facebook/sapling
1
1
Fork 0
mirror of https://github.com/facebook/sapling.git synced 2024-10-09 08:18:15 +03:00
Code Issues Projects Releases Wiki Activity

help: document sharing of revlog header with revision 0

Browse Source 
The previous docs were incorrect about there being a discrete header
on revlogs.
This commit is contained in:
Gregory Szorc 2016-03-19 15:17:33 -07:00
parent 7347261bf4
commit db9b5063c1
1 changed files with 12 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
mercurial/help/internals/revlogs.txt
View File

@ -31,7 +31,8 @@ File Format
----------- -----------
A revlog begins with a 32-bit big endian integer holding version info A revlog begins with a 32-bit big endian integer holding version info
and feature flags. and feature flags. This integer is shared with the first revision
entry.
This integer is logically divided into 2 16-bit shorts. The least This integer is logically divided into 2 16-bit shorts. The least
significant half of the integer is the format/version short. The other significant half of the integer is the format/version short. The other
@ -70,8 +71,10 @@ The following header values are common:
00 03 00 01 00 03 00 01
RevlogNG + inline + generaldelta RevlogNG + inline + generaldelta
Following the 32-bit header is *index* data. Inlined revision data is possibly Following the 32-bit header is the remainder of the first index entry.
located between index entries. More on this layout is described below. Following that are remaining *index* data. Inlined revision data is
possibly located between index entries. More on this layout is described
below.
RevlogNG Format RevlogNG Format
--------------- ---------------
@ -83,6 +86,8 @@ or between index entries (as opposed to in a separate container).
Each index entry is 64 bytes. The byte layout of each entry is as Each index entry is 64 bytes. The byte layout of each entry is as
follows, with byte 0 being the first byte (all data stored as big endian): follows, with byte 0 being the first byte (all data stored as big endian):
0-3 (4 bytes) (rev 0 only)
Revlog header
0-5 (6 bytes) 0-5 (6 bytes)
Absolute offset of revision data from beginning of revlog. Absolute offset of revision data from beginning of revlog.
6-7 (2 bytes) 6-7 (2 bytes)
@ -120,6 +125,9 @@ If revision data is not inline, then raw revision data is stored in a
separate byte container. The offsets from bytes 0-5 and the compressed separate byte container. The offsets from bytes 0-5 and the compressed
length from bytes 8-11 define how to access this data. length from bytes 8-11 define how to access this data.
The first 4 bytes of the revlog are shared between the revlog header
and the 6 byte absolute offset field from the first revlog entry.
Delta Chains Delta Chains
------------ ------------