Specialize Base.reinterpret (#13)

src/unsafe_array.jl

@@ -148,6 +148,18 @@ end
 
 Base.deepcopy(A::UnsafeArray) = copyto!(similar(A), A)
 
+function Base.reinterpret(::Type{DST}, A::UnsafeArray{SRC}) where {DST, SRC}
+    if sizeof(DST) != sizeof(SRC)
+        sz = size(A)
+        sz1, rem = divrem(sz[1] * sizeof(SRC), sizeof(DST))
+        @boundscheck if rem != zero(rem)
+            throw(ArgumentError("Resulting array would have non-integral first dimension"))
+        end
+        UnsafeArray(convert(Ptr{DST}, pointer(A)), (sz1, Base.tail(sz)...))
+    else
+        UnsafeArray(convert(Ptr{DST}, pointer(A)), size(A))
+    end
+end
 
 # # Defining Base.unaliascopy results in very bad broadcast performance for
 # # some reason, even when it shouldn't be called. By default, unaliascopy

test/unsafe_array.jl

@@ -304,4 +304,21 @@ using Random
             @test convert(Array, UA) == A
         end
     end
+
+    @testset "reinterpret" begin
+        test_A_UA(Float32, Val(3)) do A, UA
+            @test reinterpret(UInt32, UA) == reinterpret(UInt32, A)
+            @test reinterpret(UInt8, UA) == reinterpret(UInt8, A)
+        end
+
+        # NOTE: this requires sz_max[1] to be divisible by 4
+        test_A_UA(UInt8, Val(3)) do A, UA
+            @test reinterpret(UInt32, UA) == reinterpret(UInt32, A)
+            @test reinterpret(Int8, UA) == reinterpret(Int8, A)
+        end
+
+        A = UInt32[ 1, 2, 3 ]
+        UA = UnsafeArray(pointer(A), size(A))
+        @test_throws ArgumentError reinterpret(UInt64, UA)
+    end
 end