1 == code
  2 #   instruction                     effective address                                                   register    displacement    immediate
  3 # . op          subop               mod             rm32          base        index         scale       r32
  4 # . 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
  5 
  6 # read bytes from 'f' until (and including) a newline and store them into 's'
  7 # return true if no data found, false otherwise
  8 # just abort if 's' is too small
  9 read-line:  # f : (address buffered-file), s : (address stream byte) -> eof?/EAX
 10     # pseudocode:
 11     #   loop:
 12     #     if (s->write >= s->length) abort
 13     #     if (f->read >= f->write) populate stream from file
 14     #     if (f->write == 0) break
 15     #     AL = f->data[f->read]
 16     #     s->data[s->write] = AL
 17     #     ++f->read
 18     #     ++s->write
 19     #     if (AL == '\n') break
 20     # . prolog
 21     55/push-EBP
 22     89/copy                         3/mod/direct    5/rm32/EBP    .           .             .           4/r32/ESP   .               .                 # copy ESP to EBP
 23     # . save registers
 24     51/push-ECX
 25     52/push-EDX
 26     56/push-ESI
 27     57/push-EDI
 28     # ESI = f
 29     8b/copy                         1/mod/*+disp8   5/rm32/EBP    .           .             .           6/r32/ESI   8/disp8         .                 # copy *(EBP+8) to ESI
 30     # ECX = f->read
 31     8b/copy                         1/mod/*+disp8   6/rm32/ESI    .           .             .           1/r32/ECX   8/disp8         .                 # copy *(ESI+8) to ECX
 32     # EDI = s
 33     8b/copy                         1/mod/*+disp8   5/rm32/EBP    .           .             .           7/r32/EDI   0xc/disp8       .                 # copy *(EBP+12) to EDI
 34     # EDX = s->write
 35     8b/copy                         0/mod/indirect  7/rm32/EDI    .           .             .           2/r32/EDX   .               .                 # copy *EDI to EDX
 36 $read-line:loop:
 37     # if (s->write >= s->length) abort
 38     3b/compare                      1/mod/*+disp8   7/rm32/EDI    .           .             .           2/r32/EDX   8/disp8         .                 # compare EDX with *(EDI+8)
 39     7d/jump-if-greater-or-equal  $read-line:abort/disp8
 40     # if (f->read >= f->write) populate stream from file
 41     3b/compare                      1/mod/*+disp8   6/rm32/ESI    .           .             .           1/r32/ECX   4/disp8         .                 # compare ECX with *(ESI+4)
 42     7c/jump-if-lesser  $read-line:from-stream/disp8
 43     # . clear-stream(stream = f+4)
 44     # . . push args
 45     8d/copy-address                 1/mod/*+disp8   6/rm32/ESI    .           .             .           0/r32/EAX   4/disp8         .                 # copy ESI+4 to EAX
 46     50/push-EAX
 47     # . . call
 48     e8/call  clear-stream/disp32
 49     # . . discard args
 50     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add to ESP
 51     # . f->read must now be 0; update its cache at ECX
 52     31/xor                          3/mod/direct    1/rm32/ECX    .           .             .           1/r32/ECX   .               .                 # clear ECX
 53     # . EAX = read(f->fd, stream = f+4)
 54     # . . push args
 55     50/push-EAX
 56     ff          6/subop/push        0/mod/indirect  6/rm32/ESI    .           .             .           .           .               .                 # push *ESI
 57     # . . call
 58     e8/call  read/disp32
 59     # . . discard args
 60     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
 61     # if (f->write == 0) return true
 62     # since f->read was initially 0, EAX is the same as f->write
 63     # . if (EAX == 0) return true
 64     81          7/subop/compare     3/mod/direct    0/rm32/EAX    .           .             .           .           .               0/imm32           # compare EAX
 65     75/jump-if-not-equal  $read-line:from-stream/disp8
 66     b8/copy-to-EAX  0xffffffff/imm32/Eof
 67     eb/jump  $read-line:end/disp8
 68 $read-line:from-stream:
 69     # AL = f->data[f->read]
 70     31/xor                          3/mod/direct    0/rm32/EAX    .           .             .           0/r32/EAX   .               .                 # clear EAX
 71     8a/copy-byte                    1/mod/*+disp8   4/rm32/sib    6/base/ESI  1/index/ECX   .           0/r32/AL    0x10/disp8      .                 # copy byte at *(ESI+ECX+16) to AL
