add static huffman tables
as it turns out, the static huffman tables are completely and utterly useless, and I don't think any modern compressor actually uses them, but we should probably implement them instead of panickingpng-branch
parent
bd13092188
commit
f832a45f36
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@ -99,12 +99,10 @@ pub fn load_deflate(b: &[u8]) -> ResultS<(usize, Vec<u8>)>
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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], p: usize) -> ResultS<usize>
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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)?;
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let btype = read_bits_l(b, p + 1, 2)?;
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let p = p + 3;
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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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@ -177,30 +175,21 @@ fn stream_dynamic(v: &mut Vec<u8>, b: &[u8], mut p: usize) -> ResultS<usize>
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let lst = alphabet[i - 1];
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p += 2;
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for _ in 0..len {
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alphabet[i] = lst;
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i += 1;
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}
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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 {
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alphabet[i] = 0;
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i += 1;
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}
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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 {
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alphabet[i] = 0;
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i += 1;
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}
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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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@ -221,15 +210,28 @@ fn stream_dynamic(v: &mut Vec<u8>, b: &[u8], mut p: usize) -> ResultS<usize>
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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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fn stream_s_table(v: &mut Vec<u8>, b: &[u8], p: usize) -> ResultS<usize>
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{
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unimplemented!()
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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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@ -280,6 +282,7 @@ fn output_tables(v: &mut Vec<u8>,
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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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@ -287,22 +290,27 @@ fn output_tables(v: &mut Vec<u8>,
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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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Err(err_msg("invalid fixed code"))
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} else {
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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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@ -311,6 +319,7 @@ fn output_tables(v: &mut Vec<u8>,
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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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@ -319,7 +328,6 @@ fn output_tables(v: &mut Vec<u8>,
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}
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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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@ -46,4 +46,13 @@ fn defl_must_not_succeed()
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assert!(defl::load_gzip_header(include_bytes!("data/gzbad7.bin")).is_err());
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}
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#[test]
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#[allow(unused_must_use)]
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fn defl_must_not_panic()
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{
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for inp in &RANDOM {
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defl::load_deflate(inp);
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}
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}
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// EOF
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