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# Read a character from stdin, save it to a local on the stack, write it to stdout.
#
# To run:
# $ bootstrap/bootstrap translate ex5.subx -o ex5
# $ bootstrap/bootstrap run ex5
== 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:
# 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-to-ebx 0/imm32
# . data = 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-to-edx 1/imm32
# . syscall
e8/call syscall_read/disp32
# syscall(write, stdout, x, 1)
# . fd = 1 (stdout)
bb/copy-to-ebx 1/imm32
# . data = 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-to-edx 1/imm32
# . syscall
e8/call syscall_write/disp32
# exit(ebx)
e8/call syscall_exit/disp32
# . . vim:nowrap:textwidth=0
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