407 lines
9.8 KiB
Rust
407 lines
9.8 KiB
Rust
//! DEFLATE loader.
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use crate::durandal::{bit::*, err::*};
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use std::cmp::Ordering;
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/// Loads a ZLIB file header.
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pub fn load_zlib_header(b: &[u8]) -> ResultS<usize>
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{
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const CM: u8 = 0b0000_1111;
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const CINFO: u8 = 0b1111_0000;
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const FDICT: u8 = 0b0010_0000;
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read_data! {
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2, BE in b =>
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fcheck = u16[0];
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cmf = u8[0];
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flg = u8[1];
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}
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let cm = cmf & CM;
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let cinfo = cmf & CINFO >> 4;
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if cm != 8 || fcheck % 31 != 0 || cinfo > 7 {
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bail!("not zlib format");
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}
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if flg & FDICT != 0 {
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bail!("dictionary not supported");
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}
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Ok(2)
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}
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/// Loads a GZIP file header.
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pub fn load_gzip_header(b: &[u8]) -> ResultS<usize>
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{
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const FHCRC: u8 = 1 << 1;
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const FEXTRA: u8 = 1 << 2;
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const FNAME: u8 = 1 << 3;
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const FCOMMENT: u8 = 1 << 4;
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const FRESERVED: u8 = 0xE0;
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read_data! {
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10, LE in b =>
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id = u16[0];
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cm = u8[2];
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fl = u8[3];
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}
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if id != 0x8B1F || cm != 8 {
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bail!("not gzip format");
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}
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let mut p = 10;
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if fl & FRESERVED != 0 {
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bail!("reserved flags set");
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}
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if fl & FEXTRA != 0 {
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read_data!(p + 2, LE in b => xlen = u16[p] usize;);
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check_data!(p + 2 + xlen, b);
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p += xlen;
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}
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if fl & FNAME != 0 {
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p += skip_zero_terminated_item(&b[p..])?;
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}
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if fl & FCOMMENT != 0 {
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p += skip_zero_terminated_item(&b[p..])?;
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}
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if fl & FHCRC != 0 {
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check_data!(p + 2, b);
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p += 2;
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}
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Ok(p)
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}
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fn skip_zero_terminated_item(b: &[u8]) -> ResultS<usize>
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{
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if let Some(i) = b.iter().position(|&n| n == 0) {
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Ok(i + 1)
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} else {
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bail!("no end of zero terminated item");
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}
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}
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/// Decompresses a DEFLATE compressed bitstream.
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pub fn load_deflate(b: &[u8]) -> ResultS<(usize, Vec<u8>)>
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{
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let mut v = Vec::new();
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let p = stream_deflate(&mut v, b, 0)?;
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Ok((p / 8, v))
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}
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fn stream_deflate(v: &mut Vec<u8>, b: &[u8], mut p: usize) -> ResultS<usize>
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{
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let bfinal = read_bits_l(b, p, 1)?; p += 1;
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let btype = read_bits_l(b, p, 2)?; p += 2;
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let p = match btype {
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0b10 => stream_dynamic(v, b, p)?,
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0b01 => stream_s_table(v, b, p)?,
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0b00 => stream_literal(v, b, p)?,
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_ => bail!("bad btype"),
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};
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if bfinal == 0 {
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stream_deflate(v, b, p)
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} else {
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Ok(p)
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}
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}
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fn stream_dynamic(v: &mut Vec<u8>, b: &[u8], mut p: usize) -> ResultS<usize>
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{
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const CODE_ORDERING: [usize; NUM_CODES] = [
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16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15
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];
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const NUM_CODES: usize = 19;
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const MAX_LIT_CODES: usize = 286;
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const MAX_DST_CODES: usize = 30;
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// read header (number of literal alphabet codes, number of distance
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// alphabet codes, and number of lengths for decoding the alphabet)
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let hlit = read_bits_l(b, p, 5)?; p += 5;
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let hdist = read_bits_l(b, p, 5)?; p += 5;
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let hclen = read_bits_l(b, p, 4)?; p += 4;
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let hlit = 257 + hlit as usize;
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let hdist = 1 + hdist as usize;
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let hclen = 4 + hclen as usize;
