Include installation date within asset files

* src/android.c (setEmacsParams): Set `emacs_installation_time'
to the mtime of the class path file, which happens to be the
time of Emacs's installation.
(emacs_installation_time): New variable.

* src/android.h (emacs_installation_time): Export new variable.

* src/androidvfs.c (android_afs_stat): If
emacs_installation_time is a valid timespec, set st_mtime to it.

src/android.c

@@ -18,6 +18,7 @@ You should have received a copy of the GNU General Public License
 along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.  */
 
 #include <config.h>
+
 #include <allocator.h>
 #include <assert.h>
 #include <careadlinkat.h>
@@ -31,12 +32,15 @@ along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.  */
 #include <pthread.h>
 #include <semaphore.h>
 #include <signal.h>
+#include <stat-time.h>
 #include <stdckdint.h>
 #include <string.h>
-#include <sys/param.h>
 #include <timespec.h>
 #include <unistd.h>
 
+#include <sys/param.h>
+#include <sys/stat.h>
+
 /* Old NDK versions lack MIN and MAX.  */
 #include <minmax.h>
 
@@ -47,6 +51,7 @@ along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.  */
 #include "blockinput.h"
 #include "coding.h"
 #include "epaths.h"
+#include "systime.h"
 
 /* Whether or not Emacs is running inside the application process and
    Android windowing should be enabled.  */
@@ -187,6 +192,10 @@ static struct android_emacs_window window_class;
 /* Various methods associated with the EmacsCursor class.  */
 static struct android_emacs_cursor cursor_class;
 
+/* The time at which Emacs was installed, which also supplies the
+   mtime of asset files.  */
+struct timespec emacs_installation_time;
+
 /* The last event serial used.  This is a 32 bit value, but it is
    stored in unsigned long to be consistent with X.  */
 unsigned int event_serial;
@@ -1247,6 +1256,7 @@ NATIVE_NAME (setEmacsParams) (JNIEnv *env, jobject object,
   int pipefd[2];
   pthread_t thread;
   const char *java_string;
+  struct stat statb;
 
   /* Set the Android API level early, as it is used by
      `android_vfs_init'.  */
@@ -1341,13 +1351,24 @@ NATIVE_NAME (setEmacsParams) (JNIEnv *env, jobject object,
 
       android_class_path = strdup ((const char *) java_string);
 
-      if (!android_files_dir)
+      if (!android_class_path)
 	emacs_abort ();
 
       (*env)->ReleaseStringUTFChars (env, (jstring) class_path,
 				     java_string);
     }
 
+  /* Derive the installation date from the modification time of the
+     file constitituing the class path.  */
+
+  emacs_installation_time = invalid_timespec ();
+
+  if (class_path)
+    {
+      if (!stat (android_class_path, &statb))
+	emacs_installation_time = get_stat_mtime (&statb);
+    }
+
   /* Calculate the site-lisp path.  */
 
   android_site_load_path = malloc (PATH_MAX + 1);

src/android.h

@@ -299,6 +299,10 @@ extern jobject emacs_service;
 /* Various methods associated with the EmacsService.  */
 extern struct android_emacs_service service_class;
 
+/* The time at which Emacs was installed, which also supplies the
+   mtime of asset files.  */
+extern struct timespec emacs_installation_time;
+
 #define ANDROID_DELETE_LOCAL_REF(ref)				\
   ((*android_java_env)->DeleteLocalRef (android_java_env,	\
 					(ref)))

src/androidvfs.c

@@ -26,6 +26,7 @@ along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.  */
 #include <errno.h>
 #include <minmax.h>
 #include <string.h>
+#include <systime.h>
 #include <semaphore.h>
 
 #include <sys/stat.h>
@@ -2058,7 +2059,7 @@ android_afs_stat (struct android_vnode *vnode, struct stat *statb)
       /* Concoct a nonexistent device and an inode number.  */
       statb->st_dev = -1;
       statb->st_ino = 0;
-      return 0;
+      goto set_file_times;
     }
 
   /* AASSET_MODE_STREAMING is fastest here.  */
@@ -2083,6 +2084,24 @@ android_afs_stat (struct android_vnode *vnode, struct stat *statb)
 
   /* Close the asset.  */
   AAsset_close (asset_desc);
+
+ set_file_times:
+
+  /* If the installation date can be ascertained, return that as the
+     file's modification time.  */
+
+  if (timespec_valid_p (emacs_installation_time))
+    {
+#ifdef STAT_TIMESPEC
+      STAT_TIMESPEC (statb, st_mtim) = emacs_installation_time;
+#else /* !STAT_TIMESPEC */
+      /* Headers supplied by the NDK r10b contain a `struct stat'
+	 without POSIX fields for nano-second timestamps.  */
+      statb->st_mtime = emacs_installation_time.tv_sec;
+      statb->st_mtime_nsec = emacs_installation_time.tv_nsec;
+#endif /* STAT_TIMESPEC */
+    }
+
   return 0;
 }