[Libguestfs] [PATCH v4 4/6] mllib: modify nsplit to take optional noempty and count arguments

[Tomáš Golembiovský]

Added two new optional arguments to nsplit:

* noempty: if set to false empty elements are not stored in the returned
  list. The default is to keep the empty elements

* count: specifies how many splits to perform; negative count
  (the default) means do as many splits as possible

Added tests for nsplit.

Signed-off-by: Tomáš Golembiovský <tgolembi at redhat.com>
---
 mllib/common_utils.ml       | 12 +++++++++---
 mllib/common_utils.mli      | 12 ++++++++++--
 mllib/common_utils_tests.ml | 26 ++++++++++++++++++++++++++
 3 files changed, 45 insertions(+), 5 deletions(-)

diff --git a/mllib/common_utils.ml b/mllib/common_utils.ml
index f948dce..b6f3046 100644
--- a/mllib/common_utils.ml
+++ b/mllib/common_utils.ml
@@ -130,15 +130,21 @@ module String = struct
       done;
       if not !r then s else Bytes.to_string b2
 
-    let rec nsplit sep str =
+    let rec nsplit ?(noempty = true) ?(count = -1) sep str =
       let len = length str in
       let seplen = length sep in
       let i = find str sep in
-      if i = -1 then [str]
+      if i = -1 || count = 0 then [str]
       else (
         let s' = sub str 0 i in
         let s'' = sub str (i+seplen) (len-i-seplen) in
-        s' :: nsplit sep s''
+        let elem, count =
+          if s' = "" && noempty then
+            [], count
+          else
+            [s'], if count > 0 then count-1 else count
+        in
+        elem @ nsplit ~noempty:noempty ~count:count sep s''
       )
 
     let split sep str =
diff --git a/mllib/common_utils.mli b/mllib/common_utils.mli
index 4a6ddd6..fd0ef49 100644
--- a/mllib/common_utils.mli
+++ b/mllib/common_utils.mli
@@ -80,9 +80,17 @@ module String : sig
         [str] with [s2]. *)
     val replace_char : string -> char -> char -> string
     (** Replace character in string. *)
-    val nsplit : string -> string -> string list
+    val nsplit : ?noempty:bool -> ?count:int -> string -> string -> string list
     (** [nsplit sep str] splits [str] into multiple strings at each
-        separator [sep]. *)
+        separator [sep].
+
+        If [noempty] is set to true empty elements are not included in the
+        list. By default empty elements are kept.
+
+        If [count] is specified it says how many splits to perform. I.e. the
+        returned array will have at most [count]+1 elements. Negative [count]
+        (the default) means do as many splits as possible.
+        *)
     val split : string -> string -> string * string
     (** [split sep str] splits [str] at the first occurrence of the
         separator [sep], returning the part before and the part after.
diff --git a/mllib/common_utils_tests.ml b/mllib/common_utils_tests.ml
index ee27b93..ef5665f 100644
--- a/mllib/common_utils_tests.ml
+++ b/mllib/common_utils_tests.ml
@@ -109,6 +109,32 @@ let test_string_find ctx =
   assert_equal_int (-1) (String.find "" "baz");
   assert_equal_int (-1) (String.find "foobar" "baz")
 
+(* Test Common_utils.String.nsplit *)
+let test_string_nsplit ctx =
+  (* Basic functionality *)
+  assert_equal_stringlist [""] (String.nsplit "," "");
+  assert_equal_stringlist ["A"] (String.nsplit "," "A");
+  assert_equal_stringlist ["A"; "B"] (String.nsplit "," "A,B");
+  assert_equal_stringlist ["A"; "B"; "C"] (String.nsplit "," "A,B,C");
+  assert_equal_stringlist ["A"; "B"; "C"; "D"] (String.nsplit "," "A,B,C,D");
+  assert_equal_stringlist [""; "A"; ""] (String.nsplit "," ",A,");
+  assert_equal_stringlist ["A"; ""; ""; "B"] (String.nsplit "," "A,,,B");
+  assert_equal_stringlist ["A"; "B"; "C"; "D"] (String.nsplit "<>" "A<>B<>C<>D");
+
+  (* noemty option *)
+  assert_equal_stringlist ["A"] (String.nsplit ~noempty:true "," ",A,");
+  assert_equal_stringlist ["A"; "B"] (String.nsplit ~noempty:true "," "A,,,B");
+
+  (* count option *)
+  assert_equal_stringlist ["A"; "B"; "C"; "D"] (String.nsplit ~count:(-1) "," "A,B,C,D");
+  assert_equal_stringlist ["A,B,C,D"] (String.nsplit ~count:0 "," "A,B,C,D");
+  assert_equal_stringlist ["A"; "B,C,D"] (String.nsplit ~count:1 "," "A,B,C,D");
+  assert_equal_stringlist ["A"; "B"; "C,D"] (String.nsplit ~count:2 "," "A,B,C,D");
+  assert_equal_stringlist ["A"; "B"; "C"; "D"] (String.nsplit ~count:10 "," "A,B,C,D");
+
+  (* count and noempty together *)
+  assert_equal_stringlist ["A"; "B"; "C,D"] (String.nsplit ~noempty:true ~count:2 "," ",,,A,,,,B,,,,C,D")
+
 (* Test Common_utils.String.lines_split. *)
 let test_string_lines_split ctx =
   assert_equal_stringlist [""] (String.lines_split "");
-- 
2.10.2