From mboxrd@z Thu Jan 1 00:00:00 1970 From: =?UTF-8?q?Nguy=E1=BB=85n=20Th=C3=A1i=20Ng=E1=BB=8Dc=20Duy?= Subject: [PATCH] doc: technical details about the index file format Date: Wed, 1 Sep 2010 19:53:45 +1000 Message-ID: <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: =?UTF-8?q?Nguy=E1=BB=85n=20Th=C3=A1i=20Ng=E1=BB=8Dc=20Duy?= To: git@vger.kernel.org, Junio C Hamano , robin.rosenberg@dewire.com, srabbelier@gmail.com X-From: git-owner@vger.kernel.org Wed Sep 01 11:54:13 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 1Oqk1E-0007lt-G7 for gcvg-git-2@lo.gmane.org; Wed, 01 Sep 2010 11:54:13 +0200 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754352Ab0IAJyI convert rfc822-to-quoted-printable (ORCPT ); Wed, 1 Sep 2010 05:54:08 -0400 Received: from mail-pz0-f46.google.com ([209.85.210.46]:45777 "EHLO mail-pz0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751870Ab0IAJyF (ORCPT ); Wed, 1 Sep 2010 05:54:05 -0400 Received: by pzk9 with SMTP id 9so2763015pzk.19 for ; Wed, 01 Sep 2010 02:54:03 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:received:from:to:cc:subject :date:message-id:x-mailer:mime-version:content-type :content-transfer-encoding; bh=qFUmv8e7JI3zWR8YYhAGZiwvAUPz6gBTd64oIldP7z0=; b=dlxPONvtXgEU75nqk7xJs+r/tRzUVUhGe1420gDAxsd9zy2jW9IYV2eBaRVlZcRNAs tL/DJEbJm6gvgdEB7o/rXlpw8z9W1KDOJhuEglFW8A4Z1IVpwGpU8onu1clHQIJP4O84 drMj25jv4PgaFji6CUyaJGWRmLQ1aOnrOE21w= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=from:to:cc:subject:date:message-id:x-mailer:mime-version :content-type:content-transfer-encoding; b=MBdsIAYV433ZZwhil1Irt04FF4sFEhjFz7DUb/ojvRk7LvSa9inadX7zF4bozbu9lO nKx3pPxtq/QViclINqWFYn6q7BRGyJobl4lrQ5+BfPijUl3ya5BHXrRVgI9FKV8iWCAp hY7WXZJitsRU4JPGzayGdwBhPnZ33aoCvxFvg= Received: by 10.142.135.2 with SMTP id i2mr7000964wfd.279.1283334843657; Wed, 01 Sep 2010 02:54:03 -0700 (PDT) Received: from dektop ([119.12.250.225]) by mx.google.com with ESMTPS id j5sm3485200wff.20.2010.09.01.02.53.58 (version=TLSv1/SSLv3 cipher=RC4-MD5); Wed, 01 Sep 2010 02:54:02 -0700 (PDT) Received: by dektop (sSMTP sendmail emulation); Wed, 1 Sep 2010 19:53:52 +1000 X-Mailer: git-send-email 1.7.1.rc1.69.g24c2f7 Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Archived-At: This bases on the original work by Robin Rosenberg: http://thread.gmane.org/gmane.comp.version-control.git/73471 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. Other changes: - mention of version 3 - added ino and mode - added extended flags (v3) - entry sort order Again I don't realy know REUC extension, so only placeholder Documentation/technical/index-format.txt | 139 ++++++++++++++++++++++= ++++++++ 1 files changed, 139 insertions(+), 0 deletions(-) create mode 100644 Documentation/technical/index-format.txt diff --git a/Documentation/technical/index-format.txt b/Documentation/t= echnical/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 described + 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. + + 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 + (without leading slash). '/' is used as path separator. Special + paths ".", ".." and ".git" (without quotes) are disallowed. + Trailing slash is also disallowed. + + 1-8 nul bytes as necessary to pad the entry to a multiple ot eight b= ytes + while keeping the name NUL-terminated. + +=3D=3D Extensions + +=3D=3D=3D Tree cache + + Tree cache extension contains pre-computes hashes for all trees that + 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 fo= r + 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 --=20 1.7.1.rc1.69.g24c2f7