/* File: grib_seek.c based on Decoder's trqgetmsg() func;
Revised by:
28oct96 Alice T. Nakajima (ATN), SAIC, Monterey
18jun97 ATN check Edition before reading in entire msg;
27aug97 ATN *SEEK_SET to 0 (gcc complains)
20Oct97 ATN print #bytes read when fread fails;
03nov97 ATN -Realloc
22oct98 ATN *error msg;
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include "dprints.h" /* for dprints */
#include "gribfuncs.h" /* prototypes */
/*
**********************************************************************
* A. FUNCTION: grib_seek
* search the input file starting at the given offset for a GRIB
* message. If found, return it in GRIB_HDR structure.
*
* INTERFACE:
* int grib_seek (InFile, offset, Read_Index, gh, errmsg)
*
* ARGUMENTS (I=input, O=output, I&O=input and output):
* (I) char *InFile;
* name of input file to search for message;
* (I&O) long *offset;
* number of bytes to skip from the beginning of file;
* gets updated upon leaving to absolute #bytes from beginning of
* file to beginning of message found;
* (I) int Read_Index;
* if set, only proceed if 'GRIB' starts exactly at the given
* byte offset;
* (O) GRIB_HDR *gh;
* empty upon entry; to hold the Message found and its info;
* (O) char *errmsg;
* empty array, only filled if error occurred;
*
* RETURN CODE:
* 0> no errors, may or may not have a valid message;
* If no Msg was Found:
* a) errmsg will hold the Warning msg;
* If a valid Msg was Found:
* a) long *offset: if succesful, gets updated to absolute
* beginning of Mesg;
* b) struct GRIB_HDR holds its info:
* entire_msg: is assigned to newly MAlloced
* unsigned char * array to hold entire message;
* msg_length: size of entire_msg array in bytes;
* ids_len, pds_len, gds_len, bms_len, bds_len, eds_len:
* size of each defined sections in bytes;
* ids_ptr: pts to message's Ident Data Sect;
* pds_ptr: pts to message's Prod Defn Sect;
* gds_ptr: pts to message's Grid Defn Sect;
* bms_ptr: pts to message's Bitmap Defn Sect;
* bds_ptr: pts to message's Binary Data Sect;
* eds_ptr: pts to message's End Data Sect;
* c) errmsg remains empty;
* 1> fseek/fread error, all ptrs in grib_hdr set to null; errmsg filled;
* 2> got end of file, all ptrs in grib_hdr set to null; errmsg filled;
* 3> Null entire_msg pointer; errmsg filled;
* 4> unable to open input file; errmsg filled;
*
**********************************************************************
*/
#if PROTOTYPE_NEEDED
int grib_seek ( char *InFile, long *offset, int Read_Index,
GRIB_HDR *gh, char *errmsg)
#else
int grib_seek (InFile, offset, Read_Index,gh,errmsg)
char *InFile;
long *offset;
int Read_Index;
GRIB_HDR *gh;
char *errmsg;
#endif
{
char *func="grib_seek";
FILE *fp=NULL;
int status=0;
DPRINT3 ("Entering %s\nfile=%s, offs=%ld \n", func, InFile, *offset);
/*
*
* A.2 OPEN Input file
* IF (fails) RETURN w/ error stat 4 !errmsg filled
*/
if ((fp = fopen (InFile, "rb")) == NULL) {
DPRINT2 ("%s: Cannot open input file %s\n", func,InFile );
sprintf (errmsg,"%s: Cannot open input file '%s'\n", func,InFile );
status = 4;
goto DONE;
}
status = grib_fseek(fp,offset,Read_Index,gh,errmsg);
DONE:
/*
*
* A.4 CLOSE input file; !get here when found no messages
