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Ocean Color Science Software

ocssw V2022
pdsmerge.c
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1 /********************************************************************
2  * *
3  * Copyright (C) 2007, 2008 *
4  * Charles Darwin University, Darwin, Australia *
5  * *
6  * This program is free software; you can redistribute it and/or *
7  * modify it under the terms of the GNU General Public License as *
8  * published by the Free Software Foundation; either version 2 of *
9  * the License, or (at your option) any later version. *
10  * *
11  * This program is distributed in the hope that it will be *
12  * useful, but WITHOUT ANY WARRANTY; without even the implied *
13  * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR *
14  * PURPOSE. See the GNU General Public License for more details. *
15  * *
16  * You should have received a copy of the GNU General Public *
17  * License along with this program; if not, write to the Free *
18  * Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, *
19  * MA 02111-1307 USA *
20  * *
21  ********************************************************************
22  * *
23  * merge multiple PDS files into one file *
24  * *
25  * 12/12/2007 S. W. Maier start of work *
26  * 12/12/2007 S. W. Maier initial version *
27  * 25/12/2007 S. W. Maier added start and end date parameters *
28  * 10/06/2008 S. W. Maier increased data buffer and test for *
29  * packet size before reading *
30  * 10/10/2008 S. W. Maier increased data buffer *
31  * *
32  ********************************************************************
33  * *
34  * usage: pdsmerge start_date end_date APID <input 1> [<input 2> *
35  * [...]] output *
36  * *
37  ********************************************************************
38  * *
39  * to do: *
40  * - support other sensors *
41  * *
42  * known issues: *
43  * - doesn't take into account leap seconds *
44  * *
45  ********************************************************************
46  * *
47  * build: cc pdsmerge.c -lm -o pdsmerge *
48  * *
49  ********************************************************************/
50 
51 #include <stdio.h>
52 #include <stdlib.h>
53 #include <math.h>
54 #include <string.h>
55 
56 
57 /********************************************************************
58  * *
59  * defines *
60  * *
61  ********************************************************************/
62 /* name */
63 #define NAME "pdsmerge"
64 /* version */
65 #define VERSION 1
66 /* revision */
67 #define REVISION 3
68 /* usage */
69 #define USAGE "start_date end_date APID <input 1> [<input 2> [...]] output\nstart_date/end_date: YYYY/MM/DD,hh:mm:ss or -"
70 /* primary header size */
71 #define PRI_HDR_SIZE 6
72 /* MODIS secondary header size */
73 #define MODIS_HDR_SIZE 12
74 /* data buffer size */
75 #define DATA_SIZE 100000
76 /* Julian Day of MODIS reference date (01/01/1958)*/
77 #define MODIS_REF_DATE 2436205.0
78 
79 
80 /********************************************************************
81  * *
82  * structure definitions *
83  * *
84  ********************************************************************/
85 
86 /* primary header */
87 struct pri_hdr {
88  int flag;
89  int version;
90  int type;
91  int sec_hdr_flag;
92  int apid;
93  int seq_flags;
94  int pkt_count;
95  int pkt_length;
96 };
97 
98 /* MODIS header */
99 struct modis_hdr {
100  int days;
101  unsigned long int millisec;
102  int microsec;
103  int ql;
