dted_api.c

把dem文件转换为dted格式文件的程序

                memcpy( panData + i, pabyRecord + 8+i*2, 2 );
                panData[i] = CPL_MSBWORD16( panData[i] );

                if( !bWarned )
                {
                    bWarned = TRUE;
                    CPLError( CE_Warning, CPLE_AppDefined,
                              "The DTED driver found values less than -16000, and has adjusted\n"
                              "them assuming they are improperly two-complemented.  No more warnings\n"
                              "will be issued in this session about this operation." );
                }
            }
        }
    }

    CPLFree( pabyRecord );

    return TRUE;
}

/************************************************************************/
/*                          DTEDWriteProfile()                          */
/************************************************************************/

int DTEDWriteProfile( DTEDInfo * psDInfo, int nColumnOffset,
                     GInt16 * panData )

{
    int         nOffset;
    int         i, nCheckSum = 0;
    GByte       *pabyRecord;

/* -------------------------------------------------------------------- */
/*      Format the data record.                                         */
/* -------------------------------------------------------------------- */
    pabyRecord = (GByte *) CPLMalloc(12 + psDInfo->nYSize*2);
    
    for( i = 0; i < psDInfo->nYSize; i++ )
    {
        int     nABSVal = ABS(panData[psDInfo->nYSize-i-1]);
        pabyRecord[8+i*2] = (GByte) ((nABSVal >> 8) & 0x7f);
        pabyRecord[8+i*2+1] = (GByte) (nABSVal & 0xff);

        if( panData[psDInfo->nYSize-i-1] < 0 )
            pabyRecord[8+i*2] |= 0x80;
    }

    pabyRecord[0] = 0xaa;
    pabyRecord[1] = 0;
    pabyRecord[2] = (GByte) (nColumnOffset / 256);
    pabyRecord[3] = (GByte) (nColumnOffset % 256);
    pabyRecord[4] = (GByte) (nColumnOffset / 256);
    pabyRecord[5] = (GByte) (nColumnOffset % 256);
    pabyRecord[6] = 0;
    pabyRecord[7] = 0;

/* -------------------------------------------------------------------- */
/*      Compute the checksum.                                           */
/* -------------------------------------------------------------------- */
    for( i = 0; i < psDInfo->nYSize*2 + 8; i++ )
        nCheckSum += pabyRecord[i];

    pabyRecord[8+psDInfo->nYSize*2+0] = (GByte) ((nCheckSum >> 24) & 0xff);
    pabyRecord[8+psDInfo->nYSize*2+1] = (GByte) ((nCheckSum >> 16) & 0xff);
    pabyRecord[8+psDInfo->nYSize*2+2] = (GByte) ((nCheckSum >> 8) & 0xff);
    pabyRecord[8+psDInfo->nYSize*2+3] = (GByte) (nCheckSum & 0xff);

/* -------------------------------------------------------------------- */
/*      Write the record.                                               */
/* -------------------------------------------------------------------- */
    nOffset = psDInfo->nDataOffset + nColumnOffset * (12+psDInfo->nYSize*2);

    if( VSIFSeek( psDInfo->fp, nOffset, SEEK_SET ) != 0
        || VSIFWrite( pabyRecord,(12+psDInfo->nYSize*2),1,psDInfo->fp ) != 1)
    {
        CPLFree( pabyRecord );
#ifndef AVOID_CPL
        CPLError( CE_Failure, CPLE_FileIO,
#else
        fprintf( stderr, 
#endif
                  "Failed to seek to, or write profile %d at offset %d\n"
                  "in DTED file.\n",
                  nColumnOffset, nOffset );
        return FALSE;
    }

    CPLFree( pabyRecord );

    return TRUE;
    
}

/************************************************************************/
/*                      DTEDGetMetadataLocation()                       */
/************************************************************************/

static void DTEDGetMetadataLocation( DTEDInfo *psDInfo, 
                                     DTEDMetaDataCode eCode, 
                                     char **ppszLocation, int *pnLength )
{
    switch( eCode )
    {
      case DTEDMD_VERTACCURACY_UHL:
        *ppszLocation = psDInfo->pachUHLRecord + 28;
        *pnLength = 4;
        break;

      case DTEDMD_SECURITYCODE_UHL:
        *ppszLocation = psDInfo->pachUHLRecord + 32;
        *pnLength = 3;
        break;

      case DTEDMD_UNIQUEREF_UHL:
        *ppszLocation = psDInfo->pachUHLRecord + 35;
        *pnLength = 12;
        break;

      case DTEDMD_DATA_EDITION:
        *ppszLocation = psDInfo->pachDSIRecord + 87;
        *pnLength = 2;
        break;

      case DTEDMD_MATCHMERGE_VERSION:
        *ppszLocation = psDInfo->pachDSIRecord + 89;
        *pnLength = 1;
        break;

      case DTEDMD_MAINT_DATE:
        *ppszLocation = psDInfo->pachDSIRecord + 90;
        *pnLength = 4;
        break;

