From mboxrd@z Thu Jan 1 00:00:00 1970 From: Robin Rosenberg Subject: Re: [PATCH] doc: technical details about the index file format Date: Wed, 1 Sep 2010 20:54:20 +0200 Message-ID: <201009012054.20482.robin.rosenberg@dewire.com> References: <1283334825-18309-1-git-send-email-pclouds@gmail.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: git@vger.kernel.org, Junio C Hamano , srabbelier@gmail.com To: =?utf-8?q?Nguy=E1=BB=85n_Th=C3=A1i_Ng=E1=BB=8Dc_Duy?= X-From: git-owner@vger.kernel.org Wed Sep 01 21:22:57 2010 Return-path: Envelope-to: gcvg-git-2@lo.gmane.org Received: from vger.kernel.org ([209.132.180.67]) by lo.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1OqstW-0000XN-2W for gcvg-git-2@lo.gmane.org; Wed, 01 Sep 2010 21:22:50 +0200 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753036Ab0IATWo convert rfc822-to-quoted-printable (ORCPT ); Wed, 1 Sep 2010 15:22:44 -0400 Received: from mail.dewire.com ([83.140.172.130]:13134 "EHLO dewire.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752750Ab0IATWn convert rfc822-to-8bit (ORCPT ); Wed, 1 Sep 2010 15:22:43 -0400 X-Greylist: delayed 1698 seconds by postgrey-1.27 at vger.kernel.org; Wed, 01 Sep 2010 15:22:42 EDT Received: from localhost (localhost [127.0.0.1]) by dewire.com (Postfix) with ESMTP id 316FE1469E2B; Wed, 1 Sep 2010 20:54:23 +0200 (CEST) X-Virus-Scanned: by amavisd-new at dewire.com Received: from dewire.com ([127.0.0.1]) by localhost (torino.dewire.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id PvBGePs-Nxyp; Wed, 1 Sep 2010 20:54:22 +0200 (CEST) Received: from sleipner.localnet (unknown [10.9.0.3]) by dewire.com (Postfix) with ESMTP id B11F3138BF5A; Wed, 1 Sep 2010 20:54:21 +0200 (CEST) User-Agent: KMail/1.13.2 (Linux/2.6.32-24-generic; KDE/4.4.2; i686; ; ) In-Reply-To: <1283334825-18309-1-git-send-email-pclouds@gmail.com> Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Archived-At: onsdagen den 1 september 2010 11.53.45 skrev Nguy=E1=BB=85n Th=C3=A1i = Ng=E1=BB=8Dc Duy: > This bases on the original work by Robin Rosenberg: >=20 > http://thread.gmane.org/gmane.comp.version-control.git/73471 No need for this. My name is enough >=20 > Signed-off-by: Nguy=E1=BB=85n Th=C3=A1i Ng=E1=BB=8Dc Duy Add Signed-off-by: Nguy=E1=BB=85n Th=C3=A1i Ng=E1=BB=8Dc Duy > --- > I split index entry out so the overall format is clearer. >=20 > Other changes: > - mention of version 3 > - added ino and mode > - added extended flags (v3) > - entry sort order >=20 > Again I don't realy know REUC extension, so only placeholder >=20 > Documentation/technical/index-format.txt | 139 > ++++++++++++++++++++++++++++++ 1 files changed, 139 insertions(+), 0 > deletions(-) > create mode 100644 Documentation/technical/index-format.txt >=20 > diff --git a/Documentation/technical/index-format.txt > b/Documentation/technical/index-format.txt new file mode 100644 > index 0000000..3e113ca > --- /dev/null > +++ b/Documentation/technical/index-format.txt > @@ -0,0 +1,139 @@ > +GIT index format > +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > + > +=3D The git index file has the following format > + > + All binary numbers are in network byte order. Version 2 is describ= ed > + here unless stated otherwise. > + > + - A 12-byte header consisting of > + > + 4-byte signature: > + The signature is { 'D', 'I', 'R', 'C' } > + > + 4-byte version number: > + The current supported versions are 2 and 3. > + > + 32-bit number of index entries. > + > + - A number of sorted index entries > + > + - Extensions > + > + Extensions are identified by signature. Optional extensions can > + be ignored if GIT does not understand them. > + > + GIT currently supports tree cache and resolve undo extensions. > + > + 4-byte extension signature. If the first byte is 'A'..'Z' the > + extension is optional and can be ignored. > + > + 32-bit size of the extension > + > + Extension data > + > + - 160-bit SHA-1 over the content of the index file before this > + checksum. > + > +=3D=3D Index entry > + > + Index entries are sorted with memcmp() by entry name. Entries with > + the same name are sorted by their stage. Index entries are sorted in ascending order on the name field, interpre= ted as a string of unsigned bytes. > + > + 32-bit ctime seconds, the last time a file's metadata changed > + this is stat(2) data > + > + 32-bit ctime nanoseconds (modulo 1G) > + this is stat(2) data > + > + 32-bit mtime seconds, the last time a file's data changed > + this is stat(2) data > + > + 32-bit mtime nanoseconds (modulo 1G) > + this is stat(2) data > + > + 32-bit dev > + this is stat(2) data > + > + 32-bit ino > + this is stat(2) data > + > + 32-bit mode, split into (high to low bits) > + > + 4-bit object type > + valid values in binary are 1000 (blob), 1010 (symbolic link) > + and 1110 (gitlink) > + > + 3-bit unused > + > + 9-bit unix permission (only 0755 and 0644 are valid) > + > + 32-bit uid > + this is stat(2) data > + > + 32-bit gid > + this is stat(2) data > + > + 32-bit file size > + This is the on-disk size from stat(2) > + > + 160-bit SHA-1 for the represented object > + > + A 16-bit field split into (high to low bits) > + > + 1-bit assume-valid flag > + > + 1-bit extended flag (must be zero in version 2) > + > + 2-bit stage (during merge) > + > + 12-bit name length if the length is less than 0x0FFF > + > + (Version 3) A 16-bit field, only applicable if the "extended flag" > + above is 1, split into (high to low bits). > + > + 1-bit reserved for future > + > + 1-bit skip-worktree flag (used by sparse checkout) > + > + 1-bit intent-to-add flag (used by "git add -N") > + > + 13-bit unused, must be zero > + > + Entry path name (variable length) relative to top-level directory =2E..to the top level... > + (without leading slash). '/' is used as path separator. Special The special... > + paths ".", ".." and ".git" (without quotes) are disallowed. > + Trailing slash is also disallowed. Why would anyone even consider adding a trailing slash to a _file_ name= ? The exact encoding is undefined, but the '.', and '/' characters are encoded in 7-bit ASCII and the encoding cannot contain a nul byt= e. Generally a superset of ASCII > + > + 1-8 nul bytes as necessary to pad the entry to a multiple ot eight= bytes =2E..of eight bytes A typo of mine. > + while keeping the name NUL-terminated. > + > +=3D=3D Extensions > + > +=3D=3D=3D Tree cache > + > + Tree cache extension contains pre-computes hashes for all trees th= at > + can be derived from the index > + > + - Extension tag { 'T', 'R', 'E', 'E' } > + > + - 32-bit size > + > + - A number of entries > + > + NUL-terminated tree name > + > + Blank-terminated ASCII decimal number of entries in this tree > + > + Newline-terminated position of this tree in the parent tree. 0 = for > + the root tree > + > + 160-bit SHA-1 for this tree and it's children > + > +=3D=3D=3D Resolve undo > + > + TODO > + > + - Extension tag { 'R', 'E', 'U', 'C' } > + > + - 32-bit size