104  int pkt_type;
105  int scan_count;
106  int mirror_side;
107  int src1;
108  int src2;
109  int conf;
110  int sci_state;
111  int sci_abnorm;
112  int checksum;
113 };
114 
115 
116 /********************************************************************
117  * *
118  * function declarations *
119  * *
120  ********************************************************************/
121 int ReadPriHdr(FILE *f, unsigned char *buf);
122 int WritePriHdr(FILE *f, unsigned char *buf);
123 int DecodePriHdr(unsigned char *buf, struct pri_hdr *hdr);
124 int DecodeMODISHdr(unsigned char *buf, int len,
125  struct modis_hdr *hdr);
126 void julday(int minute, int hour, int day, int month, int year,
127  double *jul);
128 void caldat(int *minute, int *hour, int *day, int *month, int *year,
129  double jul);
130 int CalcChecksum12(unsigned char *buf, int n);
131 
132 /********************************************************************
133  * *
134  * main function *
135  * *
136  ********************************************************************/
137 int main(int argc, char *argv[]) {
138  /* pointer to input file pointer array */
139  FILE **fin;
140  /* output file pointer */
141  FILE *fout;
142  /* pointer to primary header structure pointer array */
143  struct pri_hdr **hdr;
144  /* pointer to MODIS header structure pointer array */
145  struct modis_hdr **mhdr;
146  /* pointer to header buffer pointer array */
147  unsigned char **buf_hdr;
148  /* pointer to data buffer pointer array */
149  unsigned char **buf_data;
150  /* number of input files */
151  int n;
152  /* APID */
153  int apid;
154  /* checksum */
155  int chksum;
156  /* input stream with oldest packet */
157  int oldest;
158  /* flag for valid packet available */
159  int valpkt;
160  /* counter */
161  int i;
162  /* error code */
163  int error;
164  /* date/time */
165  int year, month, day, hour, min, sec;
166  /* start date/time */
167  int startday;
168  unsigned long startmillisec;
169  /* end date/time */
170  int endday;
171  unsigned long endmillisec;
172  /* buffer */
173  double x;
174  /* last packet date/time/pktcount */
175  int lastdays = 0, lastmicrosec = 0, lastpktcount = 0;
176  unsigned long int lastmillisec = 0;
177  /* packet difference */
178  int pktdiff;
179 
180 
181  /* print version information */
182  fprintf(stderr, "%s V%d.%d ("__DATE__")\n",
183  NAME, VERSION, REVISION);
184 
185  /* check number of arguments */
186  if (argc < 6) {
187  fprintf(stderr, "USAGE: %s %s\n", NAME, USAGE);
188  return (20);
189  }
190 
191  /* determine number of input files */
192  n = argc - 5;
193 
194  /* get start date */
195  if (strcmp(argv[1], "-") == 0) {
196  startday = 0;
197  startmillisec = 0;
198  } else {
199  if (sscanf(argv[1], " %d/%d/%d,%d:%d:%d",
200  &year, &month, &day, &hour, &min, &sec) != 6) {
201  fprintf(stderr, "USAGE: %s %s\n", NAME, USAGE);
202  return (20);
203  }
204  if ((year < 1958) ||
205  (month < 1) || (month > 12) ||
206  (day < 1) || (day > 31) ||
207  (hour < 0) || (hour > 23) ||
208  (min < 0) || (min > 59) ||
209  (sec < 0) || (sec > 59)) {
210  fprintf(stderr, "USAGE: %s %s\n", NAME, USAGE);
211  return (10);
212  }
213  julday(0, 0, day, month, year, &x);
214  startday = (int) (x - MODIS_REF_DATE);
215  startmillisec =
216  (unsigned long) hour * 60L * 60L * 1000L +
217  (unsigned long) min * 60L * 1000L +
218  (unsigned long) sec * 1000L;
219  }
220 
221  /* get end date */
222  if (strcmp(argv[2], "-") == 0) {
