1 # Port of https://github.com/akkartik/crenshaw/blob/master/tutor2.1.pas
  2 # which corresponds to the section "single digits" in https://compilers.iecc.com/crenshaw/tutor2.txt
  3 # except that we support hex digits.
  4 #
  5 # To run (from the subx/ directory):
  6 #   $ ./subx translate *.subx apps/crenshaw2-1.subx -o apps/crenshaw2-1
  7 #   $ echo '3'  |./subx run apps/crenshaw2-1
  8 # Expected output:
  9 #   # syscall(exit, 3)
 10 #   bb/copy-to-EBX  3/imm32
 11 #   b8/copy-to-EAX  1/imm32/exit
 12 #   cd/syscall  0x80/imm8
 13 #
 14 # To run the generated output:
 15 #   $ echo '3'  |./subx run apps/crenshaw2-1 > z1.subx
 16 #   $ ./subx translate z1.subx -o z1
 17 #   $ ./subx run z1
 18 #   $ echo $?
 19 #   3
 20 #
 21 # Stdin must contain just a single hex digit. Other input will print an error:
 22 #   $ echo 'xyz'  |./subx run apps/crenshaw2-1
 23 #   Error: integer expected
 24 #
 25 # Names in this file sometimes follow Crenshaw's original rather than my usual
 26 # naming conventions.
 27 
 28 == code
 29 #   instruction                     effective address                                                   register    displacement    immediate
 30 # . op          subop               mod             rm32          base        index         scale       r32
 31 # . 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
 32 
 33 Entry:  # run tests if necessary, call 'compile' if not
 34 
 35 #?     # for debugging: run a single test; don't bother setting status code
 36 #?     e8/call test-get-num-reads-single-digit/disp32
 37 #?     eb/jump  $main:end/disp8
 38 
 39     # . prolog
 40     89/copy                         3/mod/direct    5/rm32/EBP    .           .             .           4/r32/ESP   .               .                 # copy ESP to EBP
 41     # - if argc > 1 and argv[1] == "test", then return run_tests()
 42     # . argc > 1
 43     81          7/subop/compare     1/mod/*+disp8   5/rm32/EBP    .           .             .           .           0/disp8         1/imm32           # compare *EBP
 44     7e/jump-if-lesser-or-equal  $run-main/disp8
 45     # . argv[1] == "test"
 46     # . . push args
 47     68/push  "test"/imm32
 48     ff          6/subop/push        1/mod/*+disp8   5/rm32/EBP    .           .             .           .           8/disp8         .                 # push *(EBP+8)
 49     # . . call
 50     e8/call  kernel-string-equal?/disp32
 51     # . . discard args
 52     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
 53     # . check result
 54     3d/compare-EAX  1/imm32
 55     75/jump-if-not-equal  $run-main/disp8
 56     # . run-tests()
 57     e8/call  run-tests/disp32
 58     8b/copy                         0/mod/indirect  5/rm32/.disp32            .             .           3/r32/EBX   Num-test-failures/disp32          # copy *Num-test-failures to EBX
 59     eb/jump  $main:end/disp8
 60 $run-main:
 61     # - otherwise read a program from stdin and emit its translation to stdout
 62     # var ed/EAX : exit-descriptor
 63     81          5/subop/subtract    3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # subtract from ESP
 64     89/copy                         3/mod/direct    0/rm32/EAX    .           .             .           4/r32/ESP   .               .                 # copy ESP to EAX
 65     # configure ed to really exit()
 66     # . ed->target = 0
 67     c7          0/subop/copy        0/mod/direct    0/rm32/EAX    .           .             .           .           .               0/imm32           # copy to *EAX
 68     # return compile(Stdin, 1/stdout, 2/stderr, ed)
 69     # . . push args
 70     50/push-EAX/ed
 71     68/push  2/imm32/stderr
 72     68/push  1/imm32/stdout
 73     68/push  Stdin/imm32
 74     # . . call
 75     e8/call  compile/disp32
 76     # . . discard args
