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File List | 1991-07-21 | 26.4 KB | 499 lines

Turbo Assembler Version 2.5 07/21/91 16:39:26 Page 1 dates.ASM 1 %PAGESIZE 58,124 2 ;******************************************************************************* 3 ; 4 ; ZDAY and ZDATE 5 ; 6 ; These are routines for converting Gregorian dates to and from Day Numbers. 7 ; 8 ; The routines are called using the PASCAL calling sequence, and are FAR calls. 9 ; All pointers are FAR pointers. 10 ; 11 ; The routines are written to run on an 8088 so as to be compatible with all 12 ; machines based on this architecture, and use the Borland "PASCAL" calling 13 ; sequence so as to be callable from programs compiled with both Borland's C 14 ; and Pascal compilers. 15 ; 16 ; The Borland Turbo Assembler (V2.0 or better) is required to assemble this code. 17 ; 18 ;=============================================================================== 19 ; 20 ; The C calling sequences are defined by these prototypes: 21 ; 22 ; unsigned long int far pascal ZDay( unsigned int Year, unsigned int Month, 23 ; unsigned int Day ); 24 ; 25 ; int far pascal ZDate(unsigned long int DayNumber, unsigned int far *Year, 26 ; unsigned int far *Month, unsigned int far *Day ); 27 ; 28 ;------------------------------------------------------------------------------- 29 ; 30 ; The PASCAL prototypes (you will $L the object code from this assembly into 31 ; a TPU) would be: 32 ; 33 ; function ZDay(Year, Month, Day : word) : longint; 34 ; 35 ; function ZDate(DayNumber : longint; var Year, Month, Day : word ) : boolean; 36 ; 37 ;------------------------------------------------------------------------------- 38 ; 39 ; ZDay returns a 32-bit unsigned integer representing the Day Number calculated 40 ; from the supplied Gregorian date. Although the Pascal call defines it as a 41 ; longint, you will not have to worry about getting a negative number back. 42 ; 43 ; If the resulting Day Number is zero, you have supplied a Gregorian date that 44 ; is too early or too far in the future for the calculations to be performed 45 ; correctly with this routine's methods. 46 ; 47 ; The Year, Month and Day parameters are all unsigned 16-bit integers, Year 48 ; must be the FULL YEAR. 1902 must be supplied as 1902, not 02. It must be 49 ; in the range 1 to 25599 or zero will be returned. Month and Day must be in 50 ; the range 0-65535. These restrictions should not be too restrictive for most 51 ; purposes. 52 ; 53 ; Note that Day, Month and Year are all UNSIGNED. When you are doing weird Turbo Assembler Version 2.5 07/21/91 16:39:26 Page 2 dates.ASM 54 ; date calculations you must NEVER try to supply negative values for these. 55 ; This is also true of the any Day Number you give to ZDate! Negative numbers 56 ; look like large positive numbers and will give Wrong Results! 57 ; 58 ; The same parameters are used with ZDate, except no value is returned since it 59 ; is a procedure (void function) rather than a function. Just supply the Day 60 ; Number, and ZDate fills in the Year, Month and Day for you. The supplied Day 61 ; Number should be greater than 121 and less than 23920640. For Day Numbers 62 ; outside this range, ZDate returns a Gregorian date of 0-0-0 and a return 63 ; value of 0 (FALSE in both Pascal and C). A good conversion returns 1 (TRUE 64 ; in both C and Pascal). 