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Index Page dasrdc_c

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Procedure Abstract Required_Reading Keywords Brief_I/O Detailed_Input | Detailed_Output Parameters Exceptions Files Particulars Examples | Restrictions Literature_References Author_and_Institution Version Index_Entries

#### Procedure

       dasrdc_c ( DAS, read data, character )

       void dasrdc_c ( SpiceInt            handle,
                       SpiceInt            first,
                       SpiceInt            last,
                       SpiceInt            bpos,
                       SpiceInt            epos,
                       SpiceInt            datlen,
                       void              * data   )

#### Abstract

       Read character data from a range of DAS logical addresses.

#### Required_Reading

       DAS

#### Keywords

       ARRAY
       ASSIGNMENT
       DAS
       FILES

#### Brief_I/O

       VARIABLE  I/O  DESCRIPTION
       --------  ---  --------------------------------------------------
       handle     I   DAS file handle.
       first,
       last       I   Range of DAS character logical addresses.
       bpos,
       epos       I   Begin and end positions of substrings.
       datlen     I   Common length of the character arrays in `data'.
       data       O   Data having addresses `first' through `last'.

#### Detailed_Input

       handle      is a file handle for an open DAS file.

       first,
       last        are a range of DAS character logical addresses.
                   `first' and `last' must be greater than or equal to
                   1 and less than or equal to the highest character
                   logical address in the DAS file designated by
                   `handle'.

       bpos,
       epos        are begin and end character positions that define
                   the substrings of the elements of the output array
                   `data' into which character data is to be read.

       datlen      is the common length of the character arrays in `data'.

#### Detailed_Output

       data        is two-dimensional character array. On output, the character
                   words in the logical address range `first' through `last' are
                   copied into the characters

                      data[0][bpos],
                      data[0][bpos+1],
                                  .
                                  .
                                  .
                      data[0][epos],
                      data[1][bpos],
                      data[1][bpos+1],
                                  .
                                  .
                                  .
                      data[r-1][bpos]
                      data[r-1][bpos+1]
                                  .
                                  .
                                  .

                   in that order. Note that the character positions of `data'
                   **other** than the ones shown in the diagram remain
                   unmodified.

                   `data' must be declared at least as

                      SpiceChar            data   [r][epos+1]

                   with the dimension `r' being at least

                      r = int( ( last - first + sublen ) / sublen )

                   and `sublen', the length of each of the substrings read
                   into the array elements from the DAS file, being

                      sublen  =  epos - bpos + 1

#### Parameters

       None.

#### Exceptions

       1)  If the input file handle is invalid, an error is signaled
           by a routine in the call tree of this routine. `data' will
           not be modified.

       2)  If `epos' or `bpos' are outside of the range

              [  0,  datlen-1 ]

           or if epos < bpos, the error SPICE(BADSUBSTRINGBOUNDS) is
           signaled by a routine in the call tree of this routine.

       3)  If `first' or `last' are out of range, an error is signaled by a
           routine in the call tree of this routine. `data' will not be
           modified.

       4)  If `first' is greater than `last', `data' is left unchanged.

       5)  If `data' is declared with an `r' dimension of less than

              ( last - first + ( epos-bpos+1 )  ) / ( epos-bpos+1 )

           the error cannot be diagnosed by this routine.

       6)  If the `data' output string pointer is null, the error
           SPICE(NULLPOINTER) is signaled.

       7)  If the `data' output string has length less than one character,
           the error SPICE(NOROOMFORDATA) is signaled.

#### Files

       See the description of the argument `handle' in -Detailed_Input.

#### Particulars

       DAS is a low-level format meant to store and transmit data. As
       such, character data in DAS files are not interpreted by CSPICE
       DAS input or output routines. There are no limits on which
       character values may be placed in the virtual character array of a
       DAS file.

       This routine provides random read access to the character data in
       a DAS file. These data are logically structured as a
       one-dimensional array of characters.

       However, the interface of this routine provides for extraction of data
       from a DAS file into a two-dimensional array of characters.

       dasrdc_c allows the caller to control the amount of character data
       read into each array element. This feature allows a program to
       read character data into an array that has a different string
       length from the one used to write the character data, without
       losing the correspondence between input and output array elements.
       For example, an array of strings of 32 characters can be written
       to a DAS file and read back by dasrdc_c into a buffer of strings
       having length 80 characters, mapping each 32-character string to
       characters 1--32 of the output buffer.