*
*/
if (fp) fclose(fp);
/*
* A.6 RETURN with status
*/
return (status);
}
#if PROTOTYPE_NEEDED
int grib_fseek ( FILE *fp, long *offset, int Read_Index,
GRIB_HDR *gh, char *errmsg)
#else
int grib_fseek (fp, offset, Read_Index,gh,errmsg)
FILE *fp;
long *offset;
int Read_Index;
GRIB_HDR *gh;
char *errmsg;
#endif
{
char *func="grib_fseek";
char *GG, sm_blk[5004], *fwa_msg=NULL;
unsigned long lMessageSize;
unsigned long Edition;
long pos; /* current byte offs fr. beg. of file */
int bytenum; /* Index w/in sm_blk */
int bytestoread=5004; /* #bytes to read into sm_blk at a time */
int check_limit; /* #bytes in sm_blk to check */
int gotone = 0; /* set if found good msg */
int nread; /* #bytes got back from Read */
int status;
unsigned long iskip; /* for getbyte */
int gdsbmsflag, bit_set, sect_len; /* working vars */
char *ptr, *end_ptr;
DPRINT2 ("Entering %s\n, offs=%ld \n", func, *offset);
/*
* A.1 INIT variables
* !gh structure is cleared out
*/
if (gh->entire_msg==NULL) {
DPRINT1 ( "%s: expecting non-null Grib Hdr;\n",func);
sprintf(errmsg, "%s: expecting non-NULL Grib Hdr;\n",func);
status= 3;
goto DONE;
}
gh->msg_length = 0;
gh->ids_ptr=gh->pds_ptr= 0;
gh->gds_ptr=gh->bms_ptr=gh->bds_ptr=gh->eds_ptr=0;
memset ((void *)gh->entire_msg, '\0', gh->abs_size);
DPRINT2 ("gh= %ld, gh->entire_msg=%ld\n", gh, gh->entire_msg);
/*
*
* A.3 FOR (loop while no error) !read a block at a time
*/
for (status=0, pos= *offset, gotone= 0; status == 0; pos += check_limit)
{
/*
* A.3.1 IF (cannot SET file position to correct place)
* THEN
* SET Status to 1 !fseek err
* CONTINUE (Loop around to A.3)
* ENDIF
*/
if (fseek(fp, pos, 0)!=0) {
DPRINT2 ("%s: Got fseek error to pos= %ld\n",func, pos);
sprintf(errmsg,"%s: Got fseek error to pos= %ld\n",func,pos);
perror("");
status = 1;
goto DONE;
}
/*
* A.3.2 IF (read less than 40 bytes)
* THEN
* FILL error buffer
* RETURN status 2 !eof or <40 bytes left, errmsg filled
* ENDIF
*/
nread= fread (sm_blk,sizeof(char), bytestoread,fp);
if (nread <= 40)
{
if (nread<=4) {
DPRINT0 ("No bytes left to check for msg;\n");
/* Errmsg left blank cuz its just EOF */
}
else {
sprintf(errmsg,"%s: skip last %d bytes, too few for a Msg\n",
func, nread);
DPRINT1 ("Only read %d bytes, too few to check for msg;\n",nread);
}
status= 2;
goto DONE;
}
else check_limit= nread - 4;
/*
* ! search block for the next the 'G'
* ! load entire Msg if everything is ok;
* ! if No 'G' found, then quit right away if no 'G'
* ! if GRIB is not at absolute Offset address, quit too;
* !
* A.3.3 WHILE (there is another 'G' in this block) DO
*/
bytenum= 0;
while ((GG= (char *) memchr (sm_blk, 'G', check_limit)))
{
/*--- Saw 'G' ---*/
/*
* A.3.3.1 IF ('RIB' is not after 'G') THEN
* IF (Offset from Index file) THEN
* ABORT search; !Break out of loop
* ELSE
* CLEAR out the 'G' in temp block
* CONTINUE !Loop around to A.3.3
* ENDIF
* ENDIF
*/
if (strncmp(GG, "GRIB",4)) /* not 'RIB' after the 'G' */
if ( Read_Index)
break; /* Offset IS from Indexfile: Quit here */
else
{ /* offset is NOT fr. IndexFile: keep looping; */
*GG='-'; /* no RIB after G, clear it */
