== code # 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 # prolog 55/push-EBP 89/copy 3/mod/direct 5/rm32/EBP . . . 4/r32/ESP . . # copy ESP to EBP # save registers 51/push-ECX 52/push-EDX 53/push-EBX 56/push-ESI 57/push-EDI # 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 5/base/EBP 4/index/none . 7/r32/EDI 8/disp8 . # copy *(EBP+8) to EDI # initialize benchmark length n into EDX 8b/copy 1/mod/*+disp8 4/rm32/sib 5/base/EBP 4/index/none . 2/r32/EDX 0xc/disp8 . # copy *(EBP+12) 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 5/base/EBP 4/index/none . 6/r32/ESI 0xc/disp8 . # copy *(EBP+12) 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 eb/jump $argv_end/disp8 # return false $argv_fail: b8/copy . . . . . . . 0/imm32 # copy 0 to EAX $argv_end: # restore registers 5f/pop-to-EDI 5e/pop-to-ESI 5b/pop-to-EBX 5a/pop-to-EDX 59/pop-to-ECX # end 89/copy 3/mod/direct 4/rm32/ESP . . . 5/r32/EBP . . # copy EBP to ESP 5d/pop-to-EBP c3/return ## tests test_compare_null_argv_with_empty_array: # EAX = argv_equal(Null_argv, "") # push args 68/push ""/imm32 68/push Null_argv/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, msg) # push args 68/push "F - test_compare_null_argv_with_empty_array"/imm32 68/push 1/imm32/true 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 12 to ESP c3/return test_compare_null_argv_with_non_empty_array: # EAX = argv_equal(Null_argv, "Abc") # push args 68/push "Abc"/imm32 68/push Null_argv/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, msg) # push args 68/push "F - test_compare_null_argv_with_non_empty_array"/imm32 68/push 0/imm32/false 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 12 to ESP c3/return test_compare_argv_with_equal_array: # EAX = argv_equal(Abc_argv, "Abc") # push args 68/push "Abc"/imm32 68/push Abc_argv/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, msg) # push args 68/push "F - test_compare_argv_with_equal_array"/imm32 68/push 1/imm32/true 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 12 to ESP c3/return test_compare_argv_with_inequal_array: # EAX = argv_equal(Abc_argv, "Adc") # push args 68/push "Adc"/imm32 68/push Abc_argv/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, msg) # push args 68/push "F - test_compare_argv_with_equal_array"/imm32 68/push 0/imm32/false 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 12 to ESP c3/return test_compare_argv_with_empty_array: # EAX = argv_equal(Abc_argv, "") # push args 68/push ""/imm32 68/push Abc_argv/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) # push args 68/push "F - test_compare_argv_with_equal_array"/imm32 68/push 0/imm32/false 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 12 to ESP c3/return test_compare_argv_with_shorter_array: # EAX = argv_equal(Abc_argv, "Ab") # push args 68/push "Ab"/imm32 68/push Abc_argv/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) # push args 68/push "F - test_compare_argv_with_shorter_array"/imm32 68/push 0/imm32/false 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 12 to ESP c3/return test_compare_argv_with_longer_array: # EAX = argv_equal(Abc_argv, "Abcd") # push args 68/push "Abcd"/imm32 68/push Abc_argv/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) # push args 68/push "F - test_compare_argv_with_longer_array"/imm32 68/push 0/imm32/false 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 12 to ESP c3/return == data Null_argv: 00/null Abc_argv: 41/A 62/b 63/c 00/null