65 ; 66 ; NOTE: ZDay can convert certain dates into Day Numbers that are outside the 67 ; range that ZDate can convert back. These dates, however, involve years 68 ; that are either zero or very, very large, and are well outside the range of 69 ; dates that we are likely to be interested in. 70 ; 71 ; A call to ZDay uses 14 bytes of space on the stack; a call to ZDate uses 26. 72 ; 73 ;=============================================================================== 74 ; 75 ; WHAT'S IT ALL FOR, ANYWAY? 76 ; 77 ; All dates, valid or not, convert to Day Numbers of some kind. All Day 78 ; Numbers convert to valid Gregorian dates. So if you convert a Gregorian 79 ; date to a Day Number and back, if the resulting Gregorian date doesn't match 80 ; the original, the original was invalid. 81 ; 82 ; The Day Number is related to the Julian Day Number, but is not the same. 83 ; It is valid only for the years since the Gregorian calendar was introduced. 84 ; 85 ; You can use the Day Numbers of two dates to find the number of days between 86 ; them. 87 ; 88 ; The remainder resulting when the Day Number is divided by 7 is the day of the 89 ; week, with 0 (Sunday) thru 6 (Saturday). 90 ; 91 ; To find the last day of a month, begin with the Gregorian date. Add 1 to 92 ; the month (even to December), set the Day to 0, convert to a Day Number, then 93 ; back to Gregorian. 94 ; 95 ; To find the Julian day of the year (different from the Julian Day Number!), 96 ; convert the given Gregorian date to a Day Number. Then subtract from this 97 ; the Day Number of January 0 (NOT 1!) of the same year. 98 ; 99 ; Convert a Julian Date to Gregorian by taking the Day Number of of January 100 ; ZERO of the year. Add the Julian day of the year to this, then convert 101 ; to a Gregorian date. 102 ; 103 ;******************************************************************************* 104 ; (c) Copyright 1991 Crazy Jack 105 ; All Rights Reserved Turbo Assembler Version 2.5 07/21/91 16:39:26 Page 3 dates.ASM 106 %NEWPAGE 107 IDEAL 108 0000 MODEL LARGE 109 0000 CODESEG 110 ; 111 ; The simplest routine converts the Gregorian date to a Day Number: 112 ; 113 0000 PROC PASCAL ZDAY FAR Year:WORD, Month:WORD, Day:WORD 114 PUBLIC ZDAY 1 115 0000 55 PUSH BP 1 116 0001 8B EC MOV BP,SP 1 117 0003 8B 4E 0A MOV CX, [Year] ;Get Year. 118 0006 8B 5E 08 MOV BX, [Month] ;Get Month. 119 0009 83 FB 0E CMP BX, 14 ;Month greater than 14 will give 120 000C 77 5A JA FIXMNTH ;incorrect results. 121 000E MNTHOK: 122 000E 80 FB 02 CMP BL, 2 ;Is Month January or February? 123 0011 77 08 JA NOADJ ;Jump if not, 124 125 0013 0B C9 OR CX, CX ;else be sure year isn't zero (we're 126 0015 74 60 JZ DATEBAD ;in trouble if we decrement zero), 127 0017 49 DEC CX ;then shift calculations to joint 128 0018 83 C3 0C ADD BX, 12 ;between February and March. 129 001B NOADJ: 130 001B 80 FD 64 CMP CH, 100 ;Any year too big to be divided by 100 131 001E 73 57 JAE DATEBAD ;16-by-8-bit will cause divide overflow. 132 0020 43 INC BX ;Need a little adjustment here---. 