| 1 | C----------------------------------------------------------------------- |
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| 2 | SUBROUTINE SKGB(LUGB,ISEEK,MSEEK,LSKIP,LGRIB) |
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| 3 | C$$$ SUBPROGRAM DOCUMENTATION BLOCK |
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| 4 | C |
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| 5 | C SUBPROGRAM: SKGB SEARCH FOR NEXT GRIB MESSAGE |
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| 6 | C PRGMMR: IREDELL ORG: W/NMC23 DATE: 93-11-22 |
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| 7 | C |
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| 8 | C ABSTRACT: THIS SUBPROGRAM SEARCHES A FILE FOR THE NEXT GRIB 1 MESSAGE. |
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| 9 | C A GRIB 1 MESSAGE IS IDENTIFIED BY ITS INDICATOR SECTION, I.E. |
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| 10 | C AN 8-BYTE SEQUENCE WITH 'GRIB' IN BYTES 1-4 AND 1 IN BYTE 8. |
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| 11 | C IF FOUND, THE LENGTH OF THE MESSAGE IS DECODED FROM BYTES 5-7. |
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| 12 | C THE SEARCH IS DONE OVER A GIVEN SECTION OF THE FILE. |
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| 13 | C THE SEARCH IS TERMINATED IF AN EOF OR I/O ERROR IS ENCOUNTERED. |
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| 14 | C |
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| 15 | C PROGRAM HISTORY LOG: |
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| 16 | C 93-11-22 IREDELL |
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| 17 | C 95-10-31 IREDELL ADD CALL TO BAREAD |
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| 18 | C 97-03-14 IREDELL CHECK FOR '7777' |
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| 19 | C 2001-12-05 GILBERT MODIFIED TO ALSO LOOK FOR GRIB2 MESSAGES |
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| 20 | C |
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| 21 | C USAGE: CALL SKGB(LUGB,ISEEK,MSEEK,LSKIP,LGRIB) |
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| 22 | C INPUT ARGUMENTS: |
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| 23 | C LUGB INTEGER LOGICAL UNIT OF INPUT GRIB FILE |
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| 24 | C ISEEK INTEGER NUMBER OF BYTES TO SKIP BEFORE SEARCH |
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| 25 | C MSEEK INTEGER MAXIMUM NUMBER OF BYTES TO SEARCH |
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| 26 | C OUTPUT ARGUMENTS: |
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| 27 | C LSKIP INTEGER NUMBER OF BYTES TO SKIP BEFORE MESSAGE |
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| 28 | C LGRIB INTEGER NUMBER OF BYTES IN MESSAGE (0 IF NOT FOUND) |
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| 29 | C |
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| 30 | C SUBPROGRAMS CALLED: |
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| 31 | C BAREAD BYTE-ADDRESSABLE READ |
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| 32 | C G2LIB_GBYTE GET INTEGER DATA FROM BYTES |
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| 33 | C |
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| 34 | C ATTRIBUTES: |
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| 35 | C LANGUAGE: FORTRAN |
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| 36 | C |
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| 37 | C$$$ |
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| 38 | PARAMETER(LSEEK=128) |
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| 39 | CHARACTER Z(LSEEK) |
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| 40 | CHARACTER Z4(4) |
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| 41 | C - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - |
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| 42 | LGRIB=0 |
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| 43 | KS=ISEEK |
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| 44 | KN=MIN(LSEEK,MSEEK) |
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| 45 | KZ=LSEEK |
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| 46 | C - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - |
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| 47 | C LOOP UNTIL GRIB MESSAGE IS FOUND |
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| 48 | DOWHILE(LGRIB.EQ.0.AND.KN.GE.8.AND.KZ.EQ.LSEEK) |
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| 49 | C READ PARTIAL SECTION |
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| 50 | CALL BAREAD(LUGB,KS,KN,KZ,Z) |
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| 51 | KM=KZ-8+1 |
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| 52 | K=0 |
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| 53 | C LOOK FOR 'GRIB...1' IN PARTIAL SECTION |
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| 54 | DOWHILE(LGRIB.EQ.0.AND.K.LT.KM) |
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| 55 | CALL G2LIB_GBYTE(Z,I4,(K+0)*8,4*8) |
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| 56 | CALL G2LIB_GBYTE(Z,I1,(K+7)*8,1*8) |
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| 57 | IF(I4.EQ.1196575042.AND.(I1.EQ.1.OR.I1.EQ.2)) THEN |
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| 58 | C LOOK FOR '7777' AT END OF GRIB MESSAGE |
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| 59 | IF (I1.EQ.1) CALL G2LIB_GBYTE(Z,KG,(K+4)*8,3*8) |
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| 60 | IF (I1.EQ.2) CALL G2LIB_GBYTE(Z,KG,(K+12)*8,4*8) |
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| 61 | CALL BAREAD(LUGB,KS+K+KG-4,4,K4,Z4) |
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| 62 | IF(K4.EQ.4) THEN |
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| 63 | CALL G2LIB_GBYTE(Z4,I4,0,4*8) |
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| 64 | IF(I4.EQ.926365495) THEN |
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| 65 | C GRIB MESSAGE FOUND |
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| 66 | LSKIP=KS+K |
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| 67 | LGRIB=KG |
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| 68 | ENDIF |
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| 69 | ENDIF |
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| 70 | ENDIF |
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| 71 | K=K+1 |
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| 72 | ENDDO |
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| 73 | KS=KS+KM |
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| 74 | KN=MIN(LSEEK,ISEEK+MSEEK-KS) |
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| 75 | ENDDO |
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| 76 | C - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - |
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| 77 | RETURN |
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| 78 | END |
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