[PATCH 07/14] bundle: add is_bundle_buf helper

[Jeff King <peff@peff.net>]

This is similar to is_bundle, but checks an in-memory buffer
rather than a file. It also works on a partial buffer,
checking only the bundle signature. This means the result is
a three-way conditional: yes, no, or "we do not have enough
data yet".

Signed-off-by: Jeff King <peff@peff.net>
---
 bundle.c |   14 ++++++++++++++
 bundle.h |    1 +
 2 files changed, 15 insertions(+), 0 deletions(-)

diff --git a/bundle.c b/bundle.c
index e48fe2f..6f911bc 100644
--- a/bundle.c
+++ b/bundle.c
@@ -122,6 +122,20 @@ int is_bundle(const char *path, int quiet)
 	return (fd >= 0);
 }
 
+int is_bundle_buf(const char *s, int len)
+{
+	if (len > strlen(bundle_signature))
+		len = strlen(bundle_signature);
+	/* If we don't match what we already have, then definitely not. */
+	if (memcmp(s, bundle_signature, len))
+		return 0;
+	/* If we have enough bytes, we can say yes */
+	if (len == strlen(bundle_signature))
+		return 1;
+	/* otherwise, we can only say "maybe" */
+	return -1;
+}
+
 static int list_refs(struct ref_list *r, int argc, const char **argv)
 {
 	int i;
diff --git a/bundle.h b/bundle.h
index 675cc97..8bec44d 100644
--- a/bundle.h
+++ b/bundle.h
@@ -15,6 +15,7 @@ struct bundle_header {
 };
 
 int is_bundle(const char *path, int quiet);
+int is_bundle_buf(const char *s, int len);
 int read_bundle_header(const char *path, struct bundle_header *header);
 int create_bundle(struct bundle_header *header, const char *path,
 		int argc, const char **argv);
-- 
1.7.7.2.7.g9f96f