11using System ;
22using System . Diagnostics . CodeAnalysis ;
33using System . IO ;
4- using System . IO . MemoryMappedFiles ;
54using System . Threading ;
65
76namespace Coverlet . Core . Instrumentation
@@ -17,12 +16,7 @@ namespace Coverlet.Core.Instrumentation
1716 [ ExcludeFromCodeCoverage ]
1817 public static class ModuleTrackerTemplate
1918 {
20- public const int HitsResultHeaderSize = 2 ;
21- public const int HitsResultUnloadStarted = 0 ;
22- public const int HitsResultUnloadFinished = 1 ;
23-
2419 public static string HitsFilePath ;
25- public static string HitsMemoryMapName ;
2620 public static int [ ] HitsArray ;
2721
2822 static ModuleTrackerTemplate ( )
@@ -63,72 +57,56 @@ public static void UnloadModule(object sender, EventArgs e)
6357
6458 // The same module can be unloaded multiple times in the same process via different app domains.
6559 // Use a global mutex to ensure no concurrent access.
66- using ( var mutex = new Mutex ( true , HitsMemoryMapName + "_Mutex" , out bool createdNew ) )
60+ using ( var mutex = new Mutex ( true , Path . GetFileNameWithoutExtension ( HitsFilePath ) + "_Mutex" , out bool createdNew ) )
6761 {
6862 if ( ! createdNew )
6963 mutex . WaitOne ( ) ;
7064
71- MemoryMappedFile memoryMap = null ;
72-
65+ bool failedToCreateNewHitsFile = false ;
7366 try
7467 {
75- try
68+ using ( var fs = new FileStream ( HitsFilePath , FileMode . CreateNew ) )
69+ using ( var bw = new BinaryWriter ( fs ) )
7670 {
77- memoryMap = MemoryMappedFile . OpenExisting ( HitsMemoryMapName ) ;
78- }
79- catch ( PlatformNotSupportedException )
80- {
81- memoryMap = MemoryMappedFile . CreateFromFile ( HitsFilePath , FileMode . Open , null , ( HitsArray . Length + HitsResultHeaderSize ) * sizeof ( int ) ) ;
71+ bw . Write ( hitsArray . Length ) ;
72+ foreach ( int hitCount in hitsArray )
73+ {
74+ bw . Write ( hitCount ) ;
75+ }
8276 }
77+ }
78+ catch
79+ {
80+ failedToCreateNewHitsFile = true ;
81+ }
8382
84- // Tally hit counts from all threads in memory mapped area
85- var accessor = memoryMap . CreateViewAccessor ( ) ;
86- using ( var buffer = accessor . SafeMemoryMappedViewHandle )
83+ if ( failedToCreateNewHitsFile )
84+ {
85+ // Update the number of hits by adding value on disk with the ones on memory.
86+ // This path should be triggered only in the case of multiple AppDomain unloads.
87+ using ( var fs = new FileStream ( HitsFilePath , FileMode . Open , FileAccess . ReadWrite , FileShare . None ) )
88+ using ( var br = new BinaryReader ( fs ) )
89+ using ( var bw = new BinaryWriter ( fs ) )
8790 {
88- unsafe
91+ int hitsLength = br . ReadInt32 ( ) ;
92+ if ( hitsLength != hitsArray . Length )
8993 {
90- byte * pointer = null ;
91- buffer . AcquirePointer ( ref pointer ) ;
92- try
93- {
94- var intPointer = ( int * ) pointer ;
95-
96- // Signal back to coverage analysis that we've started transferring hit counts.
97- // Use interlocked here to ensure a memory barrier before the Coverage class reads
98- // the shared data.
99- Interlocked . Increment ( ref * ( intPointer + HitsResultUnloadStarted ) ) ;
100-
101- for ( var i = 0 ; i < hitsArray . Length ; i ++ )
102- {
103- var count = hitsArray [ i ] ;
104-
105- // By only modifying the memory map pages where there have been hits
106- // unnecessary allocation of all-zero pages is avoided.
107- if ( count > 0 )
108- {
109- var hitLocationArrayOffset = intPointer + i + HitsResultHeaderSize ;
110-
111- // No need to use Interlocked here since the mutex ensures only one thread updates
112- // the shared memory map.
113- * hitLocationArrayOffset += count ;
114- }
115- }
94+ throw new InvalidOperationException (
95+ $ "{ HitsFilePath } has { hitsLength } entries but on memory { nameof ( HitsArray ) } has { hitsArray . Length } ") ;
96+ }
11697
117- // Signal back to coverage analysis that all hit counts were successfully tallied.
118- Interlocked . Increment ( ref * ( intPointer + HitsResultUnloadFinished ) ) ;
119- }
120- finally
121- {
122- buffer . ReleasePointer ( ) ;
123- }
98+ for ( int i = 0 ; i < hitsLength ; ++ i )
99+ {
100+ int oldHitCount = br . ReadInt32 ( ) ;
101+ bw . Seek ( - sizeof ( int ) , SeekOrigin . Current ) ;
102+ bw . Write ( hitsArray [ i ] + oldHitCount ) ;
124103 }
125104 }
126105 }
127- finally
128- {
129- mutex . ReleaseMutex ( ) ;
130- memoryMap ? . Dispose ( ) ;
131- }
106+
107+ // On purpose this is not under a try-finally: it is better to have an exception if there was any error writing the hits file
108+ // this case is relevant when instrumenting corelib since multiple processes can be running against the same instrumented dll.
109+ mutex . ReleaseMutex ( ) ;
132110 }
133111 }
134112 }
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