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| author | Derrick Stolee <stolee@gmail.com> | 2018-07-12 21:39:32 +0200 |
|---|---|---|
| committer | Junio C Hamano <gitster@pobox.com> | 2018-07-20 20:27:28 +0200 |
| commit | 662148c4356620f6567b0a689602079339ebadb7 (patch) | |
| tree | f48a63aa641e6b9bc8720e85ce3161e56bf89dcc /Documentation/technical | |
| parent | midx: write object id fanout chunk (diff) | |
| download | git-662148c4356620f6567b0a689602079339ebadb7.tar.xz git-662148c4356620f6567b0a689602079339ebadb7.zip | |
midx: write object offsets
The final pair of chunks for the multi-pack-index file stores the object
offsets. We default to using 32-bit offsets as in the pack-index version
1 format, but if there exists an offset larger than 32-bits, we use a
trick similar to the pack-index version 2 format by storing all offsets
at least 2^31 in a 64-bit table; we use the 32-bit table to point into
that 64-bit table as necessary.
We only store these 64-bit offsets if necessary, so create a test that
manipulates a version 2 pack-index to fake a large offset. This allows
us to test that the large offset table is created, but the data does not
match the actual packfile offsets. The multi-pack-index offset does match
the (corrupted) pack-index offset, so a future feature will compare these
offsets during a 'verify' step.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Diffstat (limited to 'Documentation/technical')
| -rw-r--r-- | Documentation/technical/pack-format.txt | 15 |
1 files changed, 14 insertions, 1 deletions
diff --git a/Documentation/technical/pack-format.txt b/Documentation/technical/pack-format.txt index 3215f7bfcd..cab5bdd2ff 100644 --- a/Documentation/technical/pack-format.txt +++ b/Documentation/technical/pack-format.txt @@ -311,7 +311,20 @@ CHUNK DATA: The OIDs for all objects in the MIDX are stored in lexicographic order in this chunk. - (This section intentionally left incomplete.) + Object Offsets (ID: {'O', 'O', 'F', 'F'}) + Stores two 4-byte values for every object. + 1: The pack-int-id for the pack storing this object. + 2: The offset within the pack. + If all offsets are less than 2^31, then the large offset chunk + will not exist and offsets are stored as in IDX v1. + If there is at least one offset value larger than 2^32-1, then + the large offset chunk must exist. If the large offset chunk + exists and the 31st bit is on, then removing that bit reveals + the row in the large offsets containing the 8-byte offset of + this object. + + [Optional] Object Large Offsets (ID: {'L', 'O', 'F', 'F'}) + 8-byte offsets into large packfiles. TRAILER: |