223  endday = 4000000;
224  endmillisec = 90000000L;
225  } else {
226  if (sscanf(argv[2], " %d/%d/%d,%d:%d:%d",
227  &year, &month, &day, &hour, &min, &sec) != 6) {
228  fprintf(stderr, "USAGE: %s %s\n", NAME, USAGE);
229  return (20);
230  }
231  if ((year < 1958) ||
232  (month < 1) || (month > 12) ||
233  (day < 1) || (day > 31) ||
234  (hour < 0) || (hour > 23) ||
235  (min < 0) || (min > 59) ||
236  (sec < 0) || (sec > 59)) {
237  fprintf(stderr, "USAGE: %s %s\n", NAME, USAGE);
238  return (10);
239  }
240  julday(0, 0, day, month, year, &x);
241  endday = (int) (x - MODIS_REF_DATE);
242  endmillisec =
243  (unsigned long) hour * 60L * 60L * 1000L +
244  (unsigned long) min * 60L * 1000L +
245  (unsigned long) sec * 1000L;
246  }
247 
248  /* check if end date/time is after start date/time */
249  if ((endday < startday) ||
250  ((endday == startday) && (endmillisec <= startmillisec))) {
251  fprintf(stderr, "USAGE: %s %s\n", NAME, USAGE);
252  return (10);
253  }
254 
255  /* get APID */
256  apid = atoi(argv[3]);
257  if ((apid < 64) || (apid > 127)) {
258  fprintf(stderr, "only APID 64 to 127 supported\n");
259  return (10);
260  }
261 
262  /* allocate pointer memory */
263  if (!(fin = malloc(sizeof (FILE *) * n))) {
264  fprintf(stderr, "not enough memory\n");
265  return (10);
266  }
267  if (!(hdr = malloc(sizeof (struct pri_hdr *) * n))) {
268  fprintf(stderr, "not enough memory\n");
269  return (10);
270  }
271  if (!(mhdr = malloc(sizeof (struct modis_hdr *) * n))) {
272  fprintf(stderr, "not enough memory\n");
273  return (10);
274  }
275  if (!(buf_hdr = malloc(sizeof (unsigned char *) * n))) {
276  fprintf(stderr, "not enough memory\n");
277  return (10);
278  }
279  if (!(buf_data = malloc(sizeof (unsigned char *) * n))) {
280  fprintf(stderr, "not enough memory\n");
281  return (10);
282  }
283 
284  /* allocate data memory */
285  for (i = 0; i < n; i++) {
286  if (!(hdr[i] = malloc(sizeof (struct pri_hdr)))) {
287  fprintf(stderr, "not enough memory\n");
288  return (10);
289  }
290  hdr[i]->flag = 0;
291  if (!(mhdr[i] = malloc(sizeof (struct modis_hdr)))) {
292  fprintf(stderr, "not enough memory\n");
293  return (10);
294  }
295  if (!(buf_hdr[i] = malloc(sizeof (unsigned char) * PRI_HDR_SIZE))) {
296  fprintf(stderr, "not enough memory\n");
297  return (10);
298  }
299  if (!(buf_data[i] = malloc(sizeof (unsigned char) * DATA_SIZE))) {
300  fprintf(stderr, "not enough memory\n");
301  return (10);
302  }
303  }
304 
305  /* open input files */
306  for (i = 0; i < n; i++) {
307  if (!(fin[i] = fopen(argv[i + 4], "rb"))) {
308  fprintf(stderr, "can't open input file (%s)\n", argv[i + 4]);
309  return (10);
310  }
311  }
312 
313  /* open output file */
314  if (!(fout = fopen(argv[n + 4], "wb"))) {
315  fprintf(stderr, "can't create output file (%s)\n", argv[n + 4]);
316  return (10);
317  }
318 
319  /* main loop */
320  for (;;) {
321  /* for each input file */
322  for (i = 0; i < n; i++) {
323  /* do until we have a valid packet or we have reached EOF */
324  for (; hdr[i]->flag == 0;) {
325  /* read primary header */
326  if (ReadPriHdr(fin[i], buf_hdr[i])) {
327  /* end of file? */
328  if (feof(fin[i])) {
329  hdr[i]->flag = -1;
330  break;
331  } else {
332  fprintf(stderr,
333  "error reading input file (%s)\n",
334  argv[i + 4]);
335  return (5);
336  }
337  }
338 
339  /* decode primary header */
340  switch (error = DecodePriHdr(buf_hdr[i], hdr[i])) {
341  case 0:
342  break;
343  case -1:
344  fprintf(stderr,
