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grib_seek.c

Last change on this file was 11, checked in by aslmd, 14 years ago
spiga@svn-planeto:ajoute le modele meso-echelle martien
File size: 19.0 KB

Line
1	/* File: grib_seek.c based on Decoder's trqgetmsg() func;
2	Revised by:
3	28oct96 Alice T. Nakajima (ATN), SAIC, Monterey
4	18jun97 ATN check Edition before reading in entire msg;
5	27aug97 ATN *SEEK_SET to 0 (gcc complains)
6	20Oct97 ATN print #bytes read when fread fails;
7	03nov97 ATN -Realloc
8	22oct98 ATN *error msg;
9	*/
10	#include <stdio.h>
11	#include <stdlib.h>
12	#include <string.h>
13	#include <math.h>
14	#include "dprints.h" /* for dprints */
15	#include "gribfuncs.h" /* prototypes */
16
17	/*
18	**********************************************************************
19	* A. FUNCTION: grib_seek
20	* search the input file starting at the given offset for a GRIB
21	* message. If found, return it in GRIB_HDR structure.
22	*
23	* INTERFACE:
24	* int grib_seek (InFile, offset, Read_Index, gh, errmsg)
25	*
26	* ARGUMENTS (I=input, O=output, I&O=input and output):
27	* (I) char *InFile;
28	* name of input file to search for message;
29	* (I&O) long *offset;
30	* number of bytes to skip from the beginning of file;
31	* gets updated upon leaving to absolute #bytes from beginning of
32	* file to beginning of message found;
33	* (I) int Read_Index;
34	* if set, only proceed if 'GRIB' starts exactly at the given
35	* byte offset;
36	* (O) GRIB_HDR *gh;
37	* empty upon entry; to hold the Message found and its info;
38	* (O) char *errmsg;
39	* empty array, only filled if error occurred;
40	*
41	* RETURN CODE:
42	* 0> no errors, may or may not have a valid message;
43	* If no Msg was Found:
44	* a) errmsg will hold the Warning msg;
45	* If a valid Msg was Found:
46	* a) long *offset: if succesful, gets updated to absolute
47	* beginning of Mesg;
48	* b) struct GRIB_HDR holds its info:
49	* entire_msg: is assigned to newly MAlloced
50	* unsigned char * array to hold entire message;
51	* msg_length: size of entire_msg array in bytes;
52	* ids_len, pds_len, gds_len, bms_len, bds_len, eds_len:
53	* size of each defined sections in bytes;
54	* ids_ptr: pts to message's Ident Data Sect;
55	* pds_ptr: pts to message's Prod Defn Sect;
56	* gds_ptr: pts to message's Grid Defn Sect;
57	* bms_ptr: pts to message's Bitmap Defn Sect;
58	* bds_ptr: pts to message's Binary Data Sect;
59	* eds_ptr: pts to message's End Data Sect;
60	* c) errmsg remains empty;
61	* 1> fseek/fread error, all ptrs in grib_hdr set to null; errmsg filled;
62	* 2> got end of file, all ptrs in grib_hdr set to null; errmsg filled;
63	* 3> Null entire_msg pointer; errmsg filled;
64	* 4> unable to open input file; errmsg filled;
65	*
66	**********************************************************************
67	*/
68
69	#if PROTOTYPE_NEEDED
70	int grib_seek ( char InFile, long offset, int Read_Index,
71	GRIB_HDR gh, char errmsg)
72	#else
73	int grib_seek (InFile, offset, Read_Index,gh,errmsg)
74	char *InFile;
75	long *offset;
76	int Read_Index;
77	GRIB_HDR *gh;
78	char *errmsg;
79	#endif
80	{
81	char *func="grib_seek";
82	FILE *fp=NULL;
83	int status=0;
84
85	DPRINT3 ("Entering %s\nfile=%s, offs=%ld \n", func, InFile, *offset);
86
87	/*
88	*
89	* A.2 OPEN Input file
90	* IF (fails) RETURN w/ error stat 4 !errmsg filled
