lib/core: Added new `append_substring` service to avoid creating ephemeral instances

Signed-off-by: Lucas Bajolet <r4pass@hotmail.com>

diff --git a/lib/core/text/abstract_text.nit b/lib/core/text/abstract_text.nit
index 6c2acd4..c9d1279 100644 (file)
--- a/lib/core/text/abstract_text.nit
+++ b/lib/core/text/abstract_text.nit
@@ -1514,6 +1514,42 @@ abstract class Buffer
        # In Buffers, the internal sequence of character is mutable
        # Thus, `chars` can be used to modify the buffer.
        redef fun chars: Sequence[Char] is abstract
+
+       # Appends `length` chars from `s` starting at index `from`
+       #
+       # ~~~nit
+       #       var b = new Buffer
+       #       b.append_substring("abcde", 1, 2)
+       #       assert b == "bc"
+       #       b.append_substring("vwxyz", 2, 3)
+       #       assert b == "bcxyz"
+       #       b.append_substring("ABCDE", 4, 300)
+       #       assert b == "bcxyzE"
+       #       b.append_substring("VWXYZ", 400, 1)
+       #       assert b == "bcxyzE"
+       # ~~~
+       fun append_substring(s: Text, from, length: Int) do
+               if from < 0 then
+                       length += from
+                       from = 0
+               end
+               var ln = s.length
+               if (length + from) > ln then length = ln - from
+               if length <= 0 then return
+               append_substring_impl(s, from, length)
+       end
+
+       # Unsafe version of `append_substring` for performance
+       #
+       # NOTE: Use only if sure about `from` and `length`, no checks
+       # or bound recalculation is done
+       fun append_substring_impl(s: Text, from, length: Int) do
+               var pos = from
+               for i in [0 .. length[ do
+                       self.add s[pos]
+                       pos += 1
+               end
+       end
 end
 
 # View for chars on Buffer objects, extends Sequence

diff --git a/lib/core/text/flat.nit b/lib/core/text/flat.nit
index 45ad144..83cae37 100644 (file)
--- a/lib/core/text/flat.nit
+++ b/lib/core/text/flat.nit
@@ -411,7 +411,7 @@ abstract class FlatString
 
                if from < 0 then
                        count += from
-                       if count < 0 then return ""
+                       if count <= 0 then return ""
                        from = 0
                end
 
@@ -1054,6 +1054,21 @@ class FlatBuffer
                return new FlatBuffer.with_infos(r_items, byte_length, byte_length, count)
        end
 
+       redef fun append_substring_impl(s, from, length) do
+               if length <= 0 then return
+               if not s isa FlatText then
+                       super
+                       return
+               end
+               var bytest = s.char_to_byte_index(from)
+               var bytend = s.char_to_byte_index(from + length - 1)
+               var btln = bytend - bytest + 1
+               enlarge(btln + _bytelen)
+               s._items.copy_to(_items, btln, bytest, _bytelen)
+               _bytelen += btln
+               _length += length
+       end
+
        redef fun reverse
        do
                written = false