如何将字符串转换为ushort []

Question

I have been scouring the web for a solution to the conversion problem I have been facing where I am required to write into the User Memory of a RF Tag. The API accepts an ushort[] . I have created an app that accepts ASCII inputs as a test field. For instance, if the user enters Hurrah , then I need that to be converted to ushort[] { 0x4875, 0x7272, 0x6168} . Here is how far I have gotten with this:

    [TestMethod]
    public void AsciiToHexConversionTest()
    {
        IList<ushort> outputList = new List<ushort>();
        var inputStr = "Hurrah";
        IList<char> output = new List<char>();

        char[] values = inputStr.ToCharArray();
        foreach (char letter in values)
        {
            // Get the integral value of the character. 
            var value = Convert.ToInt32(letter);

            // Convert the decimal value to a hexadecimal value in string form. 
            // uncommenting this line results in an error, and I cant figure out how to convert int to hex without it being a string
            //output.Add(string.Format("{0:X}", value));

        }

        // use bitwise or to package two bytes to a ushort value
        for (int i = 0; i < output.ToArray().Length; i++)
        {
            outputList.Add((ushort)((output[i] << 8) | output[i + 1]));
        }

        Assert.AreEqual(outputList, "487572726168");

    }

Any pointers will be much appreciated.

Answer 1

Update

I think you are thinking that a number can either be in decimal or binary or hexadecimal, etc. But that's not how it works. Numbers are numeric values that specify magnitude--decimal vs. hexadecimal is just how those values are represented. So the numbers in listOfUshorts have a numeric value that can be expressed in either hexadecimal or any other base, such as decimal (the underlying base is actually binary, neither hex or decimal).

I've updated the code below to prove this: I have inserted new Debug.Asserts below, where I assert that each item is the expected hexadecimal value. I also assert their equivalent decimal value, and then I assert that the hexadecimal and decimal values are directly equivalent to each other.

---

Original

Seems to me like you basically had it. However, the only time you need to convert to hex is for human-readable-comparison purposes. So you don't need two lists ( output and outputList ). Internally you can always deal with the numeric values as they are, without conversion, as long as you always deal with them in the same base (whether decimal or hexadecimal or anything else).

Here's basically the same thing, with a few tweaks. I don't have it as a test fixture, so I don't have Assert.AreEqual --I used Debug.Assert instead. I also put the hex formatting for display/comparison into its own function, since it's only needed for test purposes.

using System;
using System.Collections.Generic;
using System.Text;
using System.Diagnostics;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            ushort[] result = AsciiToHexConversionTest();

            String outputAsHexString = DecodeToHexString(result);

            Debug.Assert(outputAsHexString == "0x4875,0x7272,0x6168");

            Console.WriteLine(outputAsHexString);
            var readKey = Console.ReadKey();
        }

        public static ushort[] AsciiToHexConversionTest()
        {
            var inputStr = "Hurrah";

            char[] values = inputStr.ToCharArray();
            List<ushort> listOfUshorts = new List<ushort>();

            ushort mask = (ushort)0x00FF;
            for (int i = 0; i < values.Length; i += 2)
            {
                //This approach assumes stuffing the lower 8 bits of two chars into the upper and lower half of a ushort
                ushort first = values[i];
                ushort second = (ushort)(mask & values[i + 1]); //mask is for safety.  Must ensure that top byte is 0 so that | below goes ok.
                listOfUshorts.Add((ushort)((first << 8) | second));
            }

            //demonstrate hexadecimal values
            Debug.Assert(listOfUshorts[0] == 0x4875);
            Debug.Assert(listOfUshorts[1] == 0x7272);
            Debug.Assert(listOfUshorts[2] == 0x6168);

            //demonstrate decimal values
            Debug.Assert(listOfUshorts[0] == 18549);
            Debug.Assert(listOfUshorts[1] == 29298);
            Debug.Assert(listOfUshorts[2] == 24936);

            //directly demonstrate equality of decimal and hexadecimal representations
            Debug.Assert(0x4875 == 18549);
            Debug.Assert(0x7272 == 29298);
            Debug.Assert(0x6168 == 24936);

            return listOfUshorts.ToArray();
        }

        public static string DecodeToHexString(ushort[] list)
        {
            StringBuilder finalOutput = new StringBuilder();
            foreach (var item in list)
            {
                finalOutput.Append(String.Format("0x{0:X},", item));
            }
            finalOutput.Remove(finalOutput.Length - 1, 1); //Remove final comma
            return finalOutput.ToString();
        }
    }
}

Answer 2

@Purusartha, there is an error in the ushort[] you give, the final hex value should be 0x6168 not 0x6148. I did it like this:

string inputStr = "Hurrah";
char[] values = inputStr.ToCharArray();
ushort[] packed = new ushort[values.Length / 2];
for (int i = 0; i < values.Length - 1; i+=2)
{
    packed[i / 2] = (ushort)(values[i] * 0x100 + values[i + 1]);
}