Re: [PATCH 17/16] http-push: refactor parsing of remote object names

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On Thu, Jun 19, 2014 at 05:58:10PM -0400, Jeff King wrote:

> It's still a little more magical than I would like, but I think this is
> the best we can do while still building on get_sha1_hex. Parsing it
> left-to-right would be better, but we would essentially end up
> reimplementing get_sha1_hex.

Just for fun, that would look something like this (on top):

diff --git a/http-push.c b/http-push.c
index c5c95e8..2425c61 100644
--- a/http-push.c
+++ b/http-push.c
@@ -1016,20 +1016,34 @@ static void remote_ls(const char *path, int flags,
 		      void (*userFunc)(struct remote_ls_ctx *ls),
 		      void *userData);
 
+static inline int parse_one_hex(unsigned char **to, const char **from)
+{
+	unsigned int val;
+
+	/* avoid reading past end-of-string for from[1] */
+	if (!(*from)[0])
+		return -1;
+	val = (hexval((*from)[0]) << 4) | hexval((*from)[1]);
+	if (val & ~0xff)
+		return -1;
+	*(*to)++ = val;
+	(*from) += 2;
+	return 0;
+}
+
 /* extract hex from sharded "xx/x{40}" filename */
 static int get_sha1_hex_from_objpath(const char *path, unsigned char *sha1)
 {
-	char hex[40];
+	int i;
 
-	if (strlen(path) != 41)
+	if (parse_one_hex(&sha1, &path) < 0)
 		return -1;
-
-	memcpy(hex, path, 2);
-	path += 2;
-	path++; /* skip '/' */
-	memcpy(hex, path, 38);
-
-	return get_sha1_hex(hex, sha1);
+	if (*path++ != '/')
+		return -1;
+	for (i = 1; i < 20; i++)
+		if (parse_one_hex(&sha1, &path) < 0)
+			return -1;
+	return 0;
 }
 
 static void process_ls_object(struct remote_ls_ctx *ls)

In theory we could factor parse_one_hex to share with get_sha1_hex, but
I am hesitant to touch get_sha1_hex, as it is used in a lot of tight
loops.

-Peff
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