[RFC PATCH 01/22] hex: introduce parsing variants taking hash algorithms

["brian m. carlson" <sandals@xxxxxxxxxxxxxxxxxxxx>]

Introduce variants of get_oid_hex and parse_oid_hex that parse an
arbitrary hash algorithm, implementing internal functions to avoid
duplication.  These functions can be used in the transport code to parse
refs properly.

Signed-off-by: brian m. carlson <sandals@xxxxxxxxxxxxxxxxxxxx>
---
 cache.h |  7 +++++++
 hex.c   | 35 +++++++++++++++++++++++++++--------
 2 files changed, 34 insertions(+), 8 deletions(-)

diff --git a/cache.h b/cache.h
index cbfaead23a..493d57febe 100644
--- a/cache.h
+++ b/cache.h
@@ -1480,6 +1480,9 @@ int set_disambiguate_hint_config(const char *var, const char *value);
 int get_sha1_hex(const char *hex, unsigned char *sha1);
 int get_oid_hex(const char *hex, struct object_id *sha1);
 
+/* Like get_oid_hex, but for an arbitrary hash algorithm. */
+int get_oid_hex_algop(const char *hex, struct object_id *oid, const struct git_hash_algo *algop);
+
 /*
  * Read `len` pairs of hexadecimal digits from `hex` and write the
  * values to `binary` as `len` bytes. Return 0 on success, or -1 if
@@ -1515,6 +1518,10 @@ char *oid_to_hex(const struct object_id *oid);						/* same static buffer */
  */
 int parse_oid_hex(const char *hex, struct object_id *oid, const char **end);
 
+/* Like parse_oid_hex, but for an arbitrary hash algorithm. */
+int parse_oid_hex_algop(const char *hex, struct object_id *oid, const char **end,
+			const struct git_hash_algo *algo);
+
 /*
  * This reads short-hand syntax that not only evaluates to a commit
  * object name, but also can act as if the end user spelled the name
diff --git a/hex.c b/hex.c
index fd7f00c43f..10e24dc2e4 100644
--- a/hex.c
+++ b/hex.c
@@ -47,30 +47,49 @@ int hex_to_bytes(unsigned char *binary, const char *hex, size_t len)
 	return 0;
 }
 
-int get_sha1_hex(const char *hex, unsigned char *sha1)
+static int get_hash_hex_algop(const char *hex, unsigned char *hash,
+			      const struct git_hash_algo *algop)
 {
 	int i;
-	for (i = 0; i < the_hash_algo->rawsz; i++) {
+	for (i = 0; i < algop->rawsz; i++) {
 		int val = hex2chr(hex);
 		if (val < 0)
 			return -1;
-		*sha1++ = val;
+		*hash++ = val;
 		hex += 2;
 	}
 	return 0;
 }
 
+int get_sha1_hex(const char *hex, unsigned char *sha1)
+{
+	return get_hash_hex_algop(hex, sha1, the_hash_algo);
+}
+
+int get_oid_hex_algop(const char *hex, struct object_id *oid,
+		      const struct git_hash_algo *algop)
+{
+	return get_hash_hex_algop(hex, oid->hash, algop);
+}
+
 int get_oid_hex(const char *hex, struct object_id *oid)
 {
-	return get_sha1_hex(hex, oid->hash);
+	return get_oid_hex_algop(hex, oid, the_hash_algo);
+}
+
+int parse_oid_hex_algop(const char *hex, struct object_id *oid,
+			const char **end,
+			const struct git_hash_algo *algop)
+{
+	int ret = get_hash_hex_algop(hex, oid->hash, algop);
+	if (!ret)
+		*end = hex + algop->hexsz;
+	return ret;
 }
 
 int parse_oid_hex(const char *hex, struct object_id *oid, const char **end)
 {
-	int ret = get_oid_hex(hex, oid);
-	if (!ret)
-		*end = hex + the_hash_algo->hexsz;
-	return ret;
+	return parse_oid_hex_algop(hex, oid, end, the_hash_algo);
 }
 
 char *hash_to_hex_algop_r(char *buffer, const unsigned char *hash,