      case DTEDMD_MATCHMERGE_DATE:
        *ppszLocation = psDInfo->pachDSIRecord + 94;
        *pnLength = 4;
        break;

      case DTEDMD_MAINT_DESCRIPTION:
        *ppszLocation = psDInfo->pachDSIRecord + 98;
        *pnLength = 4;
        break;

      case DTEDMD_PRODUCER:
        *ppszLocation = psDInfo->pachDSIRecord + 102;
        *pnLength = 8;
        break;

      case DTEDMD_VERTDATUM:
        *ppszLocation = psDInfo->pachDSIRecord + 141;
        *pnLength = 3;
        break;

      case DTEDMD_DIGITIZING_SYS:
        *ppszLocation = psDInfo->pachDSIRecord + 149;
        *pnLength = 10;
        break;

      case DTEDMD_COMPILATION_DATE:
        *ppszLocation = psDInfo->pachDSIRecord + 159;
        *pnLength = 4;
        break;

      case DTEDMD_HORIZACCURACY:
        *ppszLocation = psDInfo->pachACCRecord + 3;
        *pnLength = 4;
        break;

      case DTEDMD_REL_HORIZACCURACY:
        *ppszLocation = psDInfo->pachACCRecord + 11;
        *pnLength = 4;
        break;

      case DTEDMD_REL_VERTACCURACY:
        *ppszLocation = psDInfo->pachACCRecord + 15;
        *pnLength = 4;
        break;

      case DTEDMD_VERTACCURACY_ACC:
        *ppszLocation = psDInfo->pachACCRecord + 7;
        *pnLength = 4;
        break;

      case DTEDMD_SECURITYCODE_DSI:
        *ppszLocation = psDInfo->pachDSIRecord + 3;
        *pnLength = 1;
        break;

      case DTEDMD_UNIQUEREF_DSI:
        *ppszLocation = psDInfo->pachDSIRecord + 64;
        *pnLength = 15;
        break;

      default:
        *ppszLocation = NULL;
        *pnLength = 0;
    }
}

/************************************************************************/
/*                          DTEDGetMetadata()                           */
/************************************************************************/

char *DTEDGetMetadata( DTEDInfo *psDInfo, DTEDMetaDataCode eCode )

{
    int nFieldLen;
    char *pszFieldSrc;
    char *pszResult;

    DTEDGetMetadataLocation( psDInfo, eCode, &pszFieldSrc, &nFieldLen );
    if( pszFieldSrc == NULL )
        return VSIStrdup( "" );

    pszResult = (char *) malloc(nFieldLen+1);
    strncpy( pszResult, pszFieldSrc, nFieldLen );
    pszResult[nFieldLen] = '\0';

    return pszResult;
}

/************************************************************************/
/*                          DTEDSetMetadata()                           */
/************************************************************************/

int DTEDSetMetadata( DTEDInfo *psDInfo, DTEDMetaDataCode eCode, 
                     const char *pszNewValue )

{
    int nFieldLen;
    char *pszFieldSrc;

    if( !psDInfo->bUpdate )
        return FALSE;

/* -------------------------------------------------------------------- */
/*      Get the location in the headers to update.                      */
/* -------------------------------------------------------------------- */
    DTEDGetMetadataLocation( psDInfo, eCode, &pszFieldSrc, &nFieldLen );
    if( pszFieldSrc == NULL )
        return FALSE;

/* -------------------------------------------------------------------- */
/*      Update it, padding with spaces.                                 */
/* -------------------------------------------------------------------- */
    memset( pszFieldSrc, ' ', nFieldLen );
    strncpy( pszFieldSrc, pszNewValue, 
             MIN(strlen(pszFieldSrc),strlen(pszNewValue)) );

/* -------------------------------------------------------------------- */
/*      Write all headers back to disk.                                 */
/* -------------------------------------------------------------------- */
    VSIFSeek( psDInfo->fp, psDInfo->nUHLOffset, SEEK_SET );
    VSIFWrite( psDInfo->pachUHLRecord, 1, DTED_UHL_SIZE, psDInfo->fp );

    VSIFSeek( psDInfo->fp, psDInfo->nDSIOffset, SEEK_SET );
    VSIFWrite( psDInfo->pachDSIRecord, 1, DTED_DSI_SIZE, psDInfo->fp );

    VSIFSeek( psDInfo->fp, psDInfo->nACCOffset, SEEK_SET );
    VSIFWrite( psDInfo->pachACCRecord, 1, DTED_ACC_SIZE, psDInfo->fp );

    return TRUE;
}

/************************************************************************/
/*                             DTEDClose()                              */
/************************************************************************/

void DTEDClose( DTEDInfo * psDInfo )

{
    VSIFClose( psDInfo->fp );

    CPLFree( psDInfo->pachUHLRecord );
    CPLFree( psDInfo->pachDSIRecord );
    CPLFree( psDInfo->pachACCRecord );
    
    CPLFree( psDInfo );
}