133 134 0021 B8 AB51 MOV AX, 43857 ;Calculate number of days due to months: 135 0024 F7 E3 MUL BX ;First multiply by 306001, more than 16 136 0026 D1 E3 SHL BX, 1 ;bits worth. The upper word is 4. We 137 0028 D1 E3 SHL BX, 1 ;use shifts for speed. Earlier test 138 002A 03 D3 ADD DX, BX ;against 2141 ensures no overflow and 139 002C BB 2710 MOV BX, 10000 ;that we can divide by 10000. 140 002F F7 F3 DIV BX ;This gives INT(month * 30.6001). 141 0031 8B D8 MOV BX, AX ;Save the result (days due to months). 142 143 0033 B8 016D MOV AX, 365 ;Now for days due to years: 144 0036 F7 E1 MUL CX ;Gives days in normal years. 145 0038 03 C3 ADD AX, BX ;Add in days due to months. 146 003A 83 D2 00 ADC DX, 0 ;(There will be no carry from this!) 147 003D 50 PUSH AX ;We need the AX for another divide. 148 149 003E D1 E9 SHR CX, 1 ;Find number of extra days due to 150 0040 D1 E9 SHR CX, 1 ;leap years (add a year for every 4). 151 0042 8B C1 MOV AX, CX ;Remove days for 400-year 152 0044 B3 19 MOV BL, 25 ;Gregorian rule: 153 0046 F6 F3 DIV BL ;First remove leap year day for each 154 0048 32 E4 XOR AH, AH ;century--- 155 004A 2B C8 SUB CX, AX ;Result will always be positive. 156 004C D0 E8 SHR AL, 1 ;Then add back a leap year day for 157 004E D0 E8 SHR AL, 1 ;each 400 years. 158 0050 03 C1 ADD AX, CX ;No carry will occur. Why? Turbo Assembler Version 2.5 07/21/91 16:39:26 Page 4 dates.ASM 159 160 0052 5B POP BX 161 0053 03 C3 ADD AX, BX ;Add leap year days to days due to 162 0055 83 D2 00 ADC DX, 0 ;month and year. 163 0058 03 46 06 ADD AX, [Day] ;Fold in day of the month. 164 005B 83 D2 00 ADC DX, 0 165 005E 2D 0001 SUB AX, 1 ;Finally, adjust so remainder from 166 0061 83 DA 00 SBB DX, 0 ;divide by 7 gives day of week. 167 ;Back to caller with Day Number 168 0064 GONE: ;Day Number in DX:AX. 1 169 0064 5D POP BP 1 170 0065 CA 0006 RET 0006h 171 ; 172 0068 FIXMNTH: ;Sigh. Month is too big to give valid 173 0068 8B C3 MOV AX, BX ;results, so we must reduce it. We put 174 006A 33 D2 XOR DX, DX ;this here since it won't happen often 175 006C BB 000C MOV BX, 12 ;and we don't want to slow the main line. 176 006F F7 F3 DIV BX ;We convert it to years and months. 177 0071 8B DA MOV BX, DX ;Remainder becomes new month. 178 0073 03 C8 ADD CX, AX ;Quotient is years. Add to given year. 179 0075 73 97 JNC MNTHOK ;Back to conversion if still in range. 180 ; 181 0077 DATEBAD: 182 0077 33 C0 XOR AX, AX ;If something's wrong, we clear the 183 0079 8B D0 MOV DX, AX ;Day Number in DX:AX to zero 184 007B EB E7 JMP GONE ;and clear out. 185 ; 186 007D ENDP ZDAY Turbo Assembler Version 2.5 07/21/91 16:39:26 Page 5 dates.ASM 187 %NEWPAGE 188 ; 189 ; Converting a Day Number back to a Gregorian date is more complicated: 190 ; 191 007D PROC PASCAL ZDATE FAR DayNumber:WORD:2, Year:FAR PTR WORD, Month:FAR PTR + 192 WORD, Day:FAR PTR WORD 193 PUBLIC ZDATE 1 194 007D 55 PUSH BP 1 195 007E 8B EC MOV BP,SP 1 196 0080 56 PUSH SI 197 0081 57 PUSH DI 198 0082 8B 56 14 MOV DX, [DayNumber+2] ;Get Day Number from caller. 199 0085 81 FA 016D CMP DX, 365 ;Bigger than this and we can't 200 0089 73 69 JAE RELAY2 ;extract the year! 201 008B 8B 46 12 MOV AX, [DayNumber] ;Okay, get the rest of the Day Number. 202 203 008E 8B F0 MOV SI, AX ;We save a copy of it. 204 0090 8B FA MOV DI, DX 205 0092 2D 0079 SUB AX, 121 ;First we back out the 400-year 206 0095 83 DA 00 SBB DX, 0 ;Gregorian rule. 207 0098 72 53 JC RELAY1 ;Day number must be greater than 120. 