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	zrsh.c - libzahl - big integer library
	git clone git://git.suckless.org/libzahl
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	zrsh.c (906B)
	---
	1 /* See LICENSE file for copyright and license details. */
	2 #include "internals.h"
	3
	4
	5 void
	6 zrsh(z_t a, z_t b, size_t bits)
	7 {
	8 size_t i, chars, cbits;
	9
	10 if (unlikely(!bits)) {
	11 SET(a, b);
	12 return;
	13 }
	14
	15 chars = FLOOR_BITS_TO_CHARS(bits);
	16
	17 if (unlikely(zzero(b) \|\| chars >= b->used \|\| zbits(b) <= bits)) {
	18 SET_SIGNUM(a, 0);
	19 return;
	20 }
	21
	22 bits = BITS_IN_LAST_CHAR(bits);
	23 cbits = BITS_PER_CHAR - bits;
	24
	25 if (likely(chars) && likely(a == b)) {
	26 a->used -= chars;
	27 zmemmove(a->chars, a->chars + chars, a->used);
	28 } else if (unlikely(a != b)) {
	29 a->used = b->used - chars;
	30 ENSURE_SIZE(a, a->used);
	31 zmemcpy(a->chars, b->chars + chars, a->used);
	32 }
	33
	34 if (unlikely(bits)) { /* This if statement is very important in …
	35 a->chars[0] >>= bits;
	36 for (i = 1; i < a->used; i++) {
	37 a->chars[i - 1] \|= a->chars[i] << cbits;
	38 a->chars[i] >>= bits;
	39 }
	40 TRIM_NONZERO(a);
	41 }
	42
	43 SET_SIGNUM(a, zsignum(b));
	44 }