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Diffstat (limited to 'subx/examples/ex11.subx')
| -rw-r--r-- | subx/examples/ex11.subx | 304 |
1 files changed, 304 insertions, 0 deletions
diff --git a/subx/examples/ex11.subx b/subx/examples/ex11.subx new file mode 100644 index 00000000..460c3430 --- /dev/null +++ b/subx/examples/ex11.subx @@ -0,0 +1,304 @@ +## Null-terminated vs length-prefixed ascii strings. +# +# By default we create strings with a 4-byte length prefix rather than a null suffix. +# However, commandline arguments come null-prefixed from the Linux kernel. +# This example shows a helper that can compare a commandline argument with the +# (length-prefixed) literal string "target". +# +# To run: +# $ subx translate ex11.subx ex11 +# $ subx run ex11 # runs a series of tests +# ...... # all tests pass +# +# (We can't yet run the tests when given a "test" commandline argument, +# because checking for it would require the function being tested! Breakage +# would cause tests to not run, rather than to fail as we'd like.) + +== 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: + e8/call run_tests/disp32 # 'run_tests' is a function created automatically by SubX. It calls all functions that start with 'test_'. + # exit(EAX) + 89/copy 3/mod/direct 3/rm32/EBX . . . 0/r32/EAX . . # copy EAX to EBX + b8/copy . . . . . . . 1/imm32 # copy 1 to EAX + cd/syscall 0x80/imm8 + +# compare a null-terminated ascii string with a more idiomatic length-prefixed byte array +# reason for the name: the only place we should have null-terminated ascii strings is from commandline args +argv_equal: # s : null-terminated ascii string, benchmark : length-prefixed ascii string -> EAX : boolean + # pseudocode: + # initialize n = b.length + # initialize s1 = s + # initialize s2 = b.data + # i = 0 + # for (i = 0; i < n; ++n) + # c1 = *s1 + # c2 = *s2 + # if c1 == 0 + # return false + # if c1 != c2 + # return false + # return *s1 == 0 + + # initialize s into EDI + 8b/copy 1/mod/*+disp8 4/rm32/sib 4/base/ESP 4/index/none . 7/r32/EDI 8/disp8 . # copy *(ESP+8) to EDI + # initialize benchmark length n into EDX + 8b/copy 1/mod/*+disp8 4/rm32/sib 4/base/ESP 4/index/none . 2/r32/EDX 4/disp8 . # copy *(ESP+4) to EDX + 8b/copy 0/mod/indirect 2/rm32/EDX . . . 2/r32/EDX . . # copy *EDX to EDX + # initialize benchmark data into ESI + 8b/copy 1/mod/*+disp8 4/rm32/sib 4/base/ESP 4/index/none . 6/r32/ESI 4/disp8 . # copy *(ESP+4) to ESI + 81 0/subop/add 3/mod/direct 6/rm32/ESI . . . . . 4/imm32 # add 4 to ESI + # initialize loop counter i into ECX + b9/copy . . . . . . . 0/imm32/exit # copy 1 to ECX + # while (i/ECX < n/EDX) +$argv_loop: + 39/compare 3/mod/direct 1/rm32/ECX . . . 2/r32/EDX . . # compare ECX with EDX + 74/jump-if-equal $argv_break/disp8 + # c1/EAX, c2/EBX = *s, *benchmark + b8/copy 0/imm32 # clear EAX + 8a/copy 0/mod/indirect 7/rm32/EDI . . . 0/r32/EAX . . # copy byte at *EDI to lower byte of EAX + bb/copy 0/imm32 # clear EBX + 8a/copy 0/mod/indirect 6/rm32/ESI . . . 3/r32/EBX . . # copy byte at *ESI to lower byte of EBX + # if (c1 == 0) return false + 3d/compare . . . . . . . 0/imm32 # compare EAX with 0 + 74/jump-if-equal $argv_fail/disp8 + # if (c1 != c2) return false + 39/compare 3/mod/direct 0/rm32/EAX . . . 