| 1 | /* gribgetbms.c June 17, 1996 by Alice Nakajima, SAIC */ |
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| 2 | #include <stdio.h> |
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| 3 | #include <stdlib.h> |
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| 4 | #include <string.h> |
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| 5 | #include "dprints.h" /* for dprints */ |
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| 6 | #include "gribfuncs.h" /* prototypes */ |
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| 7 | |
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| 8 | /* |
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| 9 | * |
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| 10 | ************************************************************************ |
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| 11 | * A. FUNCTION: gribgetbms |
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| 12 | * decode the Bitmap Section from the provided pointer location |
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| 13 | * and store its info in the internal BMS structure. |
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| 14 | * Pre-defined Bitmap case is not supported. |
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| 15 | * |
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| 16 | * INTERFACE: |
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| 17 | * int gribgetbms ( curr_ptr, bms, gds_flag, ulGrid_size, errmsg) |
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| 18 | * |
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| 19 | * ARGUMENTS (I=input, O=output, I&O=input and output): |
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| 20 | * (I) char *curr_ptr; |
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| 21 | * pointer to location where Bitmap Section to decode is expected; |
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| 22 | * (O) BMS_INPUT *bms; |
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| 23 | * pointer to empty BMS structure; will hold decoded BMS info; |
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| 24 | * (I) int gds_flag; |
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| 25 | * flag set if GDS is present |
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| 26 | * (I) unsigned long ulGrid_size; |
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| 27 | * size of grid as in Binary Data Section struct |
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| 28 | * (O) char *errmsg |
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| 29 | * returned filled if error occurred; |
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| 30 | * |
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| 31 | * RETURN CODE: |
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| 32 | * 0> BMS info stored in BMS structure if not using pre-defined bitmap; |
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| 33 | * 1> error, corrupted bms; msg in errmsg; |
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| 34 | ************************************************************************ |
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| 35 | */ |
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| 36 | |
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| 37 | #if PROTOTYPE_NEEDED |
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| 38 | int gribgetbms ( char *curr_ptr, BMS_INPUT *bms, int gds_flag, |
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| 39 | unsigned long ulGrid_size, char *errmsg) |
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| 40 | #else |
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| 41 | int gribgetbms (curr_ptr, bms, gds_flag, ulGrid_size, errmsg) |
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| 42 | char *curr_ptr; |
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| 43 | BMS_INPUT *bms; |
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| 44 | int gds_flag; |
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| 45 | unsigned long ulGrid_size; |
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| 46 | char *errmsg; |
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| 47 | #endif |
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| 48 | { |
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| 49 | char *func= "gribgetbms"; |
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| 50 | char *pp; |
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| 51 | int totbits,val, bitpos,stopbit; /* tmp working vars */ |
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| 52 | unsigned long SectLength; /* message and section size */ |
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| 53 | unsigned long ulvar; /* tmp var */ |
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| 54 | unsigned long skip=0; |
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| 55 | |
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| 56 | /* |
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| 57 | * |
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| 58 | * A.0 INIT Status to no error |
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| 59 | */ |
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| 60 | int status=0; |
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| 61 | |
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| 62 | DPRINT0 ("Entering gribgetbms():\n"); |
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| 63 | /* |
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| 64 | * |
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| 65 | * A.1 FUNCTION gbyte !get bitmap length |
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| 66 | */ |
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| 67 | skip=0; |
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| 68 | gbyte(curr_ptr,(unsigned long *)&SectLength,&skip,24); |
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| 69 | DPRINT0 ("SectLength\n"); |
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| 70 | bms->uslength= (unsigned long) SectLength; |
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| 71 | |
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| 72 | /* |
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| 73 | * |
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| 74 | * A.2 FUNCTION gbyte !get number of unused bits |
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| 75 | */ |
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| 76 | gbyte(curr_ptr,&ulvar,&skip,8); |
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| 77 | DPRINT0 ("bms->usUnused_bits\n"); |
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| 78 | bms->usUnused_bits= (unsigned short) ulvar; |
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| 79 | |
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| 80 | /* |
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| 81 | * |
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| 82 | * A.3 FUNCTION gbyte !get bitmap id (non-zero for a pre-defined bitmap) |
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| 83 | */ |
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| 84 | gbyte(curr_ptr,&ulvar,&skip,16); |
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| 85 | DPRINT0 ("bms->usBMS_id\n"); |
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| 86 | bms->usBMS_id= (unsigned short) ulvar; |
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| 87 | |
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| 88 | /* |
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| 89 | * |
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| 90 | * A.4 IF (Bitmap follows) !not a predefined bitmap |
