[Libguestfs] [PATCH v8 1/4] mllib: add subdirectory function to common_utils

[Tomáš Golembiovský]

Signed-off-by: Tomáš Golembiovský <tgolembi at redhat.com>
---
 mllib/common_utils.ml       |  9 +++++++++
 mllib/common_utils.mli      | 10 ++++++++++
 mllib/common_utils_tests.ml |  7 +++++++
 3 files changed, 26 insertions(+)

diff --git a/mllib/common_utils.ml b/mllib/common_utils.ml
index e9ae6a4a2..a79abdd7e 100644
--- a/mllib/common_utils.ml
+++ b/mllib/common_utils.ml
@@ -236,6 +236,15 @@ end
 let (//) = Filename.concat
 let quote = Filename.quote
 
+let subdirectory parent path =
+  if path = parent then
+    ""
+  else if String.is_prefix path (parent // "") then
+    let len = String.length parent in
+    String.sub path (len+1) (String.length path - len-1)
+  else
+    raise (Invalid_argument (sprintf "%S is not a path prefix of %S" parent path))
+
 let ( +^ ) = Int64.add
 let ( -^ ) = Int64.sub
 let ( *^ ) = Int64.mul
diff --git a/mllib/common_utils.mli b/mllib/common_utils.mli
index 722e528e5..977ce6576 100644
--- a/mllib/common_utils.mli
+++ b/mllib/common_utils.mli
@@ -116,6 +116,16 @@ val ( // ) : string -> string -> string
 val quote : string -> string
 (** Shell-safe quoting of a string (alias for {!Filename.quote}). *)
 
+val subdirectory : string -> string -> string
+(** [subdirectory parent path] returns subdirectory part of [path] relative
+    to the [parent]. If [path] and [parent] point to the same directory empty
+    string is returned.
+
+    Note: path normalization on arguments is NOT performed!
+
+    If [parent] is not a path prefix of [path] the function raises
+    [Invalid_argument]. *)
+
 val ( +^ ) : int64 -> int64 -> int64
 val ( -^ ) : int64 -> int64 -> int64
 val ( *^ ) : int64 -> int64 -> int64
diff --git a/mllib/common_utils_tests.ml b/mllib/common_utils_tests.ml
index 77b0524c1..aacc01e04 100644
--- a/mllib/common_utils_tests.ml
+++ b/mllib/common_utils_tests.ml
@@ -27,6 +27,12 @@ let assert_equal_int = assert_equal ~printer:(fun x -> string_of_int x)
 let assert_equal_int64 = assert_equal ~printer:(fun x -> Int64.to_string x)
 let assert_equal_stringlist = assert_equal ~printer:(fun x -> "(" ^ (String.escaped (String.concat "," x)) ^ ")")
 
+let test_subdirectory ctx =
+  assert_equal_string "" (subdirectory "/foo" "/foo");
+  assert_equal_string "" (subdirectory "/foo" "/foo/");
+  assert_equal_string "bar" (subdirectory "/foo" "/foo/bar");
+  assert_equal_string "bar/baz" (subdirectory "/foo" "/foo/bar/baz")
+
 (* Test Common_utils.int_of_le32 and Common_utils.le32_of_int. *)
 let test_le32 ctx =
   assert_equal_int64 0x20406080L (int_of_le32 "\x80\x60\x40\x20");
@@ -129,6 +135,7 @@ let test_string_lines_split ctx =
 let suite =
   "mllib Common_utils" >:::
     [
+      "subdirectory" >:: test_subdirectory;
       "numeric.le32" >:: test_le32;
       "sizes.parse_resize" >:: test_parse_resize;
       "sizes.human_size" >:: test_human_size;
-- 
2.11.0