#![allow(unused_imports)]
use crate::bitstream::BitStreamReader;
use crate::constants::{
DEFLATE_BLOCKTYPE_DYNAMIC_HUFFMAN, DEFLATE_BLOCKTYPE_RESERVED, DEFLATE_BLOCKTYPE_STATIC,
DEFLATE_BLOCKTYPE_UNCOMPRESSED, DEFLATE_MAX_CODEWORD_LENGTH,
DEFLATE_MAX_LITLEN_CODEWORD_LENGTH, DEFLATE_MAX_NUM_SYMS, DEFLATE_MAX_OFFSET_CODEWORD_LENGTH,
DEFLATE_MAX_PRE_CODEWORD_LEN, DEFLATE_NUM_LITLEN_SYMS, DEFLATE_NUM_OFFSET_SYMS,
DEFLATE_NUM_PRECODE_SYMS, DEFLATE_PRECODE_LENS_PERMUTATION, DELFATE_MAX_LENS_OVERRUN,
FASTCOPY_BYTES, FASTLOOP_MAX_BYTES_WRITTEN, HUFFDEC_END_OF_BLOCK, HUFFDEC_EXCEPTIONAL,
HUFFDEC_LITERAL, HUFFDEC_SUITABLE_POINTER, LITLEN_DECODE_BITS, LITLEN_DECODE_RESULTS,
LITLEN_ENOUGH, LITLEN_TABLE_BITS, OFFSET_DECODE_RESULTS, OFFSET_ENOUGH, OFFSET_TABLEBITS,
PRECODE_DECODE_RESULTS, PRECODE_ENOUGH, PRECODE_TABLE_BITS
};
use crate::errors::{DecodeErrorStatus, InflateDecodeErrors};
#[cfg(feature = "gzip")]
use crate::gzip_constants::{
GZIP_CM_DEFLATE, GZIP_FCOMMENT, GZIP_FEXTRA, GZIP_FHCRC, GZIP_FNAME, GZIP_FOOTER_SIZE,
GZIP_FRESERVED, GZIP_ID1, GZIP_ID2
};
use crate::utils::{copy_rep_matches, fixed_copy, fixed_copy_within, make_decode_table_entry};
struct DeflateHeaderTables
{
litlen_decode_table: [u32; LITLEN_ENOUGH],
offset_decode_table: [u32; OFFSET_ENOUGH]
}
impl Default for DeflateHeaderTables
{
fn default() -> Self
{
DeflateHeaderTables {
litlen_decode_table: [0; LITLEN_ENOUGH],
offset_decode_table: [0; OFFSET_ENOUGH]
}
}
}
/// Options that can influence decompression
/// in Deflate/Zlib/Gzip
///
/// To use them, pass a customized options to
/// the deflate decoder.
#[derive(Copy, Clone)]
pub struct DeflateOptions
{
limit: usize,
confirm_checksum: bool,
size_hint: usize
}
impl Default for DeflateOptions
{
fn default() -> Self
{
DeflateOptions {
limit: 1 << 30,
confirm_checksum: true,
size_hint: 37000
}
}
}
impl DeflateOptions
{
/// Get deflate/zlib limit option
///
/// The decoder won't extend the inbuilt limit and will
/// return an error if the limit is exceeded
///
/// # Returns
/// The currently set limit of the instance
/// # Note
/// This is provided as a best effort, correctly quiting
/// is detrimental to speed and hence this should not be relied too much.
pub const fn get_limit(&self) -> usize
{
self.limit
}
/// Set a limit to the internal vector
/// used to store decoded zlib/deflate output.
///
/// # Arguments
/// limit: The new decompressor limit
/// # Returns
/// A modified version of DeflateDecoder
///
/// # Note
/// This is provided as a best effort, correctly quiting
/// is detrimental to speed and hence this should not be relied too much
#[must_use]
pub fn set_limit(mut self, limit: usize) -> Self
{
self.limit = limit;
self
}
/// Get whether the decoder will confirm a checksum
/// after decoding
pub const fn get_confirm_checksum(&self) -> bool
{
self.confirm_checksum
}
/// Set whether the decoder should confirm a checksum
/// after decoding
///
/// Note, you should definitely confirm your checksum, use
/// this with caution, otherwise data returned may be corrupt
///
/// # Arguments
/// - yes: When true, the decoder will confirm checksum
/// when false, the decoder will skip checksum verification
/// # Notes
/// This does not have an influence for deflate decoding as
/// it does not have a checksum
pub fn set_confirm_checksum(mut self, yes: bool) -> Self
{
self.confirm_checksum = yes;
self
}
/// Get the default set size hint for the decompressor
///
/// The decompressor initializes the internal storage for decompressed bytes
/// with this size and will reallocate the vec if the decompressed size becomes bigger
/// than this, but when the user currently knows how big the output will be, can be used
/// to prevent unnecessary re-allocations
pub const fn get_size_hint(&self) -> usize
{
self.size_hint
}
/// Set the size hint for the decompressor
///
/// This can be used to prevent multiple re-allocations
#[must_use]
pub const fn set_size_hint(mut self, hint: usize) -> Self
{
self.size_hint = hint;
self
}
}
/// A deflate decoder instance.
///
/// The decoder manages output buffer as opposed to requiring the caller to provide a pre-allocated buffer
/// it tracks number of bytes written and on successfully reaching the
/// end of the block, will return a vector with exactly
/// the number of decompressed bytes.
///
/// This means that it may use up huge amounts of memory if not checked, but
/// there are [options] that can prevent that
///
/// [options]: DeflateOptions
pub struct DeflateDecoder<'a>
{
data: &'a [u8],
position: usize,
stream: BitStreamReader<'a>,
is_last_block: bool,
static_codes_loaded: bool,
deflate_header_tables: DeflateHeaderTables,
options: DeflateOptions
}
impl<'a> DeflateDecoder<'a>
{
/// Create a new decompressor that will read compressed
/// data from `data` and return a new vector containing new data
///
/// # Arguments
/// - `data`: The compressed data. Data can be of any type
/// gzip,zlib or raw deflate.
///
/// # Returns
/// A decoder instance which will pull compressed data from `data` to inflate the output output
///
/// # Note
///
/// The default output size limit is **1 GiB.**
/// this is to protect the end user against ddos attacks as deflate does not specify it's
/// output size upfront
///
/// The checksum will be verified depending on the called function.
