Use CRC32 instead of MD5 for hashing the file content.

src/Microsoft.AspNet.Mvc.Razor/Compilation/CompilerCache.cs

@@ -134,7 +134,7 @@ private CompilerCacheEntry GetOrAdd(RelativeFileInfo relativeFileInfo,
 
                 // Timestamp doesn't match but it might be because of deployment, compare the hash.
                 if (cacheEntry.IsPreCompiled &&
-                    string.Equals(cacheEntry.Hash, RazorFileHash.GetHash(fileInfo), StringComparison.Ordinal))
+                    cacheEntry.Hash == RazorFileHash.GetHash(fileInfo, cacheEntry.HashAlgorithmVersion))
                 {
                     // Cache hit, but we need to update the entry.
                     // Assigning to LastModified is an atomic operation and will result in a safe race if it is

src/Microsoft.AspNet.Mvc.Razor/Compilation/CompilerCacheEntry.cs

@@ -22,6 +22,8 @@ public CompilerCacheEntry([NotNull] RazorFileInfo info, [NotNull] Type compiledT
             Length = info.Length;
             LastModified = info.LastModified;
             Hash = info.Hash;
+            HashAlgorithmVersion = info.HashAlgorithmVersion;
+            IsPreCompiled = true;
         }
 
         /// <summary>
@@ -40,17 +42,17 @@ public CompilerCacheEntry([NotNull] RelativeFileInfo info, [NotNull] Type compil
         /// <summary>
         /// Gets the <see cref="Type"/> produced as a result of compilation.
         /// </summary>
-        public Type CompiledType { get; private set; }
+        public Type CompiledType { get; }
 
         /// <summary>
         /// Gets the path of the compiled file relative to the root of the application.
         /// </summary>
-        public string RelativePath { get; private set; }
+        public string RelativePath { get; }
 
         /// <summary>
         /// Gets the size of file (in bytes) on disk.
         /// </summary>
-        public long Length { get; private set; }
+        public long Length { get; }
 
         /// <summary>
         /// Gets or sets the last modified <see cref="DateTimeOffset"/> for the file at the time of compilation.
@@ -60,18 +62,20 @@ public CompilerCacheEntry([NotNull] RelativeFileInfo info, [NotNull] Type compil
         /// <summary>
         /// Gets the file hash, should only be available for pre compiled files.
         /// </summary>
-        public string Hash { get; private set; }
+        public long Hash { get; }
+
+        /// <summary>
+        /// Gets the version of the hash algorithm used to generate <see cref="Hash"/>.
+        /// </summary>
+        /// <remarks>
+        /// This value is only initialized for precompiled views.
+        /// </remarks>
+        public int HashAlgorithmVersion { get; }
 
         /// <summary>
         /// Gets a flag that indicates if the file is precompiled.
         /// </summary>
-        public bool IsPreCompiled
-        {
-            get
-            {
-                return Hash != null;
-            }
-        }
+        public bool IsPreCompiled { get; }
 
         /// <summary>
         /// Gets or sets the <see cref="CompilerCacheEntry"/> for the nearest ViewStart that the compiled type

