Question

I would like to put a string into a byte array, but the string may be too big to fit. In the case where it’s too large, I would like to put as much of the string as possible into the array. Is there an efficient way to find out how many characters will fit?

Answer 1

In order to truncate a string to a UTF8 byte array without splitting in the middle of a character I use this:

static string Truncate(string s, int maxLength) {     if (Encoding.UTF8.GetByteCount(s) <= maxLength)         return s;     var cs = s.ToCharArray();     int length = 0;     int i = 0;     while (i < cs.Length){         int charSize = 1;         if (i < (cs.Length - 1) && char.IsSurrogate(cs[i]))             charSize = 2;         int byteSize = Encoding.UTF8.GetByteCount(cs, i, charSize);         if ((byteSize + length) <= maxLength){             i = i + charSize;             length += byteSize;         }         else             break;     }     return s.Substring(0, i); } 

The returned string can then be safely transferred to a byte array of length maxLength.