From acb60970039be631ba24fd8db23b6942be367746 Mon Sep 17 00:00:00 2001
From: David Hall <dahall@byu.net>
Date: Tue, 7 Aug 2018 17:21:43 -0600
Subject: [PATCH] Added GitBits and SetBits methods

---
 Core/Extensions/BitHelper.cs | 35 +++++++++++++++++++++++++++++++++--
 1 file changed, 33 insertions(+), 2 deletions(-)

diff --git a/Core/Extensions/BitHelper.cs b/Core/Extensions/BitHelper.cs
index 67f77e2b..d32691f4 100644
--- a/Core/Extensions/BitHelper.cs
+++ b/Core/Extensions/BitHelper.cs
@@ -1,4 +1,5 @@
 using System;
+using System.Runtime.InteropServices;
 
 namespace Vanara.Extensions
 {
@@ -8,9 +9,22 @@ namespace Vanara.Extensions
 		/// <summary>Gets the bit value at the specified index in a bit vector.</summary>
 		/// <typeparam name="T">The type of the bit vector. Must be of type <see cref="IConvertible"/>.</typeparam>
 		/// <param name="bits">The bit vector.</param>
-		/// <param name="idx">The index of the bit to get.</param>
+		/// <param name="idx">The zero-based index of the bit to get.</param>
 		/// <returns><see langword="true"/> if the bit is set (1); <see langword="false"/> otherwise.</returns>
-		public static bool GetBit<T>(ref T bits, byte idx) where T : IConvertible => (bits.ToInt64(null) & 1 << idx) != 0;
+		public static bool GetBit<T>(T bits, byte idx) where T : IConvertible => (idx < (Marshal.SizeOf(typeof(T)) * 8)) ? (bits.ToInt64(null) & 1 << idx) != 0 : throw new ArgumentOutOfRangeException(nameof(idx));
+
+		/// <summary>Gets the bit array value from the specified range in a bit vector.</summary>
+		/// <typeparam name="T">The type of the bit vector. Must be of type <see cref="IConvertible"/>.</typeparam>
+		/// <param name="bits">The bit vector.</param>
+		/// <param name="startIdx">The zero-based start index of the bit range to get.</param>
+		/// <param name="count">The number of sequential bits to fetch starting at <paramref name="startIdx"/>.</param>
+		/// <returns>The value of the requested bit range.</returns>
+		public static T GetBits<T>(T bits, byte startIdx, byte count) where T : IConvertible
+		{
+			if (startIdx >= (Marshal.SizeOf(typeof(T)) * 8)) throw new ArgumentOutOfRangeException(nameof(startIdx));
+			if (count + startIdx > (Marshal.SizeOf(typeof(T)) * 8)) throw new ArgumentOutOfRangeException(nameof(count));
+			return (T)Convert.ChangeType((bits.ToInt64(null) >> startIdx) & ((1 << count) - 1), typeof(T));
+		}
 
 		/// <summary>Sets the bit value at the specified index in a bit vector.</summary>
 		/// <typeparam name="T">The type of the bit vector. Must be of type <see cref="IConvertible"/>.</typeparam>
@@ -19,9 +33,26 @@ namespace Vanara.Extensions
 		/// <param name="value">If set to <see langword="true"/>, set the bit (= 1); otherwise, clear the bit (= 0).</param>
 		public static void SetBit<T>(ref T bits, byte idx, bool value) where T : IConvertible
 		{
+			if (idx >= (Marshal.SizeOf(typeof(T)) * 8)) throw new ArgumentOutOfRangeException(nameof(idx));
 			long bit = 1 << idx;
 			var l = bits.ToInt64(null);
 			bits = (T)Convert.ChangeType(value ? l | bit : l & ~bit, typeof(T));
 		}
+
+		/// <summary>Sets the bit values at the specified range in a bit vector.</summary>
+		/// <typeparam name="T">The type of the bit vector. Must be of type <see cref="IConvertible"/>.</typeparam>
+		/// <typeparam name="TValue">The type of the value. Must be of type <see cref="IConvertible"/>.</typeparam>
+		/// <param name="bits">The bit vector.</param>
+		/// <param name="startIdx">The zero-based start index of the bit range to set.</param>
+		/// <param name="count">The number of sequential bits to set starting at <paramref name="startIdx"/>.</param>
+		/// <param name="value">The value to set within the specified range of <paramref name="bits"/>.</param>
+		public static void SetBits<T, TValue>(ref T bits, byte startIdx, byte count, TValue value) where T : IConvertible where TValue : IConvertible
+		{
+			if (startIdx >= (Marshal.SizeOf(typeof(T)) * 8)) throw new ArgumentOutOfRangeException(nameof(startIdx));
+			if (count + startIdx > (Marshal.SizeOf(typeof(T)) * 8)) throw new ArgumentOutOfRangeException(nameof(count));
+			var val = value.ToInt64(null);
+			if (val >= (1 << count)) throw new ArgumentOutOfRangeException(nameof(value));
+			bits = (T)Convert.ChangeType(bits.ToInt64(null) & ~(((1 << count) - 1) << startIdx) | (val << startIdx), typeof(T));
+		}
 	}
 }
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