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[104.178.186.189]) by smtp.gmail.com with ESMTPSA id c19-20020a37e113000000b00783fb14c67bsm3192563qkm.48.2024.01.31.14.52.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 31 Jan 2024 14:52:29 -0800 (PST) Date: Wed, 31 Jan 2024 17:52:29 -0500 From: Taylor Blau To: git@vger.kernel.org Cc: Jeff King , Junio C Hamano , Jonathan Tan , SZEDER =?utf-8?b?R8OhYm9y?= Subject: [PATCH v6 04/16] gitformat-commit-graph: describe version 2 of BDAT Message-ID: <56a9fdaff02e8b4488a44d4995a25651f33ccc2c.1706741516.git.me@ttaylorr.com> References: Precedence: bulk X-Mailing-List: git@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: From: Jonathan Tan The code change to Git to support version 2 will be done in subsequent commits. Signed-off-by: Jonathan Tan Signed-off-by: Junio C Hamano Signed-off-by: Taylor Blau --- Documentation/gitformat-commit-graph.txt | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/Documentation/gitformat-commit-graph.txt b/Documentation/gitformat-commit-graph.txt index 31cad585e2..3e906e8030 100644 --- a/Documentation/gitformat-commit-graph.txt +++ b/Documentation/gitformat-commit-graph.txt @@ -142,13 +142,16 @@ All multi-byte numbers are in network byte order. ==== Bloom Filter Data (ID: {'B', 'D', 'A', 'T'}) [Optional] * It starts with header consisting of three unsigned 32-bit integers: - - Version of the hash algorithm being used. We currently only support - value 1 which corresponds to the 32-bit version of the murmur3 hash + - Version of the hash algorithm being used. We currently support + value 2 which corresponds to the 32-bit version of the murmur3 hash implemented exactly as described in https://en.wikipedia.org/wiki/MurmurHash#Algorithm and the double hashing technique using seed values 0x293ae76f and 0x7e646e2 as described in https://doi.org/10.1007/978-3-540-30494-4_26 "Bloom Filters - in Probabilistic Verification" + in Probabilistic Verification". Version 1 Bloom filters have a bug that appears + when char is signed and the repository has path names that have characters >= + 0x80; Git supports reading and writing them, but this ability will be removed + in a future version of Git. - The number of times a path is hashed and hence the number of bit positions that cumulatively determine whether a file is present in the commit. - The minimum number of bits 'b' per entry in the Bloom filter. If the filter