core/array: provide a better implementation of `copy_to` (not native yet)

Signed-off-by: Jean Privat <jean@pryen.org>

diff --git a/lib/core/collection/array.nit b/lib/core/collection/array.nit
index e8f57c0..d196333 100644 (file)
--- a/lib/core/collection/array.nit
+++ b/lib/core/collection/array.nit
@@ -111,7 +111,6 @@ abstract class AbstractArrayRead[E]
        #     assert b      ==  [10, 20, 2, 3, 50]
        fun copy_to(start: Int, len: Int, dest: AbstractArray[E], new_start: Int)
        do
-               # TODO native one
                if start < new_start then
                        var i = len
                        while i > 0 do
@@ -373,6 +372,32 @@ class Array[E]
                _length = nl
        end
 
+       redef fun copy_to(start, len, dest, new_start)
+       do
+               # Fast code when source and destination are two arrays
+
+               if not dest isa Array[E] then
+                       super
+                       return
+               end
+
+               # Enlarge dest if required
+               var dest_len = new_start + len
+               if dest_len > dest.length then
+                       dest.enlarge(dest_len)
+                       dest.length = dest_len
+               end
+
+               # Get underlying native arrays
+               var items = self.items
+               if items == null then return
+               var dest_items = dest.items
+               assert dest_items != null
+
+               # Native copy
+               items.memmove(start, len, dest_items, new_start)
+       end
+
        redef fun enlarge(cap)
        do
                var c = _capacity
@@ -966,6 +991,25 @@ universal NativeArray[E]
 
        # Copy `length` items to `dest`.
        fun copy_to(dest: NativeArray[E], length: Int) is intern
+
+       # Copy `length` items to `dest` starting from `dest`.
+       fun memmove(start: Int, length: Int, dest: NativeArray[E], dest_start: Int) do
+               # TODO native one
+               if start < dest_start then
+                       var i = length
+                       while i > 0 do
+                               i -= 1
+                               dest[dest_start+i] = self[start+i]
+                       end
+               else
+                       var i = 0
+                       while i < length do
+                               dest[dest_start+i] = self[start+i]
+                               i += 1
+                       end
+               end
+       end
+
        #fun =(o: NativeArray[E]): Bool is intern
        #fun !=(o: NativeArray[E]): Bool is intern
 end