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use crate::blocks::block::BlockType;
use alloc::vec::Vec;
#[derive(Debug)]
pub struct BlockHeader {
/// Signals if this block is the last one.
/// The frame will end after this block.
pub last_block: bool,
/// Influences the meaning of `block_size`.
pub block_type: BlockType,
/// - For `Raw` blocks, this is the size of the block's
/// content in bytes.
/// - For `RLE` blocks, there will be a single byte follwing
/// the header, repeated `block_size` times.
/// - For `Compressed` blocks, this is the length of
/// the compressed data.
///
/// **This value must not be greater than 21 bits in length.**
pub block_size: u32,
}
impl BlockHeader {
/// Write encoded binary representation of this header into the provided buffer.
pub fn serialize(self, output: &mut Vec<u8>) {
vprintln!("Serializing block with the header: {self:?}");
output.extend_from_slice(&self.to_le_bytes());
}
/// The fixed 3-byte little-endian block header. Block headers are always
/// exactly 3 bytes (RFC 8878 §3.1.1.2), so callers that reserved space
/// up front can backfill the header in place via this array without a
/// `Vec` round-trip (the compress-into-output emit path relies on this).
#[inline]
pub fn to_le_bytes(&self) -> [u8; 3] {
let encoded_block_type = match self.block_type {
BlockType::Raw => 0u32,
BlockType::RLE => 1,
BlockType::Compressed => 2,
BlockType::Reserved => panic!("You cannot use a reserved block type"),
};
let mut block_header = self.block_size << 3;
block_header |= encoded_block_type << 1;
block_header |= self.last_block as u32;
let le = block_header.to_le_bytes();
[le[0], le[1], le[2]]
}
}
#[cfg(test)]
mod tests;