src/Microsoft.AspNet.Mvc.Razor/Razor/Crc32.cs

@@ -0,0 +1,91 @@
+// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System.IO;
+
+namespace Microsoft.AspNet.Mvc.Razor
+{
+    internal static class Crc32
+    {
+        private static readonly int BufferSize = 4 * 1024;
+
+        private static readonly uint[] _crcTable = new uint[256]
+        {
+            0x00000000u, 0x77073096u, 0xee0e612cu, 0x990951bau, 0x076dc419u,
+            0x706af48fu, 0xe963a535u, 0x9e6495a3u, 0x0edb8832u, 0x79dcb8a4u,
+            0xe0d5e91eu, 0x97d2d988u, 0x09b64c2bu, 0x7eb17cbdu, 0xe7b82d07u,
+            0x90bf1d91u, 0x1db71064u, 0x6ab020f2u, 0xf3b97148u, 0x84be41deu,
+            0x1adad47du, 0x6ddde4ebu, 0xf4d4b551u, 0x83d385c7u, 0x136c9856u,
+            0x646ba8c0u, 0xfd62f97au, 0x8a65c9ecu, 0x14015c4fu, 0x63066cd9u,
+            0xfa0f3d63u, 0x8d080df5u, 0x3b6e20c8u, 0x4c69105eu, 0xd56041e4u,
+            0xa2677172u, 0x3c03e4d1u, 0x4b04d447u, 0xd20d85fdu, 0xa50ab56bu,
+            0x35b5a8fau, 0x42b2986cu, 0xdbbbc9d6u, 0xacbcf940u, 0x32d86ce3u,
+            0x45df5c75u, 0xdcd60dcfu, 0xabd13d59u, 0x26d930acu, 0x51de003au,
+            0xc8d75180u, 0xbfd06116u, 0x21b4f4b5u, 0x56b3c423u, 0xcfba9599u,
+            0xb8bda50fu, 0x2802b89eu, 0x5f058808u, 0xc60cd9b2u, 0xb10be924u,
+            0x2f6f7c87u, 0x58684c11u, 0xc1611dabu, 0xb6662d3du, 0x76dc4190u,
+            0x01db7106u, 0x98d220bcu, 0xefd5102au, 0x71b18589u, 0x06b6b51fu,
+            0x9fbfe4a5u, 0xe8b8d433u, 0x7807c9a2u, 0x0f00f934u, 0x9609a88eu,
+            0xe10e9818u, 0x7f6a0dbbu, 0x086d3d2du, 0x91646c97u, 0xe6635c01u,
+            0x6b6b51f4u, 0x1c6c6162u, 0x856530d8u, 0xf262004eu, 0x6c0695edu,
+            0x1b01a57bu, 0x8208f4c1u, 0xf50fc457u, 0x65b0d9c6u, 0x12b7e950u,
+            0x8bbeb8eau, 0xfcb9887cu, 0x62dd1ddfu, 0x15da2d49u, 0x8cd37cf3u,
+            0xfbd44c65u, 0x4db26158u, 0x3ab551ceu, 0xa3bc0074u, 0xd4bb30e2u,
+            0x4adfa541u, 0x3dd895d7u, 0xa4d1c46du, 0xd3d6f4fbu, 0x4369e96au,
+            0x346ed9fcu, 0xad678846u, 0xda60b8d0u, 0x44042d73u, 0x33031de5u,
+            0xaa0a4c5fu, 0xdd0d7cc9u, 0x5005713cu, 0x270241aau, 0xbe0b1010u,
+            0xc90c2086u, 0x5768b525u, 0x206f85b3u, 0xb966d409u, 0xce61e49fu,
+            0x5edef90eu, 0x29d9c998u, 0xb0d09822u, 0xc7d7a8b4u, 0x59b33d17u,
+            0x2eb40d81u, 0xb7bd5c3bu, 0xc0ba6cadu, 0xedb88320u, 0x9abfb3b6u,
+            0x03b6e20cu, 0x74b1d29au, 0xead54739u, 0x9dd277afu, 0x04db2615u,
+            0x73dc1683u, 0xe3630b12u, 0x94643b84u, 0x0d6d6a3eu, 0x7a6a5aa8u,
