make deflate functions non-recursive (sad)
parent
499c25fb93
commit
0c0591f5ce
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@ -94,41 +94,31 @@ fn skip_zero_terminated_item(b: &[u8]) -> ResultS<usize>
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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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let mut p = 0;
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Ok((p / 8, v))
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}
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loop {
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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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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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match btype {
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0b10 => p = stream_dynamic(&mut v, b, p)?,
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0b01 => p = stream_s_table(&mut v, b, p)?,
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0b00 => p = stream_literal(&mut v, b, p)?,
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_ => bail!("bad btype"),
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}
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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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if bfinal == 1 {
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return Ok((p / 8, v));
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}
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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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const CODE_ORDERING: [usize; 19] = [
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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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@ -139,80 +129,30 @@ fn stream_dynamic(v: &mut Vec<u8>, b: &[u8], mut p: usize) -> ResultS<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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let mut code_table = [0; 19];
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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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code_table[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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let code_table = HuffmanTable::new(&code_table)?;
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let mut alphabet = vec![0; hlit + hdist];
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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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p = read_alphabet(b, p, &mut alphabet, code_table)?;
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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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let table_len = HuffmanTable::new(&alphabet[ 0..hlit ])?;
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let table_dst = HuffmanTable::new(&alphabet[hlit..hlit + hdist])?;
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output_tables(v, b, p, table_len, table_dst)
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}
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@ -251,6 +191,60 @@ fn stream_literal(v: &mut Vec<u8>, b: &[u8], p: usize) -> ResultS<usize>
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Ok((p + len) * 8)
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}
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fn read_alphabet(b: &[u8],
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mut p: usize,
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alphabet: &mut [u16],
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code_table: HuffmanTable)
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-> ResultS<usize>
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{
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let mut i = 0;
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while i < alphabet.len() {
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let (bits, sym) = code_table.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.len() {
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bail!("too many codes");
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}
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}
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Ok(p)
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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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@ -278,54 +272,53 @@ fn output_tables(v: &mut Vec<u8>,
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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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loop {
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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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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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}
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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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Ordering::Equal => {
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return 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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// 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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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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}
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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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