structured_zstd/decoding/
errors.rs

1//! Errors that might occur while decoding zstd formatted data
2
3use crate::bit_io::GetBitsError;
4use crate::blocks::block::BlockType;
5use crate::blocks::literals_section::LiteralsSectionType;
6use crate::io::Error;
7use alloc::vec::Vec;
8use core::fmt;
9#[cfg(feature = "std")]
10use std::error::Error as StdError;
11
12#[derive(Debug)]
13#[non_exhaustive]
14pub enum FrameDescriptorError {
15    InvalidFrameContentSizeFlag { got: u8 },
16}
17
18impl fmt::Display for FrameDescriptorError {
19    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
20        match self {
21            Self::InvalidFrameContentSizeFlag { got } => write!(
22                f,
23                "Invalid Frame_Content_Size_Flag; Is: {got}, Should be one of: 0, 1, 2, 3"
24            ),
25        }
26    }
27}
28
29#[cfg(feature = "std")]
30impl StdError for FrameDescriptorError {}
31
32#[derive(Debug)]
33#[non_exhaustive]
34pub enum FrameHeaderError {
35    WindowTooBig { got: u64 },
36    WindowTooSmall { got: u64 },
37    FrameDescriptorError(FrameDescriptorError),
38    DictIdTooSmall { got: usize, expected: usize },
39    MismatchedFrameSize { got: usize, expected: u8 },
40    FrameSizeIsZero,
41    InvalidFrameSize { got: u8 },
42}
43
44impl fmt::Display for FrameHeaderError {
45    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
46        match self {
47            Self::WindowTooBig { got } => write!(
48                f,
49                "window_size bigger than allowed maximum. Is: {}, Should be lower than: {}",
50                got,
51                crate::common::MAX_WINDOW_SIZE
52            ),
53            Self::WindowTooSmall { got } => write!(
54                f,
55                "window_size smaller than allowed minimum. Is: {}, Should be greater than: {}",
56                got,
57                crate::common::MIN_WINDOW_SIZE
58            ),
59            Self::FrameDescriptorError(e) => write!(f, "{e:?}"),
60            Self::DictIdTooSmall { got, expected } => write!(
61                f,
62                "Not enough bytes in dict_id. Is: {got}, Should be: {expected}"
63            ),
64            Self::MismatchedFrameSize { got, expected } => write!(
65                f,
66                "frame_content_size does not have the right length. Is: {got}, Should be: {expected}"
67            ),
68            Self::FrameSizeIsZero => write!(f, "frame_content_size was zero"),
69            Self::InvalidFrameSize { got } => write!(
70                f,
71                "Invalid frame_content_size. Is: {got}, Should be one of 1, 2, 4, 8 bytes"
72            ),
73        }
74    }
75}
76
77#[cfg(feature = "std")]
78impl StdError for FrameHeaderError {
79    fn source(&self) -> Option<&(dyn StdError + 'static)> {
80        match self {
81            FrameHeaderError::FrameDescriptorError(source) => Some(source),
82            _ => None,
83        }
84    }
85}
86
87impl From<FrameDescriptorError> for FrameHeaderError {
88    fn from(error: FrameDescriptorError) -> Self {
89        Self::FrameDescriptorError(error)
90    }
91}
92
93#[derive(Debug)]
94#[non_exhaustive]
95pub enum ReadFrameHeaderError {
96    MagicNumberReadError(Error),
97    BadMagicNumber(u32),
98    FrameDescriptorReadError(Error),
99    InvalidFrameDescriptor(FrameDescriptorError),
100    WindowDescriptorReadError(Error),
101    DictionaryIdReadError(Error),
102    FrameContentSizeReadError(Error),
103    SkipFrame { magic_number: u32, length: u32 },
104}
105
106impl fmt::Display for ReadFrameHeaderError {
107    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
108        match self {
109            Self::MagicNumberReadError(e) => write!(f, "Error while reading magic number: {e}"),
110            Self::BadMagicNumber(e) => write!(f, "Read wrong magic number: 0x{e:X}"),