/// this only works for zlib and gzip since deflate does not have a checksum
///
/// These defaults can be overridden via [new_with_options()](Self::new_with_options).
pub fn new(data: &'a [u8]) -> DeflateDecoder<'a>
{
let options = DeflateOptions::default();
Self::new_with_options(data, options)
}
/// Create new decoder with specified options
///
/// This can be used to fine tune the decoder to the user's
/// needs.
///
///
/// # Arguments
/// - `data`: The compressed data. Data can be of any format i.e
/// gzip, zlib or raw deflate.
/// - `options` : A set of user defined options which tune how the decompressor
///
/// # Returns
/// A decoder instance which will pull compressed data from `data` to inflate output
///
/// # Example
/// ```no_run
/// use zune_inflate::{DeflateDecoder, DeflateOptions};
/// let data = [37];
/// let options = DeflateOptions::default()
/// .set_confirm_checksum(true) // confirm the checksum for zlib and gzip
/// .set_limit(1000); // how big I think the input will be
/// let mut decoder = DeflateDecoder::new_with_options(&data,options);
/// // do some stuff and then call decode
/// let data = decoder.decode_zlib();
///
/// ```
pub fn new_with_options(data: &'a [u8], options: DeflateOptions) -> DeflateDecoder<'a>
{
// create stream
DeflateDecoder {
data,
position: 0,
stream: BitStreamReader::new(data),
is_last_block: false,
static_codes_loaded: false,
deflate_header_tables: DeflateHeaderTables::default(),
options
}
}
/// Decode zlib-encoded data returning the uncompressed in a `Vec<u8>`
/// or an error if something went wrong.
///
/// Bytes consumed will be from the data passed when the
/// `new` method was called.
///
/// # Arguments
/// - None
/// # Returns
/// Result type containing the decoded data.
///
/// - `Ok(Vec<u8>)`: Decoded vector containing the uncompressed bytes
/// - `Err(InflateDecodeErrors)`: Error that occurred during decoding
///
/// It's possible to recover bytes even after an error occurred, bytes up
/// to when error was encountered are stored in [InflateDecodeErrors]
///
///
/// # Note
/// This needs the `zlib` feature enabled to be available otherwise it's a
/// compile time error
///
/// [InflateDecodeErrors]:crate::errors::InflateDecodeErrors
///
#[cfg(feature = "zlib")]
pub fn decode_zlib(&mut self) -> Result<Vec<u8>, InflateDecodeErrors>
{
use crate::utils::calc_adler_hash;
if self.data.len()
< 2 /* zlib header */
+ 4
/* Deflate */
{
return Err(InflateDecodeErrors::new_with_error(
DecodeErrorStatus::InsufficientData
));
}
// Zlib flags
// See https://www.ietf.org/rfc/rfc1950.txt for
// the RFC
let cmf = self.data[0];
let flg = self.data[1];
let cm = cmf & 0xF;
let cinfo = cmf >> 4;
// let fcheck = flg & 0xF;
// let fdict = (flg >> 4) & 1;
// let flevel = flg >> 5;
// confirm we have the right deflate methods
if cm != 8
{
if cm == 15
{
return Err(InflateDecodeErrors::new_with_error(DecodeErrorStatus::Generic(
"CM of 15 is preserved by the standard,currently don't know how to handle it"
)));
}
return Err(InflateDecodeErrors::new_with_error(
DecodeErrorStatus::GenericStr(format!("Unknown zlib compression method {cm}"))
));
}
if cinfo > 7
{
return Err(InflateDecodeErrors::new_with_error(
DecodeErrorStatus::GenericStr(format!(
"Unknown cinfo `{cinfo}` greater than 7, not allowed"
))
));
}
let flag_checks = (u16::from(cmf) * 256) + u16::from(flg);
if flag_checks % 31 != 0
{
return Err(InflateDecodeErrors::new_with_error(
DecodeErrorStatus::Generic("FCHECK integrity not preserved")
));
}
self.position = 2;
let data = self.decode_deflate()?;
if self.options.confirm_checksum
{
// Get number of consumed bytes from the input
let out_pos = self.stream.get_position() + self.position + self.stream.over_read;
// read adler
if let Some(adler) = self.data.get(out_pos..out_pos + 4)
{
let adler_bits: [u8; 4] = adler.try_into().unwrap();
let adler32_expected = u32::from_be_bytes(adler_bits);
let adler32_found = calc_adler_hash(&data);
if adler32_expected != adler32_found
{
let err_msg =
DecodeErrorStatus::MismatchedAdler(adler32_expected, adler32_found);
let err = InflateDecodeErrors::new(err_msg, data);
return Err(err);
}
}
else
{
let err = InflateDecodeErrors::new(DecodeErrorStatus::InsufficientData, data);
return Err(err);
}
}
Ok(data)
}
/// Decode a gzip encoded data and return the uncompressed data in a
/// `Vec<u8>` or an error if something went wrong
///
/// Bytes consumed will be from the data passed when the
/// `new` method was called.
///
/// # Arguments
/// - None
/// # Returns
/// Result type containing the decoded data.
