Fix storage encoding

[shargon]

Description

We wrote the id in the OS format, but we always read it in LittleEndian

neo/src/Neo/SmartContract/StorageKey.cs

Line 40 in 95708b5

Id = BinaryPrimitives.ReadInt32LittleEndian(cache);

Type of change

• Bug fix (non-breaking change which fixes an issue)

[shargon]

@Jim8y The bug was here, it was stored in the OS format, but it was readed in LittleEndian, in our test is the same, but in a BigEndian machine, it will fault.

[cschuchardt88]

Its still wrong. You need to check the machine. Use

if (BitConverter.IsLittleEndian)
    Id = BinaryPrimitives.ReadInt32LittleEndian(cache);
else
    Id = BinaryPrimitives.ReadInt32BigEndian(cache);

[cschuchardt88]

Every machine OS is different. Some use little and some use Big you need to do an OS check.

[cschuchardt88]

Need more tests. @superboyiii needs to check states after this is finished.

[shargon]

Every machine OS is different. Some use little and some use Big you need to do an OS check.

Why? We need to write always in the same way, that's why I removed the unsafe methods

[shargon]

Need more tests. @superboyiii needs to check states after this is finished.

In big endian machine the states will change, but it becomes to be the same as little endian.

Note: no one use it in BigEndian, because it didn't work.

[cschuchardt88]

Need more tests. @superboyiii needs to check states after this is finished.

In big endian machine the states will change, but it becomes to be the same as little endian.

Note: no one use it in BigEndian, because it didn't work.

The reason it didn't work because the OS stores in BigEndian. So you have to write it in the same way. If you do a check if the OS is Big or Little you can use the right one. Instead of forcing one on a developer.

if (BitConverter.IsLittleEndian)
    Id = BinaryPrimitives.ReadInt32LittleEndian(cache);
else
    Id = BinaryPrimitives.ReadInt32BigEndian(cache);

Also if the OS is big it will always write the data to disk or memory as big even if its written in little.

[roman-khimov]

The fix itself is correct, maybe we can improve Add and constructor documentation though to mention endianness.

Is LevelDB binary format endian-agnostic, btw?

[shargon]

Instead of forcing one on a developer.

We want deterministic storage, no sense to store in different format in different os.

[cschuchardt88]

Also if the OS is big it will always write the data to disk or memory as big even if its written in little.

So when you go to read it would be in big again? I'm pretty sure. I don't have machine to check. Machine won't use odd address spaces. ONLY even address spaces. Its a hardware thing. But maybe the OS sets a bit or something for if it was written in little or big. I'm not 100% sure on that though. I do know i had problems before. Where you would write it as little and when you read it, the data would be in Big again.

[Jim8y]

How about banning BigEndian machine once for all. Now its the world of little endian. Kill the bigendian from neo.

If none of you can not even find a Bigendian machine to test, what is the debating means here.

Just little endian everywhere.

[Jim8y]

if (BitConverter.IsLittleEndian){throw exception "sorry, we dont like bigendian"}

[cschuchardt88]

Nevermind after checking dotnet does it no matter what.

[MethodImpl(MethodImplOptions.AggressiveInlining)]
public static void WriteInt64BigEndian(Span<byte> destination, long value)
{
    if (BitConverter.IsLittleEndian)
    {
        long tmp = ReverseEndianness(value);
        MemoryMarshal.Write(destination, ref tmp);
    }
    else
    {
        MemoryMarshal.Write(destination, ref value);
    }
}