91	*/
92	if ((fp = fopen (InFile, "rb")) == NULL) {
93	DPRINT2 ("%s: Cannot open input file %s\n", func,InFile );
94	sprintf (errmsg,"%s: Cannot open input file '%s'\n", func,InFile );
95	status = 4;
96	goto DONE;
97	}
98
99	status = grib_fseek(fp,offset,Read_Index,gh,errmsg);
100
101	DONE:
102	/*
103	*
104	* A.4 CLOSE input file; !get here when found no messages
105	*
106	*/
107	if (fp) fclose(fp);
108
109	/*
110	* A.6 RETURN with status
111	*/
112	return (status);
113
114	}
115
116
117
118	#if PROTOTYPE_NEEDED
119	int grib_fseek ( FILE fp, long offset, int Read_Index,
120	GRIB_HDR gh, char errmsg)
121	#else
122	int grib_fseek (fp, offset, Read_Index,gh,errmsg)
123	FILE *fp;
124	long *offset;
125	int Read_Index;
126	GRIB_HDR *gh;
127	char *errmsg;
128	#endif
129	{
130	char *func="grib_fseek";
131	char GG, sm_blk[5004], fwa_msg=NULL;
132	unsigned long lMessageSize;
133	unsigned long Edition;
134	long pos; /* current byte offs fr. beg. of file */
135	int bytenum; /* Index w/in sm_blk */
136	int bytestoread=5004; /* #bytes to read into sm_blk at a time */
137	int check_limit; /* #bytes in sm_blk to check */
138	int gotone = 0; /* set if found good msg */
139	int nread; /* #bytes got back from Read */
140	int status;
141	unsigned long iskip; /* for getbyte */
142	int gdsbmsflag, bit_set, sect_len; /* working vars */
143	char ptr, end_ptr;
144
145	DPRINT2 ("Entering %s\n, offs=%ld \n", func, *offset);
146	/*
147	* A.1 INIT variables
148	* !gh structure is cleared out
149	*/
150	if (gh->entire_msg==NULL) {
151	DPRINT1 ( "%s: expecting non-null Grib Hdr;\n",func);
152	sprintf(errmsg, "%s: expecting non-NULL Grib Hdr;\n",func);
153	status= 3;
154	goto DONE;
155	}
156
157	gh->msg_length = 0;
158	gh->ids_ptr=gh->pds_ptr= 0;
159	gh->gds_ptr=gh->bms_ptr=gh->bds_ptr=gh->eds_ptr=0;
160	memset ((void *)gh->entire_msg, '\0', gh->abs_size);
161	DPRINT2 ("gh= %ld, gh->entire_msg=%ld\n", gh, gh->entire_msg);
162
163	/*
164	*
165	* A.3 FOR (loop while no error) !read a block at a time
166	*/
167
168	for (status=0, pos= *offset, gotone= 0; status == 0; pos += check_limit)
169	{
170	/*
171	* A.3.1 IF (cannot SET file position to correct place)
172	* THEN
173	* SET Status to 1 !fseek err
174	* CONTINUE (Loop around to A.3)
175	* ENDIF
176	*/
177	if (fseek(fp, pos, 0)!=0) {
178	DPRINT2 ("%s: Got fseek error to pos= %ld\n",func, pos);
179	sprintf(errmsg,"%s: Got fseek error to pos= %ld\n",func,pos);
180	perror("");
181	status = 1;
182	goto DONE;
183	}
184
185	/*
186	* A.3.2 IF (read less than 40 bytes)
187	* THEN
188	* FILL error buffer
189	* RETURN status 2 !eof or <40 bytes left, errmsg filled
190	* ENDIF
191	*/
192	nread= fread (sm_blk,sizeof(char), bytestoread,fp);
193	if (nread <= 40)
194	{
195	if (nread<=4) {
196	DPRINT0 ("No bytes left to check for msg;\n");
197	/* Errmsg left blank cuz its just EOF */
198	}
199	else {
200	sprintf(errmsg,"%s: skip last %d bytes, too few for a Msg\n",
201	func, nread);
202	DPRINT1 ("Only read %d bytes, too few to check for msg;\n",nread);
203	}
204	status= 2;
205	goto DONE;
206	}
207	else check_limit= nread - 4;
208
209	/*
210	* ! search block for the next the 'G'
211	* ! load entire Msg if everything is ok;
212	* ! if No 'G' found, then quit right away if no 'G'
213	* ! if GRIB is not at absolute Offset address, quit too;
214	* !
