| #![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; |
| } |
