C++ DataSource::DataSourceUngetc方法代码示例

/*****************************************************************************
 * FindGRIBMsg() -- Review 12/2002
 *
 * Arthur Taylor / MDL
 *
 * PURPOSE
 *   Jumps through a GRIB2 file looking for a specific message.  Currently
 * that message is determined by msgNum which is in the range of 1..n.
 *   In the future we may be searching based on projection or date.
 *
 * ARGUMENTS
 *      fp = The current GRIB2 file to look through. (Input)
 *  msgNum = Which message to look for. (Input)
 *  offset = Where in the file the message starts (this is before the
 *           wmo ASCII part if there is one.) (Output)
 *  curMsg = The current # of messages we have looked through. (In/Out) 
 *
 * FILES/DATABASES:
 *   An already opened "GRIB2" File
 *
 * RETURNS: int (could use errSprintf())
 *  0 = OK
 * -1 = Problems reading Section 0.
 * -2 = Ran out of file.
 *
 * HISTORY
 *  11/2002 Arthur Taylor (MDL/RSIS): Created.
 *  12/2002 (TK,AC,TB,&MS): Code Review.
 *   6/2003 Matthew T. Kallio ([email protected]):
 *          "wmo" dimension increased to WMO_HEADER_LEN + 1 (for '\0' char)
 *   8/2003 AAT: Removed dependence on offset and fileLen.
 *
 * NOTES
 *****************************************************************************
 */
int FindGRIBMsg (DataSource &fp, int msgNum, sInt4 *offset, int *curMsg)
{
   int cnt;             /* The current message we are looking at. */
   char *buff;          /* Holds the info between records. */
   uInt4 buffLen;       /* Length of info between records. */
   sInt4 sect0[SECT0LEN_WORD]; /* Holds the current Section 0. */
   uInt4 gribLen;       /* Length of the current GRIB message. */
   int version;         /* Which version of GRIB is in this message. */
   int c;               /* Determine if end of the file without fileLen. */
   sInt4 jump;          /* How far to jump to get to past GRIB message. */

   cnt = *curMsg + 1;
   buff = NULL;
   buffLen = 0;
   while ((c = fp.DataSourceFgetc()) != EOF) {
      fp.DataSourceUngetc(c);
      if (cnt >= msgNum) {
         /* 12/1/2004 version 1.63 forgot to free buff */
         free (buff);
         *curMsg = cnt;
         return 0;
      }
      /* Read section 0 to find gribLen and wmoLen. */
      if (ReadSECT0 (fp, &buff, &buffLen, GRIB_LIMIT, sect0, &gribLen,
                     &version) < 0) {
         preErrSprintf ("Inside FindGRIBMsg\n");
         free (buff);
         return -1;
      }
      myAssert ((version == 1) || (version == 2) || (version == -1));
      /* Continue on to the next grib message. */
      if ((version == 1) || (version == -1)) {
         jump = gribLen - 8;
      } else {
         jump = gribLen - 16;
      }
      fp.DataSourceFseek(jump, SEEK_CUR);
      *offset = *offset + gribLen + buffLen;
      cnt++;
   }
   free (buff);
   *curMsg = cnt - 1;
   /* Return -2 since we reached the end of file. This may not be an error
    * (multiple file option). */
   return -2;
/*
   errSprintf ("ERROR: Ran out of file looking for msgNum %d.\n", msgNum);
   errSprintf ("       Current msgNum %d\n", cnt);
*/
}

/*****************************************************************************
 * GRIB2SectJump() --
 *
 * Arthur Taylor / MDL
 *
 * PURPOSE
 *    To jump past a GRIB2 section.  Reads in secLen and checks that the
 * section is valid.
 *
 * ARGUMENTS
 *      fp = Opened file pointing to the section in question. (Input/Output)
 * gribLen = The total length of the grib message. (Input)
 *    sect = Which section we think we are reading.
 *           If it is -1, then set it to the section the file says we are
 *           reading (useful for optional sect 2)) (Input/Output).
 *  secLen = The length of this section (Output)
 *
 * FILES/DATABASES:
 *    An already opened GRIB2 file pointer, already at section in question.
 *
 * RETURNS: int (could use errSprintf())
 *  0 = Ok.
 * -1 = Ran out of file.
 * -2 = Section was miss-labeled.
 *
 * HISTORY
 *   3/2003 Arthur Taylor (MDL/RSIS): Created.
 *   8/2003 AAT: Removed dependence on curTot, which was used to compute if
 *          the file should be large enough for the fseek, but didn't check
 *          if it actually was.
 *
 * NOTES
 *   May want to put this in degrib2.c
 *****************************************************************************
 */
static int GRIB2SectJump (DataSource &fp,
                          CPL_UNUSED sInt4 gribLen, sChar *sect, uInt4 *secLen)
{
   char sectNum;        /* Validates that we are on the correct section. */
   int c;               /* Check that the fseek is still inside the file. */