 72     # s->data[s->write] = AL
 73     88/copy-byte                    1/mod/*+disp8   4/rm32/sib    7/base/EDI  2/index/EDX   .           0/r32/AL    0xc/disp8       .                 # copy AL to *(EDI+EDX+12)
 74     # ++f->read
 75     41/increment-ECX
 76     # ++s->write
 77     42/increment-EDX
 78     # if (AL == '\n') return false
 79     81          7/subop/compare     3/mod/direct    0/rm32/EAX    .           .             .           .           .               0xa/imm32         # compare EAX
 80     75/jump-if-not-equal  $read-line:loop/disp8
 81     31/xor                          3/mod/direct    0/rm32/EAX    .           .             .           0/r32/EAX   .               .                 # clear EAX
 82 $read-line:end:
 83     # save f->read
 84     89/copy                         1/mod/*+disp8   6/rm32/ESI    .           .             .           1/r32/ECX   8/disp8         .                 # copy ECX to *(ESI+8)
 85     # save s->write
 86     89/copy                         0/mod/indirect  7/rm32/EDI    .           .             .           2/r32/EDX   .               .                 # copy EDX to *EDI
 87     # . restore registers
 88     5f/pop-to-EDI
 89     5e/pop-to-ESI
 90     5a/pop-to-EDX
 91     59/pop-to-ECX
 92     # . epilog
 93     89/copy                         3/mod/direct    4/rm32/ESP    .           .             .           5/r32/EBP   .               .                 # copy EBP to ESP
 94     5d/pop-to-EBP
 95     c3/return
 96 
 97 $read-line:abort:
 98     # . _write(2/stderr, error)
 99     # . . push args
100     68/push  "read-line: line too long"/imm32
101     68/push  2/imm32/stderr
102     # . . call
103     e8/call  _write/disp32
104     # . . discard args
105     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
106     # . syscall(exit, 1)
107     bb/copy-to-EBX  1/imm32
108     b8/copy-to-EAX  1/imm32/exit
109     cd/syscall  0x80/imm8
110     # never gets here
111 
112 test-read-line:
113     # - check that read-line stops at a newline
114     # setup
115     # . clear-stream(_test-stream)
116     # . . push args
117     68/push  _test-stream/imm32
118     # . . call
119     e8/call  clear-stream/disp32
120     # . . discard args
121     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add to ESP
122     # . clear-stream(_test-buffered-file+4)
123     # . . push args
124     b8/copy-to-EAX  _test-buffered-file/imm32
125     05/add-to-EAX  4/imm32
126     50/push-EAX
127     # . . call
128     e8/call  clear-stream/disp32
129     # . . discard args
130     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add to ESP
131     # . clear-stream(_test-tmp-stream)
132     # . . push args
133     68/push  _test-tmp-stream/imm32
134     # . . call
135     e8/call  clear-stream/disp32
136     # . . discard args
137     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add to ESP
138     # write(_test-stream, "ab\ncd")
139     # . write(_test-stream, "ab")
140     # . . push args
141     68/push  "ab"/imm32
142     68/push  _test-stream/imm32
143     # . . call
144     e8/call  write/disp32
145     # . . discard args
146     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
147     # . write(_test-stream, "\n")
148     # . . push args
149     68/push Newline/imm32
150     68/push  _test-stream/imm32
151     # . . call
152     e8/call  write/disp32
153     # . . discard args
154     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
155     # . write(_test-stream, "cd")
156     # . . push args
157     68/push  "cd"/imm32
158     68/push  _test-stream/imm32
159     # . . call
160     e8/call  write/disp32
161     # . . discard args
162     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
163     # read a line from _test-stream (buffered by _test-buffered-file) into _test-tmp-stream
164     # . EAX = read-line(_test-buffered-file, _test-tmp-stream)
165     # . . push args
166     68/push  _test-tmp-stream/imm32
167     68/push  _test-buffered-file/imm32
168     # . . call
169     e8/call  read-line/disp32
170     # . . discard args
171     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
172     # check-ints-equal(EAX, 0/not-at-Eof, msg)
173     # . . push args
174     68/push  "F - test-read-line: return value"/imm32
175     68/push  0/imm32/not-at-Eof
176     50/push-EAX
177     # . . call
178     e8/call  check-ints-equal/disp32
179     # . . discard args
180     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               0xc/imm32         # add to ESP