208 009A BB BE3B MOV BX, 48699 ;There are 146097 days in 400 years. 209 009D F7 F3 DIV BX ;146097 = 48699 * 3. We divide in 210 009F 8B CA MOV CX, DX ;two steps, first by 48699, then by 3. 211 00A1 33 D2 XOR DX, DX 212 00A3 BB 0003 MOV BX, 3 213 00A6 F7 F3 DIV BX ;The resulting quotient 1/3 of the leap 214 00A8 03 F0 ADD SI, AX ;year days removed by the 4000-year rule. 215 00AA 83 D7 00 ADC DI, 0 ;We add them back 3 times, which is 216 00AD 03 F0 ADD SI, AX ;quicker than multiplying by 3. 217 00AF 83 D7 00 ADC DI, 0 218 00B2 40 INC AX ;Here's the quickest place to add back 219 00B3 03 F0 ADD SI, AX ;the 1 we subtracted in ZDay to aid in 220 00B5 83 D7 00 ADC DI, 0 ;finding the day of the week. 221 00B8 B8 BE3B MOV AX, 48699 ;We now finish calculating the remainder 222 00BB F7 E2 MUL DX ;from the two divisions which gives us 223 00BD 03 C1 ADD AX, CX ;the number of days into the current 400 224 00BF 83 D2 00 ADC DX, 0 ;years. 225 00C2 8B CA MOV CX, DX ;Is there a remainder? 226 00C4 0B C8 OR CX, AX 227 00C6 74 10 JZ GREGOUT ;If not, we save some calculation time. 228 229 00C8 2D 0001 SUB AX, 1 ;Now we calculate the number of leap 230 00CB 83 DA 00 SBB DX, 0 ;years dropped so far THIS 400 years--- 231 00CE B9 8EAC MOV CX, 36524 ;(Number of days in 3 out of 4 232 00D1 F7 F1 DIV CX ;centuries.) 233 00D3 03 F0 ADD SI, AX ;---and add THAT back in. 234 00D5 83 D7 00 ADC DI, 0 235 00D8 GREGOUT: 236 00D8 8B C7 MOV AX, DI ;We now the divide adjusted Day Number 237 00DA BB 0064 MOV BX, 100 ;by 365.25 to get the year. The 238 00DD F7 E3 MUL BX ;remainder will be the day of the year. 239 00DF 8B C8 MOV CX, AX Turbo Assembler Version 2.5 07/21/91 16:39:26 Page 6 dates.ASM 240 00E1 8B C6 MOV AX, SI 241 00E3 F7 E3 MUL BX 242 00E5 03 D1 ADD DX, CX 243 00E7 2D 2FB2 SUB AX, 12210 244 00EA 83 DA 00 SBB DX, 0 245 00ED 72 64 RELAY1: JC DAYBAD ;Don't sweat the speed loss on errors. 246 00EF B9 8EAD MOV CX, 36525 247 00F2 3B D1 CMP DX, CX ;Be sure we can divide adjusted value. 248 00F4 73 5D RELAY2: JAE DAYBAD 249 00F6 F7 F1 DIV CX 250 00F8 8B F8 MOV DI, AX ;Year (or year-1) now in the DI. 251 252 00FA B8 05B5 MOV AX, 1461 ;Note that this gives us a number of 253 00FD F7 E7 MUL DI ;days beyond the calculated year, which 254 00FF D1 DA RCR DX, 1 ;is NOT the remainder from the previous 255 0101 D1 D8 RCR AX, 1 ;divide. 256 0103 D1 DA RCR DX, 1 ;1461/4 = 365.25, our multiplier. 257 0105 D1 D8 RCR AX, 1 ;Since the difference can't exceed 258 0107 2B F0 SUB SI, AX ;487 we only subtract low-order words. 259 260 0109 B8 2710 MOV AX, 10000 ;We must now divide the days beyond the 261 010C F7 E6 MUL SI ;calculated year by 30.6001 to get the 262 010E BB 268F MOV BX, 9871 ;unadjusted month. To do this we multi- 263 0111 F7 F3 DIV BX ;ply by 10000, then divide by 306001, 264 0113 B9 001F MOV CX, 31 ;which is more than 16 bits long. Since 265 0116 F6 F1 DIV CL ;306001 = 31*9871, we divide in 2 steps. 266 0118 8A C8 MOV CL, AL ;Got the unadjusted month now in the BX. 267 268 011A 87 D3 XCHG DX, BX ;We must now finish getting the 269 011C 8A C4 MOV AL, AH ;remainder which is 10000 times the 270 011E 8A E5 MOV AH, CH ;day of the month. 