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Diffstat (limited to 'mpi/mpi-scan.c')
| -rw-r--r-- | mpi/mpi-scan.c | 88 |
1 files changed, 88 insertions, 0 deletions
diff --git a/mpi/mpi-scan.c b/mpi/mpi-scan.c new file mode 100644 index 000000000..8626032a0 --- /dev/null +++ b/mpi/mpi-scan.c @@ -0,0 +1,88 @@ +/* mpi-scan.c - MPI functions + * Copyright (c) 1997 by Werner Koch (dd9jn) + * + * This file is part of G10. + * + * G10 is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * G10 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 General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA + */ + +#include <config.h> +#include <stdio.h> +#include <stdlib.h> +#include "mpi-internal.h" + +/**************** + * Scan through an mpi and return byte for byte. a -1 is returned to indicate + * the end of the mpi. Scanning is done from the lsb to the msb, returned + * values are in the range of 0 .. 255. + * + * FIXME: This code is VERY ugly! + */ +int +mpi_getbyte( MPI a, unsigned index ) +{ + int i, j; + unsigned n; + mpi_ptr_t ap; + mpi_limb_t limb; + + ap = a->d; + for(n=0,i=0; i < a->nlimbs; i++ ) { + limb = ap[i]; + for( j=0; j < BYTES_PER_MPI_LIMB; j++, n++ ) + if( n == index ) + return (limb >> j*8) & 0xff; + } + return -1; +} + + +/**************** + * Put a value at position INDEX into A. index counts from lsb to msb + */ +void +mpi_putbyte( MPI a, unsigned index, int c ) +{ + int i, j; + unsigned n; + mpi_ptr_t ap; + mpi_limb_t limb; + +#if BYTES_PER_MPI_LIMB != 4 + #error please enhance this function, its ugly - i know. +#endif + c &= 0xff; + ap = a->d; + for(n=0,i=0; i < a->alloced; i++ ) { + limb = ap[i]; + for( j=0; j < BYTES_PER_MPI_LIMB; j++, n++ ) + if( n == index ) { + if( j == 0 ) + limb = (limb & 0xffffff00) | c; + else if( j == 1 ) + limb = (limb & 0xffff00ff) | (c<<8); + else if( j == 2 ) + limb = (limb & 0xff00ffff) | (c<<16); + else + limb = (limb & 0x00ffffff) | (c<<24); + if( a->nlimbs <= i ) + a->nlimbs = i+1; + ap[i] = limb; + return; + } + } + abort(); /* index out of range */ +} + |