| dasrdc_c |
|
Table of contents
Procedure
dasrdc_c ( DAS, read data, character )
void dasrdc_c ( SpiceInt handle,
SpiceInt first,
SpiceInt last,
SpiceInt bpos,
SpiceInt epos,
SpiceInt datlen,
void * data )
AbstractRead character data from a range of DAS logical addresses. Required_ReadingDAS KeywordsARRAY ASSIGNMENT DAS FILES Brief_I/OVARIABLE 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
ParametersNone. 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.
FilesSee the description of the argument `handle' in -Detailed_Input. ParticularsDAS 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.
RestrictionsNone. Literature_ReferencesNone. Author_and_InstitutionJ. Diaz del Rio (ODC Space) Version-CSPICE Version 1.0.0, 19-MAY-2021 (JDR) Index_Entriesread character data from a DAS file |
Fri Dec 31 18:41:04 2021