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use super::codes::{DecodeResult, Decoder}; use super::{tables, Error, Result}; use arraydeque::ArrayDeque; /// Low-level decompression interface. /// /// This provides low-level access to the decompression algorithm. If /// possible, prefer using [`explode`](fn.explode.html) or /// [`ExplodeReader`](struct.ExplodeReader.html) as they are simpler /// to use. /// /// The usual control flow with this interface is to provide a buffer /// to decompress into with [`with_buffer`](#method.with_buffer), and /// then to feed the resulting /// [`ExplodeBuffer`](struct.ExplodeBuffer.html) handle with bytes /// until it returns `Ok`. Then you can retrieve the filled portion of /// the buffer containing your decompressed data. /// /// ``` /// # fn main() -> explode::Result<()> { /// use explode::{Error, Explode}; /// /// // some test data to decompress /// let input = vec![0x00, 0x04, 0x82, 0x24, 0x25, 0x8f, 0x80, 0x7f]; /// // which byte we are currently feeding in /// let mut i = 0; /// // our output buffer /// let mut outbuf: [u8; 256] = [0; 256]; /// /// // decompress /// let mut ex = explode::Explode::new(); /// let mut exbuf = ex.with_buffer(&mut outbuf); /// // loop while we have more input, and decompression is not done /// while i < input.len() && !exbuf.done() { /// // note we feed exbuf the *same byte* every loop, until it requests /// // more input with Error::IncompleteInput. /// match exbuf.feed(input[i]) { /// Ok(()) => { /// // buffer is full. use exbuf.get() to get the filled portion /// println!("{:?}", exbuf.get()); /// // compression may not be finished, so reset and loop again /// exbuf.reset(); /// } /// /// Err(Error::IncompleteInput) => { /// // advance our input cursor /// i += 1; /// } /// /// Err(e) => { /// // any other error is a sign the input is invalid /// panic!("{:?}", e); /// } /// } /// } /// /// if !exbuf.done() { /// // we ran out of input, but decompression isn't done! /// panic!("unexpected end of input"); /// } /// # Ok(()) } /// ``` /// /// Be careful that the input byte you provide to /// [`ExplodeBuffer::feed`](struct.ExplodeBuffer.html#method.feed) /// only changes when requested by /// [`Error::IncompleteInput`](enum.Error.html#variant.IncompleteInput). If /// the input changes at any other time, decompression will fail or /// produce incorrect output. #[derive(Debug)] pub struct Explode { state: ExplodeState<Decoder<'static, &'static [u8]>>, // header info lit: Option<u8>, dict: Option<u8>, // input management input: ExplodeInput, // store our window (which cannot exceed 4096 bytes) window: ArrayDeque<[u8; 4096], arraydeque::behavior::Wrapping>, } // hold a byte until it's ready to use #[derive(Debug)] enum ExplodeInputState { Available(u8), Taken, Waiting, } // help manage the bitstream input #[derive(Debug)] struct ExplodeInput { next: ExplodeInputState, // store unused bits read in bitbuf: u32, bitcount: u8, } // explode state. D is the Huffman decoder type #[derive(Debug)] enum ExplodeState<D> { Start, Length { decoder: D }, LengthExtra { symbol: usize }, Distance { len: usize, decoder: D }, DistanceExtra { len: usize, symbol: usize }, Copy { idx: usize, len: usize }, Literal, LiteralCoded { decoder: D }, End, } /// A handle to feed input to the decompressor. /// /// This is the primary interface for low-level decompression. You can /// get an instance of this by providing an output buffer to /// [`Explode::with_buffer`](struct.Explode.html#method.with_buffer). /// /// For a high-level example of how to use this interface, see /// [`Explode`](struct.Explode.html). #[derive(Debug)] pub struct ExplodeBuffer<'a> { parent: &'a mut Explode, buf: &'a mut [u8], pos: usize, } impl ExplodeInputState { fn feed(&mut self, value: u8) { if let ExplodeInputState::Waiting = self { *self = ExplodeInputState::Available(value); } } fn take(&mut self) -> Result<u8> { match self { ExplodeInputState::Available(value) => { let v = *value; *self = ExplodeInputState::Taken; Ok(v) } ExplodeInputState::Taken => { *self = ExplodeInputState::Waiting; Err(Error::IncompleteInput) } ExplodeInputState::Waiting => { panic!