-GIT pack format
+Git pack format
===============
== pack-*.pack files have the following format:
The signature is: {'P', 'A', 'C', 'K'}
4-byte version number (network byte order):
- GIT currently accepts version number 2 or 3 but
+ Git currently accepts version number 2 or 3 but
generates version 2 only.
4-byte number of objects contained in the pack (network byte order)
(deltified representation)
n-byte type and length (3-bit type, (n-1)*7+4-bit length)
- 20-byte base object name
+ 20-byte base object name if OBJ_REF_DELTA or a negative relative
+ offset from the delta object's position in the pack if this
+ is an OBJ_OFS_DELTA object
compressed delta data
Observation: length of each object is encoded in a variable
length format and is not constrained to 32-bit or anything.
- - The trailer records 20-byte SHA1 checksum of all of the above.
+ - The trailer records 20-byte SHA-1 checksum of all of the above.
== Original (version 1) pack-*.idx files have the following format:
- The file is concluded with a trailer:
- A copy of the 20-byte SHA1 checksum at the end of
+ A copy of the 20-byte SHA-1 checksum at the end of
corresponding packfile.
- 20-byte SHA1-checksum of all of the above.
+ 20-byte SHA-1-checksum of all of the above.
Pack Idx file:
If it is not DELTA, then deflated bytes (the size above
is the size before compression).
If it is REF_DELTA, then
- 20-byte base object name SHA1 (the size above is the
+ 20-byte base object name SHA-1 (the size above is the
size of the delta data that follows).
delta data, deflated.
If it is OFS_DELTA, then
- A 256-entry fan-out table just like v1.
- - A table of sorted 20-byte SHA1 object names. These are
+ - A table of sorted 20-byte SHA-1 object names. These are
packed together without offset values to reduce the cache
footprint of the binary search for a specific object name.
- The same trailer as a v1 pack file:
- A copy of the 20-byte SHA1 checksum at the end of
+ A copy of the 20-byte SHA-1 checksum at the end of
corresponding packfile.
- 20-byte SHA1-checksum of all of the above.
+ 20-byte SHA-1-checksum of all of the above.