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	zlsh.c - libzahl - big integer library
	git clone git://git.suckless.org/libzahl
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	zlsh.c (874B)
	---
	1 /* See LICENSE file for copyright and license details. */
	2 #include "internals.h"
	3
	4
	5 void
	6 zlsh(z_t a, z_t b, size_t bits)
	7 {
	8 size_t i, chars, cbits;
	9 zahl_char_t carry = 0, tcarry;
	10
	11 if (unlikely(zzero(b))) {
	12 SET_SIGNUM(a, 0);
	13 return;
	14 }
	15
	16 chars = FLOOR_BITS_TO_CHARS(bits);
	17 bits = BITS_IN_LAST_CHAR(bits);
	18 cbits = BITS_PER_CHAR - bits;
	19
	20 ENSURE_SIZE(a, b->used + chars + 1);
	21 if (likely(a == b)) {
	22 zmemmoveb(a->chars + chars, b->chars, b->used);
	23 } else {
	24 zmemcpy(a->chars + chars, b->chars, b->used);
	25 }
	26 zmemset_precise(a->chars, 0, chars);
	27 a->used = b->used + chars;
	28
	29 if (likely(bits)) { /* This if statement is very important in C.…
	30 for (i = chars; i < a->used; i++) {
	31 tcarry = a->chars[i] >> cbits;
	32 a->chars[i] <<= bits;
	33 a->chars[i] \|= carry;
	34 carry = tcarry;
	35 }
	36 if (carry)
	37 a->chars[a->used++] = carry;
	38 }
	39
	40 SET_SIGNUM(a, zsignum(b));
	41 }