pub const FONT_CHUNK_HEADER_LEN: usize = 4;
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum FontChunkKind {
Grayscale,
Sdf,
}
impl FontChunkKind {
pub fn from_u8(b: u8) -> Option<Self> {
match b {
0 => Some(Self::Grayscale),
1 => Some(Self::Sdf),
_ => None,
}
}
pub fn to_u8(self) -> u8 {
match self {
Self::Grayscale => 0,
Self::Sdf => 1,
}
}
}
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub struct FontChunkHeader {
pub kind: FontChunkKind,
pub format: u8,
pub size: u16,
}
impl FontChunkHeader {
pub fn parse(payload: &[u8]) -> Option<Self> {
if payload.len() < FONT_CHUNK_HEADER_LEN {
return None;
}
Some(Self {
kind: FontChunkKind::from_u8(payload[0])?,
format: payload[1],
size: u16::from_le_bytes([payload[2], payload[3]]),
})
}
pub fn write(&self, out: &mut [u8]) {
out[0] = self.kind.to_u8();
out[1] = self.format;
out[2..4].copy_from_slice(&self.size.to_le_bytes());
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn header_round_trips() {
let orig = FontChunkHeader {
kind: FontChunkKind::Grayscale,
format: 4,
size: 16,
};
let mut buf = [0u8; FONT_CHUNK_HEADER_LEN];
orig.write(&mut buf);
assert_eq!(FontChunkHeader::parse(&buf), Some(orig));
}
#[test]
fn parse_rejects_short_payload() {
assert_eq!(FontChunkHeader::parse(&[0, 0, 0]), None);
}
#[test]
fn parse_rejects_unknown_kind() {
assert_eq!(FontChunkHeader::parse(&[9, 4, 16, 0]), None);
}
}