///
/// - `Ok(Vec<u8>)`: Decoded vector containing the uncompressed bytes
/// - `Err(InflateDecodeErrors)`: Error that occurred during decoding
///
/// It's possible to recover bytes even after an error occurred, bytes up
/// to when error was encountered are stored in [InflateDecodeErrors]
///
/// # Note
/// This needs the `gzip` feature enabled to be available, otherwise it's a
/// compile time error
///
/// [InflateDecodeErrors]:crate::errors::InflateDecodeErrors
///
#[cfg(feature = "gzip")]
pub fn decode_gzip(&mut self) -> Result<Vec<u8>, InflateDecodeErrors>
{
if self.data.len() < 18
{
return Err(InflateDecodeErrors::new_with_error(
DecodeErrorStatus::InsufficientData
));
}
if self.data[self.position] != GZIP_ID1
{
return Err(InflateDecodeErrors::new_with_error(
DecodeErrorStatus::CorruptData
));
}
self.position += 1;
if self.data[self.position] != GZIP_ID2
{
return Err(InflateDecodeErrors::new_with_error(
DecodeErrorStatus::CorruptData
));
}
self.position += 1;
if self.data[self.position] != GZIP_CM_DEFLATE
{
return Err(InflateDecodeErrors::new_with_error(
DecodeErrorStatus::CorruptData
));
}
self.position += 1;
let flg = self.data[self.position];
self.position += 1;
// skip mtime
self.position += 4;
// skip xfl
self.position += 1;
// skip os
self.position += 1;
if (flg & GZIP_FRESERVED) != 0
{
return Err(InflateDecodeErrors::new_with_error(
DecodeErrorStatus::CorruptData
));
}
// extra field
if (flg & GZIP_FEXTRA) != 0
{
let len_bytes = self.data[self.position..self.position + 2]
.try_into()
.unwrap();
let xlen = usize::from(u16::from_le_bytes(len_bytes));
self.position += 2;
if self.data.len().saturating_sub(self.position) < xlen + GZIP_FOOTER_SIZE
{
return Err(InflateDecodeErrors::new_with_error(
DecodeErrorStatus::CorruptData
));
}
self.position += xlen;
}
// original file name zero terminated
if (flg & GZIP_FNAME) != 0
{
loop
{
if let Some(byte) = self.data.get(self.position)
{
self.position += 1;
if *byte == 0
{
break;
}
}
else
{
return Err(InflateDecodeErrors::new_with_error(
DecodeErrorStatus::InsufficientData
));
}
}
}
// File comment zero terminated
if (flg & GZIP_FCOMMENT) != 0
{
loop
{
if let Some(byte) = self.data.get(self.position)
{
self.position += 1;
if *byte == 0
{
break;
}
}
else
{
return Err(InflateDecodeErrors::new_with_error(
DecodeErrorStatus::InsufficientData
));
}
}
}
// crc16 for gzip header
if (flg & GZIP_FHCRC) != 0
{
self.position += 2;
}
if self.position + GZIP_FOOTER_SIZE > self.data.len()
{
return Err(InflateDecodeErrors::new_with_error(
DecodeErrorStatus::InsufficientData
));
}
let data = self.decode_deflate()?;
let mut out_pos = self.stream.get_position() + self.position + self.stream.over_read;
if self.options.confirm_checksum
{
// Get number of consumed bytes from the input
if let Some(crc) = self.data.get(out_pos..out_pos + 4)
{
let crc_bits: [u8; 4] = crc.try_into().unwrap();
let crc32_expected = u32::from_le_bytes(crc_bits);
let crc32_found = !crate::crc::crc32(&data, !0);
if crc32_expected != crc32_found
{
let err_msg = DecodeErrorStatus::MismatchedCRC(crc32_expected, crc32_found);
let err = InflateDecodeErrors::new(err_msg, data);
return Err(err);
}
}
else
{
let err = InflateDecodeErrors::new(DecodeErrorStatus::InsufficientData, data);
return Err(err);
}
}
//checksum
out_pos += 4;
if let Some(val) = self.data.get(out_pos..out_pos + 4)
{
let actual_bytes: [u8; 4] = val.try_into().unwrap();
let ac = u32::from_le_bytes(actual_bytes) as usize;
if data.len() != ac
{
let err = DecodeErrorStatus::Generic("ISIZE does not match actual bytes");
let err = InflateDecodeErrors::new(err, data);
return Err(err);
}
}
else
{
let err = InflateDecodeErrors::new(DecodeErrorStatus::InsufficientData, data);
return Err(err);
}
Ok(data)
}
/// Decode a deflate stream returning the data as `Vec<u8>` or an error
/// indicating what went wrong.
/// # Arguments
/// - None
/// # Returns
/// Result type containing the decoded data.
///
/// - `Ok(Vec<u8>)`: Decoded vector containing the uncompressed bytes
/// - `Err(InflateDecodeErrors)`: Error that occurred during decoding
///
/// It's possible to recover bytes even after an error occurred, bytes up
/// to when error was encountered are stored in [InflateDecodeErrors]
///
///
/// # Example
/// ```no_run
/// let data = [42]; // answer to life, the universe and everything
///
/// let mut decoder = zune_inflate::DeflateDecoder::new(&data);
/// let bytes = decoder.decode_deflate().unwrap();
/// ```
///
/// [InflateDecodeErrors]:crate::errors::InflateDecodeErrors
pub fn decode_deflate(&mut self) -> Result<Vec<u8>, InflateDecodeErrors>
{
self.start_deflate_block()
}
/// Main inner loop for decompressing deflate data
#[allow(unused_assignments)]
fn start_deflate_block(&mut self) -> Result<Vec<u8>, InflateDecodeErrors>
{
// start deflate decode
// re-read the stream so that we can remove code read by zlib
self.stream = BitStreamReader::new(&self.data[self.position..]);
self.stream.refill();
// Output space for our decoded bytes.
let mut out_block = vec![0; self.options.size_hint];
// bits used
let mut src_offset = 0;
let mut dest_offset = 0;
loop
{
self.stream.refill();
self.is_last_block = self.stream.get_bits(1) == 1;
let block_type = self.stream.get_bits(2);
if block_type == DEFLATE_BLOCKTYPE_UNCOMPRESSED
{
/*
* Uncompressed block: copy 'len' bytes literally from the input
* buffer to the output buffer.
*/
/*
* The RFC says that
* skip any remaining bits in current partially
* processed byte
* read LEN and NLEN (see next section)
* copy LEN bytes of data to output
*/
if self.stream.over_read > usize::from(self.stream.get_bits_left() >> 3)
{
out_block.truncate(dest_offset);
let err_msg = DecodeErrorStatus::Generic("over-read stream");
let error = InflateDecodeErrors::new(err_msg, out_block);
return Err(error);
}
let partial_bits = self.stream.get_bits_left() & 7;
self.stream.drop_bits(partial_bits);
let len = self.stream.get_bits(16) as u16;
let nlen = self.stream.get_bits(16) as u16;
// copy to deflate
if len != !nlen
{
out_block.truncate(dest_offset);
let err_msg = DecodeErrorStatus::Generic("Len and nlen do not match");
let error = InflateDecodeErrors::new(err_msg, out_block);
return Err(error);
}
let len = len as usize;
let start = self.stream.get_position() + self.position + self.stream.over_read;
// ensure there is enough space for a fast copy
if dest_offset + len + FASTCOPY_BYTES > out_block.len()
{
// and if there is not, resize
let new_len = out_block.len() + RESIZE_BY + len;
out_block.resize(new_len, 0);
}
if self.data.get((start + len).saturating_sub(1)).is_none()
{
out_block.truncate(dest_offset);
let err_msg = DecodeErrorStatus::CorruptData;
let error = InflateDecodeErrors::new(err_msg, out_block);
return Err(error);
}
if out_block.len() > self.options.limit
{
out_block.truncate(dest_offset);
let err_msg =
DecodeErrorStatus::OutputLimitExceeded(self.options.limit, out_block.len());
let error = InflateDecodeErrors::new(err_msg, out_block);
return Err(error);
}
out_block[dest_offset..dest_offset + len]
.copy_from_slice(&self.data[start..start + len]);
dest_offset += len;
// get the new position to write.
