Change hits file instrumentation to be memory mapped

src/coverlet.core/Coverage.cs

@@ -164,73 +164,74 @@ private void CalculateCoverage()
         {
             foreach (var result in _results)
             {
-                if (!File.Exists(result.HitsFilePath))
+                if (!Directory.Exists(result.HitsDirectoryPath))
                 {
-                    // File not instrumented, or nothing in it called.  Warn about this?
+                    // File not instrumented.  Warn about this?
                     continue;
                 }
 
                 List<Document> documents = result.Documents.Values.ToList();
 
-                using (var fs = new FileStream(result.HitsFilePath, FileMode.Open))
-                using (var br = new BinaryReader(fs))
+                foreach (var file in Directory.EnumerateFiles(result.HitsDirectoryPath))
                 {
-                    int hitCandidatesCount = br.ReadInt32();
-
-                    // TODO: hitCandidatesCount should be verified against result.HitCandidates.Count
+                    using (var fs = new FileStream(Path.Combine(result.HitsDirectoryPath, file), FileMode.Open))
+                    using (var br = new BinaryReader(fs))
+                    {
+                        int hitCandidatesCount = br.ReadInt32();
 
-                    var documentsList = result.Documents.Values.ToList();
+                        // TODO: hitCandidatesCount should be verified against result.HitCandidates.Count
 
-                    for (int i = 0; i < hitCandidatesCount; ++i)
-                    {
-                        var hitLocation = result.HitCandidates[i];
+                        for (int i = 0; i < hitCandidatesCount; ++i)
+                        {
+                            var hitLocation = result.HitCandidates[i];
 
-                        var document = documentsList[hitLocation.docIndex];
+                            var document = documents[hitLocation.docIndex];
 
-                        int hits = br.ReadInt32();
+                            int hits = br.ReadInt32();
 
-                        if (hitLocation.isBranch)
-                        {
-                            var branch = document.Branches[(hitLocation.start, hitLocation.end)];
-                            branch.Hits += hits;
-                        }
-                        else
-                        {
-                            for (int j = hitLocation.start; j <= hitLocation.end; j++)
+                            if (hitLocation.isBranch)
+                            {
+                                var branch = document.Branches[(hitLocation.start, hitLocation.end)];
+                                branch.Hits += hits;
+                            }
+                            else
                             {
-                                var line = document.Lines[j];
-                                line.Hits += hits;
+                                for (int j = hitLocation.start; j <= hitLocation.end; j++)
+                                {
+                                    var line = document.Lines[j];
+                                    line.Hits += hits;
+                                }
                             }
                         }
                     }
                 }
 
-                // for MoveNext() compiler autogenerated method we need to patch false positive (IAsyncStateMachine for instance) 
-                // we'll remove all MoveNext() not covered branch              
-                foreach (var document in result.Documents)
-                {
-                    List<KeyValuePair<(int, int), Branch>> branchesToRemove = new List<KeyValuePair<(int, int), Branch>>();
-                    foreach (var branch in document.Value.Branches)
-                    {
-                        //if one branch is covered we search the other one only if it's not covered
-                        if (CecilSymbolHelper.IsMoveNext(branch.Value.Method) && branch.Value.Hits > 0)
-                        {
-                            foreach (var moveNextBranch in document.Value.Branches)
-                            {
-                                if (moveNextBranch.Value.Method == branch.Value.Method && moveNextBranch.Value != branch.Value && moveNextBranch.Value.Hits == 0)
-                                {
-                                    branchesToRemove.Add(moveNextBranch);
-                                }
-                            }
-                        }
-                    }
-                    foreach (var branchToRemove in branchesToRemove)
-                    {
-                        document.Value.Branches.Remove(branchToRemove.Key);
-                    }
+                // for MoveNext() compiler autogenerated method we need to patch false positive (IAsyncStateMachine for instance) 
+                // we'll remove all MoveNext() not covered branch              
+                foreach (var document in result.Documents)
+                {
+                    List<KeyValuePair<(int, int), Branch>> branchesToRemove = new List<KeyValuePair<(int, int), Branch>>();
+                    foreach (var branch in document.Value.Branches)
+                    {
+                        //if one branch is covered we search the other one only if it's not covered
+                        if (CecilSymbolHelper.IsMoveNext(branch.Value.Method) && branch.Value.Hits > 0)
+                        {
+                            foreach (var moveNextBranch in document.Value.Branches)
+                            {
+                                if (moveNextBranch.Value.Method == branch.Value.Method && moveNextBranch.Value != branch.Value && moveNextBranch.Value.Hits == 0)
+                                {
+                                    branchesToRemove.Add(moveNextBranch);
+                                }
+                            }
+                        }
+                    }
+                    foreach (var branchToRemove in branchesToRemove)
+                    {
+                        document.Value.Branches.Remove(branchToRemove.Key);
+                    }
                 }
 
-                InstrumentationHelper.DeleteHitsFile(result.HitsFilePath);
+                InstrumentationHelper.DeleteHitsDirectory(result.HitsDirectoryPath);
             }
         }
     }

src/coverlet.core/Helpers/InstrumentationHelper.cs

@@ -61,12 +61,12 @@ public static void RestoreOriginalModule(string module, string identifier)
             }, retryStrategy, 10);
         }
 
