BitConverter: ToDouble, ToSingle, Int64BitsToDouble, Int32BitsToDouble #2977
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area-System.Runtime
Pri3
Indicates issues/PRs that are low priority
untriaged
New issue has not been triaged by the area owner
Comments
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Tagging @pgovind @tannergooding for triage. |
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Thanks! This repros on .NET Core using: var xb = new byte[] { 1, 0, 0, 0, 0, 0, 0xf0, 0x7f };
var yb = new byte[] { 1, 0, 0, 0, 0, 0, 0xf8, 0x7f };
var x = BitConverter.ToDouble(xb);
var y = BitConverter.ToDouble(yb);
Console.WriteLine(Environment.Is64BitProcess);
Console.WriteLine($"{x} {BitConverter.DoubleToInt64Bits(x):X16}");
Console.WriteLine($"{y} {BitConverter.DoubleToInt64Bits(y):X16}");I'd like to investigate a bit more and determine "why" the value is being changed (I expect it might be due to the x87 FPU stack). |
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Another curiosity I found with respect to NaN. In .NET, Where the so-called "sign bit" of the value (topmost bit of the last byte) is set. Whereas in Java, for example, the equivalent This shows once again the multi-faced nature of NaN. Related: WebAssembly/interface-types#134 |
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Link to article:
https://docs.microsoft.com/en-us/dotnet/api/system.bitconverter.todouble?view=netstandard-2.0
Problem:
Mention that it might not be possible to use these methods to produce what are so-called _signaling NaN_s in x86, x64, and certain other instruction set architectures. A signaling NaN is an NaN with the most significant bit of the mantissa area clear (as opposed to a quiet NaN where that bit is set). An example of a signaling NaN is as follows (with little-endian byte ordering):
At least in x86, using ToDouble and converting the resulting
doubleback will convert the signaling NaN to a quiet NaN as follows:This can be an issue if the application works with binary serialization formats that store
doubleorfloatvalues in the form of the bits that make them up, because converting those bits todoubleorfloatwith these BitConverter methods may make round-tripping thatdoubleorfloatnot always possible.The text was updated successfully, but these errors were encountered: