More efficient and correct Base.copy

* Do not copy the underlying memory only to overwrite it
* Return a new copy of the same type as the input

Author: jakobnissen

Project.toml

@@ -1,6 +1,6 @@
 name = "MemoryViews"
 uuid = "a791c907-b98b-4e44-8f4d-e4c2362c6b2f"
-version = "0.3.0"
+version = "0.3.1"
 authors = ["Jakob Nybo Nissen <jakobnybonissen@gmail.com>"]
 
 [weakdeps]

src/basic.jl

@@ -328,14 +328,17 @@ function Base.reverse!(mem::MutableMemoryView)
     mem
 end
 
-# TODO: No need to copy
 function Base.reverse(mem::MemoryView)
-    cp = MutableMemoryView(unsafe, copy(mem))
+    cp = similar(mem)
     stop = length(cp) + 1
     @inbounds for i in 1:length(cp)
         cp[i] = mem[stop - i]
     end
-    cp
+    return if mem isa MutableMemoryView
+        cp
+    else
+        ImmutableMemoryView(cp)
+    end
 end
 
 struct ReverseMemoryView{T}

test/runtests.jl

@@ -388,10 +388,15 @@ end
             @test reverse!(MemoryView(copy(v))) == MemoryView(reverse(v))
             mem = MemoryView(v)
             rev = reverse(mem)
+            @test typeof(rev) == typeof(mem)
             @test rev.ref != mem.ref
             @test rev == reverse(v)
             @test_throws Exception reverse!(ImmutableMemoryView(v))
         end
+        mem = MemoryView("abcd")
+        rev = reverse(mem)
+        @test rev == b"dcba"
+        @test rev isa ImmutableMemoryView{UInt8}
     end
 
     @testset "Cmp" begin