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Diffstat (limited to 'ext/bcmath/libbcmath/src/doaddsub.c')
| -rw-r--r-- | ext/bcmath/libbcmath/src/doaddsub.c | 232 |
1 files changed, 232 insertions, 0 deletions
diff --git a/ext/bcmath/libbcmath/src/doaddsub.c b/ext/bcmath/libbcmath/src/doaddsub.c new file mode 100644 index 0000000..5458fc5 --- /dev/null +++ b/ext/bcmath/libbcmath/src/doaddsub.c @@ -0,0 +1,232 @@ +/* doaddsub.c: bcmath library file. */ +/* + Copyright (C) 1991, 1992, 1993, 1994, 1997 Free Software Foundation, Inc. + Copyright (C) 2000 Philip A. Nelson + + This library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2 of the License, or (at your option) any later version. + + This library 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 + Lesser General Public License for more details. (COPYING.LIB) + + You should have received a copy of the GNU Lesser General Public + License along with this library; if not, write to: + + The Free Software Foundation, Inc. + 59 Temple Place, Suite 330 + Boston, MA 02111-1307 USA. + + You may contact the author by: + e-mail: philnelson@acm.org + us-mail: Philip A. Nelson + Computer Science Department, 9062 + Western Washington University + Bellingham, WA 98226-9062 + +*************************************************************************/ + +#include <config.h> +#include <stdio.h> +#include <assert.h> +#include <stdlib.h> +#include <ctype.h> +#include <stdarg.h> +#include "bcmath.h" +#include "private.h" + + +/* Perform addition: N1 is added to N2 and the value is + returned. The signs of N1 and N2 are ignored. + SCALE_MIN is to set the minimum scale of the result. */ + + bc_num +_bc_do_add (n1, n2, scale_min) + bc_num n1, n2; + int scale_min; +{ + bc_num sum; + int sum_scale, sum_digits; + char *n1ptr, *n2ptr, *sumptr; + int carry, n1bytes, n2bytes; + int count; + + /* Prepare sum. */ + sum_scale = MAX (n1->n_scale, n2->n_scale); + sum_digits = MAX (n1->n_len, n2->n_len) + 1; + sum = bc_new_num (sum_digits, MAX(sum_scale, scale_min)); + + /* Zero extra digits made by scale_min. */ + if (scale_min > sum_scale) + { + sumptr = (char *) (sum->n_value + sum_scale + sum_digits); + for (count = scale_min - sum_scale; count > 0; count--) + *sumptr++ = 0; + } + + /* Start with the fraction part. Initialize the pointers. */ + n1bytes = n1->n_scale; + n2bytes = n2->n_scale; + n1ptr = (char *) (n1->n_value + n1->n_len + n1bytes - 1); + n2ptr = (char *) (n2->n_value + n2->n_len + n2bytes - 1); + sumptr = (char *) (sum->n_value + sum_scale + sum_digits - 1); + + /* Add the fraction part. First copy the longer fraction.*/ + if (n1bytes != n2bytes) + { + if (n1bytes > n2bytes) + while (n1bytes>n2bytes) + { *sumptr-- = *n1ptr--; n1bytes--;} + else + while (n2bytes>n1bytes) + { *sumptr-- = *n2ptr--; n2bytes--;} + } + + /* Now add the remaining fraction part and equal size integer parts. */ + n1bytes += n1->n_len; + n2bytes += n2->n_len; + carry = 0; + while ((n1bytes > 0) && (n2bytes > 0)) + { + *sumptr = *n1ptr-- + *n2ptr-- + carry; + if (*sumptr > (BASE-1)) + { + carry = 1; + *sumptr -= BASE; + } + else + carry = 0; + sumptr--; + n1bytes--; + n2bytes--; + } + + /* Now add carry the longer integer part. */ + if (n1bytes == 0) + { n1bytes = n2bytes; n1ptr = n2ptr; } + while (n1bytes-- > 0) + { + *sumptr = *n1ptr-- + carry; + if (*sumptr > (BASE-1)) + { + carry = 1; + *sumptr -= BASE; + } + else + carry = 0; + sumptr--; + } + + /* Set final carry. */ + if (carry == 1) + *sumptr += 1; + + /* Adjust sum and return. */ + _bc_rm_leading_zeros (sum); + return sum; +} + + +/* Perform subtraction: N2 is subtracted from N1 and the value is + returned. The signs of N1 and N2 are ignored. Also, N1 is + assumed to be larger than N2. SCALE_MIN is the minimum scale + of the result. */ + + bc_num +_bc_do_sub (n1, n2, scale_min) + bc_num n1, n2; + int scale_min; +{ + bc_num diff; + int diff_scale, diff_len; + int min_scale, min_len; + char *n1ptr, *n2ptr, *diffptr; + int borrow, count, val; + + /* Allocate temporary storage. */ + diff_len = MAX (n1->n_len, n2->n_len); + diff_scale = MAX (n1->n_scale, n2->n_scale); + min_len = MIN (n1->n_len, n2->n_len); + min_scale = MIN (n1->n_scale, n2->n_scale); + diff = bc_new_num (diff_len, MAX(diff_scale, scale_min)); + + /* Zero extra digits made by scale_min. */ + if (scale_min > diff_scale) + { + diffptr = (char *) (diff->n_value + diff_len + diff_scale); + for (count = scale_min - diff_scale; count > 0; count--) + *diffptr++ = 0; + } + + /* Initialize the subtract. */ + n1ptr = (char *) (n1->n_value + n1->n_len + n1->n_scale -1); + n2ptr = (char *) (n2->n_value + n2->n_len + n2->n_scale -1); + diffptr = (char *) (diff->n_value + diff_len + diff_scale -1); + + /* Subtract the numbers. */ + borrow = 0; + + /* Take care of the longer scaled number. */ + if (n1->n_scale != min_scale) + { + /* n1 has the longer scale */ + for (count = n1->n_scale - min_scale; count > 0; count--) + *diffptr-- = *n1ptr--; + } + else + { + /* n2 has the longer scale */ + for (count = n2->n_scale - min_scale; count > 0; count--) + { + val = - *n2ptr-- - borrow; + if (val < 0) + { + val += BASE; + borrow = 1; + } + else + borrow = 0; + *diffptr-- = val; + } + } + + /* Now do the equal length scale and integer parts. */ + + for (count = 0; count < min_len + min_scale; count++) + { + val = *n1ptr-- - *n2ptr-- - borrow; + if (val < 0) + { + val += BASE; + borrow = 1; + } + else + borrow = 0; + *diffptr-- = val; + } + + /* If n1 has more digits then n2, we now do that subtract. */ + if (diff_len != min_len) + { + for (count = diff_len - min_len; count > 0; count--) + { + val = *n1ptr-- - borrow; + if (val < 0) + { + val += BASE; + borrow = 1; + } + else + borrow = 0; + *diffptr-- = val; + } + } + + /* Clean up and return. */ + _bc_rm_leading_zeros (diff); + return diff; +} + |