 77     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               0x10/imm32        # add to ESP
 78     # . syscall(exit, 0)
 79     bb/copy-to-EBX  0/imm32
 80 $main:end:
 81     b8/copy-to-EAX  1/imm32/exit
 82     cd/syscall  0x80/imm8
 83 
 84 # the main entry point
 85 compile:  # in : (address buffered-file), out : fd or (address stream), err : fd or (address stream), ed : (address exit-descriptor) -> <void>
 86     # . prolog
 87     55/push-EBP
 88     89/copy                         3/mod/direct    5/rm32/EBP    .           .             .           4/r32/ESP   .               .                 # copy ESP to EBP
 89     # . save registers
 90     50/push-EAX
 91     51/push-ECX
 92     # prime the pump
 93     # . Look = get-char(in)
 94     # . . push args
 95     ff          6/subop/push        1/mod/*+disp8   5/rm32/EBP    .           .             .           .           8/disp8      .                    # push *(EBP+8)
 96     # . . call
 97     e8/call  get-char/disp32
 98     # . . discard args
 99     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add to ESP
100     # var num/ECX : (address stream) on the stack
101     # Numbers can be 32 bits or 8 hex bytes long. One of them will be in 'Look', so we need space for 7 bytes.
102     # Sizing the stream just right buys us overflow-handling for free inside 'get-num'.
103     # Add 12 bytes for 'read', 'write' and 'length' fields, for a total of 19 bytes, or 0x13 in hex.
104     # The stack pointer is no longer aligned, so dump_stack() can be misleading past this point.
105     81          5/subop/subtract    3/mod/direct    4/rm32/ESP    .           .             .           .           .               0x13/imm32        # subtract from ESP
106     89/copy                         3/mod/direct    1/rm32/ECX    .           .             .           4/r32/ESP   .               .                 # copy ESP to ECX
107     # initialize the stream
108     # . num->length = 7
109     c7          0/subop/copy        1/mod/*+disp8   1/rm32/ECX    .           .             .           .           8/disp8         7/imm32           # copy to *(ECX+8)
110     # . clear-stream(num)
111     # . . push args
112     51/push-ECX
113     # . . call
114     e8/call  clear-stream/disp32
115     # . . discard args
116     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add to ESP
117     # read a digit from 'in' into 'num'
118     # . get-num(in, num, err, ed)
119     # . . push args
120     ff          6/subop/push        1/mod/*+disp8   5/rm32/EBP    .           .             .           .           0x14/disp8      .                 # push *(EBP+20)
121     ff          6/subop/push        1/mod/*+disp8   5/rm32/EBP    .           .             .           .           0x10/disp8      .                 # push *(EBP+16)
122     51/push-ECX/num
123     ff          6/subop/push        1/mod/*+disp8   5/rm32/EBP    .           .             .           .           8/disp8      .                    # push *(EBP+8)
124     # . . call
125     e8/call  get-num/disp32
126     # . . discard args
127     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               0x10/imm32        # add to ESP
128     # render 'num' into the following template on 'out':
129     #   bb/copy-to-EBX  _num_
130     #   b8/copy-to-EAX  1/imm32/exit
131     #   cd/syscall  0x80/imm8
132     #
133     # . write(out, "bb/copy-to-EBX  ")
134     # . . push args
135     68/push  "bb/copy-to-EBX  "/imm32
136     ff          6/subop/push        1/mod/*+disp8   5/rm32/EBP    .           .             .           .           0xc/disp8       .                 # push *(EBP+12)
137     # . . call
138     e8/call  write/disp32
139     # . . discard args
140     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
141     # . write-stream(out, num)
142     # . . push args
