From 96204969d2611dc618f7ed72ae40612b9526c763 Mon Sep 17 00:00:00 2001
From: Stefano Zacchiroli <zack@upsilon.cc>
Date: Mon, 7 Apr 2003 13:28:01 +0000
Subject: [PATCH] - added functions "add_line" and "remove_line" to edit line
 oriented files - use some Zack helpers intstead of reinventing the wheel

---
 helm/http_getter/http_getter_misc.ml  | 54 ++++++++++++++++++++++++---
 helm/http_getter/http_getter_misc.mli |  7 ++++
 2 files changed, 55 insertions(+), 6 deletions(-)

diff --git a/helm/http_getter/http_getter_misc.ml b/helm/http_getter/http_getter_misc.ml
index 70bd814ce..9ab708297 100644
--- a/helm/http_getter/http_getter_misc.ml
+++ b/helm/http_getter/http_getter_misc.ml
@@ -41,15 +41,14 @@ let tcp_bufsiz = 4096 (* for TCP I/O *)
 
 let fold_file f init fname =
   let inchan = open_in fname in
-  let rec fold_lines' value =
-    try 
-      let line = input_line inchan in 
-      fold_lines' (f value line)
-    with End_of_file -> value
+  let res =
+    try
+      Zack.fold_in f init inchan
+    with e -> close_in inchan; raise e
   in
-  let res = (try fold_lines' init with e -> (close_in inchan; raise e)) in
   close_in inchan;
   res
+
 let iter_file f = fold_file (fun _ line -> f line) ()
 
 let hashtbl_sorted_fold f tbl init =
@@ -231,3 +230,46 @@ let http_get url =
       Some (Http_client.Convenience.http_get url)
     with Http_client.Http_error (code, _) -> None
 
+  (** apply a transformation "string list -> string list" to file lines *)
+let mangle_file ~fname f =
+  let ic = open_in fname in
+  let lines = Zack.input_lines ic in
+  close_in ic;
+  let oc = open_out fname in
+  Zack.output_lines (f lines) oc;
+  close_out oc
+;;
+
+let add_line ~fname ?position line =
+  mangle_file ~fname
+    (fun lines ->
+      match position with
+      | None -> lines @ [line]
+      | Some i ->
+          assert (i >= 0);
+          let rec add_after i = function
+            | (acc, []) -> acc @ [line] (* eof *)
+            | (acc, ((hd::tl) as l)) ->
+                if i = 0 then
+                  acc @ [line] @ l
+                else
+                  add_after (i-1) (acc @ [hd], tl)
+          in
+          add_after i ([], lines))
+;;
+
+let remove_line ~fname position =
+  mangle_file ~fname
+    (fun lines ->
+      assert (position >= 0);
+      let rec remove i = function
+        | (acc, []) -> acc  (* eof *)
+        | (acc, ((hd::tl) as l)) ->
+            if i = 0 then
+              acc @ tl
+            else
+              remove (i-1) (acc @ [hd], tl)
+      in
+      remove position ([], lines))
+;;
+
diff --git a/helm/http_getter/http_getter_misc.mli b/helm/http_getter/http_getter_misc.mli
index 2047cf204..c6e2e72c6 100644
--- a/helm/http_getter/http_getter_misc.mli
+++ b/helm/http_getter/http_getter_misc.mli
@@ -73,3 +73,10 @@ val http_get: string -> string option
   remote resources fetched via HTTP GET requests *)
 val http_get_iter_buf: callback:(string -> unit) -> string -> unit
 
+  (** add a line to a file (specified by name) _after_ a given line (defaults to
+  last line). *)
+val add_line: fname:string -> ?position:int -> string -> unit
+  (** remove a line, if any, from a file specified by line number (0 based, i.e.
+  first line of file is line 0) *)
+val remove_line: fname:string -> int -> unit
+
-- 
2.39.2