self.stream.position =
len + (self.stream.position - usize::from(self.stream.bits_left >> 3));
self.stream.reset();
if self.is_last_block
{
break;
}
continue;
}
else if block_type == DEFLATE_BLOCKTYPE_RESERVED
{
out_block.truncate(dest_offset);
let err_msg = DecodeErrorStatus::Generic("Reserved block type 0b11 encountered");
let error = InflateDecodeErrors::new(err_msg, out_block);
return Err(error);
}
// build decode tables for static and dynamic tables
match self.build_decode_table(block_type)
{
Ok(_) => (),
Err(value) =>
{
out_block.truncate(dest_offset);
let err_msg = value;
let error = InflateDecodeErrors::new(err_msg, out_block);
return Err(error);
}
};
// Tables are mutated into the struct, so at this point we know the tables
// are loaded, take a reference to them
let litlen_decode_table = &self.deflate_header_tables.litlen_decode_table;
let offset_decode_table = &self.deflate_header_tables.offset_decode_table;
/*
* This is the "fast loop" for decoding literals and matches. It does
* bounds checks on in_next and out_next in the loop conditions so that
* additional bounds checks aren't needed inside the loop body.
*
* To reduce latency, the bit-buffer is refilled and the next litlen
* decode table entry is preloaded before each loop iteration.
*/
let (mut literal, mut length, mut offset, mut entry) = (0, 0, 0, 0);
let mut saved_bitbuf;
'decode: loop
{
let close_src = 3 * FASTCOPY_BYTES < self.stream.remaining_bytes();
if close_src
{
self.stream.refill_inner_loop();
let lit_mask = self.stream.peek_bits::<LITLEN_DECODE_BITS>();
entry = litlen_decode_table[lit_mask];
'sequence: loop
{
// Resize the output vector here to ensure we can always have
// enough space for sloppy copies
if dest_offset + FASTLOOP_MAX_BYTES_WRITTEN > out_block.len()
{
let curr_len = out_block.len();
out_block.resize(curr_len + FASTLOOP_MAX_BYTES_WRITTEN + RESIZE_BY, 0)
}
// At this point entry contains the next value of the litlen
// This will always be the case so meaning all our exit paths need
// to load in the next entry.
// recheck after every sequence
// when we hit continue, we need to recheck this
// as we are trying to emulate a do while
let new_check = self.stream.src.len() < self.stream.position + 8;
if new_check
{
break 'sequence;
}
self.stream.refill_inner_loop();
/*
* Consume the bits for the litlen decode table entry. Save the
* original bit-buf for later, in case the extra match length
* bits need to be extracted from it.
*/
saved_bitbuf = self.stream.buffer;
self.stream.drop_bits((entry & 0xFF) as u8);
/*
* Begin by checking for a "fast" literal, i.e. a literal that
* doesn't need a subtable.
*/
if (entry & HUFFDEC_LITERAL) != 0
{
/*
* On 64-bit platforms, we decode up to 2 extra fast
* literals in addition to the primary item, as this
* increases performance and still leaves enough bits
* remaining for what follows. We could actually do 3,
* assuming LITLEN_TABLEBITS=11, but that actually
* decreases performance slightly (perhaps by messing
* with the branch prediction of the conditional refill
* that happens later while decoding the match offset).
*/
literal = entry >> 16;
let new_pos = self.stream.peek_bits::<LITLEN_DECODE_BITS>();
entry = litlen_decode_table[new_pos];
saved_bitbuf = self.stream.buffer;
self.stream.drop_bits(entry as u8);
let out: &mut [u8; 2] = out_block
.get_mut(dest_offset..dest_offset + 2)
.unwrap()
.try_into()
.unwrap();
out[0] = literal as u8;
dest_offset += 1;
if (entry & HUFFDEC_LITERAL) != 0
{
/*
* Another fast literal, but this one is in lieu of the
* primary item, so it doesn't count as one of the extras.
*/
// load in the next entry.
literal = entry >> 16;
let new_pos = self.stream.peek_bits::<LITLEN_DECODE_BITS>();
entry = litlen_decode_table[new_pos];
out[1] = literal as u8;
dest_offset += 1;
continue;
}
}
/*
* It's not a literal entry, so it can be a length entry, a
* subtable pointer entry, or an end-of-block entry. Detect the
* two unlikely cases by testing the HUFFDEC_EXCEPTIONAL flag.
*/
if (entry & HUFFDEC_EXCEPTIONAL) != 0
{
// Subtable pointer or end of block entry
if (entry & HUFFDEC_END_OF_BLOCK) != 0
{
// block done
break 'decode;
}
/*
* A subtable is required. Load and consume the
* subtable entry. The subtable entry can be of any
* type: literal, length, or end-of-block.
*/
let entry_position = ((entry >> 8) & 0x3F) as usize;
let mut pos = (entry >> 16) as usize;
saved_bitbuf = self.stream.buffer;
pos += self.stream.peek_var_bits(entry_position);
entry = litlen_decode_table[pos.min(LITLEN_ENOUGH - 1)];
self.stream.drop_bits(entry as u8);
if (entry & HUFFDEC_LITERAL) != 0
{
// decode a literal that required a sub table
let new_pos = self.stream.peek_bits::<LITLEN_DECODE_BITS>();
literal = entry >> 16;
entry = litlen_decode_table[new_pos];
*out_block.get_mut(dest_offset).unwrap_or(&mut 0) =
(literal & 0xFF) as u8;
dest_offset += 1;
continue;
}
if (entry & HUFFDEC_END_OF_BLOCK) != 0
{
break 'decode;
}
}
// At this point,we dropped at most 22 bits(LITLEN_DECODE is 11 and we
// can do it twice), we now just have 34 bits min remaining.
