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Pass image data directly to ZlibStream, bypassing ChunkState::raw_bytes #424

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merged 6 commits into from
Nov 14, 2023
Merged

Pass image data directly to ZlibStream, bypassing ChunkState::raw_bytes #424

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e8b6482
Renaming s/U32Value/U32ValueKind/ and other related, small refactorings.
anforowicz Oct 5, 2023
93b7ffa
Handle fdAT sequence numbers via U32 state.
anforowicz Oct 5, 2023
c65cb64
Pass image data directly to `ZlibStream`, bypassing `ChunkState::raw_…
anforowicz Oct 5, 2023
f4bc666
Move `benches/png_generator.rs` to `src/test_utils.rs`.
anforowicz Nov 14, 2023
a568f6c
Fix handling of fdAT chunks shorter than 4 bytes.
anforowicz Nov 14, 2023
e75843f
Testing sequence number of APNG frame split across 2 fdAT chunks.
anforowicz Nov 14, 2023
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190 changes: 100 additions & 90 deletions src/decoder/stream.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -27,24 +27,39 @@ pub const CHUNCK_BUFFER_SIZE: usize = 32 * 1024;
/// be used to detect that build.
const CHECKSUM_DISABLED: bool = cfg!(fuzzing);

/// Kind of `u32` value that is being read via `State::U32Byte...`.
#[derive(Debug)]
enum U32Value {
// CHUNKS
enum U32ValueKind {
/// Chunk length - see
/// http://www.libpng.org/pub/png/spec/1.2/PNG-Structure.html#Chunk-layout
Length,
Type(u32),
/// Chunk type - see
/// http://www.libpng.org/pub/png/spec/1.2/PNG-Structure.html#Chunk-layout
Type { length: u32 },
/// Chunk checksum - see
/// http://www.libpng.org/pub/png/spec/1.2/PNG-Structure.html#Chunk-layout
Crc(ChunkType),
/// Sequence number from an `fdAT` chunk - see
/// https://wiki.mozilla.org/APNG_Specification#.60fdAT.60:_The_Frame_Data_Chunk
ApngSequenceNumber,
}

#[derive(Debug)]
enum State {
Signature(u8, [u8; 7]),
U32Byte3(U32Value, u32),
U32Byte2(U32Value, u32),
U32Byte1(U32Value, u32),
U32(U32Value),
ReadChunk(ChunkType),
PartialChunk(ChunkType),
DecodeData(ChunkType, usize),
U32Byte3(U32ValueKind, u32),
U32Byte2(U32ValueKind, u32),
U32Byte1(U32ValueKind, u32),
U32(U32ValueKind),
/// In this state we are reading chunk data from external input, and appending it to
/// `ChunkState::raw_bytes`.
ReadChunkData(ChunkType),
/// In this state we check if all chunk data has been already read into `ChunkState::raw_bytes`
/// and if so then we parse the chunk. Otherwise, we go back to the `ReadChunkData` state.
ParseChunkData(ChunkType),
/// In this state we are reading image data from external input and feeding it directly into
/// `StreamingDecoder::inflater`.
ImageData(ChunkType),
}

#[derive(Debug)]
Expand Down Expand Up @@ -423,8 +438,8 @@ pub struct StreamingDecoder {
pub(crate) info: Option<Info<'static>>,
/// The animation chunk sequence number.
current_seq_no: Option<u32>,
/// Stores where in decoding an `fdAT` chunk we are.
apng_seq_handled: bool,
/// Whether we have already seen a start of an IDAT chunk. (Used to validate chunk ordering -
/// some chunk types can only appear before or after an IDAT chunk.)
have_idat: bool,
decode_options: DecodeOptions,
}
Expand Down Expand Up @@ -462,7 +477,6 @@ impl StreamingDecoder {
inflater,
info: None,
current_seq_no: None,
apng_seq_handled: false,
have_idat: false,
decode_options,
}
Expand All @@ -477,7 +491,6 @@ impl StreamingDecoder {
self.inflater.reset();
self.info = None;
self.current_seq_no = None;
self.apng_seq_handled = false;
self.have_idat = false;
}