continue; /* let Memchr find next G in block */
}
/*--- Saw 'G R I B' ----*/
/*
* A.3.3.2 CALCULATE byte position within this block
* where this message begins
*/
bytenum = GG - sm_blk; /* byte pos w/in this block */
/*
* A.3.3.3 IF (offset is from Indexfile AND
* string GRIB found is not at Absolute IndexFile's offset)
* THEN abort search; ENDIF
*/
DPRINT1 ("Found string 'GRIB' at %ld\n", pos+bytenum);
if (Read_Index && *offset != (bytenum + pos)) {
sprintf(errmsg,
"%s: No Grib msg found at offset= %ld; check Index File\n",
func, *offset);
break; /* Abort here, Ret w/ no errros & no msg too */
}
/*--- Read Mesg Length, Edition ---*/
/*
* A.3.3.4 FUNCTION gbyte !extract lMessageSize
*/
iskip=32;
gbyte (sm_blk+bytenum ,&lMessageSize, &iskip,24);
DPRINT0 ("lMessageSize\n");
/*--- Make sure it's Edition 1 first ---*/
/*
* A.3.3.5 FUNCTION gbyte !extract Grib Edition Number
* IF (not edition 1) THEN
* CLEAR out the 'G' in temp block
* CONTINUE !Loop around to A.3.3
* ENDIF
*/
gbyte (sm_blk+bytenum, &Edition, &iskip, 8);
DPRINT0 ("Edition\n");
if (Edition != 1) {
DPRINT1 ("Edition (%d) is not 1, start over\n",
Edition);
*GG='-'; /* blank out G of current GRIB location found */
continue; /* let Memchr find next G in block */
}
/*
* A.3.3.6 IF (cannot MOVE ptr to start of the message) THEN
* RETURN status 1 !errmsg filled
* ENDIF
*/
if (fseek(fp, (long)(pos+bytenum), 0)!=0) {
DPRINT2 (
"%s: FSEEK error to pos+bytenum= %ld\n",
func, pos+bytenum);
sprintf(errmsg,
"%s: FSEEK error to pos+bytenum= %ld\n",
func, pos+bytenum);
status= 1;
goto DONE;
}
/*
* A.3.3.7 INIT all section length to zero
*/
gh->ids_len= gh->pds_len= gh->gds_len= 0;
gh->bds_len= gh->bms_len= gh->eds_len= 0;
/*
* A.3.3.8 EXPAND Entire_Msg array if it's smaller than msglen
* RETURN Malloc Err (stat=2) if fails !errmsg filled
*/
if (lMessageSize > gh->abs_size ) {
/* if (realloc((void *)gh->entire_msg, lMessageSize) == NULL) {..}
* gh->abs_size = lMessageSize;
*/
if (Expand_gribhdr (gh, lMessageSize, errmsg)) {
upd_child_errmsg (func, errmsg);
status = 1; /* to get out of Outer loop */
goto DONE;
}
DPRINT1 ("Expanded entire_msg to be %ld bytes long\n",
gh->abs_size);
} /* size changed */
/*--- READ ENTIRE MSG into GRIB HEADER's Entire_Msg ---*/
/*
*
* A.3.3.9 READ the entire message into Grib Hdr's Entire_Msg;
* IF (failed) THEN
* RETURN Fread error stat=1 !errmsg filled
* ENDIF
*/
fwa_msg = (char *)gh->entire_msg;
if ((nread=fread (fwa_msg, 1, lMessageSize, fp)) != lMessageSize)
{
DPRINT2 ( "%s: failed to Fread EntireMsg (sz=%ld)\n",
func, lMessageSize);
sprintf(errmsg,
"%s has truncated msg @offs=%ld (got %ld out of %ld bytes)\n",
func, *offset, nread, lMessageSize);
status= 1; /* to get out of Outer loop */
goto DONE; /* get out of WHILE */
}
/*--- if see '7777', asssign GH's pointers & len ---*/
/*
* A.3.3.10 IF ('7777' is where expected) THEN
*/
if (!strncmp((fwa_msg + lMessageSize - 4),"7777",4))
/* && fwa_msg[7]==1) */
{
end_ptr = fwa_msg + lMessageSize;
DPRINT0 ("Found string '7777' where expected\n");
gh->msg_length= lMessageSize;
/*
* A.3.3.10.a.1 STORE loc & len of section 0 into Grib Hdr;
*/
gh->ids_ptr= (unsigned char *)fwa_msg; /* mark sect 0 */