215	* A.3.3 WHILE (there is another 'G' in this block) DO
216	*/
217	bytenum= 0;
218	while ((GG= (char *) memchr (sm_blk, 'G', check_limit)))
219	{
220	/--- Saw 'G' ---/
221	/*
222	* A.3.3.1 IF ('RIB' is not after 'G') THEN
223	* IF (Offset from Index file) THEN
224	* ABORT search; !Break out of loop
225	* ELSE
226	* CLEAR out the 'G' in temp block
227	* CONTINUE !Loop around to A.3.3
228	* ENDIF
229	* ENDIF
230	*/
231	if (strncmp(GG, "GRIB",4)) /* not 'RIB' after the 'G' */
232	if ( Read_Index)
233	break; /* Offset IS from Indexfile: Quit here */
234	else
235	{ /* offset is NOT fr. IndexFile: keep looping; */
236	GG='-'; / no RIB after G, clear it */
237	continue; /* let Memchr find next G in block */
238	}
239
240	/--- Saw 'G R I B' ----/
241	/*
242	* A.3.3.2 CALCULATE byte position within this block
243	* where this message begins
244	*/
245	bytenum = GG - sm_blk; /* byte pos w/in this block */
246
247	/*
248	* A.3.3.3 IF (offset is from Indexfile AND
249	* string GRIB found is not at Absolute IndexFile's offset)
250	* THEN abort search; ENDIF
251	*/
252	DPRINT1 ("Found string 'GRIB' at %ld\n", pos+bytenum);
253	if (Read_Index && *offset != (bytenum + pos)) {
254	sprintf(errmsg,
255	"%s: No Grib msg found at offset= %ld; check Index File\n",
256	func, *offset);
257	break; /* Abort here, Ret w/ no errros & no msg too */
258	}
259
260	/--- Read Mesg Length, Edition ---/
261	/*
262	* A.3.3.4 FUNCTION gbyte !extract lMessageSize
263	*/
264	iskip=32;
265	gbyte (sm_blk+bytenum ,&lMessageSize, &iskip,24);
266	DPRINT0 ("lMessageSize\n");
267
268	/--- Make sure it's Edition 1 first ---/
269	/*
270	* A.3.3.5 FUNCTION gbyte !extract Grib Edition Number
271	* IF (not edition 1) THEN
272	* CLEAR out the 'G' in temp block
273	* CONTINUE !Loop around to A.3.3
274	* ENDIF
275	*/
276	gbyte (sm_blk+bytenum, &Edition, &iskip, 8);
277	DPRINT0 ("Edition\n");
278	if (Edition != 1) {
279	DPRINT1 ("Edition (%d) is not 1, start over\n",
280	Edition);
281	GG='-'; / blank out G of current GRIB location found */
282	continue; /* let Memchr find next G in block */
283	}
284
285
286	/*
287	* A.3.3.6 IF (cannot MOVE ptr to start of the message) THEN
288	* RETURN status 1 !errmsg filled
289	* ENDIF
290	*/
291	if (fseek(fp, (long)(pos+bytenum), 0)!=0) {
292	DPRINT2 (
293	"%s: FSEEK error to pos+bytenum= %ld\n",
294	func, pos+bytenum);
295	sprintf(errmsg,
296	"%s: FSEEK error to pos+bytenum= %ld\n",
297	func, pos+bytenum);
298	status= 1;
299	goto DONE;
300	}
301
302	/*
303	* A.3.3.7 INIT all section length to zero
304	*/
305	gh->ids_len= gh->pds_len= gh->gds_len= 0;
306	gh->bds_len= gh->bms_len= gh->eds_len= 0;
307
308	/*
309	* A.3.3.8 EXPAND Entire_Msg array if it's smaller than msglen
310	* RETURN Malloc Err (stat=2) if fails !errmsg filled
311	*/
312	if (lMessageSize > gh->abs_size ) {
313
314	/* if (realloc((void *)gh->entire_msg, lMessageSize) == NULL) {..}
315	* gh->abs_size = lMessageSize;
316	*/
317	if (Expand_gribhdr (gh, lMessageSize, errmsg)) {
318	upd_child_errmsg (func, errmsg);
319	status = 1; /* to get out of Outer loop */