143     51/push-ECX/num
144     ff          6/subop/push        1/mod/*+disp8   5/rm32/EBP    .           .             .           .           0xc/disp8       .                 # push *(EBP+12)
145     # . . call
146     e8/call  write-stream/disp32
147     # . . discard args
148     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
149     # . write(out, Newline)
150     # . . push args
151     68/push  Newline/imm32
152     ff          6/subop/push        1/mod/*+disp8   5/rm32/EBP    .           .             .           .           0xc/disp8       .                 # push *(EBP+12)
153     # . . call
154     e8/call  write/disp32
155     # . . discard args
156     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
157     # . write(out, "b8/copy-to-EAX  1/imm32/exit")
158     # . . push args
159     68/push  "b8/copy-to-EAX  1/imm32/exit"/imm32
160     ff          6/subop/push        1/mod/*+disp8   5/rm32/EBP    .           .             .           .           0xc/disp8       .                 # push *(EBP+12)
161     # . . call
162     e8/call  write/disp32
163     # . . discard args
164     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
165     # . write(out, Newline)
166     # . . push args
167     68/push  Newline/imm32
168     ff          6/subop/push        1/mod/*+disp8   5/rm32/EBP    .           .             .           .           0xc/disp8       .                 # push *(EBP+12)
169     # . . call
170     e8/call  write/disp32
171     # . . discard args
172     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
173     # . write(out, "cd/syscall  0x80/imm8")
174     # . . push args
175     68/push  "cd/syscall  0x80/imm8"/imm32
176     ff          6/subop/push        1/mod/*+disp8   5/rm32/EBP    .           .             .           .           0xc/disp8       .                 # push *(EBP+12)
177     # . . call
178     e8/call  write/disp32
179     # . . discard args
180     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
181     # . write(out, Newline)
182     # . . push args
183     68/push  Newline/imm32
184     ff          6/subop/push        1/mod/*+disp8   5/rm32/EBP    .           .             .           .           0xc/disp8       .                 # push *(EBP+12)
185     # . . call
186     e8/call  write/disp32
187     # . . discard args
188     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
189 $compile:end:
190     # . restore registers
191     59/pop-to-ECX
192     58/pop-to-EAX
193     # . epilog
194     89/copy                         3/mod/direct    4/rm32/ESP    .           .             .           5/r32/EBP   .               .                 # copy EBP to ESP
195     5d/pop-to-EBP
196     c3/return
197 
198 # Read a single digit into 'out'. Abort if there are none, or if there is no space in 'out'.
199 # Input comes from the global variable 'Look', and we leave the next byte from
200 # 'in' into it on exit.
201 get-num:  # in : (address buffered-file), out : (address stream), err : fd or (address stream), ed : (address exit-descriptor) -> <void>
202     # pseudocode:
203     #   if (!is-digit?(Look)) expected(ed, err, "integer")
204     #   if (out->write >= out->length)
205     #     write(err, "Error: too many digits in number\n")
206     #     stop(ed, 1)
207     #   out->data[out->write] = LSB(Look)
208     #   ++out->write
209     #   Look = get-char(in)
210     #
211     # registers:
212     #   in: ESI
213     #   out: EDI
214     #   out->write: ECX (cached copy; need to keep in sync)
215     #   out->length: EDX
216     #   temporaries: EAX, EBX
217     # We can't allocate Look to a register because it gets written implicitly in
218     # get-char in each iteration of the loop. (Thereby demonstrating that it's
219     # not the right interface for us. But we'll keep it just to follow Crenshaw.)