271 0120 F7 E2 MUL DX 272 0122 03 C3 ADD AX, BX 273 0124 83 D2 00 ADC DX, 0 274 0127 BB 2710 MOV BX, 10000 ;Divide out the 10000 and the AX contains 275 012A F7 F3 DIV BX ;one less than the day of the month> 276 012C 40 INC AX 277 278 012D FE C9 DEC CL ;Adjust start of year back to between 279 012F 80 F9 0C CMP CL, 12 ;December and January. By now the month 280 0132 76 04 JBE MNTHRDY ;is less than 16 and the day is in the 281 0134 80 E9 0C SUB CL, 12 ;range 1-31. 282 0137 47 INC DI 283 0138 MNTHRDY: 284 0138 8C DA MOV DX, DS ;Begin storing results for caller. 285 013A C5 5E 06 LDS BX, [Day] 286 013D 89 07 MOV [BX], AX 287 013F B0 01 MOV AL, 1 ;Set Pascal/C TRUE for caller (AH=0). 288 0141 OUTAHERE: 289 0141 C5 5E 0A LDS BX, [Month] 290 0144 89 0F MOV [BX], CX 291 0146 C5 5E 0E LDS BX, [Year] 292 0149 89 3F MOV [BX], DI Turbo Assembler Version 2.5 07/21/91 16:39:26 Page 7 dates.ASM 293 ; 294 014B 8E DA MOV DS, DX ;Restore caller and return. 295 014D 5F POP DI 296 014E 5E POP SI 1 297 014F 5D POP BP 1 298 0150 CA 0010 RET 0010h 299 ; 300 0153 DAYBAD: 301 0153 8C DA MOV DX, DS 302 0155 33 C0 XOR AX, AX ;Supplies zero to store and to return. 303 0157 C5 5E 06 LDS BX, [Day] ;Return zeroes for all output values. 304 015A 89 07 MOV [BX], AX 305 015C 8B C8 MOV CX, AX 306 015E 8B F8 MOV DI, AX 307 0160 EB DF JMP OUTAHERE ;Go return to caller. 308 ; 309 0162 ENDP ZDATE 310 ; 311 0162 ENDS Turbo Assembler Version 2.5 07/21/91 16:39:26 Page 8 dates.ASM 312 %NEWPAGE 313 ;******************************************************************************* 314 ; 315 ; About the Claculations 316 ; 317 ; There are a number of descriptions of Day Number routines floating around. 318 ; The ones I use came from a routine I saw for the HP-65 programmable pocket 319 ; calculator to find the Julian Day Number. To it I added adjustments for the 320 ; 400-day Gregorian rule. We don't need it for the coming turn of the century 321 ; since 200 divides by 400 without a remainder and is, thus, a leap year, but 322 ; programmers are picky by nature, so -- what the heck. 323 ; 324 ; To calculate the Day Number from a Gregorian date we first adjust the year and 325 ; month so the month values run from 4 to 15, with March being 4 and February 326 ; being 15: 327 ; 328 ; if Month < 3 329 ; then 330 ; Add 13 to Month 331 ; Subtract 1 from Year 332 ; otherwise 333 ; Add 1 to Month. 334 ; 335 ; Now comes the meat of the calculation: 336 ; 337 ; Day Number = Day of the month 338 ; + The Integer Part of (Month * 30.6001) 339 ; + The Integer Part of (Year * 365.25) 340 ; - The Integer Part of (3/4 of 341 ; The Integer Part of (Year / 400) 342 ; ). 343 ; 344 ; That last mess accounts for the Gregorian 400-year rule. Now if we divide 345 ; this by 7 (to find the day of the week) we get 0 for Saturday. For a 346 ; variety of reasons, mostly related to common practice, I decided to adjust 347 ; this further by subtracting 1 from it so Sunday becomes 0. 348 ; 349 ; Converting back is not so easy. 350 ; 351 ; First we back out the Gregorian 400-year rule: 352 ; 353 ; Divide Day Number less 121 by 146097: 354 ; Q = the quotient 355 ; R = the remainder. 