about summary refs log tree commit diff stats
path: root/subx/067write-buffered.subx
blob: 343aa364fdd34486344a0f603886f0b1692ae8fa (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
# write-buffered: like 'write', but for a buffered-file

== 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

#? Entry:  # run a single test, while debugging
#?     e8/call test-write-buffered/disp32
#?     e8/call test-write-buffered-with-intermediate-flush/disp32
#?     # syscall(exit, Num-test-failures)
#?     8b/copy                         0/mod/indirect  5/rm32/.disp32            .             .           3/r32/EBX   Num-test-failures/disp32          # copy *Num-test-failures to EBX
#?     b8/copy-to-EAX  1/imm32/exit
#?     cd/syscall  0x80/imm8

write-buffered:  # f : (address buffered-file), msg : (address array byte) -> <void>
    # pseudocode:
    #   in = msg->data
    #   inend = &msg->data[msg->length]
    #   while (in < inend)
    #     if f->write >= f->length
    #       flush(f)
    #       clear-stream(f)
    #     c = *in
    #     f->data[f->write] = c
    #     ++f->write
    #     ++in
    #
    # registers:
    #   in: ESI
    #   inend: ECX
    #   f: EDI
    #   f->length: EDX
    #   f->write: EBX (cached; need to keep in sync)
    #   c: EAX
    #
    # . 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
    56/push-ESI
    57/push-EDI
    # EAX = msg
    8b/copy                         1/mod/*+disp8   5/rm32/EBP    .           .                         0/r32/EAX   0xc/disp8       .                 # copy *(EBP+12) to EAX
    # in/ESI = msg->data
    8d/copy-address                 1/mod/*+disp8   0/rm32/EAX    .           .             .           6/r32/ESI   4/disp8         .                 # copy EAX+4 to ESI
    # inend/ECX = &msg->data[msg->length]
    8b/copy                         0/mod/indirect  0/rm32/EAX    .           .             .           1/r32/ECX   .               .                 # copy *EAX to ECX
    8d/copy-address                 0/mod/indirect  4/rm32/sib    6/base/ESI  1/index/ECX   .           1/r32/ECX   .               .                 # copy ESI+ECX to ECX
    # EDI = f
    8b/copy                         1/mod/*+disp8   5/rm32/EBP    .           .                         7/r32/EDI   8/disp8         .                 # copy *(EBP+8) to EDI
    # EDX = f->length
    8b/copy                         1/mod/*+disp8   7/rm32/EDI    .           .             .           2/r32/EDX   0xc/disp8       .                 # copy *(EDI+12) to EDX
    # EBX = f->write
    8b/copy                         1/mod/*+disp8   7/rm32/EDI    .           .             .           3/r32/EBX   4/disp8         .                 # copy *(EDI+4) to EBX
$write-buffered:loop:
    # if (in >= inend) break
    39/compare                      3/mod/direct    6/rm32/ESI    .           .             .           1/r32/ECX   .               .                 # compare ESI with ECX
    7d/jump-if-greater-or-equal  $write-buffered:loop-end/disp8
    # if (f->write >= f->length) flush and clear f's stream
    39/compare                      3/mod/direct    3/rm32/EBX    .           .             .           2/r32/EDX   .               .                 # compare EBX with EDX
    7c/jump-if-lesser  $write-buffered:to-stream/disp8
    # . persist f->write
    89/copy                         1/mod/*+disp8   7/rm32/EDI    .           .             .           3/r32/EBX   4/disp8         .                 # copy EBX to *(EDI+4)
    # . flush(f)
    # . . push args
    57/push-EDI
    # . . call
    e8/call  flush/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add to ESP
    # . clear-stream(stream = f+4)
    # . . push args
    8d/copy-address                 1/mod/*+disp8   7/rm32/EDI    .           .             .           0/r32/EAX   4/disp8         .                 # copy EDI+4 to EAX
    50/push-EAX
    # . . call
    e8/call  clear-stream/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add to ESP
    # . f->write must now be 0; update its cache at EBX
    31/xor                          3/mod/direct    3/rm32/EBX    .           .             .           3/r32/EBX   .               .                 # clear EBX
$write-buffered:to-stream:
    # write to stream
    # f->data[f->write] = *in
    # . AL = *in
    31/xor                          3/mod/direct    0/rm32/EAX    .           .             .           0/r32/EAX   .               .                 # clear EAX
    8a/copy-byte                    0/mod/indirect  6/rm32/ESI    .           .             .           0/r32/AL    .               .                 # copy byte at *ESI to AL
    # . f->data[f->write] = AL
    88/copy-byte                    1/mod/*+disp8   4/rm32/sib    7/base/EDI  3/index/EBX   .           0/r32/AL    0x10/disp8      .                 # copy AL to *(EDI+EBX+16)
    # ++f->write
    43/increment-EBX
    # ++in
    46/increment-ESI
    eb/jump  $write-buffered:loop/disp8
$write-buffered:loop-end:
    # persist necessary variables from registers
    89/copy                         1/mod/*+disp8   7/rm32/EDI    .           .             .           3/r32/EBX   4/disp8         .                 # copy EBX to *(EDI+4)
$write-buffered:end:
    # . restore registers
    5f/pop-to-EDI
    5e/pop-to-ESI
    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