220     #
221     # . prolog
222     55/push-EBP
223     89/copy                         3/mod/direct    5/rm32/EBP    .           .             .           4/r32/ESP   .               .                 # copy ESP to EBP
224     # - if (is-digit?(Look)) expected(ed, err, "integer")
225     # . EAX = is-digit?(Look)
226     # . . push args
227     ff          6/subop/push        0/mod/indirect  5/rm32/.disp32            .             .           .           Look/disp32     .                 # push *Look
228     # . . call
229     e8/call  is-digit?/disp32
230     # . . discard args
231     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add to ESP
232     # . if (EAX == 0)
233     3d/compare-EAX  0/imm32
234     75/jump-if-not-equal  $get-num:main/disp8
235     # . expected(ed, err, "integer")
236     # . . push args
237     68/push  "integer"/imm32
238     ff          6/subop/push        1/mod/*+disp8   5/rm32/EBP    .           .             .           .           0x10/disp8      .                 # push *(EBP+16)
239     ff          6/subop/push        1/mod/*+disp8   5/rm32/EBP    .           .             .           .           0x14/disp8      .                 # push *(EBP+20)
240     # . . call
241     e8/call  expected/disp32  # never returns
242     # . . discard args
243     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               0xc/imm32         # add to ESP
244 $get-num:main:
245     # - otherwise read a digit
246     # . save registers
247     50/push-EAX
248     51/push-ECX
249     52/push-EDX
250     53/push-EBX
251     56/push-ESI
252     57/push-EDI
253     # read necessary variables to registers
254     # ESI = in
255     8b/copy                         1/mod/*+disp8   5/rm32/EBP    .           .             .           6/r32/ESI   8/disp8         .                 # copy *(EBP+8) to ESI
256     # EDI = out
257     8b/copy                         1/mod/*+disp8   5/rm32/EBP    .           .             .           7/r32/EDI   0xc/disp8       .                 # copy *(EBP+12) to EDI
258     # ECX = out->write
259     8b/copy                         0/mod/indirect  7/rm32/EDI    .           .             .           1/r32/ECX   .               .                 # copy *EDI to ECX
260     # EDX = out->length
261     8b/copy                         1/mod/*+disp8   7/rm32/EDI    .           .             .           2/r32/EDX   8/disp8         .                 # copy *(EDI+8) to EDX
262     # if (out->write >= out->length) error
263     39/compare                      3/mod/direct    2/rm32/EDX    .           .             .           1/r32/ECX   .               .                 # compare EDX with ECX
264     7d/jump-if-lesser  $get-num:stage2/disp8
265     # . error(ed, err, msg)  # TODO: show full number
266     # . . push args
267     68/push  "get-num: too many digits in number"/imm32
268     ff          6/subop/push        1/mod/*+disp8   5/rm32/EBP    .           .             .           .           0x10/disp8      .                 # push *(EBP+16)
269     ff          6/subop/push        1/mod/*+disp8   5/rm32/EBP    .           .             .           .           0x14/disp8      .                 # push *(EBP+20)
270     # . . call
271     e8/call  error/disp32  # never returns
272     # . . discard args
273     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               0xc/imm32         # add to ESP
274 $get-num:stage2:
275     # out->data[out->write] = LSB(Look)
276     8d/copy-address                 1/mod/*+disp8   4/rm32/sib    7/base/EDI  1/index/ECX   .           3/r32/EBX   0xc/disp8       .                 # copy EDI+ECX+12 to EBX
277     8b/copy                         0/mod/indirect  5/rm32/.disp32            .             .           0/r32/EAX   Look/disp32     .                 # copy *Look to EAX
278     88/copy-byte                    0/mod/indirect  3/rm32/EBX    .           .             .           0/r32/AL    .               .                 # copy byte at AL to *EBX
279     # ++out->write
280     41/increment-ECX
281     # Look = get-char(in)
282     # . . push args
283     56/push-ESI
284     # . . call
285     e8/call  get-char/disp32
286     # . . discard args
287     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add to ESP
288 $get-num:loop-end:
289     # persist necessary variables from registers
290     89/copy                         0/mod/indirect  7/rm32/EDI    .           .             .           1/r32/ECX   .               .                 # copy ECX to *EDI
291 $get-num:end:
292     # . restore registers
293     5f/pop-to-EDI
294     5e/pop-to-ESI
295     5b/pop-to-EBX
296     5a/pop-to-EDX
297     59/pop-to-ECX
298     58/pop-to-EAX
299     # . epilog
300     89/copy                         3/mod/direct    4/rm32/ESP    .           .             .           5/r32/EBP   .               .                 # copy EBP to ESP
301     5d/pop-to-EBP
302     c3/return
303 
304 test-get-num-reads-single-digit:
305     # - check that get-num returns first character if it's a digit
306     # This test uses exit-descriptors. Use EBP for setting up local variables.
