[crc64] Fix a subtle bug in CRC64 splice-by-8 implementation (#627)

Commit 9b88ce7 implemented a splice-by-8 version of the CRC64
algorithm which processes 8 bytes per loop iteration. However, the
code had a subtle bug which resulted in the same CRC calculated for
different strings and made some of the Xamarin.Android tests to fail.
The following strings yielded the same checksum value:
* `obj/Debug/lp/10/jl/bin/classes.jar`
* `obj/Debug/lp/11/jl/bin/classes.jar`
* `obj/Debug/lp/12/jl/bin/classes.jar`
The reason for this was subtle (a stupid oversight on my part, really):
the loop fetched values from the input array by using an index into
the array:
crc ^= (ulong)aptr[idx];
However, with `aptr` being declared as `byte* aptr` the indexing
operation returned a single *byte* instead of the required 64-bit word
(8 bytes) and, thus, on each iteration of the loop 7 bytes of the input
arrays were ignored in calculation, thus causing the collisions.
The fix is to cast `aptr` to `ulong*` and *then* index it, extracting
the required 8 bytes.
This commit also adds a test to check for this issue.

Author: grendello

src/Java.Interop.Tools.JavaCallableWrappers/Java.Interop.Tools.JavaCallableWrappers/Crc64.cs

@@ -61,7 +61,7 @@ unsafe protected override void HashCore (byte [] array, int ibStart, int cbSize)
  fixed (ulong*tptr=Table){
  fixed (byte*aptr=array){
 while(len>=8){
-crc^=(ulong)aptr[idx];
+crc^=*((ulong*)(aptr+idx));
 crc=
 tptr[7*256+(crc&0xff)]^
 tptr[6*256+((crc>>8)&0xff)]^

tests/Java.Interop.Tools.JavaCallableWrappers-Tests/Java.Interop.Tools.JavaCallableWrappers/Crc64Tests.cs

@@ -1,4 +1,5 @@
 usingSystem.Text;
+usingSystem.Security.Cryptography;
 usingJava.Interop.Tools.JavaCallableWrappers;
 usingNUnit.Framework;
 
@@ -34,13 +35,50 @@ public void Hello ()
 publicvoidXmlDocument()
 {
 varactual=ToHash("System.Xml.XmlDocument, System.Xml");
-Assert.AreEqual("b9c1bdfc7cd47543",actual);
+Assert.AreEqual("348bbd9fecf1b865",actual);
 }
 
 [Test]
 publicvoidCollision()
 {
 Assert.AreNotEqual(ToHash(""),ToHash(newbyte[32]));
 }
+
+[Test]
+publicvoidAllBytesAreProcessed()
+{
+// Slicing processes 8 bytes (a 64-bit word) at a time, and if any of the bytes are skipped we will have a
+// collision here.
+string[]inputs={
+"obj/Debug/lp/10/jl/bin/classes.jar",
+"obj/Debug/lp/11/jl/bin/classes.jar",
+"obj/Debug/lp/12/jl/bin/classes.jar",
+};
+
+string[]expected={
+"419a37c9bcfddf3c",
+"6ea5e242b7cc24a7",
+"74770a86f8b97020",
+};
+
+string[]outputs=newstring[inputs.Length];
+
+for(inti=0;i<inputs.Length;i++){
+byte[]bytes=Encoding.UTF8.GetBytes(inputs[i]);
+using(HashAlgorithmhashAlg=newCrc64()){
+byte[]hash=hashAlg.ComputeHash(bytes);
+outputs[i]=ToHash(hash);
+Assert.AreEqual(expected[i],outputs[i],$"hash {i} differs");
+}
+}
+
+for(inti=0;i<outputs.Length;i++){
+for(intj=0;j<outputs.Length;j++){
+if(j==i)
+continue;
+Assert.AreNotEqual(outputs[i],outputs[j],$"Outputs {i} and {j} are identical");
+}
+}
+}
 }
 }

tests/Java.Interop.Tools.JavaCallableWrappers-Tests/Java.Interop.Tools.JavaCallableWrappers/JavaCallableWrapperGeneratorTests.cs

