dpkg-deb: Use an enum instead of a literal string to pass tar options

This clarifies the call sites as to what they want from the extractor,
and abstracts the code to allow for a future switch to an internal tar
extractor instead of requiring an external tar program.

dpkg-deb/dpkg-deb.h

@@ -35,8 +35,21 @@ action_func do_fsystarfile;
 extern int opt_verbose;
 extern int debugflag, nocheckflag, oldformatflag;
 
+enum dpkg_tar_options {
+	/** Output the tar file directly, without any processing. */
+	DPKG_TAR_PASSTHROUGH = 0,
+	/** List tar files. */
+	DPKG_TAR_LIST = DPKG_BIT(0),
+	/** Extract tar files. */
+	DPKG_TAR_EXTRACT = DPKG_BIT(1),
+	/** Preserve tar permissions on extract. */
+	DPKG_TAR_PERMS = DPKG_BIT(2),
+	/** Do not set tar mtime on extract. */
+	DPKG_TAR_NOMTIME = DPKG_BIT(3),
+};
+
 void extracthalf(const char *debar, const char *dir,
-                 const char *taroption, int admininfo);
+                 enum dpkg_tar_options taroption, int admininfo);
 
 extern const char *showformat;
 extern struct compress_params compress_params;

dpkg-deb/extract.c

@@ -104,8 +104,8 @@ read_line(int fd, char *buf, size_t min_size, size_t max_size)
 }
 
 void
-extracthalf(const char *debar, const char *dir, const char *taroption,
-            int admininfo)
+extracthalf(const char *debar, const char *dir,
+            enum dpkg_tar_options taroption, int admininfo)
 {
   struct dpkg_error err;
   const char *errstr;
@@ -302,7 +302,19 @@ extracthalf(const char *debar, const char *dir, const char *taroption,
       command_init(&cmd, TAR, "tar");
       command_add_arg(&cmd, "tar");
 
-      command_add_arg(&cmd, taroption);
+      if ((taroption & DPKG_TAR_LIST) && (taroption & DPKG_TAR_EXTRACT))
+        command_add_arg(&cmd, "-xv");
+      else if (taroption & DPKG_TAR_EXTRACT)
+        command_add_arg(&cmd, "-x");
+      else if (taroption & DPKG_TAR_LIST)
+        command_add_arg(&cmd, "-tv");
+      else
+        internerr("unknown or missing tar action '%d'", taroption);
+
+      if (taroption & DPKG_TAR_PERMS)
+        command_add_arg(&cmd, "-p");
+      if (taroption & DPKG_TAR_NOMTIME)
+        command_add_arg(&cmd, "-m");
 
       command_add_arg(&cmd, "-f");
       command_add_arg(&cmd, "-");
@@ -349,7 +361,7 @@ extracthalf(const char *debar, const char *dir, const char *taroption,
 }
 
 static int
-controlextractvextract(int admin, const char *taroptions,
+controlextractvextract(int admin, enum dpkg_tar_options taroptions,
                        const char *const *argv)
 {
   const char *debar, *dir;
@@ -379,7 +391,7 @@ do_fsystarfile(const char *const *argv)
     badusage(_("--%s needs a .deb filename argument"),cipaction->olong);
   if (*argv)
     badusage(_("--%s takes only one argument (.deb filename)"),cipaction->olong);
-  extracthalf(debar, NULL, NULL, 0);
+  extracthalf(debar, NULL, DPKG_TAR_PASSTHROUGH, 0);
 
   return 0;
 }
@@ -387,16 +399,18 @@ do_fsystarfile(const char *const *argv)
 int
 do_control(const char *const *argv)
 {
-  return controlextractvextract(1, "x", argv);
+  return controlextractvextract(1, DPKG_TAR_EXTRACT, argv);
 }
 
 int
 do_extract(const char *const *argv)
 {
+  enum dpkg_tar_options options = DPKG_TAR_EXTRACT | DPKG_TAR_PERMS;
+
   if (opt_verbose)
-    return controlextractvextract(0, "xpv", argv);
-  else
-    return controlextractvextract(0, "xp", argv);
+    options |= DPKG_TAR_LIST;
+
+  return controlextractvextract(0, options, argv);
 }
 
 int
@@ -410,6 +424,7 @@ do_vextract(const char *const *argv)
 int
 do_raw_extract(const char *const *argv)
 {
+  enum dpkg_tar_options data_options;
   const char *debar, *dir;
   char *control_dir;
 
@@ -428,11 +443,12 @@ do_raw_extract(const char *const *argv)
 
   m_asprintf(&control_dir, "%s/%s", dir, EXTRACTCONTROLDIR);
 
+  data_options = DPKG_TAR_EXTRACT | DPKG_TAR_PERMS;
   if (opt_verbose)
-    extracthalf(debar, dir, "xpv", 0);
-  else
-    extracthalf(debar, dir, "xp", 0);
-  extracthalf(debar, control_dir, "x", 1);
+    data_options |= DPKG_TAR_LIST;
+
+  extracthalf(debar, dir, data_options, 0);
+  extracthalf(debar, control_dir, DPKG_TAR_EXTRACT, 1);
 
   free(control_dir);
 

dpkg-deb/info.c

@@ -82,7 +82,7 @@ static void info_prepare(const char *const **argvp,
   *dirp = dbuf;
 
   push_cleanup(cu_info_prepare, -1, NULL, 0, 1, (void *)dbuf);
-  extracthalf(*debarp, dbuf, "mx", admininfo);
+  extracthalf(*debarp, dbuf, DPKG_TAR_EXTRACT | DPKG_TAR_NOMTIME, admininfo);
 }
 
 static int ilist_select(const struct dirent *de) {
@@ -331,7 +331,7 @@ do_contents(const char *const *argv)
 
   if (debar == NULL || *argv)
     badusage(_("--%s takes exactly one argument"), cipaction->olong);
-  extracthalf(debar, NULL, "tv", 0);
+  extracthalf(debar, NULL, DPKG_TAR_LIST, 0);
 
   return 0;
 }