Fixes for issue #416

[sharmavishnu]

Description

Fixed format generation for hexadecimal numbers that was causing issues with ToString("Xnn") calls.

Motivation and Context

For hexadecimal numbers, there is no concept of signed/unsigned. Also, floats are not represented in hexadecimal formatting like normal int/long.

• Fixes ToString() causing hardfault Home#416

How Has This Been Tested?

Tested with the following code:

        //Integer test            
        Console.WriteLine("Min UInt32=" + UInt32.MinValue + ",as Hex=0x" + UInt32.MinValue.ToString("X16"));
        Console.WriteLine("Max UInt32=" + UInt32.MaxValue + ",as Hex=0x" + UInt32.MaxValue.ToString("X16"));
        Console.WriteLine("Min Int32=" + Int32.MinValue + ",as Hex=0x" + Int32.MinValue.ToString("X16"));
        Console.WriteLine("Max Int32=" + Int32.MaxValue + ",as Hex=0x" + Int32.MaxValue.ToString("X16"));
        
        //Float test
        Console.WriteLine("Min float=" + float.MinValue + ",as formatted=" + float.MinValue.ToString("f16"));
        Console.WriteLine("Max float=" + float.MaxValue + ",as formatted=" + float.MaxValue.ToString("f16"));
                     
        //long test
        Console.WriteLine("Min UInt64=" + UInt64.MinValue + ",as formatted=0x" + UInt64.MinValue.ToString("x16"));
        Console.WriteLine("Max UInt64=" + UInt64.MaxValue + ",as formatted=0x" + UInt64.MaxValue.ToString("x16"));
        Console.WriteLine("Min Int64=" + Int64.MinValue + ",as formatted=0x" + Int64.MinValue.ToString("x16"));
        Console.WriteLine("Max Int64=" + Int64.MaxValue + ",as formatted=0x" + Int64.MaxValue.ToString("x16"));

Screenshots

Types of changes

• Improvement (non-breaking change that improves a feature, code or algorithm)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

Signed-off-by: @sharmavishnu

[nfbot]

Hi @sharmavishnu,

I'm nanoFramework bot.
Thank you for your contribution!

A human will be reviewing it shortly. 😉

[CLAassistant]

All committers have signed the CLA.

[josesimoes]

This looks good to me. Thank you for looking into this. 👏
Let's wait on @MatthiasJentsch review and running all the others tests over this.

[MatthiasJentsch]

I've changed the else block. We don't need to check formatCh == 'X' here.

Beside that it looks good to me. Tests are also working. I've tested only on ESP32. Good work!