119 lines
6.2 KiB
Plaintext
119 lines
6.2 KiB
Plaintext
# Helper to allocate a stream on the heap.
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== code
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# instruction effective address register displacement immediate
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# . op subop mod rm32 base index scale r32
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# . 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
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new-stream: # ad : (addr allocation-descriptor), length : int, elemsize : int -> address/eax : (handle stream _)
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# . prologue
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55/push-ebp
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89/copy 3/mod/direct 5/rm32/ebp . . . 4/r32/esp . . # copy esp to ebp
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# . save registers
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52/push-edx
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# var n/eax : int = elemsize * length + 12 (for read, write and length)
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# . eax = elemsize
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8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 0/r32/eax 0x10/disp8 . # copy *(ebp+16) to eax
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# . eax *= length
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31/xor 3/mod/direct 2/rm32/edx . . . 2/r32/edx . . # clear edx
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f7 4/subop/multiply 1/mod/*+disp8 5/rm32/ebp . . 0xc/disp8 . # multiply *(ebp+12) into eax
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# . if overflow abort
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81 7/subop/compare 3/mod/direct 2/rm32/edx . . . . . 0/imm32 # compare edx
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75/jump-if-not-equal $new-stream:abort/disp8
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# . edx = elemsize*length
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89/copy 3/mod/direct 2/rm32/edx . . . 0/r32/eax . . # copy eax to edx
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# . eax += 12
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05/add-to-eax 0xc/imm32
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# var eax : (handle stream _) = allocate(ad, n)
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# . . push args
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50/push-eax
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ff 6/subop/push 1/mod/*+disp8 5/rm32/ebp . . . . 8/disp8 . # push *(ebp+8)
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# . . call
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e8/call allocate/disp32
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# . . discard args
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81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp
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# eax->length = elemsize*length
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89/copy 1/mod/*+disp8 0/rm32/eax . . . 2/r32/edx 8/disp8 . # copy edx to *(eax+8)
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# clear-stream(eax)
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# . . push args
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50/push-eax
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# . . call
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e8/call clear-stream/disp32
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# . . discard args
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81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 4/imm32 # add to esp
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$new-stream:end:
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# . restore registers
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5a/pop-to-edx
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# . epilogue
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89/copy 3/mod/direct 4/rm32/esp . . . 5/r32/ebp . . # copy ebp to esp
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5d/pop-to-ebp
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c3/return
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$new-stream:abort:
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# . _write(2/stderr, error)
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# . . push args
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68/push "new-stream: size too large\n"/imm32
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68/push 2/imm32/stderr
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# . . call
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e8/call _write/disp32
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# . . discard args
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81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp
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# . syscall(exit, 1)
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bb/copy-to-ebx 1/imm32
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b8/copy-to-eax 1/imm32/exit
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cd/syscall 0x80/imm8
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# never gets here
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test-new-stream:
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# . prologue
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55/push-ebp
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89/copy 3/mod/direct 5/rm32/ebp . . . 4/r32/esp . . # copy esp to ebp
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# var heap/ecx : (ref allocation-descriptor)
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68/push 0/imm32/limit
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68/push 0/imm32/curr
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89/copy 3/mod/direct 1/rm32/ecx . . . 4/r32/esp . . # copy esp to ecx
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# heap = new-segment(512)
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# . . push args
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51/push-ecx
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68/push 0x200/imm32
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# . . call
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e8/call new-segment/disp32
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# . . discard args
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81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp
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# var start/edx = ad->curr
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8b/copy 0/mod/indirect 1/rm32/ecx . . . 2/r32/edx . . # copy *ecx to edx
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# var eax : (handle stream byte) = new-stream(heap, 3, 2)
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# . . push args
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68/push 2/imm32
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68/push 3/imm32
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51/push-ecx
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# . . call
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e8/call new-stream/disp32
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# . . discard args
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81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp
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# check-ints-equal(eax, edx, msg)
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# . . push args
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68/push "F - test-new-stream: returns current pointer of allocation descriptor"/imm32
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52/push-edx
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50/push-eax
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# . . call
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e8/call check-ints-equal/disp32
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# . . discard args
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81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp
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# check-ints-equal(eax->length, 6, msg)
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# . . push args
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68/push "F - test-new-stream: sets length correctly"/imm32
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68/push 6/imm32
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ff 6/subop/push 1/mod/*+disp8 0/rm32/eax . . . . . 8/disp8 # push *(eax+8)
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# . . call
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e8/call check-ints-equal/disp32
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# . . discard args
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81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp
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# the rest is delegated to clear-stream() so we won't bother checking it
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# . epilogue
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89/copy 3/mod/direct 4/rm32/esp . . . 5/r32/ebp . . # copy ebp to esp
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5d/pop-to-ebp
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c3/return
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# . . vim:nowrap:textwidth=0
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