datetime.txt

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=====================
Date & Time  Routines
=====================

These routines convert DOS system times and dates to/from ASCII strings.
They appear in this section rather than conversions because we eventually
intend to add date and time arithmetic to the package.

Note the time to string conversion routines do not output the hundredths of
a second.  Most applications do not need (or want) this.  If you want
hundredths of a second you can easily write a routine (using this code) or
modify the existing code to suit your purposes.




Routine:  DTOA (2,m)
--------------------

Category:       Date/Time Routines

Author:		Randall Hyde

Registers on Entry:
			CX-	Current year (in the range 1980-2099)
			DL-	Current day
			DH-	Current month
			ES:DI-	Points at buffer with room for at least
				nine bytes (DTOA/DTOA2 only).


Registers on Return: 	ES:DI-	DTOA sticks a string of the form MM/DD/YY
				into a buffer allocated on the heap (DTOAM
				only).

			ES:DI-	Points at the zero terminating byte at the
				end of the string (DTOA2 only).

Flags Affected:       carry-	Set if memory allocation error (DTOAM only).


Example of Usage:

			mov	ah, 2ah		;Call DOS to get the system
			int	21h		; time (also see xDTOA)
			lesi	TodaysDate	;Buffer to store string.
			DTOA			;Convert date to string.

			mov	ah, 2ah
			int	21h
			lesi	TodaysDate2
			DTOA2

			mov	ah, 2ah
			int	21h
			DTOAM			;ES:DI is allocated on heap.

Description:

DTOA converts a DOS system date (in CX/DX) to an ASCII string and deposits
the characters into a buffer specified by ES:DI on input.  ES:DI must be at
least nine bytes long (eight bytes for mm/dd/yy plus the zero terminating
byte).

DTOA2 converts a DOS system date to an ASCII string just like DTOA above.
The only difference is that it does not preserve DI.  It leaves DI pointing
at the zero terminating byte at the end of the string.  This routine is use-
ful for building up long strings with a date somewhere in the middle.

DTOAM works like DTOA except you do not pass the pointer to a buffer in ES:DI.
Instead, DTOAM allocates nine bytes for the string on the heap.  It returns
a pointer to this new string in ES:DI.

Include:              stdlib.a or date.a

Routine:  xDTOA (2,m)
---------------------

Category:       Date/Time Routines

Author:		Randall Hyde

Registers on Entry:
			ES:DI-	Points at buffer with room for at least
				nine bytes (xDTOA/xDTOA2 only).


Registers on Return: 	ES:DI-	DTOA sticks a string of the form MM/DD/YY
				into a buffer allocated on the heap (xDTOAM
				only).

			ES:DI-	Points at the zero terminating byte at the
				end of the string (xDTOA2 only).

Flags Affected:       carry-	Set if memory allocation error (xDTOAM only).


Example of Usage:

			lesi	TodaysDate	;Buffer to store string.
			xDTOA			;Convert date to string.

			lesi	TodaysDate2
			xDTOA2

			mov	ah, 2ah
			int	21h
			xDTOAM			;ES:DI is allocated on heap.

Description:

These routines work just like DTOA, DTOA2, and DTOAM except you do not pass
in the date to them, they call DOS to read the current system date and
convert that to a string.

Include:              stdlib.a or date.a


Routine:  LDTOA (2,m)
---------------------

Category:       Date/Time Routines

Author:		Randall Hyde

Registers on Entry:
			CX-	Current year (in the range 1980-2099)
			DL-	Current day
			DH-	Current month
			ES:DI-	Points at buffer with room for at least
				nine bytes (DTOA/DTOA2 only).


Registers on Return: 	ES:DI-	DTOA sticks a string of the form "mmm dd, yyyy"
				into a buffer allocated on the heap (LDTOAM
				only).

			ES:DI-	Points at the zero terminating byte at the
				end of the string (LDTOA2 only).

Flags Affected:       carry-	Set if memory allocation error (LDTOAM only).


Example of Usage:

			mov	ah, 2ah		;Call DOS to get the system
			int	21h		; time (also see xDTOA)
			lesi	TodaysDate	;Buffer to store string.
			LDATE			;Convert date to string.

			mov	ah, 2ah
			int	21h
			lesi	TodaysDate2
			LDTOA2

			mov	ah, 2ah
			int	21h
			LDTOAM			;ES:DI is allocated on heap.

Description:

These routines work just like the DTOA, DTOA2, and DTOAM routines except they
output their date in the form "mmm dd, yyyy", e.g., Jan 1, 1980.

Include:              stdlib.a or date.a

Routine:  xLDTOA (2,m)
---------------------

Category:       Date/Time Routines

Author:		Randall Hyde

Registers on Entry:
			ES:DI-	Points at buffer with room for at least
				nine bytes (xLDTOA/xLDTOA2 only).


Registers on Return: 	ES:DI-	Sticks a string of the form MMM DD, YYYY
				into a buffer allocated on the heap (xLDTOAM
				only).

			ES:DI-	Points at the zero terminating byte at the
				end of the string (xLDTOA2 only).

Flags Affected:       carry-	Set if memory allocation error (xLDTOAM only).


Example of Usage:

			lesi	TodaysDate	;Buffer to store string.
			xLDTOA			;Convert date to string.

			lesi	TodaysDate2
			xLDTOA2

			mov	ah, 2ah
			int	21h
			xLDTOAM			;ES:DI is allocated on heap.