Expand Down Expand Up @@ -559,21 +572,21 @@ impl StreamingDecoder {
Signature(_, signature)
if signature == [137, 80, 78, 71, 13, 10, 26] && current_byte == 10 =>
{
self.state = Some(U32(U32Value::Length));
self.state = Some(U32(U32ValueKind::Length));
Ok((1, Decoded::Nothing))
}
Signature(..) => Err(DecodingError::Format(
FormatErrorInner::InvalidSignature.into(),
)),
U32Byte3(type_, mut val) => {
use self::U32Value::*;
use self::U32ValueKind::*;
val |= u32::from(current_byte);
match type_ {
Length => {
self.state = Some(U32(Type(val)));
self.state = Some(U32(Type { length: val }));
Ok((1, Decoded::Nothing))
}
Type(length) => {
Type { length } => {
let type_str = ChunkType([
(val >> 24) as u8,
(val >> 16) as u8,
Expand All @@ -587,7 +600,7 @@ impl StreamingDecoder {
self.current_chunk.type_ = type_str;
self.inflater.finish_compressed_chunks(image_data)?;
self.inflater.reset();
self.state = Some(U32Byte3(Type(length), val & !0xff));
self.state = Some(U32Byte3(Type { length }, val & !0xff));
return Ok((0, Decoded::ImageDataFlushed));
}
self.current_chunk.type_ = type_str;
Expand All @@ -596,9 +609,15 @@ impl StreamingDecoder {
self.current_chunk.crc.update(&type_str.0);
}
self.current_chunk.remaining = length;
self.apng_seq_handled = false;
self.current_chunk.raw_bytes.clear();
self.state = Some(ReadChunk(type_str));
self.state = match type_str {
chunk::fdAT => Some(U32(ApngSequenceNumber)),
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IDAT => {
self.have_idat = true;
Some(ImageData(type_str))
}
_ => Some(ReadChunkData(type_str)),
};
Ok((1, Decoded::ChunkBegin(length, type_str)))
}
Crc(type_str) => {
Expand All @@ -612,7 +631,7 @@ impl StreamingDecoder {
};

if val == sum || CHECKSUM_DISABLED {
self.state = Some(State::U32(U32Value::Length));
self.state = Some(State::U32(U32ValueKind::Length));
if type_str == IEND {
Ok((1, Decoded::ImageEnd))
} else {
Expand All @@ -629,6 +648,36 @@ impl StreamingDecoder {
))
}
}
ApngSequenceNumber => {
debug_assert_eq!(self.current_chunk.type_, chunk::fdAT);
let next_seq_no = val;
self.current_chunk.remaining -= 4;

if let Some(seq_no) = self.current_seq_no {
if next_seq_no != seq_no + 1 {
return Err(DecodingError::Format(
FormatErrorInner::ApngOrder {
present: next_seq_no,
expected: seq_no + 1,
}
.into(),
));
}
self.current_seq_no = Some(next_seq_no);
} else {
return Err(DecodingError::Format(
FormatErrorInner::MissingFctl.into(),
));
}

if !self.decode_options.ignore_crc {
let data = next_seq_no.to_be_bytes();
self.current_chunk.crc.update(&data);
}

self.state = Some(ImageData(chunk::fdAT));
Ok((1, Decoded::PartialChunk(chunk::fdAT)))
}
}
}
U32Byte2(type_, val) => {
Expand All @@ -643,63 +692,24 @@ impl StreamingDecoder {
self.state = Some(U32Byte1(type_, u32::from(current_byte) << 24));
Ok((1, Decoded::Nothing))
}
PartialChunk(type_str) => {
match type_str {
IDAT => {
self.have_idat = true;
self.state = Some(DecodeData(type_str, 0));
Ok((0, Decoded::PartialChunk(type_str)))
}
chunk::fdAT => {
let data_start;
if let Some(seq_no) = self.current_seq_no {
if !self.apng_seq_handled {
data_start = 4;
let mut buf = &self.current_chunk.raw_bytes[..];
let next_seq_no = buf.read_be()?;
if next_seq_no != seq_no + 1 {
return Err(DecodingError::Format(
FormatErrorInner::ApngOrder {
present: next_seq_no,
expected: seq_no + 1,
}
.into(),
));
}
self.current_seq_no = Some(next_seq_no);
self.apng_seq_handled = true;
} else {
data_start = 0;
}
} else {
return Err(DecodingError::Format(
FormatErrorInner::MissingFctl.into(),
));
}
self.state = Some(DecodeData(type_str, data_start));
Ok((0, Decoded::PartialChunk(type_str)))
}
// Handle other chunks
_ => {
if self.current_chunk.remaining == 0 {
// complete chunk
Ok((0, self.parse_chunk(type_str)?))
} else {
// Make sure we have room to read more of the chunk.
// We need it fully before parsing.
self.reserve_current_chunk()?;
ParseChunkData(type_str) => {
debug_assert!(type_str != IDAT && type_str != chunk::fdAT);
if self.current_chunk.remaining == 0 {
// Got complete chunk.
Ok((0, self.parse_chunk(type_str)?))
} else {
// Make sure we have room to read more of the chunk.
// We need it fully before parsing.
self.reserve_current_chunk()?;