("double take"); } } } } impl ExplodeInput { // read n bits fn bits(&mut self, n: u8) -> Result<u32> { while self.bitcount < n { self.bitbuf |= (self.next.take()? as u32) << self.bitcount; self.bitcount += 8; } let val = self.bitbuf; self.bitbuf >>= n; self.bitcount -= n; Ok(val & ((1 << n) - 1)) } // decode using a table fn decode(&mut self, d: &mut Decoder<&'static [u8]>) -> Result<u8> { loop { // codes in this format are inverted from canonical let bit = self.bits(1)? != 1; match d.feed(bit) { DecodeResult::Incomplete => continue, DecodeResult::Invalid => panic!( "Codebooks are under-subscribed but should not be!" ), DecodeResult::Ok(v) => return Ok(v), } } } } impl<'a> ExplodeBuffer<'a> { /// Feed in a byte `input` to decompress. /// /// Signals a full output buffer by returning `Ok(())`. You can /// then get a reference to the full buffer with /// [`get`](#method.get), and reset the output buffer to empty /// with [`reset`](#method.reset). /// /// Note that you should feed in the same byte *repeatedly* to /// this function, until it signals it is ready for more input by /// returning /// [`Error::IncompleteInput`](enum.Error.html#variant.IncompleteInput). /// Doing anything else will result in a decompression failure or /// bad output. pub fn feed(&mut self, input: u8) -> Result<()> { // lengths are funny -- base val + extra bits static LEN_BASE: &[usize] = &[3, 2, 4, 5, 6, 7, 8, 9, 10, 12, 16, 24, 40, 72, 136, 264]; static LEN_EXTRA: &[u8] = &[0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 3, 4, 5, 6, 7, 8]; self.parent.input.next.feed(input); // first byte is 0 if literals are uncoded, or 1 if coded let lit = if let Some(lit) = self.parent.lit { lit } else { let lit = self.parent.input.bits(8)? as u8; if lit > 1 { return Err(Error::BadLiteralFlag); } self.parent.lit = Some(lit); lit }; // second byte is 4, 5, or 6 for # extra bits in distance code // (distance code is 6 + this bits total) let dict = if let Some(dict) = self.parent.dict { dict } else { let dict = self.parent.input.bits(8)? as u8; if dict < 4 || dict > 6 { return Err(Error::BadDictionary); } self.parent.dict = Some(dict); dict }; // decode literals and length/distance pairs // state machine rules: // each state may only call bits() once // and decode() must store the HuffmanExplode in the state loop { use ExplodeState::*; match self.parent.state { Start => { if self.parent.input.bits(1)? > 0 { // this is a length/distance pair. length first. self.parent.state = Length { decoder: tables::LENGTH.decoder(), }; } else { // this is a literal if lit > 0 { self.parent.state = LiteralCoded { decoder: tables::LITERAL.decoder(), }; } else { self.parent.state = Literal; } } } Length { ref mut decoder } => { let symbol = self.parent.input.decode(decoder)? as usize; self.parent.state = LengthExtra { symbol }; } LengthExtra { symbol } => { let len = LEN_BASE[symbol] + self.parent.input.bits(LEN_EXTRA[symbol])? as usize; if len == 519 { // end code self.parent.state = End; } else { // distance next self.parent.state = Distance { len, decoder: tables::DISTANCE.decoder(), }; } } Distance { len, ref mut decoder, } => { let symbol = self.parent.input.decode(decoder)? as usize; self.parent.state = DistanceExtra { len, symbol }; } DistanceExtra { len, symbol } => { let extra_bits = if len == 2 { 2 } else { dict }; let mut dist = self.parent.input.bits(extra_bits)? as usize + 1; dist += symbol << extra_bits; if dist > self.parent.window.len() { // too far back return Err(Error::BadDistance); } self.parent.state = Copy { idx: self.parent.window.len() - dist, len, }; } Copy { ref mut idx, ref mut len, } => { while *len > 0 { if self.pos >= self.buf.len() { // not enough room return Ok(()); } let value = self.parent.window[*idx]; *len -= 1; if !self.parent.window.is_full() { *idx += 1; } self.parent.window.push_back(value); self.buf[self.pos] = value; self.pos += 1; } self.parent.state = Start; } Literal => { if self.pos >= self.buf.len() { // not enough room return Ok(()); } let value = self.parent.input.bits(8)? as u8; self.parent.window.push_back(value); self.buf[self.pos] = value; self.pos += 1; self.parent.state = Start; } LiteralCoded { ref mut decoder } => { if self.pos >= self.buf.len() { // not enough room return Ok(()); } let value = self.parent.input.decode(decoder)?; self.parent.window.push_back(value); self.buf[self.pos] = value; self.pos += 1; self.parent.state = Start; } End => { return Ok(()); } } } } /// Get a reference to the filled portion of the output buffer. /// /// This is usually called after [`feed`](#method.feed) returns `Ok(())`. pub fn get(&self) -> &[u8] { &self.buf[..self.pos] } /// Return the amount of output produced so far. pub fn len(&self) -> usize { self.pos } /// Reset the output buffer to empty. /// /// Note that this does *not* reset the entire decompressor state. pub fn reset(&mut self) { self.pos = 0; } /// Returns true if decompression is finished. /// /// This does the same thing as /// [`Explode::done`](struct.Explode.html#method.done) but is /// usable while a `ExplodeBuffer` is still in scope. pub fn done(&self) -> bool { self.parent.done() } } impl Explode { /// Create a new Explode decompression state. pub fn new() -> Self { Explode { state: ExplodeState::Start, lit: None, dict: None, input: ExplodeInput { next: ExplodeInputState::Waiting, bitbuf: 0, bitcount: 0, }, window: ArrayDeque::new(), } } /// Provide a buffer to decompress into. /// /// This returns a [`ExplodeBuffer`](struct.ExplodeBuffer.html) /// handle that is used for feeding input to decompress and other /// operations. pub fn with_buffer<'a>( &'a mut self, buf: &'a mut [u8], ) -> ExplodeBuffer<'a> { ExplodeBuffer { parent: self, buf, pos: 0, } } /// Returns true if decompression is finished. /// /// If this function can't be used because a /// [`ExplodeBuffer`](struct.ExplodeBuffer.html) is currently /// borrowing this object mutably, you can use /// [`ExplodeBuffer::done`](struct.ExplodeBuffer.html#method.done) /// instead. pub fn done(&self) -> bool { if let ExplodeState::End = self.state { true } else { false } } } /// Decompress a block of `data` in memory, using the given auxiliary /// buffer `buf`. /// /// This gives you control over the size of the internal buffer /// used. If you do not need that control, use /// [`explode`](fn.explode.html) instead. /// /// ``` /// # fn main() -> explode::Result<()> { /// let mut buf: [u8; 1] = [0; 1]; /// let bytes = vec![0x00, 0x04, 0x82, 0x24, 0x25, 0x8f, 0x80, 0x7f]; /// let result = explode::explode_with_buffer(&bytes, &mut buf)?; /// assert_eq!(result, "AIAIAIAIAIAIA".as_bytes()); /// # Ok(()) } /// ``` pub fn explode_with_buffer(data: &[u8], buf: &mut [u8]) -> Result<Vec<u8>> { let mut dec = Explode::new(); let mut i = 0; let mut out = Vec::with_capacity(buf.len()); loop { let mut decbuf = dec.with_buffer(buf); while i < data.len() { match decbuf.feed(data[i]) { Ok(()) => { let decompressed = decbuf.get(); out.extend_from_slice(decompressed); if decbuf.done() { // we're done return Ok(out); } decbuf.reset(); } Err(Error::IncompleteInput) => { i += 1; continue; } Err(e) => return Err(e), } } // out of input return Err(Error::IncompleteInput); } } /// Decompress a block of `data` in memory. /// /// ``` /// # fn main() -> explode::Result<()> { /// let bytes = vec![0x00, 0x04, 0x82, 0x24, 0x25, 0x8f, 0x80, 0x7f]; /// let result = explode::explode(&bytes)?; /// assert_eq!(result, "AIAIAIAIAIAIA".as_bytes()); /// # Ok(()) } /// ``` /// /// This function will internally decompress the given memory in /// blocks of 4096 bytes. If you wish to use a different block size, /// see [`explode_with_buffer`](fn.explode_with_buffer.html). pub fn explode(data: &[u8]) -> Result<Vec<u8>> { let mut buf = [0; 4096]; explode_with_buffer(data, &mut buf) } #[cfg(test)] mod tests { use super::{explode, explode_with_buffer, Error}; use crate::examples::EXAMPLES; #[test] fn explode_simple() { for (encoded, decoded) in EXAMPLES { let ours = explode(encoded).unwrap(); assert_eq!(*decoded, &ours[..]); } } #[test] fn explode_small() { let mut buf = [0; 1]; for (encoded, decoded) in EXAMPLES { let ours = explode_with_buffer(encoded, &mut buf).unwrap(); assert_eq!(*decoded, &ours[..]); } } #[test] fn explode_incomplete() { for (encoded, _) in EXAMPLES { let ours = explode(&encoded[..encoded.len() - 1]); match ours { Err(Error::IncompleteInput) => (), _ => panic!("incorrectly parsed incomplete input"), } } } #[test] fn explode_extra() { for (encoded, decoded) in EXAMPLES { let mut encodedplus: Vec<u8> = encoded.iter().cloned().collect(); encodedplus.push(42); let ours = explode(&encodedplus).unwrap(); assert_eq!(*decoded, &ours[..]); } } }