320	goto DONE;
321	}
322
323	DPRINT1 ("Expanded entire_msg to be %ld bytes long\n",
324	gh->abs_size);
325	} /* size changed */
326
327	/--- READ ENTIRE MSG into GRIB HEADER's Entire_Msg ---/
328	/*
329	*
330	* A.3.3.9 READ the entire message into Grib Hdr's Entire_Msg;
331	* IF (failed) THEN
332	* RETURN Fread error stat=1 !errmsg filled
333	* ENDIF
334	*/
335	fwa_msg = (char *)gh->entire_msg;
336	if ((nread=fread (fwa_msg, 1, lMessageSize, fp)) != lMessageSize)
337	{
338	DPRINT2 ( "%s: failed to Fread EntireMsg (sz=%ld)\n",
339	func, lMessageSize);
340	sprintf(errmsg,
341	"%s has truncated msg @offs=%ld (got %ld out of %ld bytes)\n",
342	func, *offset, nread, lMessageSize);
343	status= 1; /* to get out of Outer loop */
344	goto DONE; /* get out of WHILE */
345	}
346
347	/--- if see '7777', asssign GH's pointers & len ---/
348	/*
349	* A.3.3.10 IF ('7777' is where expected) THEN
350	*/
351	if (!strncmp((fwa_msg + lMessageSize - 4),"7777",4))
352	/* && fwa_msg[7]==1) */
353	{
354	end_ptr = fwa_msg + lMessageSize;
355
356	DPRINT0 ("Found string '7777' where expected\n");
357	gh->msg_length= lMessageSize;
358	/*
359	* A.3.3.10.a.1 STORE loc & len of section 0 into Grib Hdr;
360	*/
361	gh->ids_ptr= (unsigned char )fwa_msg; / mark sect 0 */
362	gh->ids_len= 8L;
363
364	/*
365	* A.3.3.10.a.2 STORE loc & len of PDS into Grib Hdr;
366	* FUNCTION gbyte !get 3-byte length
367	*/
368	ptr= fwa_msg + gh->ids_len;
369	gh->pds_ptr= (unsigned char )ptr; / mark PDS */
370	iskip= 0; gbyte(ptr ,(unsigned long *)&gh->pds_len,&iskip,24);
371	DPRINT0 (" pds length\n");
372	iskip= 87; gbyte(ptr ,(unsigned long)&gdsbmsflag, &iskip, 8);
373	DPRINT1 (" (%x hex) Gds/Bms flag\n", gdsbmsflag);
374	/*
375	* A.3.3.10.a.3 IF (location of next Section is out of bound) THEN
376	* PRINT message;
377	* GOTO drop this msg;
378	* ENDIF
379	*/
380	ptr += gh->pds_len;
381	if (ptr > end_ptr) {
382	sprintf(errmsg,
383	"%s: corrupt PDSlen= %ld, Totlen=%ld, drop msg @%ld;\n"
384	, func, gh->pds_len, gh->msg_length, *offset);
385	gh->pds_len= 0; /* reset */
386	goto DROPMSG_N_LOOP;
387	}
388
389	/*
390	* IF (Debug) FUNCTION hdr_print !print PDS
391	*/
392	DPRINT1 ("gh->pds_len= %ld\n", gh->pds_len);
393	HDR_PRINT("Grib_Seek's PDS",gh->pds_ptr, gh->pds_len);
394
395	/*
396	* A.3.3.10.a.4 IF (GDS is present) THEN
397	* STORE location & len of GDS into Grib Hdr's Gds_Ptr
398	* FUNCTION gbyte !get 3-byte length
399	* IF (location of next Section is out of bound) THEN
400	* PRINT message;
401	* DROP this msg & try to find another;
402	* ENDIF
403	* IF (Debug) FUNCTION hdr_print !print GDS
404	* ENDIF
405	*/
406	bit_set= gdsbmsflag >> 7 & 1; /* mark GDS if present */
407	if (bit_set) {
408	gh->gds_ptr= (unsigned char *)ptr;
409	iskip= 0; gbyte(ptr,(unsigned long*)&gh->gds_len,&iskip,24);
410	DPRINT0 (" Gds length\n");
411	ptr += gh->gds_len; /* bump PTR to sect*/
412	if (ptr > end_ptr) {
413	sprintf(errmsg,
414	"%s: corrupt GDSlen= %ld, Totlen=%ld, drop msg @%ld\n"
415	, func, gh->gds_len, gh->msg_length, *offset);
416	gh->gds_len= 0; /* reset */