self.state = Some(ReadChunk(type_str));
Ok((0, Decoded::PartialChunk(type_str)))
}
}
self.state = Some(ReadChunkData(type_str));
Ok((0, Decoded::PartialChunk(type_str)))
}
}
ReadChunk(type_str) => {
// The _previous_ event wanted to return the contents of raw_bytes, and let the
// caller consume it,
ReadChunkData(type_str) => {
debug_assert!(type_str != IDAT && type_str != chunk::fdAT);
if self.current_chunk.remaining == 0 {
self.state = Some(U32(U32Value::Crc(type_str)));
self.state = Some(U32(U32ValueKind::Crc(type_str)));
Ok((0, Decoded::Nothing))
} else {
let ChunkState {
Expand All @@ -713,7 +723,7 @@ impl StreamingDecoder {
let bytes_avail = min(buf.len(), buf_avail);
let n = min(*remaining, bytes_avail as u32);
if buf_avail == 0 {
self.state = Some(PartialChunk(type_str));
self.state = Some(ParseChunkData(type_str));
Ok((0, Decoded::Nothing))
} else {
let buf = &buf[..n as usize];
Expand All @@ -724,27 +734,27 @@ impl StreamingDecoder {

*remaining -= n;
if *remaining == 0 {
self.state = Some(PartialChunk(type_str));
self.state = Some(ParseChunkData(type_str));
} else {
self.state = Some(ReadChunk(type_str));
self.state = Some(ReadChunkData(type_str));
}
Ok((n as usize, Decoded::Nothing))
}
}
}
DecodeData(type_str, mut n) => {
let chunk_len = self.current_chunk.raw_bytes.len();
let chunk_data = &self.current_chunk.raw_bytes[n..];
let c = self.inflater.decompress(chunk_data, image_data)?;
n += c;
if n == chunk_len && c == 0 {
self.current_chunk.raw_bytes.clear();
self.state = Some(ReadChunk(type_str));
Ok((0, Decoded::ImageData))
ImageData(type_str) => {
debug_assert!(type_str == IDAT || type_str == chunk::fdAT);
let len = std::cmp::min(buf.len(), self.current_chunk.remaining as usize);
let buf = &buf[..len];
let consumed = self.inflater.decompress(buf, image_data)?;
self.current_chunk.crc.update(&buf[..consumed]);
self.current_chunk.remaining -= consumed as u32;
if self.current_chunk.remaining == 0 {
self.state = Some(U32(U32ValueKind::Crc(type_str)));
} else {
self.state = Some(DecodeData(type_str, n));
Ok((0, Decoded::ImageData))
self.state = Some(ImageData(type_str));
}
Ok((consumed, Decoded::ImageData))
}
}
}
Expand All @@ -766,7 +776,7 @@ impl StreamingDecoder {
}

fn parse_chunk(&mut self, type_str: ChunkType) -> Result<Decoded, DecodingError> {
self.state = Some(State::U32(U32Value::Crc(type_str)));
self.state = Some(State::U32(U32ValueKind::Crc(type_str)));
if self.info.is_none() && type_str != IHDR {
return Err(DecodingError::Format(
FormatErrorInner::ChunkBeforeIhdr { kind: type_str }.into(),
Expand Down
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