Create BitArray.HasAllSet() and .HasAnySet(). (#81527)

* Create BitArray.HasAllSet(). * Fix comment: use span rather than vector directly. * Create BitArray.HasAnySet(). * Fix comment: alpha order ref methods. * Create tests. * Fix comment: rename variable; check by '>= 0'. * Add xml doc. * Fix comment: add cases of other bits besides of the last bit.
dotnet · Feb 13, 2023 · cc14f35 · cc14f35
1 parent fd8298e
commit cc14f35
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diff --git a/src/libraries/System.Collections/ref/System.Collections.cs b/src/libraries/System.Collections/ref/System.Collections.cs
@@ -26,6 +26,8 @@ public sealed partial class BitArray : System.Collections.ICollection, System.Co
         public void CopyTo(System.Array array, int index) { }
         public bool Get(int index) { throw null; }
         public System.Collections.IEnumerator GetEnumerator() { throw null; }
+        public bool HasAllSet() { throw null; }
+        public bool HasAnySet() { throw null; }
         public System.Collections.BitArray LeftShift(int count) { throw null; }
         public System.Collections.BitArray Not() { throw null; }
         public System.Collections.BitArray Or(System.Collections.BitArray value) { throw null; }

diff --git a/src/libraries/System.Collections/src/System/Collections/BitArray.cs b/src/libraries/System.Collections/src/System/Collections/BitArray.cs
@@ -910,6 +910,66 @@ public unsafe void CopyTo(Array array, int index)
             }
         }
 
+        /// <summary>
+        /// Determines whether all bits in the <see cref="BitArray"/> are set to <c>true</c>.
+        /// </summary>
+        /// <returns><c>true</c> if every bit in the <see cref="BitArray"/> is set to <c>true</c>, or if <see cref="BitArray"/> is empty; otherwise, <c>false</c>.</returns>
+        public bool HasAllSet()
+        {
+            Div32Rem(m_length, out int extraBits);
+            int intCount = GetInt32ArrayLengthFromBitLength(m_length);
+            if (extraBits != 0)
+            {
+                intCount--;
+            }
+
+            const int AllSetBits = -1; // 0xFF_FF_FF_FF
+            if (m_array.AsSpan(0, intCount).IndexOfAnyExcept(AllSetBits) >= 0)
+            {
+                return false;
+            }
+
+            if (extraBits == 0)
+            {
+                return true;
+            }
+
+            Debug.Assert(GetInt32ArrayLengthFromBitLength(m_length) > 0);
+            Debug.Assert(intCount == GetInt32ArrayLengthFromBitLength(m_length) - 1);
+
+            int mask = (1 << extraBits) - 1;
+            return (m_array[intCount] & mask) == mask;
+        }
+
+        /// <summary>
+        /// Determines whether any bit in the <see cref="BitArray"/> is set to <c>true</c>.
+        /// </summary>
+        /// <returns><c>true</c> if <see cref="BitArray"/> is not empty and at least one of its bit is set to <c>true</c>; otherwise, <c>false</c>.</returns>
+        public bool HasAnySet()
+        {
+            Div32Rem(m_length, out int extraBits);
+            int intCount = GetInt32ArrayLengthFromBitLength(m_length);
+            if (extraBits != 0)
+            {
+                intCount--;
+            }
+
+            if (m_array.AsSpan(0, intCount).IndexOfAnyExcept(0) >= 0)
+            {
+                return true;
+            }
+
+            if (extraBits == 0)
+            {
+                return false;
+            }
+
+            Debug.Assert(GetInt32ArrayLengthFromBitLength(m_length) > 0);
+            Debug.Assert(intCount == GetInt32ArrayLengthFromBitLength(m_length) - 1);
+
+            return (m_array[intCount] & (1 << extraBits) - 1) != 0;
+        }
+
         public int Count => m_length;
 
         public object SyncRoot => this;

diff --git a/src/libraries/System.Collections/tests/BitArray/BitArray_GetSetTests.cs b/src/libraries/System.Collections/tests/BitArray/BitArray_GetSetTests.cs
@@ -552,5 +552,40 @@ public static void CopyTo_Byte_Hidden(string label, BitArray bits)
                 Assert.Equal((byte)((1 << remainder) - 1), data[fullBytes]);
             }
         }
+
+        [Theory]
+        [MemberData(nameof(HasAllSet_TestData))]
+        public static void HasAllSet(bool[] bits, bool expectedResult)
+        {
+            var bitArray = new BitArray(bits);
+            Assert.Equal(expectedResult, bitArray.HasAllSet());
+        }
+
+        [Theory]
+        [MemberData(nameof(HasAnySet_TestData))]
+        public static void HasAnySet(bool[] bits, bool expectedResult)
+        {
+            var bitArray = new BitArray(bits);
+            Assert.Equal(expectedResult, bitArray.HasAnySet());
+        }
+
+        public static IEnumerable<object[]> HasAllSet_TestData() => HasAnySet_TestData().Select(parameters => new object[] { ((bool[])parameters[0]).Select(bit => !bit).ToArray(), !(bool)parameters[1] });
+
+        public static IEnumerable<object[]> HasAnySet_TestData()
+        {
+            yield return new object[] { Array.Empty<bool>(), false };
+
+            foreach (int size in new[] { 1, BitsPerInt32 - 1, BitsPerInt32, BitsPerInt32 + 1, BitsPerInt32 * 2 - 1 })
+            {
+                yield return new object[] { new bool[size], false };
+
+                for (int i = 0; i < size; i++)
+                {
+                    bool[] bits = new bool[size];
+                    bits[i] = true;
+                    yield return new object[] { bits, true };
+                }
+            }
+        }
     }
 }