C
C#•2w ago
wasabi

Appending to StringBuilder by Unicode code point?

What might be the most efficient way to append a unicode code point (int32) to a StringBuilder, taking into account I need it to work on Framework.
7 Replies
Angius
Angius•2w ago
Char.ConvertFromUtf32(Int32)?
wasabi
wasabiOP•2w ago
That allocates a string[] Which would be very heavy when working with ... large amounts of text. I kinda just ended up, so far, doing it myself, writing 1 or 2 chars to a Span<char>, then appending that.
reflectronic
reflectronic•2w ago
https://github.com/microsoft/referencesource/blob/master/mscorlib/system/char.cs#L921-L940 copy this but replace the array with char* surrogate = stackalloc char[2]; then use Append(char*, int)
wasabi
wasabiOP•2w ago
I basically did that though without copying it.
reflectronic
reflectronic•2w ago
well. that is probably the most efficient way of doing it
wasabi
wasabiOP•2w ago
Figured.
Sehra
Sehra•2w ago
void Append(StringBuilder sb, int cp)
{
    if (cp > 0xFFFF)
    {
        sb.Append((char)((cp - 0x10000) / 0x400 + 0xD800));
        sb.Append((char)((cp - 0x10000) % 0x400 + 0xDC00));
    }
    else
    {
        sb.Append((char)cp);
    }
}
void Append(StringBuilder sb, int cp)
{
    if (cp > 0xFFFF)
    {
        sb.Append((char)((cp - 0x10000) / 0x400 + 0xD800));
        sb.Append((char)((cp - 0x10000) % 0x400 + 0xDC00));
    }
    else
    {
        sb.Append((char)cp);
    }
}

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