307     55/push-EBP
308     89/copy                         3/mod/direct    5/rm32/EBP    .           .             .           4/r32/ESP   .               .                 # copy ESP to EBP
309     # clear all streams
310     # . clear-stream(_test-stream)
311     # . . push args
312     68/push  _test-stream/imm32
313     # . . call
314     e8/call  clear-stream/disp32
315     # . . discard args
316     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add to ESP
317     # . clear-stream(_test-buffered-file+4)
318     # . . push args
319     b8/copy-to-EAX  _test-buffered-file/imm32
320     05/add-to-EAX  4/imm32
321     50/push-EAX
322     # . . call
323     e8/call  clear-stream/disp32
324     # . . discard args
325     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add to ESP
326     # . clear-stream(_test-output-stream)
327     # . . push args
328     68/push  _test-output-stream/imm32
329     # . . call
330     e8/call  clear-stream/disp32
331     # . . discard args
332     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add to ESP
333     # . clear-stream(_test-error-stream)
334     # . . push args
335     68/push  _test-error-stream/imm32
336     # . . call
337     e8/call  clear-stream/disp32
338     # . . discard args
339     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add to ESP
340     # initialize 'in'
341     # . write(_test-stream, "3")
342     # . . push args
343     68/push  "3"/imm32
344     68/push  _test-stream/imm32
345     # . . call
346     e8/call  write/disp32
347     # . . discard args
348     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
349     # initialize exit-descriptor 'ed' for the call to 'get-num' below
350     # . var ed/EAX : exit-descriptor
351     81          5/subop/subtract    3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # subtract from ESP
352     89/copy                         3/mod/direct    0/rm32/EAX    .           .             .           4/r32/ESP   .               .                 # copy ESP to EAX
353     # . tailor-exit-descriptor(ed, 16)
354     # . . push args
355     68/push  0x10/imm32/nbytes-of-args-for-get-num
356     50/push-EAX/ed
357     # . . call
358     e8/call  tailor-exit-descriptor/disp32
359     # . . discard args
360     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
361     # prime the pump
362     # . get-char(_test-buffered-file)
363     # . . push args
364     68/push  _test-buffered-file/imm32
365     # . . call
366     e8/call  get-char/disp32
367     # . . discard args
368     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add to ESP
369     # get-num(in, out, err, ed)
370     # . . push args
371     50/push-EAX/ed
372     68/push  _test-error-stream/imm32
373     68/push  _test-output-stream/imm32
374     68/push  _test-buffered-file/imm32
375     # . . call
376     e8/call  get-num/disp32
377     # registers except ESP may be clobbered at this point
378     # . . discard args
379     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               0x10/imm32        # add to ESP
380     # check-ints-equal(*_test-output-stream->data, '3', msg)
381     # . . push args
382     68/push  "F - test-get-num-reads-single-digit"/imm32
383     68/push  0x33/imm32
384     b8/copy-to-EAX  _test-output-stream/imm32
385     ff          6/subop/push        1/mod/*+disp8   0/rm32/EAX    .           .             .           .           0xc/disp8       .                 # push *(EAX+12)
386     # . . call
387     e8/call  check-ints-equal/disp32
388     # . . discard args
389     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               0xc/imm32         # add to ESP
390     # . reclaim locals
391     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
392     5d/pop-to-EBP
393     c3/return
394 
395 test-get-num-aborts-on-non-digit-in-Look:
396     # - check that get-num returns first character if it's a digit
397     # This test uses exit-descriptors. Use EBP for setting up local variables.
