# Helper to allocate a stream on the heap. == 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 new-stream: # ad : (address allocation-descriptor), length : int, elemsize : int -> address/EAX # . prolog 55/push-EBP 89/copy 3/mod/direct 5/rm32/EBP . . . 4/r32/ESP . . # copy ESP to EBP # . save registers 52/push-EDX # n = elemsize * length + 12 (for read, write and length) # . EAX = elemsize 8b/copy 1/mod/*+disp8 5/rm32/EBP . . . 0/r32/EAX 0x10/disp8 . # copy *(EBP+16) to EAX # . EAX *= length 31/xor 3/mod/direct 2/rm32/EDX . . . 2/r32/EDX . . # clear EDX f7 4/subop/multiply 1/mod/*+disp8 5/rm32/EBP . . 0xc/disp8 . # multiply *(EBP+12) into EAX # . if overflow abort 81 7/subop/compare 3/mod/direct 2/rm32/EDX . . . . . 0/imm32 # compare EDX 75/jump-if-not-equal $new-stream:abort/disp8 # . EDX = elemsize*length 89/copy 3/mod/direct 2/rm32/EDX . . . 0/r32/EAX . . # copy EAX to EDX # . EAX += 12 05/add-to-EAX 0xc/imm32 # allocate(ad, n) # . . push args 50/push-EAX ff 6/subop/push 1/mod/*+disp8 5/rm32/EBP . . . . 8/disp8 . # push *(EBP+8) # . . call e8/call allocate/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP # EAX->length = elemsize*length 89/copy 1/mod/*+disp8 0/rm32/EAX . . . 2/r32/EDX 8/disp8 . # copy EDX to *(EAX+8) # clear-stream(EAX) # . . push args 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 $new-stream:end: # . restore registers 5a/pop-to-EDX # . epilog 89/copy 3/mod/direct 4/rm32/ESP . . . 5/r32/EBP . . # copy EBP to ESP 5d/pop-to-EBP c3/return $new-stream:abort: # . _write(2/stderr, error) # . . push args 68/push "new-stream: size too large\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-new-stream: # . prolog 55/push-EBP 89/copy 3/mod/direct 5/rm32/EBP . . . 4/r32/ESP . . # copy ESP to EBP # var heap/ECX : (address allocation-descriptor) = {0, 0} 68/push 0/imm32/limit 68/push 0/imm32/curr 89/copy 3/mod/direct 1/rm32/ECX . . . 4/r32/ESP . . # copy ESP to ECX # heap = new-segment(512) # . . push args 51/push-ECX 68/push 0x200/imm32 # . . call e8/call new-segment/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP # var start/EDX = ad->curr 8b/copy 0/mod/indirect 1/rm32/ECX . . . 2/r32/EDX . . # copy *ECX to EDX # EAX = new-stream(heap, 3, 2) # . . push args 68/push 2/imm32 68/push 3/imm32 51/push-ECX # . . call e8/call new-stream/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 0xc/imm32 # add to ESP # check-ints-equal(EAX, EDX, msg) # . . push args 68/push "F - test-new-stream: returns current pointer of allocation descriptor"/imm32 52/push-EDX 50/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 # check-ints-equal(EAX->length, 6, msg) # . . push args 68/push "F - test-new-stream: sets length correctly"/imm32 68/push 6/imm32 ff 6/subop/push 1/mod/*+disp8 0/rm32/EAX . . . . . 8/disp8 # push *(EAX+8) # . . call e8/call check-ints-equal/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 0xc/imm32 # add to ESP # the rest is delegated to clear-stream() so we won't bother checking it # . epilog 89/copy 3/mod/direct 4/rm32/ESP . . . 5/r32/EBP . . # copy EBP to ESP 5d/pop-to-EBP c3/return # . . vim:nowrap:textwidth=0