308 lines
13 KiB
Plaintext
308 lines
13 KiB
Plaintext
# Helper to print an int32 in decimal.
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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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print-int32-decimal: # out : (address stream), n : int32
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# works by generating characters from lowest to highest and pushing them
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# to the stack, before popping them one by one into the stream
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#
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# pseudocode:
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# push sentinel
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# EAX = abs(n)
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# while true
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# sign-extend EAX into EDX
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# EAX, EDX = EAX/10, EAX%10
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# EDX += '0'
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# push EDX
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# if (EAX == 0) break
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# if n < 0
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# push '-'
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# w = out->write
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# curr = &out->data[out->write]
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# max = &out->data[out->length]
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# while true
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# pop into EAX
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# if (EAX == sentinel) break
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# if (curr >= max) abort
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# *curr = AL
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# ++curr
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# ++w
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# out->write = w
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# (based on K&R itoa: https://en.wikibooks.org/wiki/C_Programming/stdlib.h/itoa)
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# (this pseudocode contains registers because operations like division
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# require specific registers in x86)
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#
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# . prolog
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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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50/push-EAX
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51/push-ECX
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52/push-EDX
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53/push-EBX
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57/push-EDI
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# ten/ECX = 10
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b9/copy-to-ECX 0xa/imm32
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# push sentinel
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68/push 0/imm32/sentinel
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# EAX = abs(n)
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8b/copy 1/mod/*+disp8 5/rm32/EBP . . . 0/r32/EAX 0xc/disp8 . # copy *(EBP+12) to EAX
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3d/compare-EAX-with 0/imm32
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7d/jump-if-greater-or-equal $print-int32-decimal:read-loop/disp8
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$print-int32-decimal:negative:
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f7 3/subop/negate 3/mod/direct 0/rm32/EAX . . . . . . # negate EAX
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$print-int32-decimal:read-loop:
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# EAX, EDX = EAX / 10, EAX % 10
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99/sign-extend-EAX-into-EDX
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f7 7/subop/idiv 3/mod/direct 1/rm32/ECX . . . . . . # divide EDX:EAX by ECX, storing quotient in EAX and remainder in EDX
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# EDX += '0'
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81 0/subop/add 3/mod/direct 2/rm32/EDX . . . . . 0x30/imm32 # add to EDX
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# push EDX
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52/push-EDX
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# if (EAX == 0) break
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3d/compare-EAX-and 0/imm32
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7f/jump-if-greater $print-int32-decimal:read-loop/disp8
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$print-int32-decimal:read-break:
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# if (n < 0) push('-')
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81 7/subop/compare 1/mod/*+disp8 5/rm32/EBP . . . . 0xc/disp8 0/imm32 # compare *(EBP+12)
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7d/jump-if-greater-or-equal $print-int32-decimal:write/disp8
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$print-int32-decimal:push-negative:
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68/push 0x2d/imm32/-
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$print-int32-decimal:write:
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# EDI = out
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8b/copy 1/mod/*+disp8 5/rm32/EBP . . . 7/r32/EDI 8/disp8 . # copy *(EBP+8) to EDI
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# w/EDX = out->write
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8b/copy 0/mod/indirect 7/rm32/EDI . . . 2/r32/EDX . . # copy *EDI to EDX
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# curr/ECX = &out->data[out->write]
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8d/copy-address 1/mod/*+disp8 4/rm32/sib 7/base/EDI 2/index/EDX . 1/r32/ECX 0xc/disp8 . # copy EBX+EDX+12 to ECX
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# max/EBX = &out->data[out->length]
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8b/copy 1/mod/*+disp8 7/rm32/EDI . . . 3/r32/EBX 8/disp8 . # copy *(EDI+8) to EBX
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8d/copy-address 1/mod/*+disp8 4/rm32/sib 7/base/EDI 3/index/EBX . 3/r32/EBX 0xc/disp8 . # copy EDI+EBX+12 to EBX
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$print-int32-decimal:write-loop:
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# pop into EAX
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58/pop-to-EAX
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# if (EAX == sentinel) break
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3d/compare-EAX-and 0/imm32/sentinel
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74/jump-if-equal $print-int32-decimal:write-break/disp8
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# if (curr >= max) abort
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39/compare 3/mod/direct 1/rm32/ECX . . . 3/r32/EBX . . # compare ECX with EBX
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73/jump-if-greater-or-equal-unsigned $print-int32-decimal:abort/disp8
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$print-int32-decimal:write-char:
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# *curr = AL
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88/copy-byte 0/mod/indirect 1/rm32/ECX . . . 0/r32/AL . . # copy AL to byte at *ECX
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# ++curr
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41/increment-ECX
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# ++w
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42/increment-EDX
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eb/jump $print-int32-decimal:write-loop/disp8
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$print-int32-decimal:write-break:
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# out->write = w
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89/copy 0/mod/indirect 7/rm32/EDI . . . 2/r32/EDX . . # copy EDX to *EDI
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$print-int32-decimal:end:
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# . restore registers
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5f/pop-to-EDI
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5b/pop-to-EBX
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5a/pop-to-EDX
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59/pop-to-ECX
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58/pop-to-EAX
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# . epilog
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89/copy 3/mod/direct 4/rm32/ESP . . . 5/r32/EBP . . # copy EBP to ESP
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5d/pop-to-EBP
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c3/return
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$print-int32-decimal:abort:
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# . _write(2/stderr, error)
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# . . push args
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68/push "print-int32-decimal: out of space\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-print-int32-decimal:
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# - check that a single-digit number converts correctly
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# setup
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# . clear-stream(_test-stream)
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# . . push args
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68/push _test-stream/imm32