398     55/push-EBP
399     89/copy                         3/mod/direct    5/rm32/EBP    .           .             .           4/r32/ESP   .               .                 # copy ESP to EBP
400     # clear all streams
401     # . clear-stream(_test-stream)
402     # . . push args
403     68/push  _test-stream/imm32
404     # . . call
405     e8/call  clear-stream/disp32
406     # . . discard args
407     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add to ESP
408     # . clear-stream(_test-buffered-file+4)
409     # . . push args
410     b8/copy-to-EAX  _test-buffered-file/imm32
411     05/add-to-EAX  4/imm32
412     50/push-EAX
413     # . . call
414     e8/call  clear-stream/disp32
415     # . . discard args
416     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add to ESP
417     # . clear-stream(_test-output-stream)
418     # . . push args
419     68/push  _test-output-stream/imm32
420     # . . call
421     e8/call  clear-stream/disp32
422     # . . discard args
423     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add to ESP
424     # . clear-stream(_test-error-stream)
425     # . . push args
426     68/push  _test-error-stream/imm32
427     # . . call
428     e8/call  clear-stream/disp32
429     # . . discard args
430     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add to ESP
431     # initialize 'in'
432     # . write(_test-stream, "3")
433     # . . push args
434     68/push  "3"/imm32
435     68/push  _test-stream/imm32
436     # . . call
437     e8/call  write/disp32
438     # . . discard args
439     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
440     # initialize exit-descriptor 'ed' for the call to 'get-num' below
441     # . var ed/EAX : (address exit-descriptor)
442     81          5/subop/subtract    3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # subtract from ESP
443     89/copy                         3/mod/direct    0/rm32/EAX    .           .             .           4/r32/ESP   .               .                 # copy ESP to EAX
444     # . tailor-exit-descriptor(ed, 16)
445     # . . push args
446     68/push  0x10/imm32/nbytes-of-args-for-get-num
447     50/push-EAX/ed
448     # . . call
449     e8/call  tailor-exit-descriptor/disp32
450     # . . discard args
451     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
452     # *don't* prime the pump
453     # get-num(in, out, err, ed)
454     # . . push args
455     50/push-EAX/ed
456     68/push  _test-error-stream/imm32
457     68/push  _test-output-stream/imm32
458     68/push  _test-buffered-file/imm32
459     # . . call
460     e8/call  get-num/disp32
461     # registers except ESP may be clobbered at this point
462     # . . discard args
463     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               0x10/imm32        # add to ESP
464     # check that get-num tried to call exit(1)
465     # . check-ints-equal(ed->value, 2, msg)  # i.e. stop was called with value 1
466     # . . push args
467     68/push  "F - test-get-num-aborts-on-non-digit-in-Look"/imm32
468     68/push  2/imm32
469     # . . push ed->value
470     ff          6/subop/push        1/mod/*+disp8   0/rm32/EAX    .           .             .           .           4/disp8         .                 # push *(EAX+4)
471     # . . call
472     e8/call  check-ints-equal/disp32
473     # . . discard args
474     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               0xc/imm32         # add to ESP
475     # . reclaim locals
476     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
477     5d/pop-to-EBP
478     c3/return
479 
480 ## helpers
481 
482 # write(f, "Error: "+s+" expected\n") then stop(ed, 1)
483 expected:  # ed : (address exit-descriptor), f : fd or (address stream), s : (address array byte) -> <void>
484     # . prolog
485     55/push-EBP
486     89/copy                         3/mod/direct    5/rm32/EBP    .           .             .           4/r32/ESP   .               .                 # copy ESP to EBP
487     # write(f, "Error: ")
488     # . . push args
489     68/push  "Error: "/imm32
490     ff          6/subop/push        1/mod/*+disp8   5/rm32/EBP    .           .             .           .           0xc/disp8       .                 # push *(EBP+12)
491     # . . call
492     e8/call  write/disp32
493     # . . discard args
494     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
495     # write(f, s)
496     # . . push args
497     ff          6/subop/push        1/mod/*+disp8   5/rm32/EBP    .           .             .           .           0x10/disp8      .                 # push *(EBP+16)