345  "unsupported packet version (%d) in input file "
346  "(%s): "
347  "file might be corrupted, trying to resyncronise\n",
348  hdr[i]->version,
349  argv[i + 4]);
350 
351  /* read data block */
352  if (hdr[i]->pkt_length + 1 > DATA_SIZE) {
353  fprintf(stderr,
354  "buffer overflow (%d), "
355  "please contact developer\n",
356  hdr[i]->pkt_length);
357  return (20);
358  }
359  if (fread(buf_data[i], hdr[i]->pkt_length + 1, 1, fin[i]) !=
360  1) {
361  fprintf(stderr,
362  "error reading input file (%s)\n",
363  argv[i + 4]);
364  return (5);
365  }
366  continue;
367  default:
368  fprintf(stderr,
369  "unknown error (%d) while decoding primary "
370  "header\n",
371  error);
372  return (5);
373  }
374 
375  /* read data block */
376  if (hdr[i]->pkt_length + 1 > DATA_SIZE) {
377  fprintf(stderr,
378  "buffer overflow (%d), "
379  "please contact developer\n",
380  hdr[i]->pkt_length);
381  return (20);
382  }
383  if (fread(buf_data[i], hdr[i]->pkt_length + 1, 1, fin[i]) !=
384  1) {
385  fprintf(stderr,
386  "error reading input file (%s)\n",
387  argv[i + 4]);
388  return (5);
389  }
390 
391  /* is it a packet we need? */
392  if (hdr[i]->apid != apid)
393  continue;
394 
395  /* decode MODIS header */
396  DecodeMODISHdr(buf_data[i],
397  hdr[i]->pkt_length + 1,
398  mhdr[i]);
399 
400  /* calculate checksum */
401  chksum =
402  CalcChecksum12(&(buf_data[i][MODIS_HDR_SIZE]),
403  (hdr[i]->pkt_length + 1 - MODIS_HDR_SIZE) /
404  1.5 - 1);
405 
406  /* invalid packet? */
407  if (chksum != mhdr[i]->checksum)
408  continue;
409 
410  /* before startdate? */
411  if ((mhdr[i]->days < startday) ||
412  ((mhdr[i]->days == startday) &&
413  (mhdr[i]->millisec < startmillisec)))
414  continue;
415 
416  /* after enddate? */
417  if ((mhdr[i]->days > endday) ||
418  ((mhdr[i]->days == endday) &&
419  (mhdr[i]->millisec >= endmillisec)))
420  continue;
421 
422  /* set valid packet flag */
423  hdr[i]->flag = 1;
424  }
425  }
426 
427  /* find the oldest packet */
428  for (i = 0, valpkt = 0; i < n; i++) {
429  /* invalid packet? */
430  if (hdr[i]->flag != 1)
431  continue;
432 
433  /* first valid packet? */
434  if (valpkt == 0) {
435  /* set oldest to this this packet */
436  oldest = i;
437 
438  /* set flag for valid packet available */
439  valpkt = 1;
440 
441  /* next stream */
442  continue;
443  }
444 
445  /* test days */
446  if (mhdr[i]->days < mhdr[oldest]->days) {
447  oldest = i;
448  continue;
449  }
450  if (mhdr[i]->days > mhdr[oldest]->days) {
451  continue;
452  }
453 
454  /* test milliseconds */
455  if (mhdr[i]->millisec < mhdr[oldest]->millisec) {
456  oldest = i;
457  continue;
458  }
459  if (mhdr[i]->millisec > mhdr[oldest]->millisec) {
460  continue;
461  }
462 
463  /* test microseconds */
464  if (mhdr[i]->microsec < mhdr[oldest]->microsec) {
465  oldest = i;
466  continue;
467  }
468  if (mhdr[i]->microsec > mhdr[oldest]->microsec) {
469  continue;
470  }
471 
472  /* test packet count */
473  pktdiff = hdr[i]->pkt_count - hdr[oldest]->pkt_count;
474  if (pktdiff < -8191) pktdiff += 16384;
475  if (pktdiff > 8191) pktdiff -= 16384;
476  if (pktdiff < 0) {
477  oldest = i;
478  continue;
479  }
480  if (pktdiff > 0) {
481  continue;
482  }
483 
484  /* identical packets, flag packet from stream i invalid */
485  hdr[i]->flag = 0;
486  }
487 
488  /* no valid packet available? */
489  if (valpkt == 0)
490  break;
491 
492  /* avoid duplicated and old packets */
493  if (mhdr[oldest]->days < lastdays) {
