np.array(string): Performance Optimization

Author: Nucs

src/NumSharp.Core/Creation/np.array.cs

@@ -62,6 +62,20 @@ public static NDArray array(string chars)
             if (chars.Length==0)
                 return new NDArray(NPTypeCode.Char);
             return new NDArray(ArraySlice.FromArray(chars.ToArray()), Shape.Vector(chars.Length));
+
+            unsafe
+            {
+                var ret = new ArraySlice<char>(new UnmanagedMemoryBlock<char>(chars.Length));
+                fixed (char* strChars = chars)
+                {
+                    var src = strChars;
+                    var dst = ret.Address;
+                    var len = sizeof(char) * chars.Length;
+                    Buffer.MemoryCopy(src, dst, len, len);
+                }
+
+                return new NDArray(ret);
+            }
         }
 
         public static NDArray array<T>(T[][] data)

test/NumSharp.UnitTest/Backends/Unmanaged/StringApiTests.cs

@@ -11,6 +11,13 @@ public class StringApiTests
     {
         private static string hello = "hello";
 
+        [TestMethod]
+        public void np_array_string()
+        {
+            var str = NDArray.FromString(hello);
+            str.Should().BeOfType<char>().And.BeShaped(5).And.BeOfValues('h', 'e', 'l', 'l', 'o');
+        }
+
         [TestMethod]
         public void FromString()
         {