-        public static void DeleteHitsFile(string path)
+        public static void DeleteHitsDirectory(string path)
         {
-            // Retry hitting the hits file - retry up to 10 times, since the file could be locked
+            // Retry hitting the hits directory - retry up to 10 times, since the files could be locked
             // See: https://github.com/tonerdo/coverlet/issues/25
             var retryStrategy = CreateRetryStrategy();
-            RetryHelper.Retry(() => File.Delete(path), retryStrategy, 10);
+            RetryHelper.Retry(() => Directory.Delete(path, true), retryStrategy, 10);
         }
 
         public static bool IsValidFilterExpression(string filter)

src/coverlet.core/Instrumentation/Instrumenter.cs

@@ -3,7 +3,6 @@
 using System.Diagnostics.CodeAnalysis;
 using System.IO;
 using System.Linq;
-using System.Reflection;
 
 using Coverlet.Core.Attributes;
 using Coverlet.Core.Helpers;
@@ -23,8 +22,8 @@ internal class Instrumenter
         private readonly string[] _includeFilters;
         private readonly string[] _excludedFiles;
         private InstrumenterResult _result;
-        private FieldDefinition _customTrackerHitsArray;
-        private FieldDefinition _customTrackerHitsFilePath;
+        private FieldDefinition _customTrackerHitsArraySize;
+        private FieldDefinition _customTrackerHitsDirectoryPath;
         private ILProcessor _customTrackerClassConstructorIl;
         private TypeDefinition _customTrackerTypeDef;
         private MethodReference _customTrackerRecordHitMethod;
@@ -42,15 +41,17 @@ public Instrumenter(string module, string identifier, string[] excludeFilters, s
 
         public InstrumenterResult Instrument()
         {
-            string hitsFilePath = Path.Combine(
+            string hitsDirectoryPath = Path.Combine(
                 Path.GetTempPath(),
                 Path.GetFileNameWithoutExtension(_module) + "_" + _identifier
             );
 
+            Directory.CreateDirectory(hitsDirectoryPath);
+
             _result = new InstrumenterResult
             {
                 Module = Path.GetFileNameWithoutExtension(_module),
-                HitsFilePath = hitsFilePath,
+                HitsDirectoryPath = hitsDirectoryPath,
                 ModulePath = _module
             };
 
@@ -88,10 +89,9 @@ private void InstrumentModule()
                     // Fixup the custom tracker class constructor, according to all instrumented types
                     Instruction lastInstr = _customTrackerClassConstructorIl.Body.Instructions.Last();
                     _customTrackerClassConstructorIl.InsertBefore(lastInstr, Instruction.Create(OpCodes.Ldc_I4, _result.HitCandidates.Count));
-                    _customTrackerClassConstructorIl.InsertBefore(lastInstr, Instruction.Create(OpCodes.Newarr, module.TypeSystem.Int32));
-                    _customTrackerClassConstructorIl.InsertBefore(lastInstr, Instruction.Create(OpCodes.Stsfld, _customTrackerHitsArray));
-                    _customTrackerClassConstructorIl.InsertBefore(lastInstr, Instruction.Create(OpCodes.Ldstr, _result.HitsFilePath));
-                    _customTrackerClassConstructorIl.InsertBefore(lastInstr, Instruction.Create(OpCodes.Stsfld, _customTrackerHitsFilePath));
+                    _customTrackerClassConstructorIl.InsertBefore(lastInstr, Instruction.Create(OpCodes.Stsfld, _customTrackerHitsArraySize));
+                    _customTrackerClassConstructorIl.InsertBefore(lastInstr, Instruction.Create(OpCodes.Ldstr, _result.HitsDirectoryPath));
+                    _customTrackerClassConstructorIl.InsertBefore(lastInstr, Instruction.Create(OpCodes.Stsfld, _customTrackerHitsDirectoryPath));
 
                     module.Write(stream);
                 }
@@ -116,17 +116,17 @@ private void AddCustomModuleTrackerToModule(ModuleDefinition module)
 
                     _customTrackerTypeDef.Fields.Add(fieldClone);
 
-                    if (fieldClone.Name == "HitsArray")
-                        _customTrackerHitsArray = fieldClone;
-                    else if (fieldClone.Name == "HitsFilePath")
-                        _customTrackerHitsFilePath = fieldClone;
+                    if (fieldClone.Name == nameof(ModuleTrackerTemplate.hitsArraySize))
+                        _customTrackerHitsArraySize = fieldClone;
+                    else if (fieldClone.Name == nameof(ModuleTrackerTemplate.hitsDirectoryPath))
+                        _customTrackerHitsDirectoryPath = fieldClone;
                 }
 
                 foreach (MethodDefinition methodDef in moduleTrackerTemplate.Methods)
                 {
                     MethodDefinition methodOnCustomType = new MethodDefinition(methodDef.Name, methodDef.Attributes, methodDef.ReturnType);
 
-                    if (methodDef.Name == "RecordHit")
+                    if (methodDef.Name == nameof(ModuleTrackerTemplate.RecordHit))
                     {
                         foreach (var parameter in methodDef.Parameters)
                         {
@@ -179,7 +179,7 @@ private void AddCustomModuleTrackerToModule(ModuleDefinition module)
                         {
                             handler.CatchType = module.ImportReference(handler.CatchType);
                         }
-                        
+
                         methodOnCustomType.Body.ExceptionHandlers.Add(handler);
                     }
 
@@ -189,7 +189,7 @@ private void AddCustomModuleTrackerToModule(ModuleDefinition module)
                 module.Types.Add(_customTrackerTypeDef);
             }
 
-            Debug.Assert(_customTrackerHitsArray != null);
+            Debug.Assert(_customTrackerHitsArraySize != null);
             Debug.Assert(_customTrackerClassConstructorIl != null);
         }
 

src/coverlet.core/Instrumentation/InstrumenterResult.cs

@@ -41,7 +41,7 @@ public InstrumenterResult()
         }
 
         public string Module;
-        public string HitsFilePath;
+        public string HitsDirectoryPath;
         public string ModulePath;
         public Dictionary<string, Document> Documents { get; private set; }
         public List<(bool isBranch, int docIndex, int start, int end)> HitCandidates { get; private set; }