3/r32/EBX . . # compare EAX with EBX + 75/jump-if-not-equal $argv_fail/disp8 + # ++s1, ++s2, ++i + 41/inc-ECX + 46/inc-ESI + 47/inc-EDI + # end while + eb/jump $argv_loop/disp8 +$argv_break: + # if (*s/EDI == 0) return true + b8/copy 0/imm32 # clear EAX + 8a/copy 0/mod/indirect 7/rm32/EDI . . . 0/r32/EAX . . # copy byte at *EDI to lower byte of EAX + 81 7/subop/compare 3/mod/direct 0/rm32/EAX . . . . . 0/imm32 # compare EAX with 0 + 75/jump-if-not-equal $argv_fail/disp8 + b8/copy . . . . . . . 1/imm32 # copy 1 to EAX + c3/return + # return false +$argv_fail: + b8/copy . . . . . . . 0/imm32 # copy 0 to EAX + c3/return + +## tests + +test_compare_null_argv_with_empty_array: + # EAX = argv_equal(Null_argv, "") + # push args + 68/push Null_argv/imm32 + 68/push ""/imm32 + # call + e8/call argv_equal/disp32 + # discard args + 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add 8 to ESP + # call check_ints_equal(EAX, 1) + 50/push-EAX + 68/push 1/imm32/true + 68/push "F - test_compare_null_argv_with_empty_array"/imm32 + # call + e8/call check_ints_equal/disp32 + # discard args + 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 0xc/imm32 # add 12 to ESP + c3/return + +test_compare_null_argv_with_non_empty_array: + # EAX = argv_equal(Null_argv, "Abc") + # push args + 68/push Null_argv/imm32 + 68/push "Abc"/imm32 + # call + e8/call argv_equal/disp32 + # discard args + 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add 8 to ESP + # call check_ints_equal(EAX, 0) + 50/push-EAX + 68/push 0/imm32/false + 68/push "F - test_compare_null_argv_with_non_empty_array"/imm32 + # call + e8/call check_ints_equal/disp32 + # discard args + 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 0xc/imm32 # add 12 to ESP + c3/return + +test_compare_argv_with_equal_array: + # EAX = argv_equal(Abc_argv, "Abc") + # push args + 68/push Abc_argv/imm32 + 68/push "Abc"/imm32 + # call + e8/call argv_equal/disp32 + # discard args + 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add 8 to ESP + # call check_ints_equal(EAX, 1) + 50/push-EAX + 68/push 1/imm32/true + 68/push "F - test_compare_argv_with_equal_array"/imm32 + # call + e8/call check_ints_equal/disp32 + # discard args + 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 0xc/imm32 # add 12 to ESP + c3/return + +test_compare_argv_with_inequal_array: + # EAX = argv_equal(Abc_argv, "Adc") + # push args + 68/push Abc_argv/imm32 + 68/push "Adc"/imm32 + # call + e8/call argv_equal/disp32 + # discard args + 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add 8 to ESP + # call check_ints_equal(EAX, 0) + 50/push-EAX + 68/push 0/imm32/false + 68/push "F - test_compare_argv_with_equal_array"/imm32 + # call + e8/call check_ints_equal/disp32 + # discard args + 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 0xc/imm32 # add 12 to ESP + c3/return + +test_compare_argv_with_empty_array: + # EAX = argv_equal(Abc_argv, "") + # push args + 68/push Abc_argv/imm32 + 68/push ""/imm32 + # call + e8/call argv_equal/disp32 + # discard args + 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add 8 to ESP + # call check_ints_equal(EAX, 0) + 50/push-EAX + 68/push 0/imm32/false + 68/push "F - test_compare_argv_with_equal_array"/imm32 + # call + e8/call check_ints_equal/disp32 + # discard args + 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 0xc/imm32 # add 12 to ESP + c3/return + +test_compare_argv_with_shorter_array: + # EAX = argv_equal(Abc_argv, "Ab") + # push args + 68/push Abc_argv/imm32 + 68/push "Ab"/imm32 + # call + e8/call argv_equal/disp32 + # discard args + 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add 8 to ESP + # call check_ints_equal(EAX, 0) + 50/push-EAX + 68/push 0/imm32/false + 68/push "F - test_compare_argv_with_shorter_array"/imm32 + # call + e8/call check_ints_equal/disp32 + # discard args + 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 0xc/imm32 # add 12 to ESP + c3/return + +test_compare_argv_with_longer_array: + # EAX = argv_equal(Abc_argv, "Abcd") + # push args + 68/push Abc_argv/imm32 + 68/push "Abcd"/imm32 + # call + e8/call argv_equal/disp32 + # discard args + 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add 8 to ESP + # call check_ints_equal(EAX, 0) + 50/push-EAX + 68/push 0/imm32/false + 68/push "F - test_compare_argv_with_longer_array"/imm32 + # call + e8/call check_ints_equal/disp32 + # discard args + 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 0xc/imm32 # add 12 to ESP + c3/return + +## helpers + +# print msg to stderr if a != b, otherwise print "." +check_ints_equal: # (a : int, b : int, msg : (address array byte)) -> boolean + # load args into EAX, EBX and ECX + 8b/copy 1/mod/*+disp8 4/rm32/sib 4/base/ESP 4/index/none . 0/r32/EAX 0xc/disp8 . # copy *(ESP+12) to EAX + 8b/copy 1/mod/*+disp8 4/rm32/sib 4/base/ESP 4/index/none . 3/r32/EBX 0x8/disp8 . # copy *(ESP+8) to EBX + # if EAX == b/EBX + 39/compare 3/mod/direct 0/rm32/EAX . . . 3/r32/EBX . . # compare EAX and EBX + 75/jump-if-unequal $check_ints_equal:else/disp8 + # print('.') + # push args + 68/push "."/imm32 + # call + e8/call write_stderr/disp32 + # discard arg + 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 4/imm32 # add 4 to ESP + # return + c3/return + # else: +$check_ints_equal:else: + # copy msg into ECX + 8b/copy 1/mod/*+disp8 4/rm32/sib 4/base/ESP 4/index/none . 1/r32/ECX 4/disp8 . # copy *(ESP+4) to ECX + # print(ECX) + # push args + 51/push-ECX + # call + e8/call write_stderr/disp32 + # discard arg + 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 4/imm32 # add 4 to ESP + # print newline + # push args + 68/push Newline/imm32 + # call + e8/call write_stderr/disp32 + # discard arg + 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 4/imm32 # add 4 to ESP + # end + c3/return + +write_stderr: # s : (address array byte) -> <void> + # save registers + 50/push-EAX + 51/push-ECX + 52/push-EDX + 53/push-EBX + # write(2/stderr, (data) s+4, (size) *s) + # fd = 2 (stderr) + bb/copy . . . . . . . 2/imm32 # copy 2 to EBX + # x = s+4 + 8b/copy 1/mod/*+disp8 4/rm32/SIB 4/base/ESP 4/index/none . 1/r32/ECX 0x14/disp8 . # copy *(ESP+20) to ECX + 81 0/subop/add 3/mod/direct 1/rm32/ECX . . . . . 4/imm32 # add 4 to ECX + # size = *s + 8b/copy 1/mod/*+disp8 4/rm32/SIB 4/base/ESP 4/index/none . 2/r32/EDX 0x14/disp8 . # copy *(ESP+20) to EDX + 8b/copy 0/mod/indirect 2/rm32/EDX . . . 2/r32/EDX . . # copy *EDX to EDX + # call write() + b8/copy . . . . . . . 4/imm32/write # copy 1 to EAX + cd/syscall 0x80/imm8 + # restore registers + 5b/pop-EBX + 5a/pop-EDX + 59/pop-ECX + 58/pop-EAX + # end + c3/return + +== data +Newline: + # size + 01 00 00 00 + # data + 0a/newline + +# for argv_equal tests +Null_argv: + 00/null +Abc_argv: + 41/A 62/b 63/c 00/null + +# vim:ft=subx:nowrap:so=0 |