hex: introduce parse_oid_hex

Introduce a function, parse_oid_hex, which parses a hexadecimal object
ID and if successful, sets a pointer to just beyond the last character.
This allows for simpler, more robust parsing without needing to
hard-code integer values throughout the codebase.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

2 files changed, 17 insertions, 0 deletions

diff --git a/cache.h b/cache.h
index 61fc86e6d7..e03a672d15 100644
--- a/cache.h
+++ b/cache.h
@@ -1319,6 +1319,15 @@ extern char *oid_to_hex_r(char *out, const struct object_id *oid);
 extern char *sha1_to_hex(const unsigned char *sha1);	/* static buffer result! */
 extern char *oid_to_hex(const struct object_id *oid);	/* same static buffer as sha1_to_hex */
 
+/*
+ * Parse a 40-character hexadecimal object ID starting from hex, updating the
+ * pointer specified by end when parsing stops.  The resulting object ID is
+ * stored in oid.  Returns 0 on success.  Parsing will stop on the first NUL or
+ * other invalid character.  end is only updated on success; otherwise, it is
+ * unmodified.
+ */
+extern int parse_oid_hex(const char *hex, struct object_id *oid, const char **end);
+
 extern int interpret_branch_name(const char *str, int len, struct strbuf *);
 extern int get_oid_mb(const char *str, struct object_id *oid);
 
diff --git a/hex.c b/hex.c
index 845b01a874..eab7b626ee 100644
--- a/hex.c
+++ b/hex.c
@@ -53,6 +53,14 @@ int get_oid_hex(const char *hex, struct object_id *oid)
 	return get_sha1_hex(hex, oid->hash);
 }
 
+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 + GIT_SHA1_HEXSZ;
+	return ret;
+}
+
 char *sha1_to_hex_r(char *buffer, const unsigned char *sha1)
 {
 	static const char hex[] = "0123456789abcdef";