@@ -124,7 +124,7 @@ public void GenerateIndirectApplication (
 )
 {
 varactual=Generate(typeof(IndirectApplication),applicationJavaClass);
-varexpected=@"package c64r2b57424eba1fa9d27;
+varexpected=@"package c64r2197ae30a36756915;
 
 
 public class IndirectApplication
@@ -175,7 +175,7 @@ public void monodroidClearReferences ()
 publicvoidGenerateExportedMembers()
 {
 varactual=Generate(typeof(ExportsMembers));
-varexpected=@"package c64r2b57424eba1fa9d27;
+varexpected=@"package c64r2197ae30a36756915;
 
 
 public class ExportsMembers
@@ -187,7 +187,7 @@ extends java.lang.Object
 	public static final String __md_methods;
 	static {
  __md_methods = 
- ""n_GetInstance:()Lc64r2b57424eba1fa9d27/ExportsMembers;:__export__\n"" +
+ ""n_GetInstance:()Lc64r2197ae30a36756915/ExportsMembers;:__export__\n"" +
  ""n_GetValue:()Ljava/lang/String;:__export__\n"" +
  ""n_methodNamesNotMangled:()V:__export__\n"" +
  ""n_CompletelyDifferentName:(Ljava/lang/String;I)Ljava/lang/String;:__export__\n"" +
@@ -198,17 +198,17 @@ extends java.lang.Object
 	}
 
 
-	public static c64r2b57424eba1fa9d27.ExportsMembers STATIC_INSTANCE = GetInstance ();
+	public static c64r2197ae30a36756915.ExportsMembers STATIC_INSTANCE = GetInstance ();
 
 
 	public java.lang.String VALUE = GetValue ();
 
-	public static c64r2b57424eba1fa9d27.ExportsMembers GetInstance ()
+	public static c64r2197ae30a36756915.ExportsMembers GetInstance ()
 	{
  return n_GetInstance ();
 	}
 
-	private static native c64r2b57424eba1fa9d27.ExportsMembers n_GetInstance ();
+	private static native c64r2197ae30a36756915.ExportsMembers n_GetInstance ();
 
 	public java.lang.String GetValue ()
 	{
@@ -271,7 +271,7 @@ public void monodroidClearReferences ()
 publicvoidGenerateInnerClass()
 {
 varactual=Generate(typeof(ExampleOuterClass));
-varexpected=@"package c64r2b57424eba1fa9d27;
+varexpected=@"package c64r2197ae30a36756915;
 
 
 public class ExampleOuterClass

tests/Java.Interop.Tools.JavaCallableWrappers-Tests/Java.Interop.Tools.JavaCallableWrappers/JavaNativeTypeManagerTests.cs

@@ -29,7 +29,7 @@ public void TearDown ()
 publicvoidCrc64()
 {
 JavaNativeTypeManager.PackageNamingPolicy=PackageNamingPolicy.LowercaseCrc64;
-Assert.AreEqual("c64r279bf423bcb581100",JavaNativeTypeManager.GetPackageName(typeof(string)));
+Assert.AreEqual("c64r2b74743e9328eed0a",JavaNativeTypeManager.GetPackageName(typeof(string)));
 }
 
 [Test]

tests/Java.Interop.Tools.JavaCallableWrappers-Tests/Java.Interop.Tools.JavaCallableWrappers/TypeNameMapGeneratorTests.cs

