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我的任务是编写一个 NASM 程序，该程序获取下个月第一天的星期几。举个例子：如果今天是 6 月 4 日，那么程序应该这样说：

July 1st is a Thursday.

我正在使用 mktime 函数以及其他一些时间/日期函数。这是我的代码：

extern time
extern localtime
extern exit
extern printf
extern mktime
extern ctime

global main

section .data

sSun: db "Sunday", 0
sMon: db "Monday", 0
sTue: db "Tuesday", 0
sWed: db "Wednesday", 0
sThu: db "Thursday", 0
sFri: db "Friday", 0
sSat: db "Saturday", 0

format_1: db "%d", 10, 0
string: db "%s", 10, 0

section .bss
timestamp: resd 1
tmstruct: resd 1

section .text
main:
pusha

push dword 0       ; fetch the timestamp
call time
add esp, 4
mov [timestamp], eax

push timestamp
call localtime
add esp, 4

;change the localtime struct to indicate first day of next month.

;seconds, minutes, hours, day of month from 1.
mov [eax], dword 0
mov [eax + 4], dword 0
mov [eax + 8], dword 0
mov [eax + 12], dword 1
;get month # from 0, to ecx.
mov ecx, [eax + 16]
cmp ecx, 11
jne notDecember

;its december. Set date to January of next year.
mov [eax + 16], dword 0
mov ecx, [eax + 20]
inc ecx
mov [eax + 20], ecx
jmp convertDate

notDecember:

;its not december, just move up the month by 1.
mov ecx, [eax + 16]
inc ecx
mov [eax + 16], ecx

convertDate:
mov [tmstruct], eax

;make a timestamp
;push tmstruct <-- Wrong
push dword [tmstruct] ; <-- Right
call mktime
add esp, 4

;move timestamp
mov [timestamp], eax

;make a new tm struct
push timestamp
call localtime
add esp, 4

;now we have the correct date, check the day of the week
mov ecx, [eax + 24]
push ecx ;<--- preserve this value or c function calls will trash it!

;do a ctime call
;push dword eax <-- Wrong
push timestamp ; <-- Right
call ctime
add esp, 4
push dword eax
push string
call printf
add esp, 8

pop ecx ;<--- pop preserved value!
push dword ecx
call dayOfWeek

popa
call exit


dayOfWeek:

cmp [esp + 4], dword 0
je pSun

cmp [esp + 4], dword 1
je pMon

cmp [esp + 4], dword 2
je pTue

cmp [esp + 4], dword 3
je pWed

cmp [esp + 4], dword 4
je pThu

cmp [esp + 4], dword 5
je pFri

cmp [esp + 4], dword 6
je pSat

push dword esp
push format_1
call printf
add esp, 8
push format_1
jmp endDow



pSun:
push sSun
jmp endDow

pMon:
push sMon
jmp endDow

pTue:
push sTue
jmp endDow

pWed:
push sWed
jmp endDow

pThu:
push sThu
jmp endDow

pFri:
push sFri
jmp endDow

pSat:
push sSat
jmp endDow

endDow:
push string
call printf
add esp, 8
ret 4

基本上，我被告知“mktime 函数忽略结构成员 tm_wday 和 tm_yday 的指定内容......”（来自 localtime tm 结构）“......并从分解的时间结构中的其他信息重新计算它们。”

看到这种情况，我的计划是为当前时间创建一个 tm 结构，并将其所有元素简单地修改为指向下个月第一天的第一秒，然后使用 mktime 。但是，您会看到程序将“劫持”结构输出为“1969 年 12 月 31 日星期三 18:00:59”，但随后我什至从 THAT 打印出星期几，我得​​到星期天。我做了什么让这里变得如此错误？

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2 回答 2

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好的，我采用了 C 示例mktime并对其进行了修改以执行您想要的操作：

extern printf, time, mktime, exit, localtime, scanf,strftime
global main
;~ int    tm_sec   Seconds [0,60]. 
;~ int    tm_min   Minutes [0,59]. 
;~ int    tm_hour  Hour [0,23]. 
;~ int    tm_mday  Day of month [1,31]. 
;~ int    tm_mon   Month of year [0,11]. 
;~ int    tm_year  Years since 1900. 
;~ int    tm_wday  Day of week [0,6] (Sunday =0). 
;~ int    tm_yday  Day of year [0,365]. 
;~ int    tm_isdst Daylight Savings flag. 

%define tm_sec 0
%define tm_min 4
%define tm_hour 8
%define tm_mday 12
%define tm_mon 16
%define tm_year 20
%define tm_wday 24
%define tm_yday 28
%define tm_isdst 32


section .bss
timeinfo    resd    1
rawtime     resd    1
lpszBuffer  resb    80

section .data
fmtdate     db  "%B %d %Y", 0

Sun         db  "Sunday", 0
Mon         db  "Monday", 0
Tue         db  "Tuesday", 0
Wed         db  "Wednsday", 0
Thu         db  "Thursday", 0
Fri         db  "Friday", 0
Sat         db  "Saturday", 0
WeekDay     dd  Sun, Mon, Tue, Wed, Thu, Fri, Sat

szThatDay   db  "%s is a %s", 10, 0

section .text
main: 

    ;~ Get todays date
    push    rawtime
    call    time 
    add     esp, 4 * 1

    push    rawtime
    call    localtime
    add     esp, 4 * 1

    mov     dword [timeinfo], eax

    ;~ Get current month and add one
    mov     edx, dword [eax + tm_mon] 
    inc     edx 
    ;~ move updated month back to structure 
    mov     dword [eax + tm_mon], edx

    ;~ set day to the first
    mov     dword [eax + tm_mday], 1 

    push    dword [timeinfo]
    call    mktime
    add     esp, 4 * 1

    push    dword [timeinfo]
    push    fmtdate
    push    80
    push    lpszBuffer
    call    strftime
    add     esp, 4 * 4

    mov     eax, dword [timeinfo]
    mov     eax, dword [eax + tm_wday]
    mov     ecx, dword [WeekDay + 4 * eax]
    push    ecx
    push    lpszBuffer
    push    szThatDay 
    call    printf
    add     esp, 4 * 3

    call    exit

然后进行测试，我显示当前日期并运行程序，然后显示下个月的第一天是星期几。然后我更改了系统时钟并重新运行了 2 次测试。测试也可以在 Windows 下工作。

在此处输入图像描述

于 2013-10-04T03:04:07.760 回答
0

看来我在传递值时犯了一个错误。此外，一些 c 函数调用似乎想丢弃我在寄存器中的值！正确运行代码所需的更改用箭头注释。

于 2013-10-21T14:52:31.190 回答