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rattrs: Brought back LFS3_FROM_LLEB128

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This was originally dropped because it's not strictly necessary,
little-leb128s (28-bits) can always be encoded with the default leb128
encoder (31-bits). But it is useful if only for the assert.

Note this matches lfs3_data_readlleb128, which was never dropped, and is
useful for decreasing decoder DSIZEs.

Maybe it makes sense to drop both of these in the future, especially if
we start running into from-field pressure. But for now, this assert is
useful for ensuring disk compatibility with little 4-byte leb128s.

---

Surprisingly no code cost, at least by default (code alignment?). Though
it did add 4 bytes to the gbmap build (so yes, probably code alignment):

                 code          stack          ctx
  before:       35316           2176          660
  after:        35316 (+0.0%)   2176 (+0.0%)  660 (+0.0%)

                 code          stack          ctx
  gbmap before: 38168           2192          772
  gbmap after:  38172 (+0.0%)   2192 (+0.0%)  772 (+0.0%)
This commit is contained in:
Christopher Haster
2025-12-01 15:21:37 -06:00
parent e29cc23acd
commit b63237555b
1 changed files with 19 additions and 11 deletions
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lfs3.c
+19 -11
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@@ -1894,16 +1894,17 @@ enum lfs3_from {
LFS3_FROM_LE32 = 4, LFS3_FROM_LE32 = 4,
LFS3_FROM_LEB128 = 5, LFS3_FROM_LEB128 = 5,
LFS3_FROM_NAME = 6, LFS3_FROM_LLEB128 = 6,
LFS3_FROM_NAME = 7,
LFS3_FROM_ECKSUM = 7, LFS3_FROM_ECKSUM = 8,
LFS3_FROM_BRANCH = 8, LFS3_FROM_BRANCH = 9,
LFS3_FROM_BPTR = 9, LFS3_FROM_BPTR = 10,
LFS3_FROM_BTREE = 10, LFS3_FROM_BTREE = 11,
LFS3_FROM_SHRUB = 11, LFS3_FROM_SHRUB = 12,
LFS3_FROM_MPTR = 12, LFS3_FROM_MPTR = 13,
LFS3_FROM_GEOMETRY = 13, LFS3_FROM_GEOMETRY = 14,
}; };
typedef uint8_t lfs3_from_t; typedef uint8_t lfs3_from_t;
@@ -3295,6 +3296,10 @@ static int lfs3_rbyd_appendrattr_(lfs3_t *lfs3, lfs3_rbyd_t *rbyd,
lfs3_data_t data; lfs3_data_t data;
uint8_t buf[LFS3_LEB128_DSIZE]; uint8_t buf[LFS3_LEB128_DSIZE];
} leb128; } leb128;
struct {
lfs3_data_t data;
uint8_t buf[LFS3_LLEB128_DSIZE];
} lleb128;
struct { struct {
lfs3_data_t datas[2]; lfs3_data_t datas[2];
uint8_t buf[LFS3_LEB128_DSIZE]; uint8_t buf[LFS3_LEB128_DSIZE];
@@ -3373,10 +3378,13 @@ static int lfs3_rbyd_appendrattr_(lfs3_t *lfs3, lfs3_rbyd_t *rbyd,
datas = &ctx.u.le32.data; datas = &ctx.u.le32.data;
data_count = 1; data_count = 1;
// leb128? // leb128? little-leb128?
} else if (from == LFS3_FROM_LEB128) { } else if (from == LFS3_FROM_LEB128
|| from == LFS3_FROM_LLEB128) {
// leb128s should not exceed 31-bits // leb128s should not exceed 31-bits
LFS3_ASSERT(args[0] <= 0x7fffffff); LFS3_ASSERT(args[0] <= 0x7fffffff);
// little-leb128s should not exceed 28-bits
LFS3_ASSERT(from != LFS3_FROM_LLEB128 || args[0] <= 0x0fffffff);
ctx.u.leb128.data = lfs3_data_fromleb128(args[0], ctx.u.leb128.data = lfs3_data_fromleb128(args[0],
ctx.u.leb128.buf); ctx.u.leb128.buf);
datas = &ctx.u.leb128.data; datas = &ctx.u.leb128.data;
@@ -15897,7 +15905,7 @@ static int lfs3_formatinited(lfs3_t *lfs3) {
*r++ = LFS3_RATTR_ARG(lfs3_wcompat(lfs3)); *r++ = LFS3_RATTR_ARG(lfs3_wcompat(lfs3));
*r++ = LFS3_RATTR(2, LFS3_TAG_GEOMETRY, 0, LFS3_FROM_GEOMETRY); *r++ = LFS3_RATTR(2, LFS3_TAG_GEOMETRY, 0, LFS3_FROM_GEOMETRY);
*r++ = LFS3_RATTR_ARG(&geometry); *r++ = LFS3_RATTR_ARG(&geometry);
*r++ = LFS3_RATTR(2, LFS3_TAG_NAMELIMIT, 0, LFS3_FROM_LEB128); *r++ = LFS3_RATTR(2, LFS3_TAG_NAMELIMIT, 0, LFS3_FROM_LLEB128);
*r++ = LFS3_RATTR_ARG(lfs3->name_limit); *r++ = LFS3_RATTR_ARG(lfs3->name_limit);
*r++ = LFS3_RATTR(2, LFS3_TAG_FILELIMIT, 0, LFS3_FROM_LEB128); *r++ = LFS3_RATTR(2, LFS3_TAG_FILELIMIT, 0, LFS3_FROM_LEB128);
*r++ = LFS3_RATTR_ARG(lfs3->file_limit); *r++ = LFS3_RATTR_ARG(lfs3->file_limit);