/*
* Decode the match length: the length base value associated
* with the litlen symbol (which we extract from the decode
* table entry), plus the extra length bits. We don't need to
* consume the extra length bits here, as they were included in
* the bits consumed by the entry earlier. We also don't need
* to check for too-long matches here, as this is inside the
* fast loop where it's already been verified that the output
* buffer has enough space remaining to copy a max-length match.
*/
let entry_dup = entry;
entry = offset_decode_table[self.stream.peek_bits::<OFFSET_TABLEBITS>()];
length = (entry_dup >> 16) as usize;
let mask = (1 << entry_dup as u8) - 1;
length += (saved_bitbuf & mask) as usize >> ((entry_dup >> 8) as u8);
// offset requires a subtable
if (entry & HUFFDEC_EXCEPTIONAL) != 0
{
self.stream.drop_bits(OFFSET_TABLEBITS as u8);
let extra = self.stream.peek_var_bits(((entry >> 8) & 0x3F) as usize);
entry = offset_decode_table[((entry >> 16) as usize + extra) & 511];
}
saved_bitbuf = self.stream.buffer;
self.stream.drop_bits((entry & 0xFF) as u8);
let mask = (1 << entry as u8) - 1;
offset = (entry >> 16) as usize;
offset += (saved_bitbuf & mask) as usize >> ((entry >> 8) as u8);
if offset > dest_offset
{
out_block.truncate(dest_offset);
let err_msg = DecodeErrorStatus::CorruptData;
let error = InflateDecodeErrors::new(err_msg, out_block);
return Err(error);
}
src_offset = dest_offset - offset;
// Copy some bytes unconditionally
// This makes us copy smaller match lengths quicker because we don't need
// a loop + don't send too much pressure to the Memory unit.
fixed_copy_within::<FASTCOPY_BYTES>(
&mut out_block,
src_offset,
dest_offset
);
entry = litlen_decode_table[self.stream.peek_bits::<LITLEN_DECODE_BITS>()];
let mut current_position = dest_offset;
dest_offset += length;
if offset == 1
{
// RLE match, copy it in groups of 8
let rep_num = u64::from(out_block[src_offset]) * 0x0101010101010101;
let rep_byte = &rep_num.to_ne_bytes();
loop
{
fixed_copy::<8>(rep_byte, &mut out_block, 0, current_position);
current_position += 8;
if current_position > dest_offset
{
break;
}
}
}
else if offset <= FASTCOPY_BYTES
&& current_position + offset < dest_offset
{
// The second conditional ensures we only come
// here if the first copy didn't succeed to copy just enough bytes for a rep
// match to be valid, i.e we want this path to be taken the least amount
// of times possible
// the unconditional copy above copied some bytes
// don't let it go into waste
// Increment the position we are in by the number of correct bytes
// currently copied
let mut src_position = src_offset + offset;
let mut dest_position = current_position + offset;
// loop copying offset bytes in place
// notice this loop does fixed copies but increments in offset bytes :)
// that is intentional.
loop
{
fixed_copy_within::<FASTCOPY_BYTES>(
&mut out_block,
src_position,
dest_position
);
src_position += offset;
dest_position += offset;
if dest_position > dest_offset
{
break;
}
}
}
else if length > FASTCOPY_BYTES
{
current_position += FASTCOPY_BYTES;
// fast non-overlapping copy
//
// We have enough space to write the ML+FAST_COPY bytes ahead
// so we know this won't come to shoot us in the foot.
//
// An optimization is to copy FAST_COPY_BITS per invocation
// Currently FASTCOPY_BYTES is 16, this fits in nicely as we
// it's a single SIMD instruction on a lot of things, i.e x86,Arm and even
// wasm.
// current position of the match
let mut dest_src_offset = src_offset + FASTCOPY_BYTES;
// Number of bytes we are to copy
// copy in batches of FAST_BYTES
'match_lengths: loop
{
// Safety: We resized out_block hence we know it can handle
// sloppy copies without it being out of bounds
//
// Reason: This is a latency critical loop, even branches start
// to matter
fixed_copy_within::<FASTCOPY_BYTES>(
&mut out_block,
dest_src_offset,
current_position
);
dest_src_offset += FASTCOPY_BYTES;
current_position += FASTCOPY_BYTES;
if current_position > dest_offset
{
break 'match_lengths;
}
}
}
if dest_offset > self.options.limit
{
out_block.truncate(dest_offset);
let err_msg = DecodeErrorStatus::OutputLimitExceeded(
self.options.limit,
dest_offset
);
let error = InflateDecodeErrors::new(err_msg, out_block);
return Err(error);
}
if self.stream.src.len() < self.stream.position + 8
{
// close to input end, move to the slower one
break 'sequence;
}
}
}
// generic loop that does things a bit slower but it's okay since it doesn't
// deal with a lot of things
// We can afford to be more careful here, checking that we do
// not drop non-existent bits etc etc as we do not have the
// assurances of the fast loop bits above.
