How do I convert a double array to a string that matches the same conversion using memcpy in C++

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I have inherited existing C++ code that converts an array of doubles into a string, writes it to a database memo field, and then can read the string from the database memo field and convert it to an array of doubles. I want to write c# code that does the same operation of converting an array of doubles into a string such that it is compatible with the C++ code that converts it from a string to a double array. What is the proper c# code to produce the same string?

C++ code that converts the double array to a string:

C

int numValues = 3;
double stations[] = { 1.0,2.0,3.0 };
int blockSize = numValues * sizeof(double);
char* mp_memoValue = new char[blockSize + 1];
memcpy(mp_memoValue, (char*)stations, blockSize);

What I have tried:

C#

byte[] theBytesData = new byte[numBytesReqd];
Buffer.BlockCopy(stations, 0, theBytesData, 0, numBytesReqd);
theMemoField = Encoding.ASCII.GetString(theBytesData, 0, theBytesData.Length);

Also, following up on proposed solution #1, I did the following although it didn't produce the same binary string that the C++ code produces.

The idea of using the binary copy seems correct. Maybe the basic question is, what does (char*)stations do in C++ and is it possible to duplicate that behavior in C# and then do the binary copy? I may be asking the impossible, my knowledge is limited.

C#

BinaryFormatter formatter = new BinaryFormatter();
using (MemoryStream m = new MemoryStream())
{
    formatter.Serialize(m, stations);
    m.Position = 0;
    StreamReader sr = new StreamReader(m);
    theMemoField = sr.ReadToEnd();
}

Posted 20-Apr-19 4:52am

Member 14077625

Updated 22-Apr-19 9:34am

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Gerry Schmitz · Answer 1 · 2019-04-20T05:12:00

Solution 1

c# - binary formatter to string - Stack Overflow[^]

Posted 20-Apr-19 5:12am

Gerry Schmitz

#realJSOP · Answer 2 · 2019-04-20T05:29:00

You didn't show us what the string created by the C++ code looks like.

I'm going to assume (since you didn't specify) that your string of doubles is delimited in some way, probably with a comma.

I'm going to further assume that you've retrieved the string from the database.

Given those two assumptions...

To put an array of doubles into a delimited string:

C#

// convert an array of doubles to a deliimited string
string myData = string.Empty;
double[] doubles = new double[]{1.2,3.4,5.6 };
foreach(double dbl in doubles)
{
    // we only need a comma if the string is not empty
    string comma = (myData.Length == 0)?"":",";
    // convert the value to a string (you can also use TryParse if the data is not trusted to be correct)
    string value = string.Format("{0:#.00}", dbl);
    // add it to the string
    myData = string.Format("{0}{1}{2}", myData, comma, value);
}
// at this point myData should be "1.20,3.40,5.60"

//---------------------------

// now we convert the string back to an array of doubles
// split the string on the delimiter
string[] parts = myData.Split(',');
// create a double array of the same length
double[] partsDouble = new double[parts.Length];

// loop through the delimited string parts,convert the values to doubles, and 
// assign them to the approriate double array index
for (int i = 0; i < parts.Length; i++)
{
    partsDouble[i] = Convert.ToDouble(parts[i]);
}

You could get really fancy with and use Linq for this, but usually, maintainability with clear-cut code is a better solution. Besides that, sometimes it's all about completing the task with as little fuss as possible.

CPallini · Answer 3 · 2019-04-20T09:35:00

Solution 3

You the BitConverter Class (System) | Microsoft Docs[^].
See, for instance: How to Convert a Byte Array to Double in C#[^].

Posted 20-Apr-19 9:35am

CPallini

Comments

Member 14077625 22-Apr-19 15:25pm

I tried using BitConverter as follows:
byte[] theBytesData = BitConverter.GetBytes(stations[0]);
theMemoField = BitConverter.ToString(theBytesData);

But it didn't produce the same string that the C++ code produces.