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From: Junio C Hamano <gitster@pobox.com>
To: "brian m. carlson" <sandals@crustytoothpaste.net>
Cc: <git@vger.kernel.org>
Subject: Re: [RFC PATCH 02/22] hex: add functions to parse hex object IDs in any algorithm
Date: Wed, 15 Jan 2020 13:40:54 -0800
Message-ID: <xmqqv9pciejd.fsf@gitster-ct.c.googlers.com> (raw)
In-Reply-To: <20200113124729.3684846-3-sandals@crustytoothpaste.net> (brian m. carlson's message of "Mon, 13 Jan 2020 12:47:09 +0000")

"brian m. carlson" <sandals@crustytoothpaste.net> writes:

> +/*
> + * NOTE: This function relies on hash algorithms being in order from shortest
> + * length to longest length.
> + */
> +int get_oid_hex_any(const char *hex, struct object_id *oid)
> +{
> +	int i;
> +	for (i = GIT_HASH_NALGOS - 1; i > 0; i--) {
> +		if (!get_hash_hex_algop(hex, oid->hash, &hash_algos[i]))
> +			return i;
> +	}
> +	return GIT_HASH_UNKNOWN;
> +}

Two rather obvious questions are

 - what if we have more than one algos that produce hashes of the
   same length?

 - it feels that GIT_HASH_UNKNOWN being 0 wastes the first/zeroth
   element in the hash_algos[] array.

In the future, I would imagine that we would want to be able to say
"here I have a dozen hexdigits that is an abbreviated SHA2 hash",
and we would use some syntax (e.g. "sha2:123456123456") for that.
Would this function be at the layer that would be extended later to
support such a syntax, or would we have a layer higher than this to
do so?



>  int get_oid_hex(const char *hex, struct object_id *oid)
>  {
>  	return get_oid_hex_algop(hex, oid, the_hash_algo);
> @@ -87,6 +101,14 @@ int parse_oid_hex_algop(const char *hex, struct object_id *oid,
>  	return ret;
>  }
>  
> +int parse_oid_hex_any(const char *hex, struct object_id *oid, const char **end)
> +{
> +	int ret = get_oid_hex_any(hex, oid);
> +	if (ret)
> +		*end = hex + hash_algos[ret].hexsz;
> +	return ret;
> +}
> +
>  int parse_oid_hex(const char *hex, struct object_id *oid, const char **end)
>  {
>  	return parse_oid_hex_algop(hex, oid, end, the_hash_algo);

  reply index

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-13 12:47 [RFC PATCH 00/22] SHA-256 stage 4 implementation, part 1/3 brian m. carlson
2020-01-13 12:47 ` [RFC PATCH 01/22] hex: introduce parsing variants taking hash algorithms brian m. carlson
2020-01-13 12:47 ` [RFC PATCH 02/22] hex: add functions to parse hex object IDs in any algorithm brian m. carlson
2020-01-15 21:40   ` Junio C Hamano [this message]
2020-01-16  0:22     ` brian m. carlson
2020-01-13 12:47 ` [RFC PATCH 03/22] repository: require a build flag to use SHA-256 brian m. carlson
2020-01-13 12:47 ` [RFC PATCH 04/22] t: use hash-specific lookup tables to define test constants brian m. carlson
2020-01-13 12:47 ` [RFC PATCH 05/22] t6300: abstract away SHA-1-specific constants brian m. carlson
2020-01-13 12:47 ` [RFC PATCH 06/22] t6300: make hash algorithm independent brian m. carlson
2020-01-13 12:47 ` [RFC PATCH 07/22] t/helper/test-dump-split-index: initialize git repository brian m. carlson
2020-01-13 12:47 ` [RFC PATCH 08/22] t/helper: initialize repository if necessary brian m. carlson
2020-01-13 12:47 ` [RFC PATCH 09/22] t/helper: make repository tests hash independent brian m. carlson
2020-01-13 12:47 ` [RFC PATCH 10/22] setup: allow check_repository_format to read repository format brian m. carlson
2020-01-13 12:47 ` [RFC PATCH 11/22] builtin/init-db: allow specifying hash algorithm on command line brian m. carlson
2020-01-13 12:47 ` [RFC PATCH 12/22] builtin/init-db: add environment variable for new repo hash brian m. carlson
2020-01-13 12:47 ` [RFC PATCH 13/22] init-db: move writing repo version into a function brian m. carlson
2020-01-13 12:47 ` [RFC PATCH 14/22] worktree: allow repository version 1 brian m. carlson
2020-01-13 12:47 ` [RFC PATCH 15/22] commit: use expected signature header for SHA-256 brian m. carlson
2020-01-13 12:47 ` [RFC PATCH 16/22] gpg-interface: improve interface for parsing tags brian m. carlson
2020-01-13 12:47 ` [RFC PATCH 17/22] tag: store SHA-256 signatures in a header brian m. carlson
2020-01-13 12:47 ` [RFC PATCH 18/22] fast-import: permit reading multiple marks files brian m. carlson
2020-01-13 12:47 ` [RFC PATCH 19/22] fast-import: add helper function for inserting mark object entries brian m. carlson
2020-01-13 12:47 ` [RFC PATCH 20/22] fast-import: make find_marks work on any mark set brian m. carlson
2020-01-13 12:47 ` [RFC PATCH 21/22] fast-import: add a generic function to iterate over marks brian m. carlson
2020-01-13 12:47 ` [RFC PATCH 22/22] fast-import: add options for rewriting submodules brian m. carlson

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