@@ -59,12 +59,12 @@ public void WriteJavaToManaged ()
 "value-offset="+offset+"\u0000"+
 GetJ2MEntryLine(typeof(ActivityName),"activity/Name",offset,length)+
 GetJ2MEntryLine(typeof(ApplicationName),"application/Name",offset,length)+
-GetJ2MEntryLine(typeof(DefaultName),"c64r2b57424eba1fa9d27/DefaultName",offset,length)+
-GetJ2MEntryLine(typeof(DefaultName.A),"c64r2b57424eba1fa9d27/DefaultName_A",offset,length)+
-GetJ2MEntryLine(typeof(DefaultName.A.B),"c64r2b57424eba1fa9d27/DefaultName_A_B",offset,length)+
-GetJ2MEntryLine(typeof(DefaultName.C.D),"c64r2b57424eba1fa9d27/DefaultName_C_D",offset,length)+
-GetJ2MEntryLine(typeof(ExampleOuterClass),"c64r2b57424eba1fa9d27/ExampleOuterClass",offset,length)+
-GetJ2MEntryLine(typeof(ExampleOuterClass.ExampleInnerClass),"c64r2b57424eba1fa9d27/ExampleOuterClass$ExampleOuterClass_ExampleInnerClass",offset,length)+
+GetJ2MEntryLine(typeof(DefaultName),"c64r2197ae30a36756915/DefaultName",offset,length)+
+GetJ2MEntryLine(typeof(DefaultName.A),"c64r2197ae30a36756915/DefaultName_A",offset,length)+
+GetJ2MEntryLine(typeof(DefaultName.A.B),"c64r2197ae30a36756915/DefaultName_A_B",offset,length)+
+GetJ2MEntryLine(typeof(DefaultName.C.D),"c64r2197ae30a36756915/DefaultName_C_D",offset,length)+
+GetJ2MEntryLine(typeof(ExampleOuterClass),"c64r2197ae30a36756915/ExampleOuterClass",offset,length)+
+GetJ2MEntryLine(typeof(ExampleOuterClass.ExampleInnerClass),"c64r2197ae30a36756915/ExampleOuterClass$ExampleOuterClass_ExampleInnerClass",offset,length)+
 GetJ2MEntryLine(typeof(InstrumentationName),"instrumentation/Name",offset,length)+
 GetJ2MEntryLine(typeof(AbstractClass),"my/AbstractClass",offset,length)+
 GetJ2MEntryLine(typeof(ExampleActivity),"my/ExampleActivity",offset,length)+
@@ -139,14 +139,14 @@ public void WriteManagedToJava ()
 GetM2JEntryLine(typeof(AbstractClassInvoker),"my/AbstractClass",offset,length)+
 GetM2JEntryLine(typeof(ActivityName),"activity/Name",offset,length)+
 GetM2JEntryLine(typeof(ApplicationName),"application/Name",offset,length)+
-GetM2JEntryLine(typeof(DefaultName.A.B),"c64r2b57424eba1fa9d27/DefaultName_A_B",offset,length)+
-GetM2JEntryLine(typeof(DefaultName.A),"c64r2b57424eba1fa9d27/DefaultName_A",offset,length)+
-GetM2JEntryLine(typeof(DefaultName.C.D),"c64r2b57424eba1fa9d27/DefaultName_C_D",offset,length)+
-GetM2JEntryLine(typeof(DefaultName),"c64r2b57424eba1fa9d27/DefaultName",offset,length)+
+GetM2JEntryLine(typeof(DefaultName.A.B),"c64r2197ae30a36756915/DefaultName_A_B",offset,length)+
+GetM2JEntryLine(typeof(DefaultName.A),"c64r2197ae30a36756915/DefaultName_A",offset,length)+
+GetM2JEntryLine(typeof(DefaultName.C.D),"c64r2197ae30a36756915/DefaultName_C_D",offset,length)+
+GetM2JEntryLine(typeof(DefaultName),"c64r2197ae30a36756915/DefaultName",offset,length)+
 GetM2JEntryLine(typeof(ExampleActivity),"my/ExampleActivity",offset,length)+
 GetM2JEntryLine(typeof(ExampleInstrumentation),"my/ExampleInstrumentation",offset,length)+
-GetM2JEntryLine(typeof(ExampleOuterClass.ExampleInnerClass),"c64r2b57424eba1fa9d27/ExampleOuterClass$ExampleOuterClass_ExampleInnerClass",offset,length)+
-GetM2JEntryLine(typeof(ExampleOuterClass),"c64r2b57424eba1fa9d27/ExampleOuterClass",offset,length)+
+GetM2JEntryLine(typeof(ExampleOuterClass.ExampleInnerClass),"c64r2197ae30a36756915/ExampleOuterClass$ExampleOuterClass_ExampleInnerClass",offset,length)+
+GetM2JEntryLine(typeof(ExampleOuterClass),"c64r2197ae30a36756915/ExampleOuterClass",offset,length)+
 GetM2JEntryLine(typeof(InstrumentationName),"instrumentation/Name",offset,length)+
 GetM2JEntryLine(typeof(NonStaticOuterClass.NonStaticInnerClass),"register/NonStaticOuterClass$NonStaticInnerClass",offset,length)+
 GetM2JEntryLine(typeof(NonStaticOuterClass),"register/NonStaticOuterClass",offset,length)+