loop
{
self.stream.refill();
if self.stream.over_read > usize::from(self.stream.bits_left >> 3)
{
out_block.truncate(dest_offset);
let err_msg = DecodeErrorStatus::CorruptData;
let error = InflateDecodeErrors::new(err_msg, out_block);
return Err(error);
}
let literal_mask = self.stream.peek_bits::<LITLEN_DECODE_BITS>();
entry = litlen_decode_table[literal_mask];
saved_bitbuf = self.stream.buffer;
self.stream.drop_bits((entry & 0xFF) as u8);
if (entry & HUFFDEC_SUITABLE_POINTER) != 0
{
let extra = self.stream.peek_var_bits(((entry >> 8) & 0x3F) as usize);
entry = litlen_decode_table[(entry >> 16) as usize + extra];
saved_bitbuf = self.stream.buffer;
self.stream.drop_bits((entry & 0xFF) as u8);
}
length = (entry >> 16) as usize;
if (entry & HUFFDEC_LITERAL) != 0
{
resize_and_push(&mut out_block, dest_offset, length as u8);
dest_offset += 1;
continue;
}
if (entry & HUFFDEC_END_OF_BLOCK) != 0
{
break 'decode;
}
let mask = (1 << entry as u8) - 1;
length += (saved_bitbuf & mask) as usize >> ((entry >> 8) as u8);
self.stream.refill();
entry = offset_decode_table[self.stream.peek_bits::<OFFSET_TABLEBITS>()];
if (entry & HUFFDEC_EXCEPTIONAL) != 0
{
// offset requires a subtable
self.stream.drop_bits(OFFSET_TABLEBITS as u8);
let extra = self.stream.peek_var_bits(((entry >> 8) & 0x3F) as usize);
entry = offset_decode_table[((entry >> 16) as usize + extra) & 511];
}
// ensure there is enough space for a fast copy
if dest_offset + length + FASTCOPY_BYTES > out_block.len()
{
let new_len = out_block.len() + RESIZE_BY + length;
out_block.resize(new_len, 0);
}
saved_bitbuf = self.stream.buffer;
let mask = (1 << (entry & 0xFF) as u8) - 1;
offset = (entry >> 16) as usize;
offset += (saved_bitbuf & mask) as usize >> ((entry >> 8) as u8);
if offset > dest_offset
{
out_block.truncate(dest_offset);
let err_msg = DecodeErrorStatus::CorruptData;
let error = InflateDecodeErrors::new(err_msg, out_block);
return Err(error);
}
src_offset = dest_offset - offset;
self.stream.drop_bits(entry as u8);
let (dest_src, dest_ptr) = out_block.split_at_mut(dest_offset);
if src_offset + length + FASTCOPY_BYTES > dest_offset
{
// overlapping copy
// do a simple rep match
copy_rep_matches(&mut out_block, src_offset, dest_offset, length);
}
else
{
dest_ptr[0..length]
.copy_from_slice(&dest_src[src_offset..src_offset + length]);
}
dest_offset += length;
if dest_offset > self.options.limit
{
out_block.truncate(dest_offset);
let err_msg =
DecodeErrorStatus::OutputLimitExceeded(self.options.limit, dest_offset);
let error = InflateDecodeErrors::new(err_msg, out_block);
return Err(error);
}
}
}
/*
* If any of the implicit appended zero bytes were consumed (not just
* refilled) before hitting end of stream, then the data is bad.
*/
if self.stream.over_read > usize::from(self.stream.bits_left >> 3)
{
out_block.truncate(dest_offset);
let err_msg = DecodeErrorStatus::CorruptData;
let error = InflateDecodeErrors::new(err_msg, out_block);
return Err(error);
}
if self.is_last_block
{
break;
}
}
// decompression. DONE
// Truncate data to match the number of actual
// bytes written.
out_block.truncate(dest_offset);
Ok(out_block)
}
/// Build decode tables for static and dynamic
/// huffman blocks.
fn build_decode_table(&mut self, block_type: u64) -> Result<(), DecodeErrorStatus>
{
const COUNT: usize =
DEFLATE_NUM_LITLEN_SYMS + DEFLATE_NUM_OFFSET_SYMS + DELFATE_MAX_LENS_OVERRUN;
let mut lens = [0_u8; COUNT];
let mut precode_lens = [0; DEFLATE_NUM_PRECODE_SYMS];
let mut precode_decode_table = [0_u32; PRECODE_ENOUGH];
let mut litlen_decode_table = [0_u32; LITLEN_ENOUGH];
let mut offset_decode_table = [0; OFFSET_ENOUGH];
let mut num_litlen_syms = 0;
let mut num_offset_syms = 0;
if block_type == DEFLATE_BLOCKTYPE_DYNAMIC_HUFFMAN
{
const SINGLE_PRECODE: usize = 3;
self.static_codes_loaded = false;
// Dynamic Huffman block
// Read codeword lengths
if !self.stream.has(5 + 5 + 4)
{
return Err(DecodeErrorStatus::InsufficientData);
}
num_litlen_syms = 257 + (self.stream.get_bits(5)) as usize;
num_offset_syms = 1 + (self.stream.get_bits(5)) as usize;
let num_explicit_precode_lens = 4 + (self.stream.get_bits(4)) as usize;
self.stream.refill();
if !self.stream.has(3)
{
return Err(DecodeErrorStatus::InsufficientData);
}
let first_precode = self.stream.get_bits(3) as u8;
let expected = (SINGLE_PRECODE * num_explicit_precode_lens.saturating_sub(1)) as u8;
precode_lens[usize::from(DEFLATE_PRECODE_LENS_PERMUTATION[0])] = first_precode;
self.stream.refill();
if !self.stream.has(expected)
{
return Err(DecodeErrorStatus::InsufficientData);
}
for i in DEFLATE_PRECODE_LENS_PERMUTATION[1..]
.iter()
.take(num_explicit_precode_lens - 1)
{
let bits = self.stream.get_bits(3) as u8;
precode_lens[usize::from(*i)] = bits;
}
self.build_decode_table_inner(
&precode_lens,
&PRECODE_DECODE_RESULTS,
&mut precode_decode_table,
PRECODE_TABLE_BITS,
DEFLATE_NUM_PRECODE_SYMS,
DEFLATE_MAX_CODEWORD_LENGTH
)?;
/* Decode the litlen and offset codeword lengths. */
let mut i = 0;
loop
{
if i >= num_litlen_syms + num_offset_syms
{
// confirm here since with a continue loop stuff
// breaks
break;
}
let rep_val: u8;
let rep_count: u64;
if !self.stream.has(DEFLATE_MAX_PRE_CODEWORD_LEN + 7)
{
self.stream.refill();
}
// decode next pre-code symbol
let entry_pos = self
.stream
.peek_bits::<{ DEFLATE_MAX_PRE_CODEWORD_LEN as usize }>();
let entry = precode_decode_table[entry_pos];
let presym = entry >> 16;
if !self.stream.has(entry as u8)
{
return Err(DecodeErrorStatus::InsufficientData);
}
self.stream.drop_bits(entry as u8);
if presym < 16
{
// explicit codeword length
lens[i] = presym as u8;
i += 1;
continue;
}
/* Run-length encoded codeword lengths */
/*
* Note: we don't need verify that the repeat count
* doesn't overflow the number of elements, since we've
* sized the lens array to have enough extra space to
* allow for the worst-case overrun (138 zeroes when
* only 1 length was remaining).
*
* In the case of the small repeat counts (presyms 16
* and 17), it is fastest to always write the maximum
* number of entries. That gets rid of branches that
* would otherwise be required.
*
* It is not just because of the numerical order that
* our checks go in the order 'presym < 16', 'presym ==
* 16', and 'presym == 17'. For typical data this is
* ordered from most frequent to least frequent case.
*/
if presym == 16
{
if i == 0
{
return Err(DecodeErrorStatus::CorruptData);
}
if !self.stream.has(2)
{
return Err(DecodeErrorStatus::InsufficientData);
}
// repeat previous length three to 6 times
rep_val = lens[i - 1];
rep_count = 3 + self.stream.get_bits(2);
lens[i..i + 6].fill(rep_val);
i += rep_count as usize;
}
else if presym == 17
{
if !self.stream.has(3)
{
return Err(DecodeErrorStatus::InsufficientData);
}
/* Repeat zero 3 - 10 times. */
rep_count = 3 + self.stream.get_bits(3);
lens[i..i + 10].fill(0);
i += rep_count as usize;
}
else
{
if !self.stream.has(7)
{
return Err(DecodeErrorStatus::InsufficientData);
}
// repeat zero 11-138 times.
rep_count = 11 + self.stream.get_bits(7);
lens[i..i + rep_count as usize].fill(0);
i += rep_count as usize;
}
if i >= num_litlen_syms + num_offset_syms
{
break;
}
}
}
else if block_type == DEFLATE_BLOCKTYPE_STATIC
{
if self.static_codes_loaded
{
return Ok(());
}
self.static_codes_loaded = true;
lens[000..144].fill(8);
lens[144..256].fill(9);
lens[256..280].fill(7);
lens[280..288].fill(8);
lens[288..].fill(5);
num_litlen_syms = 288;
num_offset_syms = 32;
}
// build offset decode table
self.build_decode_table_inner(
&lens[num_litlen_syms..],
&OFFSET_DECODE_RESULTS,
&mut offset_decode_table,
OFFSET_TABLEBITS,
num_offset_syms,
DEFLATE_MAX_OFFSET_CODEWORD_LENGTH
)?;
self.build_decode_table_inner(
&lens,
&LITLEN_DECODE_RESULTS,
&mut litlen_decode_table,
LITLEN_TABLE_BITS,
num_litlen_syms,
DEFLATE_MAX_LITLEN_CODEWORD_LENGTH
)?;
self.deflate_header_tables.offset_decode_table = offset_decode_table;
self.deflate_header_tables.litlen_decode_table = litlen_decode_table;
Ok(())
}
/// Build the decode table for the precode
#[allow(clippy::needless_range_loop)]
fn build_decode_table_inner(
&mut self, lens: &[u8], decode_results: &[u32], decode_table: &mut [u32],
table_bits: usize, num_syms: usize, mut max_codeword_len: usize
) -> Result<(), DecodeErrorStatus>
{
const BITS: u32 = usize::BITS - 1;
let mut len_counts: [u32; DEFLATE_MAX_CODEWORD_LENGTH + 1] =
[0; DEFLATE_MAX_CODEWORD_LENGTH + 1];
let mut offsets: [u32; DEFLATE_MAX_CODEWORD_LENGTH + 1] =
[0; DEFLATE_MAX_CODEWORD_LENGTH + 1];
let mut sorted_syms: [u16; DEFLATE_MAX_NUM_SYMS] = [0; DEFLATE_MAX_NUM_SYMS];
let mut i;
// count how many codewords have each length, including 0.
for sym in 0..num_syms
{
len_counts[usize::from(lens[sym])] += 1;
}
/*
* Determine the actual maximum codeword length that was used, and
* decrease table_bits to it if allowed.
*/
while max_codeword_len > 1 && len_counts[max_codeword_len] == 0
{
max_codeword_len -= 1;
}
/*
* Sort the symbols primarily by increasing codeword length and
* A temporary array of length @num_syms.
* secondarily by increasing symbol value; or equivalently by their
* codewords in lexicographic order, since a canonical code is assumed.
*
* For efficiency, also compute 'codespace_used' in the same pass over
* 'len_counts[]' used to build 'offsets[]' for sorting.
*/
offsets[0] = 0;
offsets[1] = len_counts[0];
let mut codespace_used = 0_u32;
for len in 1..max_codeword_len
{
offsets[len + 1] = offsets[len] + len_counts[len];
codespace_used = (codespace_used << 1) + len_counts[len];
}
codespace_used = (codespace_used << 1) + len_counts[max_codeword_len];
for sym in 0..num_syms
{
let pos = usize::from(lens[sym]);
sorted_syms[offsets[pos] as usize] = sym as u16;
offsets[pos] += 1;
}
i = (offsets[0]) as usize;
/*
* Check whether the lengths form a complete code (exactly fills the
* codespace), an incomplete code (doesn't fill the codespace), or an
* overfull code (overflows the codespace). A codeword of length 'n'
* uses proportion '1/(2^n)' of the codespace. An overfull code is
* nonsensical, so is considered invalid. An incomplete code is
* considered valid only in two specific cases; see below.
*/
// Overfull code
if codespace_used > 1 << max_codeword_len
{
return Err(DecodeErrorStatus::Generic("Overflown code"));
}
// incomplete code
if codespace_used < 1 << max_codeword_len
{
let entry = if codespace_used == 0
{
/*
* An empty code is allowed. This can happen for the
* offset code in DEFLATE, since a dynamic Huffman block
* need not contain any matches.
*/
/* sym=0, len=1 (arbitrary) */
make_decode_table_entry(decode_results, 0, 1)
}
else
{
/*
* Allow codes with a single used symbol, with codeword
* length 1. The DEFLATE RFC is unclear regarding this
* case. What zlib's decompressor does is permit this
* for the litlen and offset codes and assume the
* codeword is '0' rather than '1'. We do the same
* except we allow this for precodes too, since there's
* no convincing reason to treat the codes differently.
* We also assign both codewords '0' and '1' to the
* symbol to avoid having to handle '1' specially.
