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[70.33.148.227]) by smtp.gmail.com with ESMTPSA id k126-v6sm8684638qkb.91.2018.10.02.07.34.10 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 02 Oct 2018 07:34:10 -0700 (PDT) Subject: Re: [PATCH v7 3/7] eoie: add End of Index Entry (EOIE) extension To: =?UTF-8?Q?SZEDER_G=c3=a1bor?= Cc: git@vger.kernel.org, gitster@pobox.com, pclouds@gmail.com, Ben Peart References: <20180823154053.20212-1-benpeart@microsoft.com> <20181001134556.33232-1-peartben@gmail.com> <20181001134556.33232-4-peartben@gmail.com> <20181001151716.GL23446@localhost> From: Ben Peart Message-ID: Date: Tue, 2 Oct 2018 10:34:07 -0400 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20181001151716.GL23446@localhost> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org On 10/1/2018 11:17 AM, SZEDER Gábor wrote: > On Mon, Oct 01, 2018 at 09:45:52AM -0400, Ben Peart wrote: >> From: Ben Peart >> >> The End of Index Entry (EOIE) is used to locate the end of the variable >> length index entries and the beginning of the extensions. Code can take >> advantage of this to quickly locate the index extensions without having >> to parse through all of the index entries. >> >> Because it must be able to be loaded before the variable length cache >> entries and other index extensions, this extension must be written last. >> The signature for this extension is { 'E', 'O', 'I', 'E' }. >> >> The extension consists of: >> >> - 32-bit offset to the end of the index entries >> >> - 160-bit SHA-1 over the extension types and their sizes (but not >> their contents). E.g. if we have "TREE" extension that is N-bytes >> long, "REUC" extension that is M-bytes long, followed by "EOIE", >> then the hash would be: >> >> SHA-1("TREE" + + >> "REUC" + ) >> >> Signed-off-by: Ben Peart > > I think the commit message should explicitly mention that this this > extension > > - will always be written and why, > - but is optional, so other Git implementations not supporting it will > have no troubles reading the index, > - and that it is written even to the shared index and why, and that > because of this the index checksums in t1700 had to be updated. > Sure, I'll add that additional information to the commit message on the next spin.