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Simplified how we check on-disk versions a bit

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We don't really need to do full leb128 decoding since our version
numbers are unlikely to ever actually exceed v127.127.

Worst case, if they do, the version that exceeds v127.127 can switch to
using leb128 decoding without breaking backwards compatibility.

Version attr encoding:

  .---+---+---+---+---+---.  tag (0x0004):  1 be16    2 bytes
  | x0004 | 0 | 2 |maj|min|  weight (0):    1 leb128  1 byte
  '---+---+---+---+---+---'  size (2):      1 leb128  1 byte
                             major_version: 1 leb128  1 byte
                             minor_version: 1 leb128  1 byte
                             total:                   6 bytes

Code changes:

           code          stack
  before: 34124           2880
  after:  34092 (-0.1%)   2880 (+0.0%)
This commit is contained in:
Christopher Haster
2024-03-18 01:08:59 -05:00
parent 130281ac05
commit 796be705ac
1 changed files with 7 additions and 19 deletions
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lfs.c
+7 -19
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@@ -7924,30 +7924,18 @@ static int lfsr_mountmroot(lfs_t *lfs, const lfsr_mdir_t *mroot) {
return err;
}
uint32_t major_version;
err = lfsr_data_readleb128(lfs, &data, &major_version);
if (err && err != LFS_ERR_CORRUPT) {
uint8_t version[2] = {0, 0};
lfs_ssize_t d = lfsr_data_read(lfs, &data, version, 2);
if (d < 0) {
return err;
}
if (err == LFS_ERR_CORRUPT) {
major_version = -1;
}
uint32_t minor_version;
err = lfsr_data_readleb128(lfs, &data, &minor_version);
if (err && err != LFS_ERR_CORRUPT) {
return err;
}
if (err == LFS_ERR_CORRUPT) {
minor_version = -1;
}
if (major_version != LFS_DISK_VERSION_MAJOR
|| minor_version > LFS_DISK_VERSION_MINOR) {
if (version[0] != LFS_DISK_VERSION_MAJOR
|| version[1] > LFS_DISK_VERSION_MINOR) {
LFS_ERROR("Incompatible version v%"PRId32".%"PRId32
" (!= v%"PRId32".%"PRId32")",
major_version,
minor_version,
version[0],
version[1],
LFS_DISK_VERSION_MAJOR,
LFS_DISK_VERSION_MINOR);
return LFS_ERR_INVAL;