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;

;  SNTP library

;

;  (C) 2019 Coldy

;  Thank's you for use this code and software based on it!

;  I will glad if it's will be helpful.

;

;  Distributed under terms of GPL

;

; Inline clearing register(s)

; E.g. uses:

; clear eax      ; - clearing single register

; or

; clear eax, ebx ; ... and so on - clearing multiple register

macro clear [reg]  { xor reg, reg }

macro b2bcd

;   Convert hex byte to BCD byte

;   Input:

;   al = number 0...99 (not checking)

;   Output:

;   al = number in BCD

;   Algorithm:

;   al = (al > 9) ? ((al / 10) * 6 + al) : al

;   Use registers (not restore):

;   eax, ebx, edx

{

    clear ebx, edx

    cmp al, 9         ; (al <= 9 ?)

    jle @f

    mov bl, al

    mov dl, 10

    div dl            ; al = al/10

    mov dl, 6

    mul dl            ; al = al*6

    add al, bl        ; al = al + bl

@@:

}

struct DateTime

  struct

    day   db ?

    month db ?

    year  dw ?

  ends

  struct

    hour  db ?

    min   db ?

    sec   db ?

  ends

ends

proc DateTime2bcd

   ;

   ;  Input:

   ;  eax => pointer to DateTime (UNIX time since 1.1.1970 00:00:00 GMT )

   ;

   ; Output:

   ; eax  => time in ÂÑD format

   ; edx  => date in BCD format

locals

  date dd 0

  time dd 0

endl

  mov esi, eax

  clear eax, ebx, ecx

  mov al, [esi + DateTime.day]

  cmp al, 9

  jle @f

  mov bl, al

  mov cl, 10

  div cl

  mul bl, cl

  add al, bl

@@:

endp

YEAR_EPOCH            = 1970

YEAR_FIRST_LEAP_YEAR  = 1972

SEC_IN_MINUTE         = 60

SEC_IN_HOUR           = (SEC_IN_MINUTE * 60)

SEC_IN_DAY            = (SEC_IN_HOUR * 24)

SEC_IN_YEAR           = (SEC_IN_DAY * 365)

proc timestamp2DateTime

   ;

   ;  Input:

   ;  eax => timestamp (UNIX time since 1.1.1970 00:00:00 GMT )

   ;  ebx => pointer to DateTime

   ;

   ; Output:

   ; none

   ;

   ; Use registers (not restore):

   ;

   ; History:

   ; 14.04.2019 Bug fixed: Incorrect output day (-1 day error)!!!

   ; 19.04.2019 Bug fixed: Incorrect convert of time with maximum UNIX time (0x7ffffff)

   ;

   ; Known isuues:

   ;  Not yet seen :)

   ;

locals

  timestamp  dd ?

  years      dw ?

  lyears     dw ?

  ;year       dw ?

  ;_ts        dd 0

  ;ts         dd 0

  MonthDays  db 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31

  ;month      db ?

endl

  ;pusha

  mov  [timestamp], eax

  mov  esi, ebx ; ESI => pointer to DateTime

  ; Calculate total years since year epoch

  cdq

  mov	  ebx, SEC_IN_YEAR + SEC_IN_DAY/4

  idiv	ebx

  mov [years], ax ; (AX => years)

  ; Calculate current year

  add ax, YEAR_EPOCH

  mov [esi + DateTime.year], ax ; (AX => year)

  ; Calculate leap years since year epoch

  ;xor   ecx, ecx ; Clear

  ;mov   cx, bx

  ;Fix: -1 day error

  dec   ax

  sub   ax, YEAR_FIRST_LEAP_YEAR ; - 1

  clear   ebx, edx

  mov   bx, 4

  idiv  bx

  cmp	  [esi + DateTime.year], YEAR_FIRST_LEAP_YEAR + 1

  js    @f

  inc   al

@@:

  mov [lyears], ax

  ; Drop years seconds

  mov   eax, [timestamp]

  clear   ebx

  mov   bx, [years]

  sub   bx, [lyears]

  mov   ecx, SEC_IN_YEAR

  imul  ebx, ecx                  ; ebx => (years - lyears) * SEC_IN_YEAR

  clear   ecx

  mov   cx, [lyears]

  mov   edx, SEC_IN_YEAR + SEC_IN_DAY

  imul  ecx, edx                  ; cx => lyears * (SEC_IN_YEAR + SEC_IN_DAY)

  add   ebx, ecx                  ; bx => (years - lyears) * SEC_IN_YEAR + lyears * (SEC_IN_YEAR + SEC_IN_DAY)

  sub   eax, ebx

  mov   [timestamp], eax

  ;Is leap year?

  clear ecx, edx

  mov   cx, [esi + DateTime.year]

  mov   eax, ecx

  mov   ebx, 4

  div   bx

  cmp   dx, 0

  je   leap

  mov   ax, cx

  mov  bx, 100

  div  bx

  cmp   dx, 0

  je   leap

  mov   ax, cx

  mov  bx, 400

  clear dx

  div  bx

  cmp   dx, 0

  jmp   @f

leap:

  ; Add +1 day in february if leap year

  inc [MonthDays + 1]

@@:

  ; Calculate current month

  clear  eax, ecx, edi       ; _ts, ts, month (Bug? => ecx != 0)

caclmonth:

  clear  ebx

  mov  bl, [MonthDays + edi]

  imul ebx, SEC_IN_DAY

  inc  edi

  add  eax, ebx

  ; {{ 19.4.2019 Bug was somewhere here

  cmp edi, 12

  je    @f

  ; TODO: if edi >= 12 then error!

  ;mov eax, -1

  ;mov edx, 0

  ;ret

;@@:

  cmp eax, [timestamp]

  jge    @f            ; Bug? => jg    @f

  mov  ecx, eax

  jmp  caclmonth

  ; }}

@@:

  ; Drop months seconds

  sub [timestamp], ecx

  mov eax, edi

  mov [esi + DateTime.month], al

  ; Calculate elapsed day

  mov   eax, [timestamp]

  clear   edx

  mov   ebx, SEC_IN_DAY

  idiv  ebx     ; eax => day

  ; Drop days seconds

  imul  ebx, eax, SEC_IN_DAY

  sub   [timestamp],ebx

  ; Correct current day

  add   eax, 1  ; eax => current day

  mov [esi + DateTime.day], al

  ; Calculate current hour

  mov   eax, [timestamp]

  clear   edx

  mov   ebx, SEC_IN_HOUR

  idiv  ebx

  mov [esi + DateTime.hour], al

  ; Drop hours seconds

  imul ebx, eax, SEC_IN_HOUR

  sub  [timestamp],ebx

  mov   eax, [timestamp]

  clear   edx

  mov   ebx, SEC_IN_MINUTE

  idiv  ebx

  mov [esi + DateTime.min], al

  ; Drop minutes seconds

  imul ebx, eax, SEC_IN_MINUTE

  sub  [timestamp],ebx

  mov eax, [timestamp]

  mov [esi + DateTime.sec], al

  ;popa

  ret

endp