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use super::{core::Tag, *};
use crate::DecodeOperation;
use std::io::{self, BufRead};
/// Source failure or terminal decoder failure, preserving the source chain.
#[derive(Debug, thiserror::Error)]
#[non_exhaustive]
pub enum FramedReadError {
/// Source error; WouldBlock does not end the decoder session.
#[error("framed source failed: {0}")]
Io(#[from] io::Error),
/// Terminal codec failure with exact per-call progress.
#[error("{0}")]
Decode(#[from] FramedDecodeFailure),
}
/// Lending event reader. The buffered source retains all unaccepted suffix bytes.
#[derive(Debug)]
pub struct FramedReader<'d, 'dict, R> {
session: FramedDecoderSession<'d, 'dict>,
source: R,
output: [u8; 8192],
partial: Option<ProducedFragment>,
eof: bool,
}
impl FramedDecompressor {
/// Creates an event reader; wrap an ordinary `Read` in `BufReader` first.
///
/// # Examples
/// ```
/// use mbrotli::framing::*;
/// use std::io::BufRead;
/// let mut decoder = FramedDecompressor::new(
/// FramedDecodeConfig::default().with_input_mode(InputMode::Auto))?;
/// let input = [0x3b, b'T']; // An empty raw member and a protocol suffix.
/// let mut reader = decoder.framed_reader(&input[..], Default::default())?;
/// while reader.next_event()?.is_some() {}
/// assert!(reader.is_finished());
/// assert_eq!(reader.into_inner().fill_buf()?, b"T");
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
/// # Errors
/// Returns session-start policy and lifecycle errors.
pub fn framed_reader<R: BufRead>(
&mut self,
reader: R,
stream: FramedDecodeStreamConfig,
) -> Result<FramedReader<'_, 'static, R>, FramedDecodeError> {
Ok(FramedReader {
session: self.start(stream)?,
source: reader,
output: [0; 8192],
partial: None,
eof: false,
})
}
/// Creates an event reader with a session-borrowed dictionary resolver.
/// # Errors
/// Returns session-start policy and lifecycle errors.
///
/// # Examples
///
/// ```
/// use mbrotli::framing::*;
/// let mut decoder = FramedDecompressor::new(Default::default())?;
/// struct Dictionaries;
/// impl DictionaryResolver for Dictionaries {
/// fn resolve(&self, request: ExternalDictionaryRequest) -> Option<&[u8]> {
/// (request.id == DictionaryId([7; 32])
/// && request.kind == ExternalDictionaryKind::Prefix).then_some(b"prefix")
/// }
/// }
/// let dictionaries = Dictionaries;
/// // Footerless full resource, Shared Brotli codec, one external prefix reference.
/// let mut input = vec![0x91, 10, 66, 82, 0, 40, 2, 3, 0, 1, 2, 3];
/// input.extend([7; 32]);
/// input.extend([0, 0x3b]);
/// let mut reader = decoder.framed_reader_with_dictionaries(
/// &dictionaries, input.as_slice(), Default::default())?;
/// while reader.next_event()?.is_some() {}
/// assert!(reader.is_finished());
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
pub fn framed_reader_with_dictionaries<'d, 'dict, R: BufRead>(
&'d mut self,
dictionaries: impl Into<DictionaryResolverRef<'dict>>,
reader: R,
stream: FramedDecodeStreamConfig,
) -> Result<FramedReader<'d, 'dict, R>, FramedDecodeError> {
Ok(FramedReader {
session: self.start_with_dictionaries(dictionaries, stream)?,
source: reader,
output: [0; 8192],
partial: None,
eof: false,
})
}
}
impl<R: BufRead> FramedReader<'_, '_, R> {
/// Returns one borrowed event, or `None` only after complete validation.
/// # Errors
/// Returns source or codec errors. A failing call's payload remains available
/// through `partial_output` until the next mutating call.
///
/// # Examples
///
/// ```
/// use mbrotli::framing::*;
/// let mut decoder = FramedDecompressor::new(Default::default())?;
/// let input = [0x91, 10, 66, 82, 0, 6, 2, 0, 0, b'a', b'b', b'c'];
/// let mut reader = decoder.framed_reader(&input[..], Default::default())?;
/// let mut payload = Vec::new();
/// while let Some(event) = reader.next_event()? {
/// if let FramedEvent::ResourceData(fragment) = event {
/// payload.extend_from_slice(fragment.bytes);
/// }
/// }
/// assert_eq!(payload, b"abc");
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
// The by-value failure contract preserves progress even when allocation fails;
// boxing this 128-byte record would require an allocation on the error path.