gh->ids_len= 8L;
/*
* A.3.3.10.a.2 STORE loc & len of PDS into Grib Hdr;
* FUNCTION gbyte !get 3-byte length
*/
ptr= fwa_msg + gh->ids_len;
gh->pds_ptr= (unsigned char *)ptr; /* mark PDS */
iskip= 0; gbyte(ptr ,(unsigned long *)&gh->pds_len,&iskip,24);
DPRINT0 (" pds length\n");
iskip= 8*7; gbyte(ptr ,(unsigned long*)&gdsbmsflag, &iskip, 8);
DPRINT1 (" (%x hex) Gds/Bms flag\n", gdsbmsflag);
/*
* A.3.3.10.a.3 IF (location of next Section is out of bound) THEN
* PRINT message;
* GOTO drop this msg;
* ENDIF
*/
ptr += gh->pds_len;
if (ptr > end_ptr) {
sprintf(errmsg,
"%s: corrupt PDSlen= %ld, Totlen=%ld, drop msg @%ld;\n"
, func, gh->pds_len, gh->msg_length, *offset);
gh->pds_len= 0; /* reset */
goto DROPMSG_N_LOOP;
}
/*
* IF (Debug) FUNCTION hdr_print !print PDS
*/
DPRINT1 ("gh->pds_len= %ld\n", gh->pds_len);
HDR_PRINT("Grib_Seek's PDS",gh->pds_ptr, gh->pds_len);
/*
* A.3.3.10.a.4 IF (GDS is present) THEN
* STORE location & len of GDS into Grib Hdr's Gds_Ptr
* FUNCTION gbyte !get 3-byte length
* IF (location of next Section is out of bound) THEN
* PRINT message;
* DROP this msg & try to find another;
* ENDIF
* IF (Debug) FUNCTION hdr_print !print GDS
* ENDIF
*/
bit_set= gdsbmsflag >> 7 & 1; /* mark GDS if present */
if (bit_set) {
gh->gds_ptr= (unsigned char *)ptr;
iskip= 0; gbyte(ptr,(unsigned long*)&gh->gds_len,&iskip,24);
DPRINT0 (" Gds length\n");
ptr += gh->gds_len; /* bump PTR to sect*/
if (ptr > end_ptr) {
sprintf(errmsg,
"%s: corrupt GDSlen= %ld, Totlen=%ld, drop msg @%ld\n"
, func, gh->gds_len, gh->msg_length, *offset);
gh->gds_len= 0; /* reset */
goto DROPMSG_N_LOOP;
}
DPRINT1 ("gh->gds_len= %ld\n", gh->gds_len);
HDR_PRINT("Grib_Seek's GDS",gh->gds_ptr,gh->gds_len);
}
/*
* A.3.3.10.a.5 IF (BMS is present) THEN
* STORE location & len of BMS into Grib Hdr's Bms_Ptr
* FUNCTION gbyte !get 3-byte length
* IF (location of next Section is out of bound) THEN
* PRINT message;
* DROP this msg & try to find another;
* ENDIF
* IF (Debug) FUNCTION hdr_print !byte dump
* ENDIF
*/
bit_set= gdsbmsflag >> 6 & 1; /* mark BMS if present */
if (bit_set) {
gh->bms_ptr= (unsigned char *)ptr;
iskip= 0; gbyte(ptr,(unsigned long*)&gh->bms_len,&iskip,24);
DPRINT0 (" Bms length\n");
ptr += gh->bms_len; /* bump PTR to sect */
if (ptr > end_ptr) {
sprintf(errmsg,
"%s: corrupt BMSlen= %ld, Totlen=%ld, drop msg @%ld\n"
, func, gh->bms_len, gh->msg_length, *offset);
gh->bms_len= 0; /* reset */
goto DROPMSG_N_LOOP;
}
DPRINT1 ("gh->bms_len= %ld\n", gh->bms_len);
HDR_PRINT ("Grib_Seek's BMS", gh->bms_ptr,
(gh->bms_len>100? 100: gh->bms_len));
}
/*
* A.3.3.10.a.6 STORE location and length of BDS into Grib Hdr's Bds_Ptr
* FUNCTION gbyte !get 3-byte length
* IF (location of next Section is out of bound) THEN
* PRINT message;
* DROP this msg & try to find another;
* ENDIF
* IF (Debug) FUNCTION hdr_print !byte dump
*/
gh->bds_ptr= (unsigned char *)ptr; /* mark BDS */
iskip= 0; gbyte(ptr,(unsigned long*)&gh->bds_len,&iskip,24);
DPRINT0 (" Bds length\n");
ptr += gh->bds_len;
if (ptr > end_ptr) {
sprintf(errmsg,
"%s: corrupt BDSlen= %ld, Totlen=%ld, drop msg @%ld\n"
, func, gh->gds_len, gh->msg_length, *offset);
