Struct CodecTranscodeDecoder 

pub struct CodecTranscodeDecoder<C> { /* private fields */ }

Decodes encoded units into caller-provided value buffers by using a Codec.

CodecTranscodeDecoder is a policy-free bridge from the low-level unchecked Codec contract to Transcoder and TranscodeDecoder. It leaves incomplete input tails in the caller-provided input slice while the stream remains open. Call Transcoder::transcode_eof after upstream EOF so codecs can apply their Codec::decode_eof policy to a trailing prefix.

Type Parameters

• C: Low-level codec used to decode values.

Examples

use std::convert::Infallible;
use std::num::NonZeroUsize;

use qubit_codec::Codec;
use qubit_codec::CodecTranscodeDecoder;
use qubit_codec::DecodeFailure;
use qubit_codec::Transcoder;

struct Identity;
impl Codec for Identity {
    type Value = u8;
    type Unit = u8;
    type DecodeError = Infallible;
    type EncodeError = Infallible;
    const MIN_UNITS_PER_VALUE: usize = 1;
    const MAX_DECODE_UNITS_PER_VALUE: usize = 1;
    const MAX_ENCODE_UNITS_PER_VALUE: usize = 1;
    unsafe fn decode(&mut self, input: &[u8], index: usize)
        -> Result<(u8, NonZeroUsize), DecodeFailure<Infallible>> {
        Ok((input[index], NonZeroUsize::new(1).unwrap()))
    }
    unsafe fn encode(&mut self, value: &u8, output: &mut [u8], index: usize)
        -> Result<usize, Infallible> {
        output[index] = *value;
        Ok(1)
    }
}
let mut decoder = CodecTranscodeDecoder::new(Identity);
let mut output = [0; 2];
decoder.reset(&mut output, 0).unwrap();
decoder.transcode(&[4, 7], 0, &mut output, 0).unwrap();
assert_eq!(output, [4, 7]);

Implementations

impl<C> CodecTranscodeDecoder<C>

where C: Codec,

pub fn new(codec: C) -> Self

Creates a buffered decoder backed by codec.

Parameters

• codec: Low-level codec used to decode values.

Returns

Returns a buffered decoder adapter for the supplied codec.

pub fn codec(&self) -> &C

Returns a shared reference to the wrapped codec.

Returns

A borrow of the codec that remains valid while this adapter is borrowed.

pub fn codec_mut(&mut self) -> &mut C

Returns a mutable reference to the wrapped codec.

Mutating a codec during an active stream can invalidate that stream’s assumptions; reset the adapter before continuing with the new codec configuration.

Returns

An exclusive borrow of the wrapped codec; no allocation is performed.

pub fn into_codec(self) -> C

Consumes the adapter and returns its wrapped codec.

Any buffered lifecycle state and internal hooks are discarded.

Returns

The owned codec, with its codec-specific state preserved.

Trait Implementations

impl<C: Debug> Debug for CodecTranscodeDecoder<C>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<C: Default> Default for CodecTranscodeDecoder<C>

fn default() -> Self

Returns the “default value” for a type.

impl<C> TranscodeDecoder for CodecTranscodeDecoder<C>

where C: Codec,

type DecodeError = <C as Codec>::DecodeError

Codec-specific failure retained by the decoder error wrapper.

impl<C> Transcoder for CodecTranscodeDecoder<C>

where C: Codec,

type Input = <C as Codec>::Unit

Encoded units borrowed from the caller input.

type Output = <C as Codec>::Value

Decoded values written into caller-provided storage.

type Error = TranscodeDecodeError<<C as Codec>::DecodeError>

Contract or codec failures reported by the decoding engine.

fn max_transcode_output_len( &self, input_len: usize, ) -> Result<usize, CapacityError>

Returns an upper bound for decoded values produced from input_len units.

Parameters

• input_len: Source units the caller plans to decode.

Returns

Returns a conservative upper bound for decoded values.

Errors

Returns a capacity error if the requested bound cannot fit in usize.

fn max_finish_output_len(&self) -> Result<usize, CapacityError>

Returns the global maximum values emitted by finishing internal state.

Returns

Returns the number of values that may still be emitted by finishing state.

Errors

Returns a capacity error if the combined finish bound overflows.

fn max_reset_output_len(&self) -> Result<usize, CapacityError>

Returns the global maximum values emitted when resetting internal state.

Returns

The maximum reset output capacity required by the engine.

Errors

Returns a capacity error if the combined reset bound overflows.

fn reset( &mut self, output: &mut [C::Value], output_index: usize, ) -> Result<usize, TranscodeDecodeErrorOf<C>>

Runs before-reset cleanup for decoder state.

Parameters

• output: Destination storage for reset values.
• output_index: First destination position to write.

Returns

The number of reset values written.

Errors

Returns a contract error for invalid indices or insufficient capacity, or a codec error when resetting codec state fails.

fn transcode( &mut self, input: &[C::Unit], input_index: usize, output: &mut [C::Value], output_index: usize, ) -> Result<TranscodeProgress, TranscodeDecodeErrorOf<C>>

Decodes source units into logical values.

Parameters

• input: Source unit slice.
• input_index: Absolute source index where decoding starts.
• output: Destination value slice.
• output_index: Absolute output value index where writing starts.

Returns

Returns conversion progress for consumed and written counters.

Errors

Returns a decode error when indices are invalid or when conversion fails under hook policy.

fn transcode_eof( &mut self, input: &[C::Unit], input_index: usize, output: &mut [C::Value], output_index: usize, ) -> Result<TranscodeProgress, TranscodeDecodeErrorOf<C>>

Transcodes an input segment while marking it as the end of the stream.

This forwarding implementation lets the engine apply EOF-specific decoder behavior before returning progress to the caller.

Parameters

• input: Final source unit slice.
• input_index: First source position to consume.
• output: Destination value storage.
• output_index: First destination position to write.

Returns

Consumed and written counts and the engine progress status.

Errors

Returns contract errors for invalid indices or lifecycle transitions, or decode errors for malformed or incomplete final input.

fn finish( &mut self, output: &mut [C::Value], output_index: usize, ) -> Result<usize, TranscodeDecodeErrorOf<C>>

Finishes internally retained output after EOF.

Parameters

• output: Destination value slice for final retained values.
• output_index: Absolute output value index where writing starts.

Returns

Returns the number of values written by finalization.

Errors

Returns contract errors for invalid indices, insufficient capacity, or invalid lifecycle transitions, or a codec error for invalid EOF state.

fn max_total_output_len(&self, input_len: usize) -> Result<usize, CapacityError>

Returns an upper bound for a complete reset -> transcode -> finish stream.

fn transcode_complete_into( &mut self, input: &[Self::Input], output: &mut [Self::Output], ) -> Result<usize, Self::Error>

Runs a complete one-shot reset -> transcode -> finish stream.