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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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# print-int32-decimal(_test-stream, 9)
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# . . push args
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68/push 9/imm32
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68/push _test-stream/imm32
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# . . call
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e8/call print-int32-decimal/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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# check-stream-equal(_test-stream, "9", msg)
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# . . push args
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68/push "F - test-print-int32-decimal"/imm32
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68/push "9"/imm32
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68/push _test-stream/imm32
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# . . call
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e8/call check-stream-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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# . end
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c3/return
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test-print-int32-decimal-zero:
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# - check that 0 converts correctly
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# setup
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# . clear-stream(_test-stream)
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# . . push args
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68/push _test-stream/imm32
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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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# print-int32-decimal(_test-stream, 0)
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# . . push args
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68/push 0/imm32
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68/push _test-stream/imm32
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# . . call
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e8/call print-int32-decimal/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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# check-stream-equal(_test-stream, "0", msg)
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# . . push args
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68/push "F - test-print-int32-decimal-zero"/imm32
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68/push "0"/imm32
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68/push _test-stream/imm32
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# . . call
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e8/call check-stream-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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# . end
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c3/return
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test-print-int32-decimal-multiple-digits:
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# - check that a multi-digit number converts correctly
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# setup
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# . clear-stream(_test-stream)
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# . . push args
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68/push _test-stream/imm32
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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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# print-int32-decimal(_test-stream, 10)
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# . . push args
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68/push 0xa/imm32
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68/push _test-stream/imm32
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# . . call
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e8/call print-int32-decimal/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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# check-stream-equal(_test-stream, "10", msg)
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# . . push args
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68/push "F - test-print-int32-decimal-multiple-digits"/imm32
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68/push "10"/imm32
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68/push _test-stream/imm32
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# . . call
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e8/call check-stream-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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# . end
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c3/return
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test-print-int32-decimal-negative:
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# - check that a negative single-digit number converts correctly
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# setup
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# . clear-stream(_test-stream)
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# . . push args
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68/push _test-stream/imm32
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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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# print-int32-decimal(_test-stream, -9)
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# . . push args
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68/push -9/imm32
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68/push _test-stream/imm32
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# . . call
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e8/call print-int32-decimal/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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#? # dump _test-stream {{{
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#? # . write(2/stderr, "^")
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#? # . . push args
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#? 68/push "^"/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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#? # . write-stream(2/stderr, _test-stream)
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#? # . . push args
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#? 68/push _test-stream/imm32
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#? 68/push 2/imm32/stderr
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#? # . . call
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#? e8/call write-stream/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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#? # . write(2/stderr, "$\n")
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#? # . . push args
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#? 68/push "$\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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#? # }}}
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# check-stream-equal(_test-stream, "-9", msg)
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# . . push args
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68/push "F - test-print-int32-decimal-negative"/imm32
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68/push "-9"/imm32
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68/push _test-stream/imm32
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# . . call
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e8/call check-stream-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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# . end
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c3/return
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test-print-int32-decimal-negative-multiple-digits:
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# - check that a multi-digit number converts correctly
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# setup
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# . clear-stream(_test-stream)
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# . . push args
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68/push _test-stream/imm32
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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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# print-int32-decimal(_test-stream, -10)
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# . . push args
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68/push -0xa/imm32
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68/push _test-stream/imm32
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# . . call
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e8/call print-int32-decimal/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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# check-stream-equal(_test-stream, "-10", msg)
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# . . push args
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68/push "F - test-print-int32-decimal-negative-multiple-digits"/imm32
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68/push "-10"/imm32
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68/push _test-stream/imm32
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# . . call
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e8/call check-stream-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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# . end
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c3/return
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# . . vim:nowrap:textwidth=0
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