statinfo: move stat_{data,validity} functions from cache/read-cache

These functions do not depend upon struct cache_entry or struct
index_state in any way, and it seems more logical to break them out into
this file, especially since statinfo.h already has the struct stat_data
declaration.

Diff best viewed with `--color-moved`.

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 51 insertions, 0 deletions

diff --git a/statinfo.h b/statinfo.h
index e49e3054ea..bb9b61bc47 100644
--- a/statinfo.h
+++ b/statinfo.h
@@ -1,6 +1,8 @@
 #ifndef STATINFO_H
 #define STATINFO_H
 
+struct index_state;
+
 /*
  * The "cache_time" is just the low 32 bits of the
  * time. It doesn't matter if it overflows - we only
@@ -21,4 +23,53 @@ struct stat_data {
 	unsigned int sd_size;
 };
 
+/*
+ * A struct to encapsulate the concept of whether a file has changed
+ * since we last checked it. This uses criteria similar to those used
+ * for the index.
+ */
+struct stat_validity {
+	struct stat_data *sd;
+};
+
+#define MTIME_CHANGED	0x0001
+#define CTIME_CHANGED	0x0002
+#define OWNER_CHANGED	0x0004
+#define MODE_CHANGED    0x0008
+#define INODE_CHANGED   0x0010
+#define DATA_CHANGED    0x0020
+#define TYPE_CHANGED    0x0040
+
+/*
+ * Record to sd the data from st that we use to check whether a file
+ * might have changed.
+ */
+void fill_stat_data(struct stat_data *sd, struct stat *st);
+
+/*
+ * Return 0 if st is consistent with a file not having been changed
+ * since sd was filled.  If there are differences, return a
+ * combination of MTIME_CHANGED, CTIME_CHANGED, OWNER_CHANGED,
+ * INODE_CHANGED, and DATA_CHANGED.
+ */
+int match_stat_data(const struct stat_data *sd, struct stat *st);
+
+void stat_validity_clear(struct stat_validity *sv);
+
+/*
+ * Returns 1 if the path is a regular file (or a symlink to a regular
+ * file) and matches the saved stat_validity, 0 otherwise.  A missing
+ * or inaccessible file is considered a match if the struct was just
+ * initialized, or if the previous update found an inaccessible file.
+ */
+int stat_validity_check(struct stat_validity *sv, const char *path);
+
+/*
+ * Update the stat_validity from a file opened at descriptor fd. If
+ * the file is missing, inaccessible, or not a regular file, then
+ * future calls to stat_validity_check will match iff one of those
+ * conditions continues to be true.
+ */
+void stat_validity_update(struct stat_validity *sv, int fd);
+
 #endif