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# 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
write-buffered: # f: (addr buffered-file), msg: (addr array byte)
# pseudocode:
# in = msg->data
# inend = &msg->data[msg->size]
# while (in < inend)
# if f->write >= f->size
# flush(f)
# clear-stream(f)
# c = *in
# f->data[f->write] = c
# ++f->write
# ++in
#
# registers:
# in: esi
# inend: ecx
# f: edi
# f->size: edx
# f->write: ebx (cached; need to keep in sync)
# c: eax
#
# . prologue
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
# var in/esi: (addr byte) = msg->data
8d/copy-address 1/mod/*+disp8 0/rm32/eax . . . 6/r32/esi 4/disp8 . # copy eax+4 to esi
# var inend/ecx: (addr byte) = &msg->data[msg->size]
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->size
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
73/jump-if-addr>= $write-buffered:loop-end/disp8
# if (f->write >= f->size) flush and clear f's stream
39/compare 3/mod/direct 3/rm32/ebx . . . 2/r32/edx . . # compare ebx with edx
7c/jump-if-< $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)
$write-buffered:end:
# . restore registers
5f/pop-to-edi
5e/pop-to-esi
5b/pop-to-ebx
5a/pop-to-edx
59/pop-to-ecx
58/pop-to-eax
# . epilogue
89/copy 3/mod/direct 4/rm32/esp . . . 5/r32/ebp . . # copy ebp to esp
5d/pop-to-ebp
c3/return
test-write-buffered:
# - check that write-buffered writes to the file
# setup
# . clear-stream(_test-stream)
# . . push args
68/push _test-stream/imm32
# . . call
e8/call clear-stream/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 4/imm32 # add to esp
# . clear-stream($_test-buffered-file->buffer)
# . . push args
68/push $_test-buffered-file->buffer/imm32
# . . call
e8/call clear-stream/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 4/imm32 # add to esp
# write-buffered(_test-buffered-file, "Abc")
# . . push args
68/push "Abc"/imm32
68/push _test-buffered-file/imm32
# . . call
e8/call write-buffered/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp
# flush(_test-buffered-file)
# . . push args
68/push _test-buffered-file/imm32
# . . call
e8/call flush/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 4/imm32 # add to esp
# check-stream-equal(_test-stream, "Abc", msg)
# . . push args
68/push "F - test-write-buffered-single"/imm32
68/push "Abc"/imm32
68/push _test-stream/imm32
# . . call
e8/call check-stream-equal/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp
# . end
c3/return
test-write-buffered-with-intermediate-flush:
# - check that write-buffered flushes in the middle if its buffer fills up
# setup
# . clear-stream(_test-stream)
# . . push args
68/push _test-stream/imm32
# . . call
e8/call clear-stream/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 4/imm32 # add to esp
# . clear-stream($_test-buffered-file->buffer)
# . . push args
68/push $_test-buffered-file->buffer/imm32
# . . 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
== data
# The buffered file for standard error.
Stderr: # buffered-file
# file descriptor or (addr stream byte)
2/imm32 # standard error
$Stderr->buffer:
# inlined fields for a stream
# current write index
0/imm32
# current read index
0/imm32
# size
8/imm32
# data
00 00 00 00 00 00 00 00 # 8 bytes
# TODO: 8 bytes is too small. We'll need to grow the buffer for efficiency. But
# I don't want to type in 1024 bytes here.
# . . vim:nowrap:textwidth=0
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