494  hdr[oldest]->flag = 0;
495  lastdays = mhdr[oldest]->days;
496  lastmillisec = mhdr[oldest]->millisec;
497  lastmicrosec = mhdr[oldest]->microsec;
498  lastpktcount = hdr[oldest]->pkt_count;
499  continue;
500  }
501  if (mhdr[oldest]->days == lastdays) {
502  if (mhdr[oldest]->millisec < lastmillisec) {
503  hdr[oldest]->flag = 0;
504  lastdays = mhdr[oldest]->days;
505  lastmillisec = mhdr[oldest]->millisec;
506  lastmicrosec = mhdr[oldest]->microsec;
507  lastpktcount = hdr[oldest]->pkt_count;
508  continue;
509  }
510  if (mhdr[oldest]->millisec == lastmillisec) {
511  if (mhdr[oldest]->microsec < lastmicrosec) {
512  hdr[oldest]->flag = 0;
513  lastdays = mhdr[oldest]->days;
514  lastmillisec = mhdr[oldest]->millisec;
515  lastmicrosec = mhdr[oldest]->microsec;
516  lastpktcount = hdr[oldest]->pkt_count;
517  continue;
518  }
519  if (mhdr[oldest]->microsec == lastmicrosec) {
520  pktdiff = hdr[oldest]->pkt_count - lastpktcount;
521  if (pktdiff < -8191) pktdiff += 16384;
522  if (pktdiff > 8191) pktdiff -= 16384;
523  if (pktdiff <= 0) {
524  hdr[oldest]->flag = 0;
525  lastdays = mhdr[oldest]->days;
526  lastmillisec = mhdr[oldest]->millisec;
527  lastmicrosec = mhdr[oldest]->microsec;
528  lastpktcount = hdr[oldest]->pkt_count;
529  continue;
530  /* }*/
531  }
532  }
533  }
534  }
535 
536  /* store packet date/time/sample/pktcount */
537  lastdays = mhdr[oldest]->days;
538  lastmillisec = mhdr[oldest]->millisec;
539  lastmicrosec = mhdr[oldest]->microsec;
540  lastpktcount = hdr[oldest]->pkt_count;
541 
542  /* write packet to output file */
543  if (WritePriHdr(fout, buf_hdr[oldest])) {
544  fprintf(stderr,
545  "error writing to output file (%s)\n",
546  argv[n + 4]);
547  return (5);
548  }
549  if (fwrite(buf_data[oldest],
550  hdr[oldest]->pkt_length + 1,
551  1, fout) != 1) {
552  fprintf(stderr,
553  "error writing to output file (%s)\n",
554  argv[n + 4]);
555  return (5);
556  }
557 
558  /* flag packet from stream oldest invalid */
559  hdr[oldest]->flag = 0;
560  }
561 
562  /* close output file */
563  fclose(fout);
564 
565  /* close input files */
566  for (i = 0; i < n; i++) {
567  fclose(fin[i]);
568  }
569 
570  /* free memory */
571  for (i = 0; i < n; i++) {
572  free(buf_data[i]);
573  free(buf_hdr[i]);
574  free(mhdr[i]);
575  free(hdr[i]);
576  }
577  free(buf_data);
578  free(buf_hdr);
579  free(mhdr);
580  free(hdr);
581  free(fin);
582 
583  /* Ja das war's. Der Pop-Shop ist zu Ende */
584  return (0);
585 }
586 
587 /********************************************************************
588  * *
589  * read primary header from file *
590  * *
591  * f: file pointer *
592  * buf: pointer to buffer *
593  * *
594  * result: 0 - ok *
595  * -1 - read error *
596  * *
597  ********************************************************************/
598 int ReadPriHdr(FILE *f, unsigned char *buf) {
599  /* read header */
600  if (fread(buf, PRI_HDR_SIZE, 1, f) != 1)
601  return (-1);
602 
603  /* ois rodger */
604  return (0);
605 }
606 
607 /********************************************************************
608  * *
609  * write primary header to file *
610  * *
611  * f: file pointer *
612  * buf: pointer to buffer *
613  * *
614  * result: 0 - ok *
615  * -1 - write error *
616  * *
617  ********************************************************************/
618 int WritePriHdr(FILE *f, unsigned char *buf) {
619  /* read header */
620  if (fwrite(buf, PRI_HDR_SIZE, 1, f) != 1)
621  return (-1);