181     # check-next-stream-line-equal(_test-tmp-stream, "ab", msg)
182     # . . push args
183     68/push  "F - test-read-line"/imm32
184     68/push  "ab"/imm32
185     68/push  _test-tmp-stream/imm32
186     # . . call
187     e8/call  check-next-stream-line-equal/disp32
188     # . . discard args
189     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               0xc/imm32         # add to ESP
190     # end
191     c3/return
192 
193 test-read-line-returns-true-on-Eof:
194     # setup
195     # . clear-stream(_test-stream)
196     # . . push args
197     68/push  _test-stream/imm32
198     # . . call
199     e8/call  clear-stream/disp32
200     # . . discard args
201     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add to ESP
202     # . clear-stream(_test-buffered-file+4)
203     # . . push args
204     b8/copy-to-EAX  _test-buffered-file/imm32
205     05/add-to-EAX  4/imm32
206     50/push-EAX
207     # . . call
208     e8/call  clear-stream/disp32
209     # . . discard args
210     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add to ESP
211     # . clear-stream(_test-tmp-stream)
212     # . . push args
213     68/push  _test-tmp-stream/imm32
214     # . . call
215     e8/call  clear-stream/disp32
216     # . . discard args
217     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add to ESP
218     # write nothing
219     # EAX = read-line(_test-buffered-file, _test-tmp-stream)
220     # . . push args
221     68/push  _test-tmp-stream/imm32
222     68/push  _test-buffered-file/imm32
223     # . . call
224     e8/call  read-line/disp32
225     # . . discard args
226     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
227     # check-ints-equal(EAX, Eof, msg)
228     # . . push args
229     68/push  "F - test-read-line-returns-true-on-Eof"/imm32
230     68/push  0xffffffff/imm32/Eof
231     50/push-EAX
232     # . . call
233     e8/call  check-ints-equal/disp32
234     # . . discard args
235     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               0xc/imm32         # add to ESP
236     # end
237     c3/return
238 
239 test-read-line-reads-final-line-until-Eof:
240     # setup
241     # . clear-stream(_test-stream)
242     # . . push args
243     68/push  _test-stream/imm32
244     # . . call
245     e8/call  clear-stream/disp32
246     # . . discard args
247     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add to ESP
248     # . clear-stream(_test-buffered-file+4)
249     # . . push args
250     b8/copy-to-EAX  _test-buffered-file/imm32
251     05/add-to-EAX  4/imm32
252     50/push-EAX
253     # . . call
254     e8/call  clear-stream/disp32
255     # . . discard args
256     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add to ESP
257     # . clear-stream(_test-tmp-stream)
258     # . . push args
259     68/push  _test-tmp-stream/imm32
260     # . . call
261     e8/call  clear-stream/disp32
262     # . . discard args
263     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add to ESP
264     # write(_test-stream, "cd")
265     # . . push args
266     68/push  "cd"/imm32
267     68/push  _test-stream/imm32
268     # . . call
269     e8/call  write/disp32
270     # . . discard args
271     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
272     # read a line from _test-stream (buffered by _test-buffered-file) into _test-tmp-stream
273     # . EAX = read-line(_test-buffered-file, _test-tmp-stream)
274     # . . push args
275     68/push  _test-tmp-stream/imm32
276     68/push  _test-buffered-file/imm32
277     # . . call
278     e8/call  read-line/disp32
279     # . . discard args
280     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
281     # check-ints-equal(EAX, Eof, msg)
282     # . . push args
283     68/push  "F - test-read-line-reads-final-line-until-Eof: return value"/imm32
284     68/push  0xffffffff/imm32/Eof
285     50/push-EAX
286     # . . call
287     e8/call  check-ints-equal/disp32
288     # . . discard args
289     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               0xc/imm32         # add to ESP
290     # check-stream-equal(_test-tmp-stream, "cd", msg)
291     # . . push args
292     68/push  "F - test-read-line-reads-final-line-until-Eof"/imm32
293     68/push  "cd"/imm32
294     68/push  _test-tmp-stream/imm32
295     # . . call
296     e8/call  check-stream-equal/disp32
297     # . . discard args
298     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               0xc/imm32         # add to ESP
299     # end
300     c3/return
301 
302 # . . vim:nowrap:textwidth=0