[Libguestfs] [PATCH 1/2] mllib: add and use last_part_of

[Pino Toscano]

Collect this small snippet to get the part of a string after the last
occurrency of a character; replace with it the current snippets doing
the same.

Should be just code motion.
---
 customize/password.ml                     |  5 +++--
 mllib/common_utils.ml                     |  7 +++++++
 mllib/common_utils.mli                    |  3 +++
 sysprep/sysprep_operation_user_account.ml |  5 +++--
 v2v/convert_linux.ml                      | 10 +++-------
 v2v/utils.ml                              | 16 ++++++++++------
 6 files changed, 29 insertions(+), 17 deletions(-)

diff --git a/customize/password.ml b/customize/password.ml
index 25ce901..d91c4b5 100644
--- a/customize/password.ml
+++ b/customize/password.ml
@@ -98,8 +98,9 @@ let rec set_linux_passwords ?password_crypto (g : Guestfs.guestfs) root password
   List.iter (
     fun userpath ->
       let user =
-        let i = String.rindex userpath '/' in
-        String.sub userpath (i+1) (String.length userpath -i-1) in
+        match last_part_of userpath '/' with
+        | Some x -> x
+        | None -> error "password: missing '/' in %s" userpath in
       try
         (* Each line is: "user:[!!]password:..."
          * !! at the front of the password field means the account is locked.
diff --git a/mllib/common_utils.ml b/mllib/common_utils.ml
index 3737b4c..083c5d5 100644
--- a/mllib/common_utils.ml
+++ b/mllib/common_utils.ml
@@ -738,3 +738,10 @@ let guest_arch_compatible guest_arch =
   | x, y when x = y -> true
   | "x86_64", ("i386"|"i486"|"i586"|"i686") -> true
   | _ -> false
+
+(** Return the last part of a string, after the specified separator. *)
+let last_part_of str sep =
+  try
+    let i = String.rindex str sep in
+    Some (String.sub str (i+1) (String.length str - (i+1)))
+  with Not_found -> None
diff --git a/mllib/common_utils.mli b/mllib/common_utils.mli
index a5b0a68..550f37f 100644
--- a/mllib/common_utils.mli
+++ b/mllib/common_utils.mli
@@ -178,3 +178,6 @@ val mkdir_p : string -> int -> unit
 val guest_arch_compatible : string -> bool
 (** Are guest arch and host_cpu compatible, in terms of being able
     to run commands in the libguestfs appliance? *)
+
+val last_part_of : string -> char -> string option
+(** Return the last part of a string, after the specified separator. *)
diff --git a/sysprep/sysprep_operation_user_account.ml b/sysprep/sysprep_operation_user_account.ml
index 3f3b142..78c60d0 100644
--- a/sysprep/sysprep_operation_user_account.ml
+++ b/sysprep/sysprep_operation_user_account.ml
@@ -69,8 +69,9 @@ let user_account_perform g root side_effects =
         let uid = g#aug_get uid in
         let uid = int_of_string uid in
         let username =
-          let i = String.rindex userpath '/' in
-          String.sub userpath (i+1) (String.length userpath -i-1) in
+          match last_part_of userpath '/' with
+          | Some x -> x
+          | None -> error "user-accounts: missing '/' in %s" userpath in
         if uid >= uid_min && uid <= uid_max
            && check_remove_user username then (
           changed := true;
diff --git a/v2v/convert_linux.ml b/v2v/convert_linux.ml
index 7967c0f..f5a716f 100644
--- a/v2v/convert_linux.ml
+++ b/v2v/convert_linux.ml
@@ -795,13 +795,9 @@ let rec convert ~keep_serial_console (g : G.guestfs) inspect source =
        *)
       let mkinitrd_kv =
         let modpath = kernel.ki_modpath in
-        let len = String.length modpath in
-        try
-          let i = String.rindex modpath '/' in
-          String.sub modpath (i+1) (len - (i+1))
-        with
-          Not_found ->
-            invalid_arg (sprintf "invalid module path: %s" modpath) in
+        match last_part_of modpath '/' with
+        | Some x -> x
+        | None -> invalid_arg (sprintf "invalid module path: %s" modpath) in
 
       if g#is_file ~followsymlinks:true "/sbin/dracut" then (
         (* Dracut. *)
diff --git a/v2v/utils.ml b/v2v/utils.ml
index 2aeba45..976fe85 100644
--- a/v2v/utils.ml
+++ b/v2v/utils.ml
@@ -176,9 +176,11 @@ let find_virtio_win_drivers virtio_win =
         let paths = List.filter (g#is_file ~followsymlinks:false) paths in
         List.map (
           fun path ->
-            let i = String.rindex path '/' in
-            let len = String.length path in
-            let basename = String.sub path (i+1) (len - (i+1)) in
+            let basename =
+              match last_part_of path '/' with
+              | Some x -> x
+              | None ->
+                error "v2v/find_virtio_win_drivers: missing '/' in %s" path in
             (path, sprintf "%s:%s" virtio_win path,
              basename,
              fun () -> g#read_file path)
@@ -199,9 +201,11 @@ let find_virtio_win_drivers virtio_win =
           let lc_basename = String.lowercase basename in
 
           let extension =
-            let i = String.rindex lc_basename '.' in
-            let len = String.length lc_basename in
-            String.sub lc_basename (i+1) (len - (i+1)) in
+            match last_part_of lc_basename '.' with
+            | Some x -> x
+            | None ->
+              error "v2v/find_virtio_win_drivers: missing '.' in %s"
+                lc_basename in
 
           (* Skip files without specific extensions. *)
           if extension <> "cat" && extension <> "inf" &&
-- 
2.1.0