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From: "brian m. carlson" <sandals@crustytoothpaste.net>
To: git@vger.kernel.org
Cc: Martin Ågren <martin.agren@gmail.com>,
	Junio C Hamano <gitster@pobox.com>, Jeff King <peff@peff.net>
Subject: [PATCH v2 3/5] match-trees: use hashcpy to splice trees
Date: Tue, 15 Jan 2019 00:39:43 +0000
Message-ID: <20190115003946.932078-4-sandals@crustytoothpaste.net> (raw)
In-Reply-To: <20190115003946.932078-1-sandals@crustytoothpaste.net>

When we splice trees together, we operate in place on the tree buffer.
If we're using SHA-1 for the hash algorithm, we may not have a full
GIT_MAX_RAWSZ (32) bytes to copy. Consequently, it doesn't logically
make sense for us to use a struct object_id to represent this type,
since it isn't a complete object.

Represent this value as a unsigned char pointer instead and copy it when
necessary.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
---
 match-trees.c | 24 ++++++++++++++++++------
 1 file changed, 18 insertions(+), 6 deletions(-)

diff --git a/match-trees.c b/match-trees.c
index feca48a5fd..c2b7329e09 100644
--- a/match-trees.c
+++ b/match-trees.c
@@ -179,7 +179,7 @@ static int splice_tree(const struct object_id *oid1, const char *prefix,
 	char *buf;
 	unsigned long sz;
 	struct tree_desc desc;
-	struct object_id *rewrite_here;
+	unsigned char *rewrite_here;
 	const struct object_id *rewrite_with;
 	struct object_id subtree;
 	enum object_type type;
@@ -206,9 +206,19 @@ static int splice_tree(const struct object_id *oid1, const char *prefix,
 			if (!S_ISDIR(mode))
 				die("entry %s in tree %s is not a tree", name,
 				    oid_to_hex(oid1));
-			rewrite_here = (struct object_id *)(desc.entry.path +
-							    strlen(desc.entry.path) +
-							    1);
+
+			/*
+			 * We cast here for two reasons:
+			 *
+			 *   - to flip the "char *" (for the path) to "unsigned
+			 *     char *" (for the hash stored after it)
+			 *
+			 *   - to discard the "const"; this is OK because we
+			 *     know it points into our non-const "buf"
+			 */
+			rewrite_here = (unsigned char *)(desc.entry.path +
+							 strlen(desc.entry.path) +
+							 1);
 			break;
 		}
 		update_tree_entry(&desc);
@@ -217,14 +227,16 @@ static int splice_tree(const struct object_id *oid1, const char *prefix,
 		die("entry %.*s not found in tree %s", toplen, prefix,
 		    oid_to_hex(oid1));
 	if (*subpath) {
-		status = splice_tree(rewrite_here, subpath, oid2, &subtree);
+		struct object_id tree_oid;
+		hashcpy(tree_oid.hash, rewrite_here);
+		status = splice_tree(&tree_oid, subpath, oid2, &subtree);
 		if (status)
 			return status;
 		rewrite_with = &subtree;
 	} else {
 		rewrite_with = oid2;
 	}
-	oidcpy(rewrite_here, rewrite_with);
+	hashcpy(rewrite_here, rewrite_with->hash);
 	status = write_object_file(buf, sz, tree_type, result);
 	free(buf);
 	return status;

  parent reply index

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-07 23:34 What's cooking in git.git (Jan 2019, #01; Mon, 7) Junio C Hamano
2019-01-08  9:50 ` tg/checkout-no-overlay, was " Thomas Gummerer
2019-01-08 17:51   ` Junio C Hamano
2019-01-08 17:30 ` ag/sequencer-reduce-rewriting-todo " Alban Gruin
2019-01-08 21:20 ` sb/more-repo-in-api, was " Jonathan Tan
2019-01-08 21:35   ` Junio C Hamano
2019-01-09 21:28     ` Stefan Beller
2019-01-09  7:37 ` Martin Ågren
2019-01-09 21:06   ` Martin Ågren
2019-01-10  1:02     ` brian m. carlson
2019-01-10 18:55       ` Junio C Hamano
2019-01-10 19:03       ` Martin Ågren
2019-01-10  4:25     ` [PATCH 0/5] tree-walk object_id refactor brian m. carlson
2019-01-10  4:25       ` [PATCH 1/5] tree-walk: copy object ID before use brian m. carlson
2019-01-10  4:25       ` [PATCH 2/5] match-trees: compute buffer offset correctly when splicing brian m. carlson
2019-01-10  4:25       ` [PATCH 3/5] match-trees: use hashcpy to splice trees brian m. carlson
2019-01-10  6:45         ` Jeff King
2019-01-10 23:55           ` brian m. carlson
2019-01-11 14:51             ` Jeff King
2019-01-11 14:54               ` Jeff King
2019-01-14  1:30                 ` brian m. carlson
2019-01-14 15:40                   ` Jeff King
2019-01-10  4:25       ` [PATCH 4/5] tree-walk: store object_id in a separate member brian m. carlson
2019-01-10  6:49         ` Jeff King
2019-01-10 23:57           ` brian m. carlson
2019-01-10  4:25       ` [PATCH 5/5] cache: make oidcpy always copy GIT_MAX_RAWSZ bytes brian m. carlson
2019-01-10  6:50         ` Jeff King
2019-01-10  6:40       ` [PATCH 0/5] tree-walk object_id refactor Jeff King
2019-01-11  0:17         ` brian m. carlson
2019-01-11 14:17           ` Jeff King
2019-01-15  0:39     ` [PATCH v2 " brian m. carlson
2019-01-15  0:39       ` [PATCH v2 1/5] tree-walk: copy object ID before use brian m. carlson
2019-01-15  0:39       ` [PATCH v2 2/5] match-trees: compute buffer offset correctly when splicing brian m. carlson
2019-01-15  0:39       ` brian m. carlson [this message]
2019-01-15  0:39       ` [PATCH v2 4/5] tree-walk: store object_id in a separate member brian m. carlson
2019-01-15  0:39       ` [PATCH v2 5/5] cache: make oidcpy always copy GIT_MAX_RAWSZ bytes brian m. carlson
2019-01-15 17:51       ` [PATCH v2 0/5] tree-walk object_id refactor Junio C Hamano
2019-01-09 10:28 ` What's cooking in git.git (Jan 2019, #01; Mon, 7) Jeff King
2019-01-10 19:05   ` Junio C Hamano
2019-01-10 19:46   ` Junio C Hamano
2019-01-10 18:02 ` Stefan Beller

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