump-if->  $to-decimal-digit:abort/disp8
440 $to-decimal-digit:digit:
441     # return eax - '0'
442     2d/subtract-from-eax  0x30/imm32/0
443 $to-decimal-digit:end:
444     # . epilogue
445     89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
446     5d/pop-to-ebp
447     c3/return
448 
449 $to-decimal-digit:abort:
450     (abort "to-decimal-digit: not a digit character")
451     # never gets here
452 
453 # . . vim:nowrap:textwidth=0