Code:
/ 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / DataEntity / System / Data / Mapping / metadatamappinghashervisitor.hashsourcebuilder.cs / 1508357 / metadatamappinghashervisitor.hashsourcebuilder.cs
//---------------------------------------------------------------------- //// Copyright (c) Microsoft Corporation. All rights reserved. // // @owner [....] // @backupOwner [....] //--------------------------------------------------------------------- using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Diagnostics; using System.Data.Common.Utils; using System.Security.Cryptography; using System.Globalization; using System.IO; namespace System.Data.Mapping { ////// This class keeps recomputing the hash and adding it to the front of the /// builder when the length of the string gets too long /// internal class CompressingHashBuilder : StringHashBuilder { // this max comes from the value that Md5Hasher uses for a buffer size when it is reading // from a stream private const int HashCharacterCompressionThreshold = 0x1000 / 2; // num bytes / 2 to convert to typical unicode char size private const int SpacesPerIndent = 4; private int _indent = 0; // we are starting the buffer at 1.5 times the number of bytes // for the threshold internal CompressingHashBuilder(HashAlgorithm hashAlgorithm) : base(hashAlgorithm, (HashCharacterCompressionThreshold + (HashCharacterCompressionThreshold / 2)) * 2) { } internal override void Append(string content) { base.Append(string.Empty.PadLeft(SpacesPerIndent * _indent, ' ')); base.Append(content); CompressHash(); } internal override void AppendLine(string content) { base.Append(string.Empty.PadLeft(SpacesPerIndent * _indent, ' ')); base.AppendLine(content); CompressHash(); } ////// add string like "typename Instance#1" /// /// internal void AppendObjectStartDump(object o, int objectIndex) { base.Append(string.Empty.PadLeft(SpacesPerIndent * _indent, ' ')); base.Append(o.GetType().ToString()); base.Append(" Instance#"); base.AppendLine(objectIndex.ToString(CultureInfo.InvariantCulture)); CompressHash(); this._indent++; } internal void AppendObjectEndDump() { Debug.Assert(this._indent > 0, "Indent and unindent should be paired"); this._indent--; } private void CompressHash() { if(base.CharCount >= HashCharacterCompressionThreshold) { string hash = ComputeHash(); Clear(); base.Append(hash); } } } ////// this class collects several strings together, and allows you to ( /// internal class StringHashBuilder { private HashAlgorithm _hashAlgorithm; private const string NewLine = "\n"; List_strings = new List (); int _totalLength; byte[] _cachedBuffer; internal StringHashBuilder(HashAlgorithm hashAlgorithm) { _hashAlgorithm = hashAlgorithm; } internal StringHashBuilder(HashAlgorithm hashAlgorithm, int startingBufferSize) :this(hashAlgorithm) { Debug.Assert(startingBufferSize > 0, "should be a non zero positive integer"); _cachedBuffer = new byte[startingBufferSize]; } internal int CharCount { get { return _totalLength; } } internal virtual void Append(string s) { InternalAppend(s); } internal virtual void AppendLine(string s) { InternalAppend(s); InternalAppend(NewLine); } private void InternalAppend(string s) { if (s.Length == 0) return; _strings.Add(s); _totalLength += s.Length; } internal string ComputeHash() { int byteCount = GetByteCount(); if(_cachedBuffer == null) { // assume it is a one time use, and // it will grow later if needed _cachedBuffer = new byte[byteCount]; } else if (_cachedBuffer.Length < byteCount) { // grow it by what is needed at a minimum, or 1.5 times bigger // if that is bigger than what is needed this time. We // make it 1.5 times bigger in hopes to reduce the number of allocations (consider the // case where the next one it 1 bigger) int bufferSize = Math.Max(_cachedBuffer.Length + (_cachedBuffer.Length / 2), byteCount); _cachedBuffer = new byte[bufferSize]; } int start = 0; foreach (string s in _strings) { start += Encoding.Unicode.GetBytes(s, 0, s.Length, _cachedBuffer, start); } Debug.Assert(start == byteCount, "Did we use a different calculation for these?"); byte[] hash = _hashAlgorithm.ComputeHash(_cachedBuffer, 0, byteCount); return ConvertHashToString(hash); } internal void Clear() { _strings.Clear(); _totalLength = 0; } public override string ToString() { StringBuilder builder = new StringBuilder(); _strings.ForEach(s => builder.Append(s)); return builder.ToString(); } private int GetByteCount() { int count = 0; foreach (string s in _strings) { count += Encoding.Unicode.GetByteCount(s); } return count; } private static string ConvertHashToString(byte[] hash) { StringBuilder stringData = new StringBuilder(hash.Length * 2); // Loop through each byte of the data and format each one as a // hexadecimal string for (int i = 0; i < hash.Length; i++) { stringData.Append(hash[i].ToString("x2", CultureInfo.InvariantCulture)); } return stringData.ToString(); } public static string ComputeHash(HashAlgorithm hashAlgorithm, string source) { StringHashBuilder builder = new StringHashBuilder(hashAlgorithm); builder.Append(source); return builder.ComputeHash(); } } } // File provided for Reference Use Only by Microsoft Corporation (c) 2007.
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