622 
623  /* ois rodger */
624  return (0);
625 }
626 
627 /********************************************************************
628  * *
629  * decode primary header *
630  * *
631  * buf: pointer to buffer *
632  * hdr: pointer to header structure *
633  * *
634  * result: 0 - ok *
635  * -1 - decode error (version not supported) *
636  * *
637  ********************************************************************/
638 int DecodePriHdr(unsigned char *buf, struct pri_hdr *hdr) {
639  /* version */
640  hdr->version = (buf[0] & 0xE0) >> 5;
641 
642  /* version supported? */
643  if (hdr->version != 0)
644  return (-1);
645 
646  /* type */
647  hdr->type = (buf[0] & 0x10) >> 4;
648 
649  /* secondary header flag */
650  hdr->sec_hdr_flag = (buf[0] & 0x08) >> 3;
651 
652  /* APID */
653  hdr->apid = (((int) (buf[0] & 0x07)) << 8) + buf[1];
654 
655  /* sequence flags */
656  hdr->seq_flags = (buf[2] & 0xC0) >> 6;
657 
658  /* packet count per APID */
659  hdr->pkt_count = (((int) (buf[2] & 0x3F)) << 8) + buf[3];
660 
661  /* packet length (length - 1) */
662  hdr->pkt_length = (((int) buf[4]) << 8) + buf[5];
663 
664  /* okeydokey */
665  return (0);
666 }
667 
668 /********************************************************************
669  * *
670  * decode MODIS header *
671  * *
672  * buf: pointer to buffer *
673  * len: data lengh *
674  * hdr: pointer to header structure *
675  * *
676  * result: 0 - ok *
677  * -1 - decode error *
678  * -2 - decode error *
679  * *
680  ********************************************************************/
681 int DecodeMODISHdr(unsigned char *buf, int len,
682  struct modis_hdr *hdr) {
683  /* days since 01/01/1958 */
684  hdr->days =
685  (((int) buf[0]) << 8) +
686  (((int) buf[1]));
687 
688  /* milliseconds of day */
689  hdr->millisec =
690  (((unsigned long int) buf[2]) << 24) +
691  (((unsigned long int) buf[3]) << 16) +
692  (((unsigned long int) buf[4]) << 8) +
693  (((unsigned long int) buf[5]));
694 
695  /* microseconds of milliseconds */
696  hdr->microsec =
697  (((int) buf[6]) << 8) +
698  (((int) buf[7]));
699 
700  /* quicklook flag */
701  hdr->ql = (buf[8] & 0x80) >> 7;
702 
703  /* packet type */
704  hdr->pkt_type = (buf[8] & 0x70) >> 4;
705 
706  /* scan count */
707  hdr->scan_count = (buf[8] & 0x0E) >> 1;
708 
709  /* mirror side */
710  hdr->mirror_side = (buf[8] & 1);
711 
712  /* source identification (0 = earth, 1 = calibration) */
713  hdr->src1 = (buf[9] & 0x80) >> 7;
714 
715  /* source identification (0 = eng., 1 to 1354 = sample count) */
716  hdr->src2 =
717  (((int) buf[9] & 0x7F) << 4) +
718  (((int) buf[10] & 0xF0) >> 4);
719 
720  /* FPA/AEM config */
721  hdr->conf =
722  (((int) buf[10] & 0x0F) << 6) +
723  (((int) buf[11] & 0xFC) >> 2);
724 
725  /* sci state */
726  hdr->sci_state = (((int) buf[11] & 0x02) >> 1);
727 
728  /* sci abnorm */
729  hdr->sci_abnorm = (((int) buf[11] & 0x01));
730 
731  /* check sum */
732  hdr->checksum =
733  (((int) buf[len - 2] & 0x0F) << 8) +
734  (((int) buf[len - 1]));
735 
736  return 0;
737 }
738 
739 /********************************************************************
740  * *
741  * convert calendar date to julian day *
742  * *
743  * minute: minute of time to convert *
744  * hour: hour of time to convert *
745  * day: day of date to convert *
746  * month: month of date to convert *
747  * year: year of date to convert *
748  * jul: pointer to store julian day *
749  * *
750  * result: none *
751  * *
