[PATCH v2 01/10] Define a structure for object IDs.

From: brian m. carlson <sandals@crustytoothpaste.net>
Date: Mar 7, 2015, 23:23 UTC
Message-ID: <1425770645-628957-2-git-send-email-sandals@crustytoothpaste.net>
In-Reply-To: <1425770645-628957-1-git-send-email-sandals@crustytoothpaste.net>

Many places throughout the code use "unsigned char [20]" to store object IDs (SHA-1 values). This leads to lots of hardcoded numbers throughout the codebase. It also leads to confusion about the purposes of a buffer.

Introduce a structure for object IDs. This allows us to obtain the benefits of compile-time checking for misuse. The structure is expected to remain the same size and have the same alignment requirements on all known platforms, compared to the array of unsigned char, although this is not required for correctness.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
---
 object.h | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/object.h b/object.h
index 6416247..f99b502 100644
--- a/object.h
+++ b/object.h
@@ -1,6 +1,14 @@
 #ifndef OBJECT_H
 #define OBJECT_H
 
+/* The length in bytes and in hex digits of an object name (SHA-1 value). */
+#define GIT_SHA1_RAWSZ 20
+#define GIT_SHA1_HEXSZ 40
+
+struct object_id {
+	unsigned char sha1[GIT_SHA1_RAWSZ];
+};
+
 struct object_list {
 	struct object *item;
 	struct object_list *next;

-- 
2.2.1.209.g41e5f3a