   if (FREAD_BIG (secLen, sizeof (sInt4), 1, fp) != 1) {
      if (*sect != -1) {
         errSprintf ("ERROR: Ran out of file in Section %d\n", *sect);
      } else {
         errSprintf ("ERROR: Ran out of file in GRIB2SectSkip\n");
      }
      return -1;
   }
   if (fp.DataSourceFread (&sectNum, sizeof (char), 1) != 1) {
      if (*sect != -1) {
         errSprintf ("ERROR: Ran out of file in Section %d\n", *sect);
      } else {
         errSprintf ("ERROR: Ran out of file in GRIB2SectSkip\n");
      }
      return -1;
   }
   if (*sect == -1) {
      *sect = sectNum;
   } else if (sectNum != *sect) {
       errSprintf ("ERROR: Section %d mislabeled\n", *sect);
       return -2;
   }
   /* Since fseek does not give an error if we jump outside the file, we test
    * it by using fgetc / ungetc. */
   fp.DataSourceFseek (*secLen - 5, SEEK_CUR);
   if ((c = fp.DataSourceFgetc()) == EOF) {
       errSprintf ("ERROR: Ran out of file in Section %d\n", *sect);
       return -1;
   } else {
       fp.DataSourceUngetc(c);
   }
   return 0;
}

//.........这里部分代码省略.........
   uChar prodType;      /* Which GRIB2 type of product, 0 is meteo, 1 is
                         * hydro, 2 is land, 3 is space, 10 is oceanographic. 
                         */
   int grib_limit;      /* How many bytes to look for before the first "GRIB" 
                         * in the file.  If not found, is not a GRIB file. */
   int c;               /* Determine if end of the file without fileLen. */
   sInt4 fileLen;       /* Length of the GRIB2 file. */
   unsigned short int center, subcenter; /* Who produced it. */
   // char *ptr;           /* used to find the file extension. */

   grib_limit = GRIB_LIMIT;
	 /*
   if (filename != NULL) {
      //if ((fp = fopen (filename, "rb")) == NULL) {
      //   errSprintf ("ERROR: Problems opening %s for read.", filename);
      //   return -1;
      //}
		  //fp = FileDataSource(filename);
      ptr = strrchr (filename, '.');
      if (ptr != NULL) {
         if (strcmp (ptr, ".tar") == 0) {
            grib_limit = 5000;
         }
      }
   } else {
      //fp = stdin; // TODO!!
   }
	 */
   msgNum = *MsgNum;

   buff = NULL;
   buffLen = 0;
   while ((c = fp.DataSourceFgetc()) != EOF) {
		 fp.DataSourceUngetc(c);
      // ungetc (c, fp);
      /* msgNum++ done first so any error messages range from 1..n, instead
       * of 0.. n-1. Note msgNum should end up as n not (n-1) */
      msgNum++;
/* Used when testing inventory of large TDLPack files. */
/*
#ifdef DEBUG
      myAssert (msgNum < 32500L);
      if (msgNum % 10 == 0) {
         printf ("%ld :: %f\n", msgNum, clock () / (double) CLOCKS_PER_SEC);
      }
#endif
*/
      /* Make it so the second, third, etc messages have no limit to finding
       * the "GRIB" keyword. */
      if (msgNum > 1) {
         grib_limit = -1;
      }
      /* Read in the wmo header and sect0. */
      if (ReadSECT0 (fp, &buff, &buffLen, grib_limit, sect0, &gribLen,
                     &version) < 0) {
         if (msgNum == 1) {
            /* Handle case where we couldn't find 'GRIB' in the message. */
            preErrSprintf ("Inside GRIB2Inventory, Message # %d\n", msgNum);
            free (buffer);
            free (buff);
            //fclose (fp);
            return -2;
         } else {
            /* Handle case where there are trailing bytes. */
            msg = errSprintf (NULL);
            printf ("Warning: Inside GRIB2Inventory, Message # %d\n",