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utf8EncodeImpl

unicode.utf8EncodeImpl

fn utf8EncodeImpl(c: u21, out: []u8, comptime surrogates: Surrogates) !u3

File

lib/std/unicode.zig:53

Code

fn utf8EncodeImpl(c: u21, out: []u8, comptime surrogates: Surrogates) !u3 {
    const length = try utf8CodepointSequenceLength(c);
    assert(out.len >= length);
    switch (length) {
        // The pattern for each is the same
        // - Increasing the initial shift by 6 each time
        // - Each time after the first shorten the shifted
        //   value to a max of 0b111111 (63)
        1 => out[0] = @as(u8, @intCast(c)), // Can just do 0 + codepoint for initial range
        2 => {
            out[0] = @as(u8, @intCast(0b11000000 | (c >> 6)));
            out[1] = @as(u8, @intCast(0b10000000 | (c & 0b111111)));
        },
        3 => {
            if (surrogates == .cannot_encode_surrogate_half and isSurrogateCodepoint(c)) {
                return error.Utf8CannotEncodeSurrogateHalf;
            }
            out[0] = @as(u8, @intCast(0b11100000 | (c >> 12)));
            out[1] = @as(u8, @intCast(0b10000000 | ((c >> 6) & 0b111111)));
            out[2] = @as(u8, @intCast(0b10000000 | (c & 0b111111)));
        },
        4 => {
            out[0] = @as(u8, @intCast(0b11110000 | (c >> 18)));
            out[1] = @as(u8, @intCast(0b10000000 | ((c >> 12) & 0b111111)));
            out[2] = @as(u8, @intCast(0b10000000 | ((c >> 6) & 0b111111)));
            out[3] = @as(u8, @intCast(0b10000000 | (c & 0b111111)));
        },
        else => unreachable,
    }
    return length;
}