752  ********************************************************************/
753 void julday(int minute, int hour, int day, int month, int year,
754  double *jul) {
755  /* julian day as long */
756  long ljul;
757  /* helping variables */
758  int ja, jy, jm;
759 
760 
761  jy = year;
762 
763  if (jy < 0)
764  ++jy;
765  if (month > 2) {
766  jm = month + 1;
767  } else {
768  --jy;
769  jm = month + 13;
770  }
771  ljul = (long) (floor(365.25 * jy) + floor(30.6001 * jm) + day +
772  1720995);
773  if (day + 31L * (month + 12L * year) >= (15 + 31L * (10 + 12L * 1582))) {
774  ja = (int) (0.01 * jy);
775  ljul += 2 - ja + (int) (0.25 * ja);
776  }
777 
778  *jul =
779  (double) ljul +
780  (double) hour / 24.0 +
781  (double) minute / 1440.0 +
782  0.000001; /* add about 0.1s to avoid precision problems */
783 }
784 
785 /********************************************************************
786  * *
787  * convert julian day to calendar date *
788  * *
789  * minute: pointer to store minute *
790  * hour: pointer to store hour *
791  * day: pointer to store day *
792  * month: pointer to store month *
793  * year: pointer to store year *
794  * jul: julian day *
795  * *
796  * result: none *
797  * *
798  ********************************************************************/
799 void caldat(int *minute, int *hour, int *day, int *month, int *year,
800  double jul) {
801  /* julian day as long */
802  long ljul;
803  /* helping variables */
804  long ja, jalpha, jb, jc, jd, je;
805 
806 
807  ljul = (long) floor(jul);
808  jul -= (double) ljul;
809  *hour = (int) (floor(jul * 24.0));
810  jul -= (double) *hour / 24.0;
811  *minute = (int) (floor(jul * 1440.0));
812 
813  if (ljul >= 2299161) {
814  jalpha = (long) (((float) (ljul - 1867216) - 0.25) / 36524.25);
815  ja = ljul + 1 + jalpha - (long) (0.25 * jalpha);
816  } else
817  ja = ljul;
818  jb = ja + 1524;
819  jc = (long) (6680.0 + ((float) (jb - 2439870) - 122.1) / 365.25);
820  jd = (long) (365 * jc + (0.25 * jc));
821  je = (long) ((jb - jd) / 30.6001);
822  *day = jb - jd - (long) (30.6001 * je);
823  *month = je - 1;
824  if (*month > 12)
825  *month -= 12;
826  *year = jc - 4715;
827  if (*month > 2)
828  --(*year);
829  if (*year <= 0)
830  --(*year);
831 }
832 
833 /********************************************************************
834  * *
835  * calculate 12bit checksum *
836  * *
837  * buf: pointer to data buffer *
838  * n: number of bytes in buffer *
839  * *
840  * result: checksum *
841  * *
842  ********************************************************************/
843 int CalcChecksum12(unsigned char *buf, int n) {
844  /* counter */
845  int i;
846  /* data value */
847  unsigned long x;
848  /* checksum */
849  unsigned long s = 0;
850 
851 
852  /* main loop */
853  for (i = 0; i < n; i++) {
854  /* get 1. value */
855  x =
856  (((unsigned long) buf[(int) (1.5 * i)]) << 4) +
857  (((unsigned long) buf[(int) (1.5 * i) + 1] & 0xF0) >> 4);
858 
859  /* add to checksum */
860  s = s + x;
861 
862  /* increase counter */
863  i++;
864 
865  /* do we have a second value */
866  if (i >= n)
867  break;
868 
869  /* get 2. value */
870  x =
871  (((unsigned long) buf[(int) (1.5 * (i - 1)) + 1] & 0x0F) << 8) +
872  (((unsigned long) buf[(int) (1.5 * (i - 1)) + 2]));
873 
874  /* add to checksum */
875  s = s + x;
876  }
877 
878 
879  s = s >> 4;
880  s = s & 0xFFF;
881 
882  /* return checksum */
883  return (s);
884 }
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