417	goto DROPMSG_N_LOOP;
418	}
419	DPRINT1 ("gh->gds_len= %ld\n", gh->gds_len);
420	HDR_PRINT("Grib_Seek's GDS",gh->gds_ptr,gh->gds_len);
421	}
422
423	/*
424	* A.3.3.10.a.5 IF (BMS is present) THEN
425	* STORE location & len of BMS into Grib Hdr's Bms_Ptr
426	* FUNCTION gbyte !get 3-byte length
427	* IF (location of next Section is out of bound) THEN
428	* PRINT message;
429	* DROP this msg & try to find another;
430	* ENDIF
431	* IF (Debug) FUNCTION hdr_print !byte dump
432	* ENDIF
433	*/
434	bit_set= gdsbmsflag >> 6 & 1; /* mark BMS if present */
435	if (bit_set) {
436	gh->bms_ptr= (unsigned char *)ptr;
437	iskip= 0; gbyte(ptr,(unsigned long*)&gh->bms_len,&iskip,24);
438	DPRINT0 (" Bms length\n");
439
440	ptr += gh->bms_len; /* bump PTR to sect */
441	if (ptr > end_ptr) {
442	sprintf(errmsg,
443	"%s: corrupt BMSlen= %ld, Totlen=%ld, drop msg @%ld\n"
444	, func, gh->bms_len, gh->msg_length, *offset);
445	gh->bms_len= 0; /* reset */
446	goto DROPMSG_N_LOOP;
447	}
448	DPRINT1 ("gh->bms_len= %ld\n", gh->bms_len);
449	HDR_PRINT ("Grib_Seek's BMS", gh->bms_ptr,
450	(gh->bms_len>100? 100: gh->bms_len));
451	}
452	/*
453	* A.3.3.10.a.6 STORE location and length of BDS into Grib Hdr's Bds_Ptr
454	* FUNCTION gbyte !get 3-byte length
455	* IF (location of next Section is out of bound) THEN
456	* PRINT message;
457	* DROP this msg & try to find another;
458	* ENDIF
459	* IF (Debug) FUNCTION hdr_print !byte dump
460	*/
461
462	gh->bds_ptr= (unsigned char )ptr; / mark BDS */
463	iskip= 0; gbyte(ptr,(unsigned long*)&gh->bds_len,&iskip,24);
464	DPRINT0 (" Bds length\n");
465
466	ptr += gh->bds_len;
467	if (ptr > end_ptr) {
468	sprintf(errmsg,
469	"%s: corrupt BDSlen= %ld, Totlen=%ld, drop msg @%ld\n"
470	, func, gh->gds_len, gh->msg_length, *offset);
471	gh->gds_len= 0; /* reset */
472	goto DROPMSG_N_LOOP;
473	}
474	DPRINT1 ("gh->bds_len= %ld\n", gh->bds_len);
475	HDR_PRINT ("Grib_Seek's BDS", gh->bds_ptr,
476	(gh->bds_len>100? 100: gh->bds_len));
477
478	/*
479	* A.3.3.10.a.7 STORE location & len of EDS into Grib Hdr's Eds_Ptr
480	*/
481	gh->eds_ptr= (unsigned char )ptr; / mark EDS */
482	gh->eds_len= 4;
483
484	/*
485	* A.3.3.10.a.8 SET 'gotone' flag
486	* ! Return with Msg in Grib hdr, and good stat
487	*/
488	gotone=1; /* to get out of FOR loop */
489	status=0; /* Return with Msg , good stat */
490	goto DONE;
491	/*
492	* A.3.3.10 ENDIF
493	*/
494	} /* saw 77s */
495	else
496	if (Read_Index) {
497	sprintf(errmsg,
498	"%s: no 7777 found for msg at %ld, check indexfile\n",
499	func, *offset);
500	}
501
502	/*
503	*
504	* !====================================================
505	* ! Drop Msg Area: Only get here if :
506	* ! - first G found not at Indexfile's offset;
507	* ! - no RIB after G;
508	* ! - GRIB string found not at Indexfile's offset;
509	* ! - no 7777 at expected offset;
510	* ! - got Corrupted Length;
511	* !====================================================
512	*/
513	DROPMSG_N_LOOP:
514	/* ERRMSG must already be loaded and the corrupted len reset to 0
515	so that Display GH won't go out of bound...