+            0xe40ecf0bu, 0x9309ff9du, 0x0a00ae27u, 0x7d079eb1u, 0xf00f9344u,
+            0x8708a3d2u, 0x1e01f268u, 0x6906c2feu, 0xf762575du, 0x806567cbu,
+            0x196c3671u, 0x6e6b06e7u, 0xfed41b76u, 0x89d32be0u, 0x10da7a5au,
+            0x67dd4accu, 0xf9b9df6fu, 0x8ebeeff9u, 0x17b7be43u, 0x60b08ed5u,
+            0xd6d6a3e8u, 0xa1d1937eu, 0x38d8c2c4u, 0x4fdff252u, 0xd1bb67f1u,
+            0xa6bc5767u, 0x3fb506ddu, 0x48b2364bu, 0xd80d2bdau, 0xaf0a1b4cu,
+            0x36034af6u, 0x41047a60u, 0xdf60efc3u, 0xa867df55u, 0x316e8eefu,
+            0x4669be79u, 0xcb61b38cu, 0xbc66831au, 0x256fd2a0u, 0x5268e236u,
+            0xcc0c7795u, 0xbb0b4703u, 0x220216b9u, 0x5505262fu, 0xc5ba3bbeu,
+            0xb2bd0b28u, 0x2bb45a92u, 0x5cb36a04u, 0xc2d7ffa7u, 0xb5d0cf31u,
+            0x2cd99e8bu, 0x5bdeae1du, 0x9b64c2b0u, 0xec63f226u, 0x756aa39cu,
+            0x026d930au, 0x9c0906a9u, 0xeb0e363fu, 0x72076785u, 0x05005713u,
+            0x95bf4a82u, 0xe2b87a14u, 0x7bb12baeu, 0x0cb61b38u, 0x92d28e9bu,
+            0xe5d5be0du, 0x7cdcefb7u, 0x0bdbdf21u, 0x86d3d2d4u, 0xf1d4e242u,
+            0x68ddb3f8u, 0x1fda836eu, 0x81be16cdu, 0xf6b9265bu, 0x6fb077e1u,
+            0x18b74777u, 0x88085ae6u, 0xff0f6a70u, 0x66063bcau, 0x11010b5cu,
+            0x8f659effu, 0xf862ae69u, 0x616bffd3u, 0x166ccf45u, 0xa00ae278u,
+            0xd70dd2eeu, 0x4e048354u, 0x3903b3c2u, 0xa7672661u, 0xd06016f7u,
+            0x4969474du, 0x3e6e77dbu, 0xaed16a4au, 0xd9d65adcu, 0x40df0b66u,
+            0x37d83bf0u, 0xa9bcae53u, 0xdebb9ec5u, 0x47b2cf7fu, 0x30b5ffe9u,
+            0xbdbdf21cu, 0xcabac28au, 0x53b39330u, 0x24b4a3a6u, 0xbad03605u,
+            0xcdd70693u, 0x54de5729u, 0x23d967bfu, 0xb3667a2eu, 0xc4614ab8u,
+            0x5d681b02u, 0x2a6f2b94u, 0xb40bbe37u, 0xc30c8ea1u, 0x5a05df1bu,
+            0x2d02ef8du
+        };
+
+        public static uint Calculate(Stream stream)
+        {
+            var buffer = new byte[BufferSize];
+            var crc32 = 0xffffffffU;
+            while (true)
+            {
+                var read = stream.Read(buffer, 0, BufferSize);
+                if (read == 0)
+                {
+                    break;
+                }
+
+                var offset = 0;
+                while (offset < read)
+                {
+                    crc32 = _crcTable[(crc32 ^ buffer[offset++]) & 0xFF] ^ (crc32 >> 8);
+                }
+            }
+
+            return crc32 ^ 0xffffffffU;
+        }
+    }
+}
+