*/
if codespace_used != 1 << (max_codeword_len - 1) || len_counts[1] != 1
{
return Err(DecodeErrorStatus::Generic(
"Cannot work with empty pre-code table"
));
}
make_decode_table_entry(decode_results, usize::from(sorted_syms[i]), 1)
};
/*
* Note: the decode table still must be fully initialized, in
* case the stream is malformed and contains bits from the part
* of the codespace the incomplete code doesn't use.
*/
decode_table.fill(entry);
return Ok(());
}
/*
* The lengths form a complete code. Now, enumerate the codewords in
* lexicographic order and fill the decode table entries for each one.
*
* First, process all codewords with len <= table_bits. Each one gets
* '2^(table_bits-len)' direct entries in the table.
*
* Since DEFLATE uses bit-reversed codewords, these entries aren't
* consecutive but rather are spaced '2^len' entries apart. This makes
* filling them naively somewhat awkward and inefficient, since strided
* stores are less cache-friendly and preclude the use of word or
* vector-at-a-time stores to fill multiple entries per instruction.
*
* To optimize this, we incrementally double the table size. When
* processing codewords with length 'len', the table is treated as
* having only '2^len' entries, so each codeword uses just one entry.
* Then, each time 'len' is incremented, the table size is doubled and
* the first half is copied to the second half. This significantly
* improves performance over naively doing strided stores.
*
* Note that some entries copied for each table doubling may not have
* been initialized yet, but it doesn't matter since they're guaranteed
* to be initialized later (because the Huffman code is complete).
*/
let mut codeword = 0;
let mut len = 1;
let mut count = len_counts[1];
while count == 0
{
len += 1;
if len >= len_counts.len()
{
break;
}
count = len_counts[len];
}
let mut curr_table_end = 1 << len;
while len <= table_bits
{
// Process all count codewords with length len
loop
{
let entry = make_decode_table_entry(
decode_results,
usize::from(sorted_syms[i]),
len as u32
);
i += 1;
// fill first entry for current codeword
decode_table[codeword] = entry;
if codeword == curr_table_end - 1
{
// last codeword (all 1's)
for _ in len..table_bits
{
decode_table.copy_within(0..curr_table_end, curr_table_end);
curr_table_end <<= 1;
}
return Ok(());
}
/*
* To advance to the lexicographically next codeword in
* the canonical code, the codeword must be incremented,
* then 0's must be appended to the codeword as needed
* to match the next codeword's length.
*
* Since the codeword is bit-reversed, appending 0's is
* a no-op. However, incrementing it is nontrivial. To
* do so efficiently, use the 'bsr' instruction to find
* the last (highest order) 0 bit in the codeword, set
* it, and clear any later (higher order) 1 bits. But
* 'bsr' actually finds the highest order 1 bit, so to
* use it first flip all bits in the codeword by XOR' ing
* it with (1U << len) - 1 == cur_table_end - 1.
*/
let adv = BITS - (codeword ^ (curr_table_end - 1)).leading_zeros();
let bit = 1 << adv;
codeword &= bit - 1;
codeword |= bit;
count -= 1;
if count == 0
{
break;
}
}
// advance to the next codeword length
loop
{
len += 1;
if len <= table_bits
{
// dest is decode_table[curr_table_end]
// source is decode_table(start of table);
// size is curr_table;
decode_table.copy_within(0..curr_table_end, curr_table_end);
//decode_table.copy_within(range, curr_table_end);
curr_table_end <<= 1;
}
count = len_counts[len];
if count != 0
{
break;
}
}
}
// process codewords with len > table_bits.
// Require sub-tables
curr_table_end = 1 << table_bits;
let mut subtable_prefix = usize::MAX;
let mut subtable_start = 0;
let mut subtable_bits;
loop
{
/*
* Start a new sub-table if the first 'table_bits' bits of the
* codeword don't match the prefix of the current subtable.
*/
if codeword & ((1_usize << table_bits) - 1) != subtable_prefix
{
subtable_prefix = codeword & ((1 << table_bits) - 1);
subtable_start = curr_table_end;
/*
* Calculate the subtable length. If the codeword has
* length 'table_bits + n', then the subtable needs
* '2^n' entries. But it may need more; if fewer than
* '2^n' codewords of length 'table_bits + n' remain,
* then the length will need to be incremented to bring
* in longer codewords until the subtable can be
* completely filled. Note that because the Huffman
* code is complete, it will always be possible to fill
* the sub-table eventually.
*/
subtable_bits = len - table_bits;
codespace_used = count;
while codespace_used < (1 << subtable_bits)
{
subtable_bits += 1;
if subtable_bits + table_bits > 15
{
return Err(DecodeErrorStatus::CorruptData);
}
codespace_used = (codespace_used << 1) + len_counts[table_bits + subtable_bits];
}
/*
* Create the entry that points from the main table to
* the subtable.
*/
decode_table[subtable_prefix] = (subtable_start as u32) << 16
| HUFFDEC_EXCEPTIONAL
| HUFFDEC_SUITABLE_POINTER
| (subtable_bits as u32) << 8
| table_bits as u32;
curr_table_end = subtable_start + (1 << subtable_bits);
}
/* Fill the sub-table entries for the current codeword. */
let stride = 1 << (len - table_bits);
let mut j = subtable_start + (codeword >> table_bits);
let entry = make_decode_table_entry(
decode_results,
sorted_syms[i] as usize,
(len - table_bits) as u32
);
i += 1;
while j < curr_table_end
{
decode_table[j] = entry;
j += stride;
}
//advance to the next codeword
if codeword == (1 << len) - 1
{
// last codeword
return Ok(());
}
let adv = BITS - (codeword ^ ((1 << len) - 1)).leading_zeros();
let bit = 1 << adv;
codeword &= bit - 1;
codeword |= bit;
count -= 1;
while count == 0
{
len += 1;
count = len_counts[len];
}
}
}
}
const RESIZE_BY: usize = 1024 * 4; // 4 kb
/// Resize vector if its current space wont
/// be able to store a new byte and then push an element to that new space
#[inline(always)]
fn resize_and_push(buf: &mut Vec<u8>, position: usize, elm: u8)
{
if buf.len() <= position
{
let new_len = buf.len() + RESIZE_BY;
buf.resize(new_len, 0);
}
buf[position] = elm;
}