Helpers.cs source code in C# .NET

Source code for the .NET framework in C#

                        
Code:

                         / 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 ) retrieved by traversing the tree from  using . 
        internal static IEnumerable 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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