#[expect(
clippy::result_large_err,
reason = "allocation-independent progress is part of the public contract"
)]
pub fn next_event(&mut self) -> Result<Option<FramedEvent<'_>>, FramedReadError> {
self.partial = None;
loop {
if self.session.is_finished() {
return Ok(None);
}
let operation = if self.eof {
DecodeOperation::Finish
} else {
DecodeOperation::Process
};
// Pending semantic events and buffered codec output never require a
// new transport read. In particular, a raw member can finish while
// the enclosing connection remains open.
let mut result = self.session.step(&[], &mut self.output, operation);
if matches!(result, Ok((_, _, Tag::Input))) {
let input = loop {
match self.source.fill_buf() {
Err(e) if e.kind() == io::ErrorKind::Interrupted => continue,
result => break result?,
}
};
if input.is_empty() {
self.eof = true;
}
let operation = if self.eof {
DecodeOperation::Finish
} else {
DecodeOperation::Process
};
result = self.session.step(input, &mut self.output, operation);
}
let (consumed, produced, tag) = match result {
Ok(progress) => progress,
Err(failure) => {
self.source.consume(failure.consumed);
self.partial = failure.last_output.clone();
return Err(failure.into());
}
};
self.source.consume(consumed);
match tag {
Tag::Input | Tag::Output => continue,
Tag::Finished => return Ok(None),
_ => {
return self
.session
.owner
.engine
.event(tag, &self.output[..produced])
.ok_or(FramedReadError::Decode(FramedDecodeFailure {
error: FramedDecodeError::InvalidState,
consumed,
produced,
last_output: None,
}))
.map(Some);
}
}
}
}
/// Payload produced by the last failing call, with resource-local identity.
///
/// # Examples
///
/// ```
/// use mbrotli::framing::*;
/// let mut decoder = FramedDecompressor::new(Default::default())?;
/// let input = [0x91, 10, 66, 82, 0, 6, 2, 0, 0, b'a', b'b', b'c'];
/// let mut reader = decoder.framed_reader(&input[..], Default::default())?;
/// assert!(reader.partial_output().is_none());
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
pub fn partial_output(&self) -> Option<ResourceData<'_>> {
self.partial.as_ref().map(|f| ResourceData {
position: f.position,
bytes: &self.output[f.range.clone()],
})
}
/// Borrows the buffered source.
///
/// # Examples
///
/// ```
/// use mbrotli::framing::*;
/// let mut decoder = FramedDecompressor::new(Default::default())?;
/// let input = [0x91, 10, 66, 82, 0, 6, 2, 0, 0, b'a', b'b', b'c'];
/// let mut reader = decoder.framed_reader(&input[..], Default::default())?;
/// assert_eq!(*reader.get_ref(), input.as_slice());
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
pub const fn get_ref(&self) -> &R {
&self.source
}
/// Borrows the source to repair an I/O failure. Do not consume or replace bytes.
///
/// # Examples
///
/// ```
/// use mbrotli::framing::*;
/// let mut decoder = FramedDecompressor::new(Default::default())?;
/// let input = [0x91, 10, 66, 82, 0, 6, 2, 0, 0, b'a', b'b', b'c'];
/// let mut reader = decoder.framed_reader(std::io::Cursor::new(input), Default::default())?;
/// assert_eq!(reader.get_mut().position(), 0); // Inspect without consuming source bytes.
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
pub fn get_mut(&mut self) -> &mut R {
&mut self.source
}
/// Returns the buffered source and its unaccepted suffix without performing I/O.
///
/// # Examples
///
/// ```
/// use mbrotli::framing::*;
/// let mut decoder = FramedDecompressor::new(Default::default())?;
/// let input = [0x91, 10, 66, 82, 0, 6, 2, 0, 0, b'a', b'b', b'c'];
/// let mut reader = decoder.framed_reader(&input[..], Default::default())?;
/// while reader.next_event()?.is_some() {}
/// assert!(reader.into_inner().is_empty());
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
pub fn into_inner(self) -> R {
self.source
}
/// Whether whole-object validation succeeded.
///
/// # Examples
///
/// ```
/// use mbrotli::framing::*;
/// let mut decoder = FramedDecompressor::new(Default::default())?;
/// let input = [0x91, 10, 66, 82, 0, 6, 2, 0, 0, b'a', b'b', b'c'];
/// let mut reader = decoder.framed_reader(&input[..], Default::default())?;
/// assert!(!reader.is_finished());
/// while reader.next_event()?.is_some() {}
/// assert!(reader.is_finished());
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
pub const fn is_finished(&self) -> bool {
self.session.is_finished()
}
}