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	zdivmod.c - libzahl - big integer library
	git clone git://git.suckless.org/libzahl
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	---
	zdivmod.c (1979B)
	---
	1 /* See LICENSE file for copyright and license details. */
	2 #include "internals.h"
	3
	4 #define ta libzahl_tmp_divmod_a
	5 #define tb libzahl_tmp_divmod_b
	6 #define td libzahl_tmp_divmod_d
	7 #define tds_proper libzahl_tmp_divmod_ds
	8
	9
	10 static inline void
	11 zdivmod_impl(z_t a, z_t b, z_t c, z_t d)
	12 {
	13 size_t c_bits, d_bits, bit, i;
	14 static z_t tds[BITS_PER_CHAR];
	15
	16 c_bits = zbits(c);
	17 d_bits = zbits(d);
	18
	19 bit = c_bits - d_bits;
	20 zlsh(td, d, bit);
	21 SET_SIGNUM(td, 1);
	22 if (zcmpmag(td, c) > 0) {
	23 zrsh(td, td, 1);
	24 bit -= 1;
	25 }
	26
	27 SET_SIGNUM(ta, 0);
	28 zabs(tb, c);
	29
	30 if (unlikely(bit <= BITS_PER_CHAR)) {
	31 for (;;) {
	32 if (zcmpmag(td, tb) <= 0) {
	33 zsub_unsigned(tb, tb, td);
	34 zbset(ta, ta, bit, 1);
	35 }
	36 if (!bit-- \|\| zzero(tb))
	37 goto done;
	38 zrsh(td, td, 1);
	39 }
	40 } else {
	41 for (i = 0; i < BITS_PER_CHAR; i++) {
	42 zrsh(tds_proper[i], td, i);
	43 tds[i]->used = tds_proper[i]->used;
	44 tds[i]->sign = tds_proper[i]->sign;
	45 tds[i]->chars = tds_proper[i]->chars;
	46 }
	47 for (;;) {
	48 for (i = 0; i < BITS_PER_CHAR; i++) {
	49 if (zcmpmag(tds[i], tb) <= 0) {
	50 zsub_unsigned(tb, tb, tds[i]);
	51 zbset(ta, ta, bit, 1);
	52 }
	53 if (!bit-- \|\| zzero(tb))
	54 goto done;
	55 }
	56 for (i = MIN(bit, BITS_PER_CHAR - 1) + 1; i--;)
	57 zrsh_taint(tds[i], BITS_PER_CHAR);
	58 }
	59 }
	60 done:
	61
	62 zswap(a, ta);
	63 zswap(b, tb);
	64 }
	65
	66
	67 void
	68 zdivmod(z_t a, z_t b, z_t c, z_t d)
	69 {
	70 int c_sign, sign, cmpmag;
	71
	72 c_sign = zsignum(c);
	73 sign = c_sign * zsignum(d);
	74
	75 if (unlikely(!sign)) {
	76 if (check(!zzero(c))) {
	77 libzahl_failure(-ZERROR_DIV_0);
	78 } else if (check(zzero(d))) {
	79 libzahl_failure(-ZERROR_0_DIV_0);
	80 } else {
	81 SET_SIGNUM(a, 0);
	82 SET_SIGNUM(b, 0);
	83 }
	84 return;
	85 } else if (cmpmag = zcmpmag(c, d), unlikely(cmpmag <= 0)) {
	86 if (unlikely(cmpmag == 0)) {
	87 zseti(a, sign);
	88 SET_SIGNUM(b, 0);
	89 } else {
	90 SET(b, c);
	91 SET_SIGNUM(a, 0);
	92 }
	93 return;
	94 }
	95
	96 zdivmod_impl(a, b, c, d);
	97 SET_SIGNUM(a, sign);
	98 if (zsignum(b) > 0)
	99 SET_SIGNUM(b, c_sign);
	100 }