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// $Id: tai-utc-gen.c 11971 2011-10-14 09:28:58Z andrewross $
//
// Copyright (C) 2009 Alan W. Irwin
//
// This file is part of PLplot.
// PLplot is free software; you can redistribute it and/or modify
// it under the terms of the GNU Library General Public License as published
// by the Free Software Foundation; either version 2 of the License, or
// (at your option) any later version.
//
// PLplot is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Library General Public License for more details.
//
// You should have received a copy of the GNU Library General Public License
// along with PLplot; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
//
//
// Program for generating data structure used for containing tai-utc
// conversion information (linear transforms and leap seconds).
//
// The program assumes that argv[1] will be the input file, and
// argv[2] the output file. This works cross-platform without
// worrying about shell redirects of stdin and stdout that are
// not accessible on Windows, apparently.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
//--------------------------------------------------------------------------
// Function-like macro definitions
//--------------------------------------------------------------------------
#define MemError1( a ) do { fprintf( stderr, "MEMORY ERROR %d\n" a "\n", __LINE__ ); exit( __LINE__ ); } while ( 0 )
const char header[] = "" \
"/*\n" \
" This file is part of PLplot.\n" \
" \n" \
" PLplot is free software; you can redistribute it and/or modify\n" \
" it under the terms of the GNU Library General Public License as published\n" \
" by the Free Software Foundation; either version 2 of the License, or\n" \
" (at your option) any later version.\n" \
" \n" \
" PLplot is distributed in the hope that it will be useful,\n" \
" but WITHOUT ANY WARRANTY; without even the implied warranty of\n" \
" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the\n" \
" GNU Library General Public License for more details.\n" \
" \n" \
" You should have received a copy of the GNU Library General Public License\n" \
" along with PLplot; if not, write to the Free Software\n" \
" Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA\n" \
" \n" \
" \n" \
" This header file contains the table containing the linear transforms \n" \
" for converting between TAI and UTC.\n" \
" It is an automatically generated file, so please do\n" \
" not edit it directly. Make any changes to tai-utc.dat then use\n" \
" tai-utc-gen to recreate this header file.\n" \
" \n" \
" tai-utc.dat contains four essential fields to represent the following\n" \
" formula for the linear transformation between TAI and UTC: \n" \
" TAI-UTC (seconds) = offset1 + (MJD-offset2)*slope\n" \
" There are four essential fields per line in tai-utc.dat to represent\n" \
" this formula. They are the Julian date (UTC) where the linear\n" \
" transformation implied by the line is first applied;\n" \
" offset1 (seconds); offset2 (days), and slope (secs/day).\n" \
" \n" \
"*/";
int main( int argc, char *argv[] )
{
FILE *fr, *fw;
char readbuffer[256];
int *MJDstart = NULL;
double *offset1 = NULL;
int *offset2 = NULL;
double *slope = NULL;
double sec, *leap_sec = NULL;
int jd;
int i = 0;
int number_of_lines = 0;
if ( ( argc < 2 ) || ( fr = fopen( argv[1], "r" ) ) == NULL )
{
fprintf( stderr, "Cannot open first file as readable\n" );
exit( 1 );
}
if ( ( argc < 3 ) || ( fw = fopen( argv[2], "w" ) ) == NULL )
{
fprintf( stderr, "Cannot open second file as writable\n" );
exit( 1 );
}
//
// Work out how many lines we have all up
//
while ( ( fgets( readbuffer, 255, fr ) != NULL ) )
{
++number_of_lines;
}
//
// Allocate memory to the arrays which will hold the data
//
if ( ( MJDstart = (int *) calloc( (size_t) number_of_lines, (size_t) sizeof ( int ) ) ) == NULL )
MemError1( "Allocating memory to the MJDstart table" );
if ( ( offset1 = (double *) calloc( (size_t) number_of_lines, (size_t) sizeof ( double ) ) ) == NULL )
MemError1( "Allocating memory to the offset1 table" );
if ( ( offset2 = (int *) calloc( (size_t) number_of_lines, (size_t) sizeof ( int ) ) ) == NULL )
MemError1( "Allocating memory to the offset2 table" );
if ( ( slope = (double *) calloc( (size_t) number_of_lines, (size_t) sizeof ( double ) ) ) == NULL )
MemError1( "Allocating memory to the slope table" );
if ( ( leap_sec = (double *) calloc( (size_t) number_of_lines, (size_t) sizeof ( double ) ) ) == NULL )
MemError1( "Allocating memory to the leap_sec table" );
rewind( fr ); // Go back to the start of the file
//
// Read in line by line, and copy the numbers into our arrays
//
while ( ( fgets( readbuffer, 255, fr ) != NULL ) )
{
sscanf( readbuffer, "%*s %*s %*s %*s %d.5 %*s %lf %*s %*s %*s %*s %d.) X %lf S", (int *) &jd, (double *) &offset1[i], (int *) &offset2[i], (double *) &slope[i] );
// Should be exact since all jd's in the file are integer+0.5
MJDstart[i] = jd - 2400000;
i++;
}
fclose( fr );
//
// Write the data out to file ready to be included in our source
//
fprintf( fw, "%s\n", header );
fprintf( fw, "typedef struct {\n\tint base_day;\n\tdouble time_sec_tai;\n\tdouble time_sec_utc;\n\tdouble size_prev_leap_sec;\n\tdouble offset1;\n\tint offset2;\n\tdouble slope;\n} TAI_UTC;\n\n" );
fprintf( fw, "const int number_of_entries_in_tai_utc_table=%d;\n\n", number_of_lines );
fprintf( fw, "const TAI_UTC TAI_UTC_lookup_table[%d] = {\n", number_of_lines );
for ( i = 0; i < number_of_lines; i++ )
{
sec = offset1[i] + (double) ( MJDstart[i] - offset2[i] ) * slope[i];
if ( i == 0 )
leap_sec[i] = 0.;
else
// sec is TAI-UTC in seconds calculated from UTC transformation
// (equation 1 in README.tai-utc). This calculation must be correct
// for start of epoch range. However, near end of epoch range where
// ambiguities in UTC occur, must use equivalent TAI transformation
// (equation 2 from same source) to calculate the UTC discontinuity
// unambiguously.
leap_sec[i] = sec - ( offset1[i - 1] + (double) ( MJDstart[i] + sec / 86400. - offset2[i - 1] ) * slope[i - 1] ) / ( 1. + slope[i - 1] / 86400. );
if ( fabs( leap_sec[i] ) < 1.e-14 )
leap_sec[i] = 0.;
fprintf( fw, "{%d, %15.8f, 0., %20.14f, %15.8f, %d, %15.8f},\n", MJDstart[i], sec, leap_sec[i], offset1[i], offset2[i], slope[i] );
}
fprintf( fw, "};\n" );
fclose( fw );
free( MJDstart );
free( offset1 );
free( offset2 );
free( slope );
free( leap_sec );
return ( 0 );
}
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