String.replace_all

Hi,
Here is an implementation for a function String.replace_all,
it does the same than String.replace but for all occurences.
Please tell me if you find it usefull, in which case I would provide a patch.


let find_from str sub pos =
  let len = length str
  and sublen = length sub in
  if pos >= (len - sublen) then
    raise Invalid_string;
  if sublen = 0 then
    0
  else
    let found = ref 0 in
    try 
      for i = pos to (len - sublen) do
        let j = ref 0 in 
        while unsafe_get str (i + !j) = unsafe_get sub !j do
          incr j;
          if !j = sublen then begin found := i; raise Exit; end;
        done;
      done;
      raise Invalid_string
    with
      Exit -> !found
      

let replace_all ~str ~sub ~by =
  let sublen = length sub in
  try 
    if sublen = 0 then
      raise Invalid_string;
    let strlen = length str in
    let rec find_pos acc pos =
      try
        let i = find_from str sub pos in
        find_pos ((i + sublen)::i::acc) (i + sublen)
      with
        Invalid_string -> (strlen::acc)
    in  
    let all_pos = (find_pos [0] 0) in
    if List.length all_pos = 2 then
      raise Invalid_string;
      
    let rec make_slices acc = function
      | [] -> acc
      | _::[] -> assert(false)
      | last::first::tl ->
          let this = slice ~first ~last str in
          make_slices (this::acc) tl
    in
    let slices = make_slices [] all_pos in

    let res = concat by slices in
    (true, res)
  with
    Invalid_string -> (false, String.copy str)


-- 
Cheers
Florent

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