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let alphabet_total = hlit + hdist;
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// first, get the huffman coding for the alphabet (which is also compressed)
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let mut code_lengths = [0; NUM_CODES];
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for i in 0..hclen {
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let len = read_bits_l(b, p, 3)? as u16;
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p += 3;
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code_lengths[CODE_ORDERING[i]] = len;
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}
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let code_lengths = HuffmanTable::new(&code_lengths)?;
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let mut alphabet = [0; MAX_LIT_CODES + MAX_DST_CODES];
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// then, we decode the alphabet (doing both types at the same time, because
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// they're encoded the same anyways)
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let mut i = 0;
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while i < alphabet_total {
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let (bits, sym) = code_lengths.decode(b, p)?;
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p += bits;
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match sym {
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0..=15 => {
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// raw code
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alphabet[i] = sym;
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i += 1;
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}
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16 => {
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// copy previous code 3-6 times
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if i == 0 {bail!("cannot copy on first alphabet code");}
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let len = usize::from(read_bits_l(b, p, 2)? as u8 + 3);
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let lst = alphabet[i - 1];
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p += 2;
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for _ in 0..len {alphabet[i] = lst; i += 1;}
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}
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17 => {
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// repeat '0' 3-10 times
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let len = usize::from(read_bits_l(b, p, 3)? as u8 + 3);
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p += 3;
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for _ in 0..len {alphabet[i] = 0; i += 1;}
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}
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18 => {
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// repeat '0' 11-138 times
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let len = usize::from(read_bits_l(b, p, 7)? as u8 + 11);
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p += 7;
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for _ in 0..len {alphabet[i] = 0; i += 1;}
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}
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_ => {
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bail!("bad symbol in alphabet");
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}
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}
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if i > alphabet_total {
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bail!("too many codes");
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}
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}
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if alphabet[256] == 0 {
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bail!("no way to end block");
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}
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let len_sta = 0;
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let len_end = hlit;
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let dst_sta = len_end;
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let dst_end = dst_sta + hdist;
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// build the length and distance tables from this information
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let table_len = HuffmanTable::new(&alphabet[len_sta..len_end])?;
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let table_dst = HuffmanTable::new(&alphabet[dst_sta..dst_end])?;
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output_tables(v, b, p, table_len, table_dst)
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}
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fn stream_s_table(v: &mut Vec<u8>, b: &[u8], p: usize) -> ResultS<usize>
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{
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let mut len = [0; 288];
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for len in len.iter_mut().take(144) {*len = 8;}
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for len in len.iter_mut().take(256).skip(144) {*len = 9;}
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for len in len.iter_mut().take(280).skip(256) {*len = 7;}
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for len in len.iter_mut().take(280).skip(288) {*len = 8;}
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let dst = [5; 30];
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let table_len = HuffmanTable::new(&len)?;
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let table_dst = HuffmanTable::new(&dst)?;
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output_tables(v, b, p, table_len, table_dst)
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}
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fn stream_literal(v: &mut Vec<u8>, b: &[u8], p: usize) -> ResultS<usize>
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{
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// copy data directly from byte boundary
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let mut p = p / 8 + 1;
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read_data! {
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p + 4, LE in b =>
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len = u16[p] usize;
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}
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p += 4;
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v.extend_from_slice(ok!(b.get(p..p + len), "not enough data")?);
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Ok((p + len) * 8)
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}
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fn output_tables(v: &mut Vec<u8>,
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b: &[u8],
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mut p: usize,
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table_len: HuffmanTable,
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table_dst: HuffmanTable)
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-> ResultS<usize>
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{
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const LEN_BASE: [usize; 29] = [
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3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 17, 19, 23, 27, 31, 35, 43, 51, 59,
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67, 83, 99, 115, 131, 163, 195, 227, 258
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];
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const LEN_EXTRA_BITS: [u8; 29] = [
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0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4,
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5, 5, 5, 5, 0
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];
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const DST_BASE: [usize; 30] = [
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1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49, 65, 97, 129, 193, 257, 385, 513,
