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authorValentin Popov <valentin@popov.link>2024-01-08 00:21:28 +0300
committerValentin Popov <valentin@popov.link>2024-01-08 00:21:28 +0300
commit1b6a04ca5504955c571d1c97504fb45ea0befee4 (patch)
tree7579f518b23313e8a9748a88ab6173d5e030b227 /vendor/zune-inflate/src/decoder.rs
parent5ecd8cf2cba827454317368b68571df0d13d7842 (diff)
downloadfparkan-1b6a04ca5504955c571d1c97504fb45ea0befee4.tar.xz
fparkan-1b6a04ca5504955c571d1c97504fb45ea0befee4.zip
Initial vendor packages
Signed-off-by: Valentin Popov <valentin@popov.link>
Diffstat (limited to 'vendor/zune-inflate/src/decoder.rs')
-rw-r--r--vendor/zune-inflate/src/decoder.rs1791
1 files changed, 1791 insertions, 0 deletions
diff --git a/vendor/zune-inflate/src/decoder.rs b/vendor/zune-inflate/src/decoder.rs
new file mode 100644
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--- /dev/null
+++ b/vendor/zune-inflate/src/decoder.rs
@@ -0,0 +1,1791 @@
+#![allow(unused_imports)]
+
+use alloc::vec::Vec;
+use alloc::{format, vec};
+
+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_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 dest_offset > 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];
+ // refill to handle some weird edge case where we have
+ // less bits than needed for reading the lit-len
+ }
+ 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) & 0xFF) 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;
+
+ if self.stream.bits_left < 11
+ {
+ self.stream.refill_inner_loop();
+ }
+ // 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 fill with a single byte
+ let byte_to_repeat = out_block[src_offset];
+ out_block[current_position..dest_offset].fill(byte_to_repeat);
+ }
+ 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;
+}