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use crate::compress::{Options, UnpackedSize};
use crate::encode::rangecoder;
use byteorder::{LittleEndian, WriteBytesExt};
use std::io;
pub struct Encoder<'a, W>
where
W: 'a + io::Write,
{
rangecoder: rangecoder::RangeEncoder<'a, W>,
literal_probs: [[u16; 0x300]; 8],
is_match: [u16; 4], // true = LZ, false = literal
unpacked_size: UnpackedSize,
}
const LC: u32 = 3;
const LP: u32 = 0;
const PB: u32 = 2;
impl<'a, W> Encoder<'a, W>
where
W: io::Write,
{
pub fn from_stream(stream: &'a mut W, options: &Options) -> io::Result<Self> {
let dict_size = 0x0080_0000;
// Properties
let props = (LC + 9 * (LP + 5 * PB)) as u8;
lzma_info!("Properties {{ lc: {}, lp: {}, pb: {} }}", LC, LP, PB);
stream.write_u8(props)?;
// Dictionary
lzma_info!("Dict size: {}", dict_size);
stream.write_u32::<LittleEndian>(dict_size)?;
// Unpacked size
match &options.unpacked_size {
UnpackedSize::WriteToHeader(unpacked_size) => {
let value: u64 = match unpacked_size {
None => {
lzma_info!("Unpacked size: unknown");
0xFFFF_FFFF_FFFF_FFFF
}
Some(x) => {
lzma_info!("Unpacked size: {}", x);
*x
}
};
stream.write_u64::<LittleEndian>(value)?;
}
UnpackedSize::SkipWritingToHeader => {}
};
let encoder = Encoder {
rangecoder: rangecoder::RangeEncoder::new(stream),
literal_probs: [[0x400; 0x300]; 8],
is_match: [0x400; 4],
unpacked_size: options.unpacked_size,
};
Ok(encoder)
}
pub fn process<R>(mut self, input: R) -> io::Result<()>
where
R: io::Read,
{
let mut prev_byte = 0u8;
let mut input_len = 0;
for (out_len, byte_result) in input.bytes().enumerate() {
let byte = byte_result?;
let pos_state = out_len & 3;
input_len = out_len;
// Literal
self.rangecoder
.encode_bit(&mut self.is_match[pos_state], false)?;
self.encode_literal(byte, prev_byte)?;
prev_byte = byte;
}
self.finish(input_len + 1)
}
fn finish(&mut self, input_len: usize) -> io::Result<()> {
match self.unpacked_size {
UnpackedSize::SkipWritingToHeader | UnpackedSize::WriteToHeader(Some(_)) => {}
UnpackedSize::WriteToHeader(None) => {
// Write end-of-stream marker
let pos_state = input_len & 3;
// Match
self.rangecoder
.encode_bit(&mut self.is_match[pos_state], true)?;
// New distance
self.rangecoder.encode_bit(&mut 0x400, false)?;
// Dummy len, as small as possible (len = 0)
for _ in 0..4 {
self.rangecoder.encode_bit(&mut 0x400, false)?;
}
// Distance marker = 0xFFFFFFFF
// pos_slot = 63
for _ in 0..6 {
self.rangecoder.encode_bit(&mut 0x400, true)?;
}
// num_direct_bits = 30
// result = 3 << 30 = C000_0000
// + 3FFF_FFF0 (26 bits)
// + F ( 4 bits)
for _ in 0..30 {
self.rangecoder.encode_bit(&mut 0x400, true)?;
}
// = FFFF_FFFF
}
}
// Flush range coder
self.rangecoder.finish()
}
fn encode_literal(&mut self, byte: u8, prev_byte: u8) -> io::Result<()> {
let prev_byte = prev_byte as usize;
let mut result: usize = 1;
let lit_state = prev_byte >> 5;
let probs = &mut self.literal_probs[lit_state];
for i in 0..8 {
let bit = ((byte >> (7 - i)) & 1) != 0;
self.rangecoder.encode_bit(&mut probs[result], bit)?;
result = (result << 1) ^ (bit as usize);
}
Ok(())
}
}
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