516	*/
517	DPRINT1 ("\nDropping, cause=> %s\n", errmsg);
518
519	/*
520	* A.3.3.11 IF (Debug mode) THEN
521	* FUNCTION display_gribhdr !show what got loaded sofar
522	* ENDIF
523	*/
524	if (gh->msg_length > 0)
525	DISPLAY_GRIBHDR(gh); /* before dropping msg*/
526
527	/*
528	* ! no message found yet, OR Msg Section lens are corrupted
529	* A.3.3.12 CLEAR out header struct !data in array is not valid
530	*/
531	gh->msg_length =0;
532	gh->ids_ptr=gh->pds_ptr= gh->eds_ptr=0;
533	gh->gds_ptr=gh->bms_ptr=gh->bds_ptr= 0;
534	memset ((void *)gh->entire_msg, '\0', gh->abs_size);
535
536	/*
537	* A.3.3.13 IF (Offset was read from Indexfile) !quit searching
538	* A.3.3.13.a THEN
539	* PUT Error msg in buffer
540	* RETURN with No Error status
541	* A.3.3.13.b ELSE
542	* CLEAR out 'G' in tmp block !go find next 'G'
543	* ENDIF
544	*/
545	if (Read_Index) {
546	status = 0; /* Ret w/ no errors */
547	goto DONE; /* send CAUSE back in Errmsg */
548	}
549	else {
550	GG='-'; / let Memchr find next 'G' in curr. block */
551	DPRINT1 ("'GRIB' at location %ld is not a valid message\n",
552	bytenum+pos);
553	errmsg[0]='\0'; /* clear out buff */
554	}
555	/*
556	* A.3.3 ENDWHILE
557	*/
558	} /* WHILE seeing 'G'*/
559
560
561	if (Read_Index) { /* Catch 3 cases:
562	- if no 'G' at all ;
563	- if no RIB after G ;
564	- if found GRIB but not at expected place
565	*/
566	sprintf(errmsg,
567	"%s: No Grib Msg found at IndexFile's offset = %ld; "\
568	" Check Index File\n" , func, *offset);
569	status = 0; /* Return w/no errors */
570	goto DONE; /* but w/ Warn Msg in buff*/
571	}
572
573	/*
574	A.3.4 DEBUG print !no Sect0 found in this block
575	*/
576	DPRINT2 ("No Section 0 found between address %ld and %ld\n",
577	pos, pos+check_limit);
578	/*
579	*
580	* A.3 ENDFOR !Outer Loop, stay until Status changes
581	*/
582	} /* check entire file */
583
584
585
586	DONE:
587
588	/*
589	*
590	* A.5 IF (found a msg) THEN
591	* BUMP caller's Offset to absolute Begining of Msg found;
592	* DEBUG Print
593	* ENDIF
594	*/
595	if (gotone)
596	{
597	offset = (long)(pos+bytenum); / bump offset to abs. beg. of Msg */
598	DPRINT3 ("Exiting %s w/stat=%d, offs=%d, msg in GRIB_HDR\n",
599	func, status, *offset);
600	}
601	else DPRINT2 ("Exiting %s w/stat=%d, no messages\n", func, status);
602
603	/*
604	* A.6 RETURN with status
605	*/
606	return (status);
607	/*
608	*
609	* END OF FUNCTION
610	*
611	*/
612	}

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source: trunk/WRF.COMMON/WRFV2/external/io_grib1/MEL_grib1/grib_seek.c

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