zlsh.c - libzahl - big integer library
 (HTM) git clone git://git.suckless.org/libzahl
 (DIR) Log
 (DIR) Files
 (DIR) Refs
 (DIR) README
 (DIR) LICENSE
       ---
       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 }