src/Microsoft.AspNet.Mvc.Razor/Razor/PreCompileViews/RazorFileInfo.cs

@@ -30,6 +30,11 @@ public class RazorFileInfo
         /// <summary>
         /// A hash of the file content.
         /// </summary>
-        public string Hash { get; set; }
+        public long Hash { get; set; }
+
+        /// <summary>
+        /// The version of hash algorithm used to generate <see cref="Hash"/>.
+        /// </summary>
+        public int HashAlgorithmVersion { get; set; }
     }
 }

src/Microsoft.AspNet.Mvc.Razor/Razor/PreCompileViews/RazorFileInfoCollectionGenerator.cs

@@ -51,7 +51,8 @@ protected virtual string GenerateFile([NotNull] RazorFileInfo fileInfo)
                                  fileInfo.Length,
                                  fileInfo.RelativePath,
                                  fileInfo.FullTypeName,
-                                 fileInfo.Hash);
+                                 fileInfo.Hash,
+                                 fileInfo.HashAlgorithmVersion);
         }
 
         protected virtual string Top
@@ -103,7 +104,8 @@ protected virtual string FileFormat
                 " + nameof(RazorFileInfo.Length) + @" = {1:D},
                 " + nameof(RazorFileInfo.RelativePath) + @" = @""{2}"",
                 " + nameof(RazorFileInfo.FullTypeName) + @" = @""{3}"",
-                " + nameof(RazorFileInfo.Hash) + @" = @""{4}"",
+                " + nameof(RazorFileInfo.Hash) + @" = {4},
+                " + nameof(RazorFileInfo.HashAlgorithmVersion) + @" = {5},
             }};
             fileInfos.Add(info);
 ";

src/Microsoft.AspNet.Mvc.Razor/Razor/PreCompileViews/RazorPreCompiler.cs

@@ -167,7 +167,7 @@ protected virtual PrecompilationCacheEntry GetCacheEntry([NotNull] RelativeFileI
 
                     if (fullTypeName != null)
                     {
-                        var hash = RazorFileHash.GetHash(fileInfo.FileInfo);
+                        var hash = RazorFileHash.GetHash(fileInfo.FileInfo, RazorFileHash.HashAlgorthmVersion1);
                         var razorFileInfo = new RazorFileInfo
                         {
                             RelativePath = fileInfo.RelativePath,

src/Microsoft.AspNet.Mvc.Razor/Razor/RazorFileHash.cs

@@ -2,35 +2,36 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
-using System.IO;
-using System.Security.Cryptography;
 using Microsoft.AspNet.FileProviders;
 
 namespace Microsoft.AspNet.Mvc.Razor
 {
     public static class RazorFileHash
     {
-        public static string GetHash([NotNull] IFileInfo file)
+        /// <summary>
+        /// Version 1 of the hash algorithm used for generating hashes of Razor files.
+        /// </summary>
+        public static readonly int HashAlgorthmVersion1 = 1;
+
+        public static long GetHash([NotNull] IFileInfo file, int hashAlgorithmVersion)
         {
+            if (hashAlgorithmVersion != HashAlgorthmVersion1)
+            {
+                throw new ArgumentException(Resources.RazorHash_UnsupportedHashAlgorithm,
+                                            nameof(hashAlgorithmVersion));
+            }
+
             try
             {
                 using (var stream = file.CreateReadStream())
                 {
-                    return GetHash(stream);
+                    return Crc32.Calculate(stream);
                 }
             }
             catch (Exception)
             {
                 // Don't throw if reading the file fails.
-                return string.Empty;
-            }
-        }
-
-        internal static string GetHash(Stream stream)
-        {
-            using (var md5 = MD5.Create())
-            {
-                return BitConverter.ToString(md5.ComputeHash(stream));
+                return 0;
             }
         }
     }

src/Microsoft.AspNet.Mvc.Razor/Resources.resx

@@ -183,4 +183,7 @@
   <data name="ViewMustBeContextualized" xml:space="preserve">
     <value>The '{0}' method must be called before '{1}' can be invoked.</value>
   </data>
+  <data name="RazorHash_UnsupportedHashAlgorithm" xml:space="preserve">
+    <value>Unsupported hash algorithm.</value>
+  </data>
 </root>

