odb-helper: add 'store_plain_objects' to 'struct odb_helper'

This adds a configuration option odb.<helper>.plainObjects and the
corresponding boolean variable called 'store_plain_objects' in
'struct odb_helper' to make it possible for external object
databases to store object as plain objects instead of Git objects.

The existing odb_helper_fetch_object() is renamed
odb_helper_fetch_git_object() and a new odb_helper_fetch_plain_object()
is introduce to deal with external objects that are not in Git format.

Signed-off-by: Christian Couder <chriscool@tuxfamily.org>

3 files changed, 114 insertions, 2 deletions

diff --git a/external-odb.c b/external-odb.c
index a980fbfbf2..af55377281 100644
--- a/external-odb.c
+++ b/external-odb.c
@@ -36,6 +36,8 @@ static int external_odb_config(const char *var, const char *value, void *data)
 
 	if (!strcmp(key, "command"))
 		return git_config_string(&o->cmd, var, value);
+	if (!strcmp(key, "plainobjects"))
+		o->store_plain_objects = git_config_bool(var, value);
 
 	return 0;
 }
diff --git a/odb-helper.c b/odb-helper.c
index 7b7de7380f..6b9fb7927a 100644
--- a/odb-helper.c
+++ b/odb-helper.c
@@ -153,8 +153,107 @@ int odb_helper_has_object(struct odb_helper *o, const unsigned char *sha1)
 	return !!odb_helper_lookup(o, sha1);
 }
 
-int odb_helper_fetch_object(struct odb_helper *o, const unsigned char *sha1,
-			    int fd)
+static int odb_helper_fetch_plain_object(struct odb_helper *o,
+					 const unsigned char *sha1,
+					 int fd)
+{
+	struct odb_helper_object *obj;
+	struct odb_helper_cmd cmd;
+	unsigned long total_got = 0;
+
+	char hdr[32];
+	int hdrlen;
+
+	int ret = Z_STREAM_END;
+	unsigned char compressed[4096];
+	git_zstream stream;
+	git_SHA_CTX hash;
+	unsigned char real_sha1[20];
+
+	obj = odb_helper_lookup(o, sha1);
+	if (!obj)
+		return -1;
+
+	if (odb_helper_start(o, &cmd, 0, "get %s", sha1_to_hex(sha1)) < 0)
+		return -1;
+
+	/* Set it up */
+	git_deflate_init(&stream, zlib_compression_level);
+	stream.next_out = compressed;
+	stream.avail_out = sizeof(compressed);
+	git_SHA1_Init(&hash);
+
+	/* First header.. */
+	hdrlen = xsnprintf(hdr, sizeof(hdr), "%s %lu", typename(obj->type), obj->size) + 1;
+	stream.next_in = (unsigned char *)hdr;
+	stream.avail_in = hdrlen;
+	while (git_deflate(&stream, 0) == Z_OK)
+		; /* nothing */
+	git_SHA1_Update(&hash, hdr, hdrlen);
+
+	for (;;) {
+		unsigned char buf[4096];
+		int r;
+
+		r = xread(cmd.child.out, buf, sizeof(buf));
+		if (r < 0) {
+			error("unable to read from odb helper '%s': %s",
+			      o->name, strerror(errno));
+			close(cmd.child.out);
+			odb_helper_finish(o, &cmd);
+			git_deflate_end(&stream);
+			return -1;
+		}
+		if (r == 0)
+			break;
+
+		total_got += r;
+
+		/* Then the data itself.. */
+		stream.next_in = (void *)buf;
+		stream.avail_in = r;
+		do {
+			unsigned char *in0 = stream.next_in;
+			ret = git_deflate(&stream, Z_FINISH);
+			git_SHA1_Update(&hash, in0, stream.next_in - in0);
+			write_or_die(fd, compressed, stream.next_out - compressed);
+			stream.next_out = compressed;
+			stream.avail_out = sizeof(compressed);
+		} while (ret == Z_OK);
+	}
+
+	close(cmd.child.out);
+	if (ret != Z_STREAM_END) {
+		warning("bad zlib data from odb helper '%s' for %s",
+			o->name, sha1_to_hex(sha1));
+		return -1;
+	}
+	ret = git_deflate_end_gently(&stream);
+	if (ret != Z_OK) {
+		warning("deflateEnd on object %s from odb helper '%s' failed (%d)",
+			sha1_to_hex(sha1), o->name, ret);
+		return -1;
+	}
+	git_SHA1_Final(real_sha1, &hash);
+	if (hashcmp(sha1, real_sha1)) {
+		warning("sha1 mismatch from odb helper '%s' for %s (got %s)",
+			o->name, sha1_to_hex(sha1), sha1_to_hex(real_sha1));
+		return -1;
+	}
+	if (odb_helper_finish(o, &cmd))
+		return -1;
+	if (total_got != obj->size) {
+		warning("size mismatch from odb helper '%s' for %s (%lu != %lu)",
+			o->name, sha1_to_hex(sha1), total_got, obj->size);
+		return -1;
+	}
+
+	return 0;
+}
+
+static int odb_helper_fetch_git_object(struct odb_helper *o,
+				       const unsigned char *sha1,
+				       int fd)
 {
 	struct odb_helper_object *obj;
 	struct odb_helper_cmd cmd;
@@ -242,6 +341,16 @@ int odb_helper_fetch_object(struct odb_helper *o, const unsigned char *sha1,
 	return 0;
 }
 
+int odb_helper_fetch_object(struct odb_helper *o,
+			    const unsigned char *sha1,
+			    int fd)
+{
+	if (o->store_plain_objects)
+		return odb_helper_fetch_plain_object(o, sha1, fd);
+	else
+		return odb_helper_fetch_git_object(o, sha1, fd);
+}
+
 int odb_helper_for_each_object(struct odb_helper *o,
 			       each_external_object_fn fn,
 			       void *data)
diff --git a/odb-helper.h b/odb-helper.h
index af31cc27d5..80d332139d 100644
--- a/odb-helper.h
+++ b/odb-helper.h
@@ -6,6 +6,7 @@
 struct odb_helper {
 	const char *name;
 	const char *cmd;
+	int store_plain_objects;
 
 	struct odb_helper_object {
 		unsigned char sha1[20];