git.sesse.net Git - bcachefs-tools-debian/blob - libbcachefs/varint.c

   1 // SPDX-License-Identifier: GPL-2.0
   2
   3 #include <linux/bitops.h>
   4 #include <asm/unaligned.h>
   5
   6 #include "varint.h"
   7
   8 int bch2_varint_encode(u8 *out, u64 v)
   9 {
  10         unsigned bits = fls64(v|1);
  11         unsigned bytes = DIV_ROUND_UP(bits, 7);
  12
  13         if (likely(bytes < 9)) {
  14                 v <<= bytes;
  15                 v |= ~(~0 << (bytes - 1));
  16         } else {
  17                 *out++ = 255;
  18                 bytes = 9;
  19         }
  20
  21         put_unaligned_le64(v, out);
  22         return bytes;
  23 }
  24
  25 int bch2_varint_decode(const u8 *in, const u8 *end, u64 *out)
  26 {
  27         u64 v = get_unaligned_le64(in);
  28         unsigned bytes = ffz(v & 255) + 1;
  29
  30         if (unlikely(in + bytes > end))
  31                 return -1;
  32
  33         if (likely(bytes < 9)) {
  34                 v >>= bytes;
  35                 v &= ~(~0ULL << (7 * bytes));
  36         } else {
  37                 v = get_unaligned_le64(++in);
  38         }
  39
  40         *out = v;
  41         return bytes;
  42 }