Description:

Similar to xDTOA, xDTOA2, and xDTOAM except these routines produce strings of
the form "MMM DD, YYYY".

Include:              stdlib.a or date.a

Routine:  ATOD (2)
------------------

Category:       Date/Time Routines

Author:		Randall Hyde

Registers on Entry:
			ES:DI-	Points at string containing date to convert.


Registers on Return: 	CX-	Year (1980-2099)
			DH-	Month (1-12)
			DL-	Day (1-31)
			ES:DI-	Points at first non-date string (ATOD2 only)

Flags Affected:       	carry-	Set if bad date format.


Example of Usage:

			lesi	TodaysDate	;Buffer containing string.
			ATOD			;Convert string to date.
			jc	Error

			lesi	TodaysDate	;Buffer containing string.
			ATOD2			;Convert string to date.
			jc	Error

Description:

ATOD converts an ASCII string of the form "mm/dd/yy" or "mm-dd-yy" to a DOS
format date.  It returns the carry flag set if there is a parse error (that
is, the string is not in one of these two forms) or if the month, date, or
year values are out of range (including specifying Feb 29th on non-leap years).

ATOD2 works just like ATOD except it does not preserve DI.  It leaves DI
pointing at the first non-date character encountered in the string.

Include:              stdlib.a or date.a

Routine:  ATOT (2)
------------------

Category:       Date/Time Routines

Author:		Randall Hyde

Registers on Entry:
			ES:DI-	Points at string containing time to convert.


Registers on Return: 	CH-	Hour (0..23)
			CL-	Minutes (0..59)
			DH-	Seconds (0..59)
			DL-	Seconds/100 (0..99)

			ES:DI-	Points at first character which is not a part
				of the parsed time (ATOT2 only).

Flags Affected:       	carry-	Set if bad time format.


Example of Usage:

			lesi	CurrentTime	;Buffer containing string.
			ATOT			;Convert string to time.
			jc	Error

			lesi	CurrentTime	;Buffer containing string.
			ATOT2			;Convert string to time.
			jc	Error


Description:

ATOT converts an ASCII string of the form "hh:mm:ss" or "hh:mm:ss.xxx" to a DOS
format date.  It returns the carry flag set if there is a parse error (that
is, the string is not in one of these two forms) or if the hours, minutes,
seconds, or hundredth values are out of range.  If the string does not contain
1/100ths of a second, this routine returns zero in DL.

ATOT2 works just like ATOT except it does not preserve DI.  It leaves DI
pointing at the first character beyond the time characters.

Include:              stdlib.a or time.a

Routine:  TTOA (2,m)
--------------------

Category:       Date/Time Routines

Author:		Randall Hyde

Registers on Entry:
			CH-	Hour (0..23)
			CL-	Minutes (0..59)
			DH-	Seconds (0..59)
			DL-	1/100 seconds (0..99)
			ES:DI-	Points at buffer with room for at least
				nine bytes (TTOA/TTOA2 only).


Registers on Return: 	ES:DI-	Sticks a string of the form hh:mm:ss
				into a buffer allocated on the heap (TTOAM
				only).

			ES:DI-	Points at the zero terminating byte at the
				end of the string (TTOA2 only).

Flags Affected:       carry-	Set if memory allocation error (TTOAM only).


Example of Usage:

			mov	ah, 2ch		;Call DOS to get the system
			int	21h		; time (also see xTTOA)
			lesi	CurrentTime	;Buffer to store string.
			TTOA			;Convert Time to string.

			mov	ah, 2ch
			int	21h
			lesi	CurTime2
			TTOA2

			mov	ah, 2ch
			int	21h
			TTOAM			;ES:DI is allocated on heap.

Description:

TTOA converts the DOS system time in CX/DX to a string and stores the string
at the location specified by ES:DI.  ES:DI must point at a buffer with at
least nine characters in it (for a string of the form hh:mm:ss followed by
a zero terminating byte).

TTOA2 works like TTOA except it does not preserve DI.  It leaves DI pointing
at the zero terminating byte in the string.  This is useful for generating
long strings in memory of which TTOA is one component.

TTOAM is like TTOA except it automatically allocates storage for the string
on the heap.

Include:              stdlib.a or time.a

Routine:  xTTOA (2,m)
---------------------

Category:       Date/Time Routines

Author:		Randall Hyde

Registers on Entry:
			ES:DI-	Points at buffer with room for at least
				nine bytes (xTTOA/xTTOA2 only).


Registers on Return: 	ES:DI-	Sticks a string of the form HH:MM:SS
				into a buffer allocated on the heap xTTOAM
				only).

			ES:DI-	Points at the zero terminating byte at the
				end of the string (xTTOA2 only).

Flags Affected:       carry-	Set if memory allocation error (xTTOAM only).


Example of Usage:

			lesi	CurrentTime	;Buffer to store string.
			xTTOA			;Convert time to string.

			lesi	CurTime2
			xTTOA2

			xTTOAM			;ES:DI is allocated on heap.

Description:

These routines work just like TTOA, TTOA2, and TTOAM except you do not pass
in the time to them, they call DOS to read the current system time and
convert that to a string.

Include:              stdlib.a or time.a