[PATCH/RFC v3 4/6] reflog: add backwards iterator

[Thomas Rast <trast@student.ethz.ch>]

Add for_each_reflog_ent_backward() which does the same as
for_each_reflog_ent(), except it traverses the reflog in backwards
(newest to oldest) order.

Signed-off-by: Thomas Rast <trast@student.ethz.ch>
---
 refs.c |   35 +++++++++++++++++++++++++++++++++++
 refs.h |    1 +
 2 files changed, 36 insertions(+), 0 deletions(-)

diff --git a/refs.c b/refs.c
index 3848aa0..cc78f63 100644
--- a/refs.c
+++ b/refs.c
@@ -1476,6 +1476,41 @@ int read_ref_at(const char *ref, unsigned long at_time, int cnt, unsigned char *
 	return 1;
 }
 
+int for_each_reflog_ent_backward(const char *ref, each_reflog_ent_fn fn, void *cb_data)
+{
+	const char *log_mapped, *buf, *log_end, *logfile;
+	size_t mapsz;
+	int ret = 0;
+
+	log_mapped = open_reflog(ref, &mapsz, &logfile);
+	if (!log_mapped)
+		return -1;
+	buf = log_end = log_mapped + mapsz;
+
+	while (buf > log_mapped) {
+		unsigned char osha1[20], nsha1[20];
+		char *email, *message;
+		const char *end;
+		unsigned long timestamp;
+		int tz;
+
+		while (buf > log_mapped && buf[-1] == '\n')
+			buf--;
+		end = buf;
+		while (buf > log_mapped && buf[-1] != '\n')
+			buf--;
+		parse_reflog_line(buf, end-buf+1,
+				  osha1, nsha1,
+				  &email, &timestamp, &tz, &message,
+				  logfile);
+		ret = fn(osha1, nsha1, email, timestamp, tz, message, cb_data);
+		if (ret)
+			break;
+	}
+	munmap((void*) log_mapped, mapsz);
+	return ret;
+}
+
 int for_each_reflog_ent(const char *ref, each_reflog_ent_fn fn, void *cb_data)
 {
 	const char *log_mapped, *buf, *log_end, *logfile;
diff --git a/refs.h b/refs.h
index 06ad260..723bddc 100644
--- a/refs.h
+++ b/refs.h
@@ -60,6 +60,7 @@ struct ref_lock {
 /* iterate over reflog entries */
 typedef int each_reflog_ent_fn(unsigned char *osha1, unsigned char *nsha1, const char *, unsigned long, int, const char *, void *);
 int for_each_reflog_ent(const char *ref, each_reflog_ent_fn fn, void *cb_data);
+int for_each_reflog_ent_backward(const char *ref, each_reflog_ent_fn fn, void *cb_data);
 
 /*
  * Calls the specified function for each reflog file until it returns nonzero,
-- 
1.6.1.315.g92577