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|
use super::super::decoding::bit_reader::{BitReader, GetBitsError};
pub struct LiteralsSection {
pub regenerated_size: u32,
pub compressed_size: Option<u32>,
pub num_streams: Option<u8>,
pub ls_type: LiteralsSectionType,
}
pub enum LiteralsSectionType {
Raw,
RLE,
Compressed,
Treeless,
}
#[derive(Debug, thiserror::Error)]
#[non_exhaustive]
pub enum LiteralsSectionParseError {
#[error("Illegal literalssectiontype. Is: {got}, must be in: 0, 1, 2, 3")]
IllegalLiteralSectionType { got: u8 },
#[error(transparent)]
GetBitsError(#[from] GetBitsError),
#[error("Not enough byte to parse the literals section header. Have: {have}, Need: {need}")]
NotEnoughBytes { have: usize, need: u8 },
}
impl std::fmt::Display for LiteralsSectionType {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> Result<(), std::fmt::Error> {
match self {
LiteralsSectionType::Compressed => write!(f, "Compressed"),
LiteralsSectionType::Raw => write!(f, "Raw"),
LiteralsSectionType::RLE => write!(f, "RLE"),
LiteralsSectionType::Treeless => write!(f, "Treeless"),
}
}
}
impl Default for LiteralsSection {
fn default() -> Self {
Self::new()
}
}
impl LiteralsSection {
pub fn new() -> LiteralsSection {
LiteralsSection {
regenerated_size: 0,
compressed_size: None,
num_streams: None,
ls_type: LiteralsSectionType::Raw,
}
}
pub fn header_bytes_needed(&self, first_byte: u8) -> Result<u8, LiteralsSectionParseError> {
let ls_type = Self::section_type(first_byte)?;
let size_format = (first_byte >> 2) & 0x3;
match ls_type {
LiteralsSectionType::RLE | LiteralsSectionType::Raw => {
match size_format {
0 | 2 => {
//size_format actually only uses one bit
//regenerated_size uses 5 bits
Ok(1)
}
1 => {
//size_format uses 2 bit
//regenerated_size uses 12 bits
Ok(2)
}
3 => {
//size_format uses 2 bit
//regenerated_size uses 20 bits
Ok(3)
}
_ => panic!(
"This is a bug in the program. There should only be values between 0..3"
),
}
}
LiteralsSectionType::Compressed | LiteralsSectionType::Treeless => {
match size_format {
0 | 1 => {
//Only differ in num_streams
//both regenerated and compressed sizes use 10 bit
Ok(3)
}
2 => {
//both regenerated and compressed sizes use 14 bit
Ok(4)
}
3 => {
//both regenerated and compressed sizes use 18 bit
Ok(5)
}
_ => panic!(
"This is a bug in the program. There should only be values between 0..3"
),
}
}
}
}
pub fn parse_from_header(&mut self, raw: &[u8]) -> Result<u8, LiteralsSectionParseError> {
let mut br = BitReader::new(raw);
let t = br.get_bits(2)? as u8;
self.ls_type = Self::section_type(t)?;
let size_format = br.get_bits(2)? as u8;
let byte_needed = self.header_bytes_needed(raw[0])?;
if raw.len() < byte_needed as usize {
return Err(LiteralsSectionParseError::NotEnoughBytes {
have: raw.len(),
need: byte_needed,
});
}
match self.ls_type {
LiteralsSectionType::RLE | LiteralsSectionType::Raw => {
self.compressed_size = None;
match size_format {
0 | 2 => {
//size_format actually only uses one bit
//regenerated_size uses 5 bits
self.regenerated_size = u32::from(raw[0]) >> 3;
Ok(1)
}
1 => {
//size_format uses 2 bit
//regenerated_size uses 12 bits
self.regenerated_size = (u32::from(raw[0]) >> 4) + (u32::from(raw[1]) << 4);
Ok(2)
}
3 => {
//size_format uses 2 bit
//regenerated_size uses 20 bits
self.regenerated_size = (u32::from(raw[0]) >> 4)
+ (u32::from(raw[1]) << 4)
+ (u32::from(raw[2]) << 12);
Ok(3)
}
_ => panic!(
"This is a bug in the program. There should only be values between 0..3"
),
}
}
LiteralsSectionType::Compressed | LiteralsSectionType::Treeless => {
match size_format {
0 => {
self.num_streams = Some(1);
}
1 | 2 | 3 => {
self.num_streams = Some(4);
}
_ => panic!(
"This is a bug in the program. There should only be values between 0..3"
),
};
match size_format {
0 | 1 => {
//Differ in num_streams see above
//both regenerated and compressed sizes use 10 bit
//4 from the first, six from the second byte
self.regenerated_size =
(u32::from(raw[0]) >> 4) + ((u32::from(raw[1]) & 0x3f) << 4);
// 2 from the second, full last byte
self.compressed_size =
Some(u32::from(raw[1] >> 6) + (u32::from(raw[2]) << 2));
Ok(3)
}
2 => {
//both regenerated and compressed sizes use 14 bit
//4 from first, full second, 2 from the third byte
self.regenerated_size = (u32::from(raw[0]) >> 4)
+ (u32::from(raw[1]) << 4)
+ ((u32::from(raw[2]) & 0x3) << 12);
//6 from the third, full last byte
self.compressed_size =
Some((u32::from(raw[2]) >> 2) + (u32::from(raw[3]) << 6));
Ok(4)
}
3 => {
//both regenerated and compressed sizes use 18 bit
//4 from first, full second, six from third byte
self.regenerated_size = (u32::from(raw[0]) >> 4)
+ (u32::from(raw[1]) << 4)
+ ((u32::from(raw[2]) & 0x3F) << 12);
//2 from third, full fourth, full fifth byte
self.compressed_size = Some(
(u32::from(raw[2]) >> 6)
+ (u32::from(raw[3]) << 2)
+ (u32::from(raw[4]) << 10),
);
Ok(5)
}
_ => panic!(
"This is a bug in the program. There should only be values between 0..3"
),
}
}
}
}
fn section_type(raw: u8) -> Result<LiteralsSectionType, LiteralsSectionParseError> {
let t = raw & 0x3;
match t {
0 => Ok(LiteralsSectionType::Raw),
1 => Ok(LiteralsSectionType::RLE),
2 => Ok(LiteralsSectionType::Compressed),
3 => Ok(LiteralsSectionType::Treeless),
other => Err(LiteralsSectionParseError::IllegalLiteralSectionType { got: other }),
}
}
}
|
