1//! Block header definitions.
2
3/// There are 4 different kinds of blocks, and the type of block influences the meaning of `Block_Size`.
4#[derive(Debug, Clone, Copy, PartialEq, Eq)]
5pub enum BlockType {
6 /// An uncompressed block.
7 Raw,
8 /// A single byte, repeated `Block_Size` times (Run Length Encoding).
9 RLE,
10 /// A Zstandard compressed block. `Block_Size` is the length of the compressed data.
11 Compressed,
12 /// This is not a valid block, and this value should not be used.
13 /// If this value is present, it should be considered corrupted data.
14 Reserved,
15}
16
17impl core::fmt::Display for BlockType {
18 fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> Result<(), core::fmt::Error> {
19 match self {
20 BlockType::Compressed => write!(f, "Compressed"),
21 BlockType::Raw => write!(f, "Raw"),
22 BlockType::RLE => write!(f, "RLE"),
23 BlockType::Reserved => write!(f, "Reserverd"),
24 }
25 }
26}
27
28/// A representation of a single block header. As well as containing a frame header,
29/// each Zstandard frame contains one or more blocks.
30pub struct BlockHeader {
31 /// Whether this block is the last block in the frame.
32 /// It may be followed by an optional `Content_Checksum` if it is.
33 pub last_block: bool,
34 pub block_type: BlockType,
35 /// The size of the decompressed data. If the block type
36 /// is [BlockType::Reserved] or [BlockType::Compressed],
37 /// this value is set to zero and should not be referenced.
38 pub decompressed_size: u32,
39 /// The size of the block. If the block is [BlockType::RLE],
40 /// this value will be 1.
41 pub content_size: u32,
42}
43