+// Defined in Makefile
+#ifndef NSSCASH_PASSWD_FILE
+# define NSSCASH_PASSWD_FILE "/etc/passwd.nsscash"
+#endif
+#ifndef NSSCASH_GROUP_FILE
+# define NSSCASH_GROUP_FILE "/etc/group.nsscash"
+#endif
+
+
+// header describes the on-disk (and, after loading via mmap, in-memory)
+// structure of nsscash files.
+struct header {
+ char magic[8]; // magic string
+ uint64_t version; // also doubles as byte-order check
+
+ uint64_t count; // number of entries in this file
+
+ // All offsets are relative to data
+ uint64_t off_orig_index;
+ uint64_t off_id_index;
+ uint64_t off_name_index;
+ uint64_t off_data;
+
+ char data[];
+} __attribute__((packed));
+
+// file represents an open nsscash file.