test/Microsoft.AspNet.Mvc.Razor.Test/Compilation/CompilerCacheTest.cs

@@ -82,7 +82,8 @@ public ViewCollection()
                 Add(new RazorFileInfo()
                 {
                     FullTypeName = typeof(PreCompile).FullName,
-                    Hash = RazorFileHash.GetHash(GetMemoryStream(content)),
+                    Hash = Crc32.Calculate(GetMemoryStream(content)),
+                    HashAlgorithmVersion = 1,
                     LastModified = DateTime.FromFileTimeUtc(10000),
                     Length = length,
                     RelativePath = "ab",
@@ -127,7 +128,8 @@ public void GetOrAdd_UsesFilesFromCache_IfTimestampDiffers_ButContentAndLengthAr
             var razorFileInfo = new RazorFileInfo
             {
                 FullTypeName = typeof(PreCompile).FullName,
-                Hash = RazorFileHash.GetHash(GetMemoryStream(precompiledContent)),
+                Hash = Crc32.Calculate(GetMemoryStream(precompiledContent)),
+                HashAlgorithmVersion = 1,
                 LastModified = DateTime.FromFileTimeUtc(10000),
                 Length = Encoding.UTF8.GetByteCount(precompiledContent),
                 RelativePath = "ab",
@@ -169,7 +171,8 @@ public void GetOrAdd_RecompilesFile_IfContentAndLengthAreChanged(
             var razorFileInfo = new RazorFileInfo
             {
                 FullTypeName = typeof(PreCompile).FullName,
-                Hash = RazorFileHash.GetHash(GetMemoryStream(precompiledContent)),
+                Hash = Crc32.Calculate(GetMemoryStream(precompiledContent)),
+                HashAlgorithmVersion = 1,
                 LastModified = DateTime.FromFileTimeUtc(10000),
                 Length = Encoding.UTF8.GetByteCount(precompiledContent),
                 RelativePath = "ab",
@@ -210,7 +213,8 @@ public void GetOrAdd_UsesValueFromCache_IfViewStartHasNotChanged()
             fileProvider.AddFile("_ViewStart.cshtml", viewStartFileInfo);
             var viewStartRazorFileInfo = new RazorFileInfo
             {
-                Hash = RazorFileHash.GetHash(GetMemoryStream(viewStartContent)),
+                Hash = Crc32.Calculate(GetMemoryStream(viewStartContent)),
+                HashAlgorithmVersion = 1,
                 LastModified = viewStartFileInfo.LastModified,
                 Length = viewStartFileInfo.Length,
                 RelativePath = "_ViewStart.cshtml",
@@ -295,7 +299,8 @@ public void GetOrAdd_IgnoresCachedValueIfFileIsIdentical_ButViewStartWasDeletedS
                 FullTypeName = typeof(RuntimeCompileIdentical).FullName,
                 RelativePath = viewStartFileInfo.PhysicalPath,
                 LastModified = viewStartFileInfo.LastModified,
-                Hash = RazorFileHash.GetHash(viewStartFileInfo),
+                Hash = RazorFileHash.GetHash(viewStartFileInfo, hashAlgorithmVersion: 1),
+                HashAlgorithmVersion = 1,
                 Length = viewStartFileInfo.Length
             };
             fileProvider.AddFile(viewStartFileInfo.PhysicalPath, viewStartFileInfo);
@@ -332,7 +337,8 @@ public static IEnumerable<object[]> GetOrAdd_IgnoresCachedValue_IfViewStartWasCh
 
                 var razorFileInfo = new RazorFileInfo
                 {
-                    Hash = RazorFileHash.GetHash(contentStream),
+                    Hash = Crc32.Calculate(contentStream),
+                    HashAlgorithmVersion = 1,
                     LastModified = lastModified,
                     Length = length,
                     RelativePath = path
@@ -381,7 +387,8 @@ public void GetOrAdd_IgnoresCachedValue_IfViewStartWasChangedSinceCacheWasCreate
             var razorFileInfo = new RazorFileInfo
             {
                 FullTypeName = typeof(PreCompile).FullName,
-                Hash = RazorFileHash.GetHash(fileInfo),
+                Hash = RazorFileHash.GetHash(fileInfo, hashAlgorithmVersion: 1),
+                HashAlgorithmVersion = 1,
                 LastModified = lastModified,
                 Length = Encoding.UTF8.GetByteCount(content),
                 RelativePath = fileInfo.PhysicalPath,