gh->gds_len= 0; /* reset */
goto DROPMSG_N_LOOP;
}
DPRINT1 ("gh->bds_len= %ld\n", gh->bds_len);
HDR_PRINT ("Grib_Seek's BDS", gh->bds_ptr,
(gh->bds_len>100? 100: gh->bds_len));
/*
* A.3.3.10.a.7 STORE location & len of EDS into Grib Hdr's Eds_Ptr
*/
gh->eds_ptr= (unsigned char *)ptr; /* mark EDS */
gh->eds_len= 4;
/*
* A.3.3.10.a.8 SET 'gotone' flag
* ! Return with Msg in Grib hdr, and good stat
*/
gotone=1; /* to get out of FOR loop */
status=0; /* Return with Msg , good stat */
goto DONE;
/*
* A.3.3.10 ENDIF
*/
} /* saw 77s */
else
if (Read_Index) {
sprintf(errmsg,
"%s: no 7777 found for msg at %ld, check indexfile\n",
func, *offset);
}
/*
*
* !====================================================
* ! Drop Msg Area: Only get here if :
* ! - first G found not at Indexfile's offset;
* ! - no RIB after G;
* ! - GRIB string found not at Indexfile's offset;
* ! - no 7777 at expected offset;
* ! - got Corrupted Length;
* !====================================================
*/
DROPMSG_N_LOOP:
/* ERRMSG must already be loaded and the corrupted len reset to 0
so that Display GH won't go out of bound...
*/
DPRINT1 ("\nDropping, cause=> %s\n", errmsg);
/*
* A.3.3.11 IF (Debug mode) THEN
* FUNCTION display_gribhdr !show what got loaded sofar
* ENDIF
*/
if (gh->msg_length > 0)
DISPLAY_GRIBHDR(gh); /* before dropping msg*/
/*
* ! no message found yet, OR Msg Section lens are corrupted
* A.3.3.12 CLEAR out header struct !data in array is not valid
*/
gh->msg_length =0;
gh->ids_ptr=gh->pds_ptr= gh->eds_ptr=0;
gh->gds_ptr=gh->bms_ptr=gh->bds_ptr= 0;
memset ((void *)gh->entire_msg, '\0', gh->abs_size);
/*
* A.3.3.13 IF (Offset was read from Indexfile) !quit searching
* A.3.3.13.a THEN
* PUT Error msg in buffer
* RETURN with No Error status
* A.3.3.13.b ELSE
* CLEAR out 'G' in tmp block !go find next 'G'
* ENDIF
*/
if (Read_Index) {
status = 0; /* Ret w/ no errors */
goto DONE; /* send CAUSE back in Errmsg */
}
else {
*GG='-'; /* let Memchr find next 'G' in curr. block */
DPRINT1 ("'GRIB' at location %ld is not a valid message\n",
bytenum+pos);
errmsg[0]='\0'; /* clear out buff */
}
/*
* A.3.3 ENDWHILE
*/
} /* WHILE seeing 'G'*/
if (Read_Index) { /* Catch 3 cases:
- if no 'G' at all ;
- if no RIB after G ;
- if found GRIB but not at expected place
*/
sprintf(errmsg,
"%s: No Grib Msg found at IndexFile's offset = %ld; "\
" Check Index File\n" , func, *offset);
status = 0; /* Return w/no errors */
goto DONE; /* but w/ Warn Msg in buff*/
}
/*
A.3.4 DEBUG print !no Sect0 found in this block
*/
DPRINT2 ("No Section 0 found between address %ld and %ld\n",
pos, pos+check_limit);
/*
*
* A.3 ENDFOR !Outer Loop, stay until Status changes
*/
} /* check entire file */
DONE:
/*
*
* A.5 IF (found a msg) THEN
* BUMP caller's Offset to absolute Begining of Msg found;
* DEBUG Print
* ENDIF
*/
if (gotone)
{
*offset = (long)(pos+bytenum); /* bump offset to abs. beg. of Msg */
DPRINT3 ("Exiting %s w/stat=%d, offs=%d, msg in GRIB_HDR\n",
func, status, *offset);
}
else DPRINT2 ("Exiting %s w/stat=%d, no messages\n", func, status);
/*
* A.6 RETURN with status
*/
return (status);
/*
*
* END OF FUNCTION
*
*/
}