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/ 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / DataEntity / System / Data / Common / Utils / Helpers.cs / 1305376 / Helpers.cs
//---------------------------------------------------------------------- //// Copyright (c) Microsoft Corporation. All rights reserved. // // // @owner [....] // @backupOwner [....] //--------------------------------------------------------------------- using System; using System.Collections; using System.Collections.Generic; using System.Text; using System.Globalization; using System.Diagnostics; namespace System.Data.Common.Utils { // Miscellaneous helper routines internal static class Helpers { #region Trace methods // effects: Trace args according to the CLR format string with a new line internal static void FormatTraceLine(string format, params object[] args) { Trace.WriteLine(String.Format(CultureInfo.InvariantCulture, format, args)); } // effects: Trace the string with a new line internal static void StringTrace(string arg) { Trace.Write(arg); } // effects: Trace the string without adding a new line internal static void StringTraceLine(string arg) { Trace.WriteLine(arg); } #endregion #region Misc Helpers // effects: compares two sets using the given comparer - removes // duplicates if they exist internal static bool IsSetEqual(IEnumerable list1, IEnumerable list2, IEqualityComparer comparer) { Set set1 = new Set (list1, comparer); Set set2 = new Set (list2, comparer); return set1.SetEquals(set2); } // effects: Given a stream of values of type "SubType", returns a // stream of values of type "SuperType" where SuperType is a // superclass/supertype of SubType internal static IEnumerable AsSuperTypeList (IEnumerable values) where SubType : SuperType { foreach (SubType value in values) { yield return value; } } /// /// Returns a new array with the first element equal to ///and the remaining /// elements taken from . /// The element type of the arrays /// An array that provides the successive elements of the new array /// An instance the provides the first element of the new array ///A new array containing the specified argument as the first element and the specified successive elements internal static TElement[] Prepend(TElement[] args, TElement arg) { Debug.Assert(args != null, "Ensure 'args' is non-null before calling Prepend"); TElement[] retVal = new TElement[args.Length + 1]; retVal[0] = arg; for (int idx = 0; idx < args.Length; idx++) { retVal[idx + 1] = args[idx]; } return retVal; } /// /// Builds a balanced binary tree with the specified nodes as leaves. /// Note that the current elements of ///MAY be overwritten /// as the leaves are combined to produce the tree. /// The type of each node in the tree /// The leaf nodes to combine into an balanced binary tree /// A function that produces a new node that is the combination of the two specified argument nodes ///The single node that is the root of the balanced binary tree internal static TNode BuildBalancedTreeInPlace(IList nodes, Func combinator) { EntityUtil.CheckArgumentNull(nodes, "nodes"); EntityUtil.CheckArgumentNull(combinator, "combinator"); Debug.Assert(nodes.Count > 0, "At least one node is required"); // If only one node is present, return the single node. if (nodes.Count == 1) { return nodes[0]; } // For the two-node case, simply combine the two nodes and return the result. if (nodes.Count == 2) { return combinator(nodes[0], nodes[1]); } // // Build the balanced tree in a bottom-up fashion. // On each iteration, an even number of nodes are paired off using the // combinator function, reducing the total number of available leaf nodes // by half each time. If the number of nodes in an iteration is not even, // the 'last' node in the set is omitted, then combined with the last pair // that is produced. // Nodes are collected from left to right with newly combined nodes overwriting // nodes from the previous iteration that have already been consumed (as can // be seen by 'writePos' lagging 'readPos' in the main statement of the loop below). // When a single available leaf node remains, this node is the root of the // balanced binary tree and can be returned to the caller. // int nodesToPair = nodes.Count; while (nodesToPair != 1) { bool combineModulo = ((nodesToPair & 0x1) == 1); if (combineModulo) { nodesToPair--; } int writePos = 0; for (int readPos = 0; readPos < nodesToPair; readPos += 2) { nodes[writePos++] = combinator(nodes[readPos], nodes[readPos + 1]); } if (combineModulo) { int updatePos = writePos - 1; nodes[updatePos] = combinator(nodes[updatePos], nodes[nodesToPair]); } nodesToPair /= 2; } return nodes[0]; } /// /// Uses a stack to non-recursively traverse a given tree structure and retrieve the leaf nodes. /// ///The type of each node in the tree structure /// The node that represents the root of the tree /// A function that determines whether or not a given node should be considered a leaf node /// A function that traverses the tree by retrieving the immediate descendants of a (non-leaf) node. ///An enumerable containing the leaf nodes (as determined by internal static IEnumerable) retrieved by traversing the tree from using . GetLeafNodes (TNode root, Func isLeaf, Func > getImmediateSubNodes) { EntityUtil.CheckArgumentNull(isLeaf, "isLeaf"); EntityUtil.CheckArgumentNull(getImmediateSubNodes, "getImmediateSubNodes"); Stack nodes = new Stack (); nodes.Push(root); while (nodes.Count > 0) { TNode current = nodes.Pop(); if (isLeaf(current)) { yield return current; } else { List childNodes = new List (getImmediateSubNodes(current)); for (int idx = childNodes.Count - 1; idx > -1; idx--) { nodes.Push(childNodes[idx]); } } } } #endregion } } // File provided for Reference Use Only by Microsoft Corporation (c) 2007.
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