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| 91 | */ |
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| 92 | if ( bms->uslength > 6) /* Bitmap follows */ |
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| 93 | { |
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| 94 | |
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| 95 | /* |
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| 96 | * A.4.1 CALCULATE Num of bits in bitmap |
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| 97 | */ |
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| 98 | /* = (BMS length)*8 bits - 48 header bits - # of unsused bits */ |
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| 99 | totbits=SectLength*8 - 48 - bms->usUnused_bits; |
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| 100 | |
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| 101 | /* |
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| 102 | * A.4.2 IF (GDS is present AND |
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| 103 | * #bits differs from Grid Size) !Corrupted BMS |
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| 104 | * RETURN 1 |
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| 105 | * ENDIF |
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| 106 | */ |
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| 107 | if (gds_flag && totbits != ulGrid_size) { |
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| 108 | DPRINT3( "%s: corrupted BMS, gds_flag set but "\ |
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| 109 | "totbits %d != ulgrid_sz %d\n" |
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| 110 | , func, totbits, ulGrid_size); |
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| 111 | |
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| 112 | sprintf(errmsg, "%s: corrupted BMS, gds_flag set but "\ |
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| 113 | "totbits %d != ulgrid_sz %d\n" , func, totbits, ulGrid_size); |
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| 114 | status= (1); /* Corrupted BMS */ |
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| 115 | goto BYE; |
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| 116 | } |
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| 117 | |
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| 118 | /* |
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| 119 | * A.4.3 ASSIGN bitmap pointer to 6th byte of BMS |
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| 120 | */ |
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| 121 | bms->bit_map = curr_ptr + 6; |
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| 122 | pp= bms->bit_map; |
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| 123 | bms->ulbits_set= 0; |
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| 124 | /* |
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| 125 | * |
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| 126 | * A.4.4 !SUM up total number of bits set |
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| 127 | * FOR (Each 8-bit block of Total Bits Present in BMS) |
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| 128 | */ |
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| 129 | for ( ; totbits > 0 ; totbits-=8) |
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| 130 | { |
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| 131 | /* |
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| 132 | * A.4.4.1 IF (any of the 8 bits are set) |
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| 133 | */ |
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| 134 | if ((val=(int)*pp++) != 0) |
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| 135 | { |
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| 136 | |
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| 137 | /* |
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| 138 | * A.4.4.1.1 IF (not within 8 bits of end of bitmap) |
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| 139 | * SET stopbit to 0 |
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| 140 | * ELSE |
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| 141 | * SET stopbit to end of bitmap |
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| 142 | * ENDIF |
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| 143 | */ |
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| 144 | if (totbits > 8) stopbit=0; /* check all 8 bits */ |
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| 145 | else stopbit= 7-totbits+1; /* stop at end of bitmap */ |
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| 146 | |
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| 147 | /* |
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| 148 | * A.4.4.1.2 SUM up number of bits set in this BMS byte |
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| 149 | */ |
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| 150 | for (bitpos= 7; bitpos >= stopbit; bitpos--) |
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| 151 | if (val >> bitpos & 0x0001) bms->ulbits_set += 1; |
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| 152 | /* |
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| 153 | * A.4.4.1 ENDIF ! any of 8 exists |
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| 154 | */ |
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| 155 | } |
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| 156 | /* |
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| 157 | * A.4.4 ENDFOR !each 8-bit loop |
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| 158 | */ |
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| 159 | } |
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| 160 | /* |
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| 161 | * A.4 ENDIF !Bitmap follows |
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| 162 | */ |
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| 163 | } |
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| 164 | |
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| 165 | /* else { |
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| 166 | / * Predefined Bitmap - not supported!! Could add function here |
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| 167 | to load a bitmap from local storage * / |
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| 168 | bms->uslength=6; |
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| 169 | bms->bit_map= Load_predefined_bms (bms->usBMS_id); |
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| 170 | } |
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| 171 | */ |
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| 172 | |
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| 173 | |
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| 174 | BYE: |
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| 175 | /* |
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| 176 | * |
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| 177 | * A.5 DEBUG Print |
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| 178 | * |
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| 179 | * A.6 RETURN Status |
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| 180 | */ |
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| 181 | DPRINT2 ("Exiting %s, Status=%d;\n", func, status); |
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| 182 | return (status); |
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| 183 | /* |
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| 184 | * END OF FUNCTION |
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| 185 | */ |
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| 186 | } |
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