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## read a character from stdin, save it to a local on the stack, write it to stdout
#
# To run (from the subx directory):
# $ subx translate examples/ex5.subx -o examples/ex5
# $ subx run examples/ex5
== code
# instruction effective address operand 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
# main:
# allocate x on the stack
81 5/subop/subtract 3/mod/direct 4/rm32/ESP . . . . . 4/imm32 # subtract from ESP
# read(stdin, x, 1)
# fd = 0 (stdin)
bb/copy . . . . . . . 0/imm32 # copy to EBX
# initialize x (location to write result to)
8d/copy-address 1/mod/*+disp8 4/rm32/sib 4/base/ESP 4/index/none 1/r32/ECX 4/disp8 . # copy ESP+4 to ECX
# size = 1 character
ba/copy . . . . . . . 1/imm32 # copy to EDX
# read(fd, x, size)
b8/copy . . . . . . . 3/imm32/read # copy to EAX
cd/syscall 0x80/imm8
# write(stdout, x, 1)
# fd = 1 (stdout)
bb/copy . . . . . . . 1/imm32 # copy to EBX
# initialize x (location to read from)
8d/copy-address 1/mod/*+disp8 4/rm32/sib 4/base/ESP 4/index/none 1/r32/ECX 4/disp8 . # copy ESP+4 to ECX
# size = 1 character
ba/copy . . . . . . . 1/imm32 # copy to EDX
# write(fd, x, size)
b8/copy . . . . . . . 4/imm32/write # copy to EAX
cd/syscall 0x80/imm8
# exit(EBX)
b8/copy . . . . . . . 1/imm32/exit # copy to EAX
cd/syscall 0x80/imm8
# vim:ft=subx:nowrap
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