498     ff          6/subop/push        1/mod/*+disp8   5/rm32/EBP    .           .             .           .           0xc/disp8       .                 # push *(EBP+12)
499     # . . call
500     e8/call  write/disp32
501     # . . discard args
502     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
503     # write(f, " expected")
504     # . . push args
505     68/push  " expected"/imm32
506     ff          6/subop/push        1/mod/*+disp8   5/rm32/EBP    .           .             .           .           0xc/disp8       .                 # push *(EBP+12)
507     # . . call
508     e8/call  write/disp32
509     # . . discard args
510     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
511     # write(f, Newline)
512     # . . push args
513     68/push  Newline/imm32
514     ff          6/subop/push        1/mod/*+disp8   5/rm32/EBP    .           .             .           .           0xc/disp8       .                 # push *(EBP+12)
515     # . . call
516     e8/call  write/disp32
517     # . . discard args
518     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
519     # stop(ed, 1)
520     # . . push args
521     68/push  1/imm32
522     ff          6/subop/push        1/mod/*+disp8   5/rm32/EBP    .           .             .           .           8/disp8         .                 # push *(EBP+8)
523     # . . call
524     e8/call  stop/disp32
525     # should never get past this point
526 $expected:dead-end:
527     # . epilog
528     89/copy                         3/mod/direct    4/rm32/ESP    .           .             .           5/r32/EBP   .               .                 # copy EBP to ESP
529     5d/pop-to-EBP
530     c3/return
531 
532 # read a byte from 'f', and save it in 'Look'
533 get-char:  # f : (address buffered-file) -> <void>
534     # . prolog
535     55/push-EBP
536     89/copy                         3/mod/direct    5/rm32/EBP    .           .             .           4/r32/ESP   .               .                 # copy ESP to EBP
537     # . save registers
538     50/push-EAX
539     # read-byte(f)
540     # . . push args
541     ff          6/subop/push        1/mod/*+disp8   5/rm32/EBP    .           .             .           .           8/disp8         .                 # push *(EBP+8)
542     # . . call
543     e8/call  read-byte/disp32
544     # . . discard args
545     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add to ESP
546     # save EAX to Look
547     89/copy                         0/mod/indirect  5/rm32/.disp32            .             .           0/r32/EAX   Look/disp32     .                 # copy EAX to *Look
548 $get-char:end:
549     # . restore registers
550     58/pop-to-EAX
551     # . epilog
552     89/copy                         3/mod/direct    4/rm32/ESP    .           .             .           5/r32/EBP   .               .                 # copy EBP to ESP
553     5d/pop-to-EBP
554     c3/return
555 
556 is-digit?:  # c : int -> EAX : boolean
557     # . prolog
558     55/push-EBP
559     89/copy                         3/mod/direct    5/rm32/EBP    .           .             .           4/r32/ESP   .               .                 # copy ESP to EBP
560     # EAX = false
561     b8/copy-to-EAX  0/imm32
562     # if (c < '0') return false
563     81          7/subop/compare     1/mod/*+disp8   5/rm32/EBP    .           .             .           .           8/disp8         0x30/imm32        # compare *(EBP+8)
564     7c/jump-if-lesser  $is-digit?:end/disp8
565     # if (c > '9') return false
566     81          7/subop/compare     1/mod/*+disp8   5/rm32/EBP    .           .             .           .           8/disp8         0x39/imm32        # compare *(EBP+8)
567     7f/jump-if-greater  $is-digit?:end/disp8
568     # otherwise return true
569     b8/copy-to-EAX  1/imm32
570 $is-digit?:end:
571     # . epilog
572     89/copy                         3/mod/direct    4/rm32/ESP    .           .             .           5/r32/EBP   .               .                 # copy EBP to ESP
573     5d/pop-to-EBP
574     c3/return
575 
576 == data
577 
578 Look:  # (char with some extra padding)
579     0/imm32
580 
581 _test-output-stream:
582     # current write index
583     0/imm32
584     # current read index
585     0/imm32
586     # length
587     8/imm32
588     # data
589     00 00 00 00 00 00 00 00  # 8 bytes
590 
591 _test-error-stream:
592     # current write index
593     0/imm32
594     # current read index
595     0/imm32
596     # length
597     8/imm32
598     # data
599     00 00 00 00 00 00 00 00  # 8 bytes
600 
601 # . . vim:nowrap:textwidth=0