356 ; 357 ; if R is not 0 358 ; then 359 ; Add the quotient from ( (R -1) / 36524 ) to Q. 360 ; 361 ; N = Day Number plus 1 plus Q. 362 ; 363 ; Note that 145097 is the number of days in 400 years with the 400-year rule 364 ; applied, and 36524 is the number of days in a century in which the century Turbo Assembler Version 2.5 07/21/91 16:39:26 Page 9 dates.ASM 365 ; year is NOT a leap year. 36525 is the number of days in a century where the 366 ; century year IS a leap year. Once the 400-year rule is backed out, we have 367 ; ALL centuries containing 36525 days, which simplifies our calculations. 368 ; 369 ; Now we can extract the Gregorian date from the adjusted Day Number "N". 370 ; First we get the tentative year: 371 ; 372 ; Year = The Integer Part of ( (N - 122.1) / 365.25 ). 373 ; 374 ; --and we remove the year's worth of days from the adjusted Day Number "N": 375 ; 376 ; N = N - The Integer Part of (Year * 365.25). 377 ; 378 ; From this we extract the tentative month: 379 ; 380 ; Month = The Integer Part of (N / 30.6001). 381 ; 382 ; The current day is what is left over when we remove the days due to the 383 ; months: 384 ; 385 ; Day = N - The Integer Ppart of (Month * 30.6001). 386 ; 387 ; Finally we adjust the Year and the Month: 388 ; 389 ; if Month > 13 390 ; then 391 ; Subtract 13 from Month 392 ; Add 1 to the Year 393 ; else 394 ; Subtract 1 from the Month. 395 ; 396 ; --and the deed is done. 397 ; 398 ; Since it is my intention that this set of routines be usable on all PC com- 399 ; patible systems, we can't assume the availability of a numeric coprocessor or 400 ; 32-bit arithmetic, so everything is done in 16-bit integer arithmetic using 401 ; the CPU registers and 8086 instructions. In some places it makes the code a 402 ; little awkward, but it gives its best performance on the lowliest of PCs 403 ; where it's needed the most. 404 ; 405 ; I chose the Pascal calling sequence so that I could use the code with both C 406 ; and Pascal programs. If you don't mind shoving stuff on the stack and the 407 ; other fooling around, you can use the routines with assembly code as well. 408 ; 409 END Turbo Assembler Version 2.5 07/21/91 16:39:26 Page 10 Symbol Table Symbol Name Type Value Cref (defined at #) ??DATE Text "07/21/91" ??FILENAME Text "dates " ??TIME Text "16:39:25" ??VERSION Number 0205 @CODE Text DATES_TEXT #108 #108 #109 @CODESIZE Text 1 #108 @CPU Text 0101H @CURSEG Text DATES_TEXT #109 @DATA Text DGROUP #108 @DATASIZE Text 1 #108 @FILENAME Text DATES @MODEL Text 5 #108 @WORDSIZE Text 2 #109 DATEBAD Near DATES_TEXT:0077 126 131 #181 DAY Number [DGROUP:BP+0006] #113 163 #191 285 303 DAYBAD Near DATES_TEXT:0153 245 248 #300 DAYNUMBER Number [DGROUP:BP+0012] #191 198 201 FIXMNTH Near DATES_TEXT:0068 120 #172 GONE Near DATES_TEXT:0064 #168 184 GREGOUT Near DATES_TEXT:00D8 227 #235 MNTHOK Near DATES_TEXT:000E #121 179 MNTHRDY Near DATES_TEXT:0138 280 #283 MONTH Number [DGROUP:BP+000A] #113 118 #191 289 NOADJ Near DATES_TEXT:001B 123 #129 OUTAHERE Near DATES_TEXT:0141 #288 307 RELAY1 Near DATES_TEXT:00ED 207 #245 RELAY2 Near DATES_TEXT:00F4 200 #248 YEAR Number [DGROUP:BP+000E] #113 117 #191 291 ZDATE Far DATES_TEXT:007D #191 193 ZDAY Far DATES_TEXT:0000 #113 114 Groups & Segments Bit Size Align Combine Class Cref (defined at #) DATES_TEXT 16 0162 Word Public CODE #108 108 #109 109 DGROUP Group #108 108 _DATA 16 0000 Word Public DATA #108