Imported Upstream version 4.0.0~alpha1

Former-commit-id: 806294f5ded97629b74c85c09952f2a74fe182d9

external/referencesource/System.Web/ModelBinding/PrefixContainer.cs

@@ -0,0 +1,86 @@
+namespace System.Web.ModelBinding {
+    using System;
+    using System.Collections.Generic;
+    using System.Linq;
+
+    /// <summary>
+    /// This is a container for prefix values. It normalizes all the values into dotted-form and then stores
+    /// them in a sorted array. All queries for prefixes are also normalized to dotted-form, and searches
+    /// for ContainsPrefix are done with a binary search.
+    /// </summary>
+    internal sealed class PrefixContainer {
+
+        private readonly string[] _sortedValues;
+
+        internal PrefixContainer(IEnumerable<string> values) {
+            if (values == null) {
+                throw new ArgumentNullException("values");
+            }
+
+            _sortedValues = values.Where(val => val != null).ToArray();
+            Array.Sort(_sortedValues, StringComparer.OrdinalIgnoreCase);
+        }
+
+        internal bool ContainsPrefix(string prefix) {
+            if (prefix == null) {
+                throw new ArgumentNullException("prefix");
+            }
+
+            if (prefix.Length == 0) {
+                return _sortedValues.Length > 0; // only match empty string when we have some value
+            }
+
+            return Array.BinarySearch(_sortedValues, prefix, new PrefixComparer(prefix)) > -1;
+        }
+
+        internal static bool IsPrefixMatch(string prefix, string testString) {
+            if (testString == null) {
+                return false;
+            }
+
+            if (prefix.Length == 0) {
+                return true; // shortcut - non-null testString matches empty prefix
+            }
+
+            if (prefix.Length > testString.Length) {
+                return false; // not long enough
+            }
+
+            if (!testString.StartsWith(prefix, StringComparison.OrdinalIgnoreCase)) {
+                return false; // prefix doesn't match
+            }
+
+            if (testString.Length == prefix.Length) {
+                return true; // exact match
+            }
+
+            // invariant: testString.Length > prefix.Length
+            switch (testString[prefix.Length]) {
+                case '.':
+                case '[':
+                    return true; // known delimiters
+
+                default:
+                    return false; // not known delimiter
+            }
+        }
+
+        private sealed class PrefixComparer : IComparer<String> {
+            private string _prefix;
+
+            public PrefixComparer(string prefix) {
+                _prefix = prefix;
+            }
+
+            public int Compare(string x, string y) {
+                string testString = Object.ReferenceEquals(x, _prefix) ? y : x;
+                if (IsPrefixMatch(_prefix, testString)) {
+                    return 0;
+                }
+
+                return StringComparer.OrdinalIgnoreCase.Compare(x, y);
+            }
+        }
+
+    }
+}