test-write-buffered:
    # - check that write-buffered writes to the file
    # 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
    # . clear-stream(_test-buffered-file+4)
    # . . push args
    b8/copy-to-EAX  _test-buffered-file/imm32
    05/add-to-EAX  4/imm32
    50/push-EAX
    # . . call
    e8/call  clear-stream/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add to ESP
    # write-buffered(_test-buffered-file, "Abc")
    # . . push args
    68/push  "Abc"/imm32
    68/push  _test-buffered-file/imm32
    # . . call
    e8/call  write-buffered/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
    # flush(_test-buffered-file)
    # . . push args
    68/push  _test-buffered-file/imm32
    # . . call
    e8/call  flush/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add to ESP
    # check-stream-equal(_test-stream, "Abc", msg)
    # . . push args
    68/push  "F - test-write-buffered-single"/imm32
    68/push  "Abc"/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-write-buffered-with-intermediate-flush:
    # - check that write-buffered flushes in the middle if its buffer fills up
    # 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
    # . clear-stream(_test-buffered-file+4)
    # . . push args
    b8/copy-to-EAX  _test-buffered-file/imm32
    05/add-to-EAX  4/imm32
    50/push-EAX
    # . . call
    e8/call  clear-stream/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add to ESP
    # _test-stream can hold 8 bytes, but _test-buffered-file can hold only 6.
    # Try to write 7 bytes.
    # . write-buffered(_test-buffered-file, "Abcdefg")
    # . . push args
    68/push  "Abcdefg"/imm32
    68/push  _test-buffered-file/imm32
    # . . call
    e8/call  write-buffered/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
    # don't flush
    # 6 bytes should still have gotten to _test-stream
    # . check-ints-equal(*_test-stream->write, 6, msg)
    # . . push args
    68/push  "F - test-write-buffered-with-intermediate-flush: flushed data"/imm32
    68/push  6/imm32
    # . . push *_test-stream->write
    b8/copy-to-EAX  _test-stream/imm32
    ff          6/subop/push        0/mod/indirect  0/rm32/EAX    .           .             .           .           .               .                 # push *EAX
    # . . call
    e8/call  check-ints-equal/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               0xc/imm32         # add to ESP
    # and 1 byte should still be in _test-buffered-file
    # . check-ints-equal(*_test-buffered-file->write, 1, msg)
    # . . push args
    68/push  "F - test-write-buffered-with-intermediate-flush: unflushed bytes"/imm32
    68/push  1/imm32
    # . . push *_test-buffered-file->write
    b8/copy-to-EAX  _test-buffered-file/imm32
    ff          6/subop/push        1/mod/*+disp8   0/rm32/EAX    .           .             .           .           4/disp8         .                 # push *(EAX+4)
    # . . call
    e8/call  check-ints-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