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769, 1025, 1537, 2049, 3073, 4097, 0x1801, 0x2001, 0x3001, 0x4001, 0x6001
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];
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const DST_EXTRA_BITS: [u8; 30] = [
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0, 0, 0, 0, 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6, 7, 7, 8, 8, 9, 9, 10, 10,
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11, 11, 12, 12, 13, 13
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];
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let (bits, sym) = table_len.decode(b, p)?;
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p += bits;
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match sym.cmp(&256) {
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Ordering::Less => {
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// direct byte
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v.push(sym as u8);
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output_tables(v, b, p, table_len, table_dst)
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}
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Ordering::Equal => {
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Ok(p)
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}
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Ordering::Greater => {
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// this is a <len, dst> pair
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let sym = sym - 257;
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if sym > 29 {
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bail!("invalid fixed code");
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}
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let sym = usize::from(sym);
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// first get the actual length and any extra bits it may have
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let bits = LEN_EXTRA_BITS[sym];
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let leng = LEN_BASE[sym] + read_bits_l(b, p, bits)? as usize;
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p += usize::from(bits);
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// decode the distance with its alphabet
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let (bits, sym) = table_dst.decode(b, p)?;
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p += bits;
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let sym = usize::from(sym);
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// get the actual distance and any extra bits it may have
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let bits = DST_EXTRA_BITS[sym];
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let dist = DST_BASE[sym] + read_bits_l(b, p, bits)? as usize;
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p += usize::from(bits);
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if dist > v.len() {
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bail!("bad distance");
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}
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// copy bytes from earlier
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for _ in 0..leng {
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v.push(v[v.len() - dist]);
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}
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output_tables(v, b, p, table_len, table_dst)
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}
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}
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}
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impl HuffmanTable
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{
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fn new(table: &[u16]) -> ResultS<Self>
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{
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let mut syms = vec![0; table.len()];
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let mut nums = [0; 16];
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// count the number of symbols for each bit length
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for &length in table {
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nums[usize::from(length)] += 1;
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}
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if usize::from(nums[0]) == table.len() {
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bail!("bad table lengths");
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}
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// make offsets into the symbol table for each bit count
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let mut ofs = [0; 16];
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for i in 1..=14 {
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ofs[i + 1] = ofs[i] + usize::from(nums[i]);
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}
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// make the actual bit pattern table
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for (n, &length) in table.iter().enumerate() {
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// length 0 means this code isn't used, so only try to make bit
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// patterns for codes that actually exist
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if length != 0 {
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// make sure to make each offset unique
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let offset = &mut ofs[usize::from(length)];
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syms[*offset] = n as u16;
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*offset += 1;
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}
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}
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Ok(Self{nums, syms})
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}
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fn decode(&self, b: &[u8], mut p: usize) -> ResultS<(usize, u16)>
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{
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let mut code = 0_u16;
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let mut first = 0_u16;
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let mut index = 0_u16;
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for i in 1..=15 {
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// add bit from file
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code |= read_bits_l(b, p, 1)? as u16;
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p += 1;
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// check our symbol table for this one (quick tree check)
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let count = u16::from(self.nums[i]);
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if i32::from(code) - i32::from(count) < i32::from(first) {
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return Ok((i, self.syms[usize::from(index + code - first)]));
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}
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// continue on, trying to find the correct sequence
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index += count;
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first += count;
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first <<= 1;
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code <<= 1;
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}
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Err(err_msg("code not found in symbol tree"))
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}
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}
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struct HuffmanTable
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{
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nums: [u8; 16],
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syms: Vec<u16>,
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}
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// EOF
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