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# write-int: add a single int to a stream
== 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-int: # out : (addr stream byte), n : int
# . 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
57/push-edi
# edi = out
8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 7/r32/edi 8/disp8 . # copy *(ebp+8) to edi
# ecx = out->write
8b/copy 0/mod/indirect 7/rm32/edi . . . 1/r32/ecx . . # copy *edi to ecx
# if (out->write >= out->length) abort
3b/compare 1/mod/*+disp8 7/rm32/edi . . . 1/r32/ecx 8/disp8 . # compare ecx with *(edi+8)
7d/jump-if-greater-or-equal $write-int:abort/disp8
$write-int:to-stream:
# out->data[out->write] = n
8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 0/r32/eax 0xc/disp8 . # copy *(ebp+12) to eax
89/copy 1/mod/*+disp8 4/rm32/sib 7/base/edi 1/index/ecx . 0/r32/eax 0xc/disp8 . # copy eax to *(edi+ecx+12)
# out->write += 4
81 0/subop/add 0/mod/indirect 7/rm32/edi . . . . . 4/imm32 # add to *edi
$write-int:end:
# . restore registers
5f/pop-to-edi
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
$write-int:abort:
# . _write(2/stderr, error)
# . . push args
68/push "write-int: out of space\n"/imm32
68/push 2/imm32/stderr
# . . call
e8/call _write/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp
# . syscall(exit, 1)
bb/copy-to-ebx 1/imm32
b8/copy-to-eax 1/imm32/exit
cd/syscall 0x80/imm8
# never gets here
test-write-int-single:
# - check that write-int writes to first int of 'stream'
# 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
# write-int(_test-stream, "abcd")
# . . push args
68/push 0x64636261/imm32
68/push _test-stream/imm32
# . . call
e8/call write-int/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp
# check-stream-equal(_test-stream, "abcd", msg)
# . . push args
68/push "F - test-write-int-single"/imm32
68/push "abcd"/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-byte-buffered-multiple:
# - check that write-int correctly appends multiple writes
# 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
# write-int(_test-stream, "abcd")
# . . push args
68/push 0x64636261/imm32
68/push _test-stream/imm32
# . . call
e8/call write-int/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp
# write-int(_test-stream, "efgh")
# . . push args
68/push 0x68676665/imm32
68/push _test-stream/imm32
# . . call
e8/call write-int/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp
# check-stream-equal(_test-stream, "abcdefgh", msg)
# . . push args
68/push "F - test-write-byte-buffered-multiple"/imm32
68/push "abcdefgh"/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
# . . vim:nowrap:textwidth=0
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