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DataPRO/FftSharp/Pad.cs

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+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace FftSharp
+{
+    public static class Pad
+    {
+        /// <summary>
+        /// Test if a number is an even power of 2
+        /// </summary>
+        public static bool IsPowerOfTwo(int x) => ((x & (x - 1)) == 0) && (x > 0);
+
+        /// <summary>
+        /// Return the input array (or a new zero-padded new one) ensuring length is a power of 2
+        /// </summary>
+        /// <param name="input">array of any length</param>
+        /// <returns>the input array or a zero-padded copy</returns>
+        public static Complex[] ZeroPad(Complex[] input)
+        {
+            if (IsPowerOfTwo(input.Length))
+                return input;
+
+            int targetLength = 1;
+            while (targetLength < input.Length)
+                targetLength *= 2;
+
+            int difference = targetLength - input.Length;
+            Complex[] padded = new Complex[targetLength];
+            Array.Copy(input, 0, padded, difference / 2, input.Length);
+
+            return padded;
+        }
+
+        /// <summary>
+        /// Return the input array (or a new zero-padded new one) ensuring length is a power of 2
+        /// </summary>
+        /// <param name="input">array of any length</param>
+        /// <returns>the input array or a zero-padded copy</returns>
+        public static double[] ZeroPad(double[] input)
+        {
+            if (IsPowerOfTwo(input.Length))
+                return input;
+
+            int targetLength = 1;
+            while (targetLength < input.Length)
+                targetLength *= 2;
+
+            int difference = targetLength - input.Length;
+            double[] padded = new double[targetLength];
+            Array.Copy(input, 0, padded, difference / 2, input.Length);
+
+            return padded;
+        }
+
+        /// <summary>
+        /// Return the input array zero-padded to reach a final length
+        /// </summary>
+        /// <param name="input">array of any length</param>
+        /// <param name="finalLength">pad the array with zeros a the end to achieve this final length</param>
+        /// <returns>a zero-padded copy of the input array</returns>
+        public static Complex[] ZeroPad(Complex[] input, int finalLength)
+        {
+            int difference = finalLength - input.Length;
+            Complex[] padded = new Complex[finalLength];
+            Array.Copy(input, 0, padded, difference / 2, input.Length);
+            return padded;
+        }
+
+        /// <summary>
+        /// Return the input array zero-padded to reach a final length
+        /// </summary>
+        /// <param name="input">array of any length</param>
+        /// <param name="finalLength">pad the array with zeros a the end to achieve this final length</param>
+        /// <returns>a zero-padded copy of the input array</returns>
+        public static double[] ZeroPad(double[] input, int finalLength)
+        {
+            int difference = finalLength - input.Length;
+            double[] padded = new double[finalLength];
+            Array.Copy(input, 0, padded, difference / 2, input.Length);
+            return padded;
+        }
+    }
+}