[v2,02/13] sha1-file: provide functions to look up hash algorithms
diff mbox series

Message ID 20181015021900.1030041-3-sandals@crustytoothpaste.net
State New
Headers show
Series
  • Base SHA-256 implementation
Related show

Commit Message

brian m. carlson Oct. 15, 2018, 2:18 a.m. UTC
There are several ways we might refer to a hash algorithm: by name, such
as in the config file; by format ID, such as in a pack; or internally,
by a pointer to the hash_algos array.  Provide functions to look up hash
algorithms based on these various forms and return the internal constant
used for them.  If conversion to another form is necessary, this
internal constant can be used to look up the proper data in the
hash_algos array.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
---
 hash.h      | 13 +++++++++++++
 sha1-file.c | 21 +++++++++++++++++++++
 2 files changed, 34 insertions(+)

Comments

SZEDER Gábor Oct. 17, 2018, 1:32 p.m. UTC | #1
On Mon, Oct 15, 2018 at 02:18:49AM +0000, brian m. carlson wrote:
> There are several ways we might refer to a hash algorithm: by name, such
> as in the config file; by format ID, such as in a pack; or internally,
> by a pointer to the hash_algos array.  Provide functions to look up hash
> algorithms based on these various forms and return the internal constant
> used for them.  If conversion to another form is necessary, this
> internal constant can be used to look up the proper data in the
> hash_algos array.
> 
> Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
> ---
>  hash.h      | 13 +++++++++++++
>  sha1-file.c | 21 +++++++++++++++++++++
>  2 files changed, 34 insertions(+)
> 
> diff --git a/hash.h b/hash.h
> index 7c8238bc2e..90f4344619 100644
> --- a/hash.h
> +++ b/hash.h
> @@ -98,4 +98,17 @@ struct git_hash_algo {
>  };
>  extern const struct git_hash_algo hash_algos[GIT_HASH_NALGOS];
>  
> +/*
> + * Return a GIT_HASH_* constant based on the name.  Returns GIT_HASH_UNKNOWN if
> + * the name doesn't match a known algorithm.
> + */
> +int hash_algo_by_name(const char *name);
> +/* Identical, except based on the format ID. */
> +int hash_algo_by_id(uint32_t format_id);
> +/* Identical, except for a pointer to struct git_hash_algo. */
> +inline int hash_algo_by_ptr(const struct git_hash_algo *p)

This has to be declared as static, otherwise the linker will error out
when building without optimization:

    LINK git
libgit.a(commit-graph.o): In function `oid_version':
/home/szeder/src/git/commit-graph.c:48: undefined reference to `hash_algo_by_ptr'
libgit.a(hex.o): In function `hash_to_hex':
/home/szeder/src/git/hex.c:123: undefined reference to `hash_algo_by_ptr'
libgit.a(hex.o): In function `oid_to_hex':
/home/szeder/src/git/hex.c:128: undefined reference to `hash_algo_by_ptr'
collect2: error: ld returned 1 exit status
Makefile:2055: recipe for target 'git' failed
make: *** [git] Error 1


> +{
> +	return p - hash_algos;
> +}
> +
>  #endif
> diff --git a/sha1-file.c b/sha1-file.c
> index e29825f259..3a75d515eb 100644
> --- a/sha1-file.c
> +++ b/sha1-file.c
> @@ -122,6 +122,27 @@ const char *empty_blob_oid_hex(void)
>  	return oid_to_hex_r(buf, the_hash_algo->empty_blob);
>  }
>  
> +int hash_algo_by_name(const char *name)
> +{
> +	int i;
> +	if (!name)
> +		return GIT_HASH_UNKNOWN;
> +	for (i = 1; i < GIT_HASH_NALGOS; i++)
> +		if (!strcmp(name, hash_algos[i].name))
> +			return i;
> +	return GIT_HASH_UNKNOWN;
> +}
> +
> +int hash_algo_by_id(uint32_t format_id)
> +{
> +	int i;
> +	for (i = 1; i < GIT_HASH_NALGOS; i++)
> +		if (format_id == hash_algos[i].format_id)
> +			return i;
> +	return GIT_HASH_UNKNOWN;
> +}
> +
> +
>  /*
>   * This is meant to hold a *small* number of objects that you would
>   * want read_sha1_file() to be able to return, but yet you do not want

Patch
diff mbox series

diff --git a/hash.h b/hash.h
index 7c8238bc2e..90f4344619 100644
--- a/hash.h
+++ b/hash.h
@@ -98,4 +98,17 @@  struct git_hash_algo {
 };
 extern const struct git_hash_algo hash_algos[GIT_HASH_NALGOS];
 
+/*
+ * Return a GIT_HASH_* constant based on the name.  Returns GIT_HASH_UNKNOWN if
+ * the name doesn't match a known algorithm.
+ */
+int hash_algo_by_name(const char *name);
+/* Identical, except based on the format ID. */
+int hash_algo_by_id(uint32_t format_id);
+/* Identical, except for a pointer to struct git_hash_algo. */
+inline int hash_algo_by_ptr(const struct git_hash_algo *p)
+{
+	return p - hash_algos;
+}
+
 #endif
diff --git a/sha1-file.c b/sha1-file.c
index e29825f259..3a75d515eb 100644
--- a/sha1-file.c
+++ b/sha1-file.c
@@ -122,6 +122,27 @@  const char *empty_blob_oid_hex(void)
 	return oid_to_hex_r(buf, the_hash_algo->empty_blob);
 }
 
+int hash_algo_by_name(const char *name)
+{
+	int i;
+	if (!name)
+		return GIT_HASH_UNKNOWN;
+	for (i = 1; i < GIT_HASH_NALGOS; i++)
+		if (!strcmp(name, hash_algos[i].name))
+			return i;
+	return GIT_HASH_UNKNOWN;
+}
+
+int hash_algo_by_id(uint32_t format_id)
+{
+	int i;
+	for (i = 1; i < GIT_HASH_NALGOS; i++)
+		if (format_id == hash_algos[i].format_id)
+			return i;
+	return GIT_HASH_UNKNOWN;
+}
+
+
 /*
  * This is meant to hold a *small* number of objects that you would
  * want read_sha1_file() to be able to return, but yet you do not want