Converting Hex string to decimal string

Projects Programming
1

hello
i want to convert a hex number in string to a decimal number in string i have this function but i dont know why it is not working. could you please help me?

String senderNumber = "2b39313134363539383536353631";
String decimalString = hexToDecimal(senderNumber);

String hexToDecimal(String senderNumber) {
  String decimalString;

  for (size_t i = 0; i < senderNumber.length(); i += 2) {
    String hexByte = senderNumber.substring(i, i + 2);
    // Serial.println(hexByte);
    char hexByteChars[3];
    hexByte.toCharArray(hexByteChars, 3);
    Serial.println(hexByte);
    unsigned long decimalValue = strtoul(hexByteChars, nullptr, 16);
    // Serial.println(decimalValue);
    decimalString += String(decimalValue);
  }

  return decimalString;
}
2

What does the function do and what do you expect it to do?

4

i want to convert this string which is in hex

String senderNumber = "2b39313134363539383536353631"; //  +9114659856561 in decimal

to a decimal string

5

And whλt does your function do?

edit: could it be that you want to convert a string of hex numbers to a string of chars?

6

i explain it in comments

  for (size_t i = 0; i < senderNumber.length(); i += 2) {
    String hexByte = senderNumber.substring(i, i + 2); // seperating each 2 character of String and put it to another string (hexByte)

    char hexByteChars[3];
    hexByte.toCharArray(hexByteChars, 3); // converting hexByte to chararray

    unsigned long decimalValue = strtoul(hexByteChars, nullptr, 16); //converting HEX to Decimal

    decimalString += String(decimalValue); // put the decimalValue to decimalString 
  }

  return decimalString; // returning the decimalString
}
7

i want to convert String of hex numbers to String of decimal

8

it seems that this part of function doesnt work correctly

9

i found the solution now its working
the problem was the plus sign "+" at the first of decimal number

here is the final code :

  String senderNumber = "2b39313134363539383536353631";
  char charArray[senderNumber.length() / 2 + 1]; // +1 for null terminator
  hexToCharArray(senderNumber, charArray);

  Serial.print("Hexadecimal String: ");
  Serial.println(senderNumber);
  Serial.print("Character Array: ");
  Serial.println(charArray);

    String resultString(charArray);

  Serial.print("Result String: ");
  Serial.println(resultString);

void hexToCharArray(const String& senderNumber, char* charArray) {
  for (size_t i = 0; i < senderNumber.length(); i += 2) {
    String hexByte = senderNumber.substring(i, i + 2);
    charArray[i / 2] = static_cast<char>(strtol(hexByte.c_str(), nullptr, 16));
  }
  charArray[senderNumber.length() / 2] = '\0'; // Null-terminate the character array
}
10

Just for the record: you do not convert a string with a hex number to dec (which would have 114 bits), you convert a string of 2-byte hex to a string of 1 byte chars :slight_smile:

11

yeah i will remember that. thanks @zwieblum

13

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