#### Examples

       The numerical results shown for this example may differ across
       platforms. The results depend on the SPICE kernels used as
       input, the compiler and supporting libraries, and the machine
       specific arithmetic implementation.

       1) The following example demonstrates the capabilities of the
          DAS character data routines. The reader should notice that
          in these interfaces, the character data are treated not as
          strings (or arrays of strings) but as a stream of single
          characters: DAS character data are not limited to
          human-readable text. For example, one can store images or
          DEM data as DAS character data.

          The example shows how to add a variable amount of character
          data to a new DAS file, how to update some of the character
          logical addresses within that file, and how to read that
          data out to a different array.

          Example code begins here.

          /.
             Program dasrdc_ex1
          ./
          #include <stdio.h>
          #include <string.h>
          #include "SpiceUsr.h"

          int main( )
          {

             /.
             Local parameters.
             ./
             #define FNAME        "dasrdc_ex1.das"
             #define TYPE         "TEST"

             /.
             Local variables.
             ./
             SpiceChar            cdatin [3][22];
             SpiceInt             handle;
             SpiceInt             i;

             SpiceChar            cdastr [31];
             SpiceChar            cdatou [10][30] = {
                                               "..............................",
                                               "..............................",
                                               "..............................",
                                               "..............................",
                                               "..............................",
                                               "..............................",
                                               "..............................",
                                               "..............................",
                                               "         1         2         3",
                                               "123456789012345678901234567890" };

             /.
             Open a new DAS file. Use the file name as the internal
             file name, and reserve no records for comments.
             ./
             dasonw_c ( FNAME, TYPE, FNAME, 0, &handle );

             /.
             Set the input data. Note that these data will be
             considered as a binary data stream: DAS character data
             are not limited to human-readable text. For example,
             one can store images or DEM data as DAS character data.
             ./
             strncpy( cdatin[0], "--F-345678901234567890", 22 );
             strncpy( cdatin[1], "--S-345678901234567890", 22 );
             strncpy( cdatin[2], "--T-IRDxxxxxxxxxxxxxxx", 22 );

             /.
             Add the last 20 characters of the first two elements
             of `cdatin', and the 3rd character from the third one.
             ./
             dasadc_c ( handle, 41, 2, 21, 22, cdatin );

             /.
             Update the 10th, 20th and 30th character in the DAS
             file with a vertical bar.
             ./
             for ( i = 1; i < 4; i++ )
             {
                dasudc_c ( handle, i*10, i*10, 0, 0, 1, "|" );
             }

             /.
             Close the file.
             ./
             dascls_c ( handle );

             /.
             Now verify the addition of data by opening the
             file for read access and retrieving the data.
             ./
             dasopr_c ( FNAME, &handle );

             /.
             Read the 41 characters that we stored on the DAS
             file. Update the data on the `cdatou' array, placing
             6 characters on each element, starting from the
             10th position.
             ./
             dasrdc_c ( handle, 1, 41, 9, 14, 30, cdatou );

             /.
             Dump the data to the screen. Note that the last
             three lines should remain unmodified, and that
             only 5 characters will be written on the 7th line.
             ./
             printf( "\n" );
             printf( "Data from \"%s\":\n", FNAME );
             printf( "\n" );

             for ( i = 0; i < 10; i++ )
             {

                /.
                Add null-terminating character to `cdatou[i]' in order to
                print it to the screen.
                ./
                strncpy( cdastr, cdatou[i], 30 );
                cdastr[30] = '\0';

                printf( "%s\n", cdastr );
             }

             /.
             Close the file.
             ./
             dascls_c ( handle );

             return ( 0 );
          }

          When this program was executed on a Mac/Intel/cc/64-bit
          platform, the output was:

          Data from "dasrdc_ex1.das":

          .........F-3456...............
          .........789|12...............
          .........345678...............
          .........9|S-34...............
          .........56789|...............
          .........123456...............
          .........7890T................
          ..............................
                   1         2         3
          123456789012345678901234567890

          Note that after run completion, a new DAS file exists in the
          output directory.

#### Restrictions

       None.

#### Literature_References

       None.

#### Author_and_Institution

       J. Diaz del Rio     (ODC Space)

#### Version

       -CSPICE Version 1.0.0, 19-MAY-2021 (JDR)

#### Index_Entries

       read character data from a DAS file

#### Link to routine dasrdc_c source file dasrdc_c.c

    Fri Dec 31 18:41:04 2021