111            Self::FrameDescriptorReadError(e) => {
112                write!(f, "Error while reading frame descriptor: {e}")
113            }
114            Self::InvalidFrameDescriptor(e) => write!(f, "{e:?}"),
115            Self::WindowDescriptorReadError(e) => {
116                write!(f, "Error while reading window descriptor: {e}")
117            }
118            Self::DictionaryIdReadError(e) => write!(f, "Error while reading dictionary id: {e}"),
119            Self::FrameContentSizeReadError(e) => {
120                write!(f, "Error while reading frame content size: {e}")
121            }
122            Self::SkipFrame {
123                magic_number,
124                length,
125            } => write!(
126                f,
127                "SkippableFrame encountered with MagicNumber 0x{magic_number:X} and length {length} bytes"
128            ),
129        }
130    }
131}
132
133#[cfg(feature = "std")]
134impl StdError for ReadFrameHeaderError {
135    fn source(&self) -> Option<&(dyn StdError + 'static)> {
136        match self {
137            ReadFrameHeaderError::MagicNumberReadError(source) => Some(source),
138            ReadFrameHeaderError::FrameDescriptorReadError(source) => Some(source),
139            ReadFrameHeaderError::InvalidFrameDescriptor(source) => Some(source),
140            ReadFrameHeaderError::WindowDescriptorReadError(source) => Some(source),
141            ReadFrameHeaderError::DictionaryIdReadError(source) => Some(source),
142            ReadFrameHeaderError::FrameContentSizeReadError(source) => Some(source),
143            _ => None,
144        }
145    }
146}
147
148impl From<FrameDescriptorError> for ReadFrameHeaderError {
149    fn from(error: FrameDescriptorError) -> Self {
150        Self::InvalidFrameDescriptor(error)
151    }
152}
153
154#[derive(Debug)]
155#[non_exhaustive]
156pub enum BlockHeaderReadError {
157    ReadError(Error),
158    FoundReservedBlock,
159    BlockTypeError(BlockTypeError),
160    BlockSizeError(BlockSizeError),
161}
162
163#[cfg(feature = "std")]
164impl std::error::Error for BlockHeaderReadError {
165    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
166        match self {
167            BlockHeaderReadError::ReadError(source) => Some(source),
168            BlockHeaderReadError::BlockTypeError(source) => Some(source),
169            BlockHeaderReadError::BlockSizeError(source) => Some(source),
170            BlockHeaderReadError::FoundReservedBlock => None,
171        }
172    }
173}
174
175impl ::core::fmt::Display for BlockHeaderReadError {
176    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> ::core::fmt::Result {
177        match self {
178            BlockHeaderReadError::ReadError(_) => write!(f, "Error while reading the block header"),
179            BlockHeaderReadError::FoundReservedBlock => write!(
180                f,
181                "Reserved block occured. This is considered corruption by the documentation"
182            ),
183            BlockHeaderReadError::BlockTypeError(e) => write!(f, "Error getting block type: {e}"),
184            BlockHeaderReadError::BlockSizeError(e) => {
185                write!(f, "Error getting block content size: {e}")
186            }
187        }
188    }
189}
190
191impl From<Error> for BlockHeaderReadError {
192    fn from(val: Error) -> Self {
193        Self::ReadError(val)
194    }
195}
196
197impl From<BlockTypeError> for BlockHeaderReadError {
198    fn from(val: BlockTypeError) -> Self {
199        Self::BlockTypeError(val)
200    }
201}
202
203impl From<BlockSizeError> for BlockHeaderReadError {
204    fn from(val: BlockSizeError) -> Self {
205        Self::BlockSizeError(val)
206    }
207}
208
209#[derive(Debug)]
210#[non_exhaustive]
211pub enum BlockTypeError {
212    InvalidBlocktypeNumber { num: u8 },
213}
214
215#[cfg(feature = "std")]
216impl std::error::Error for BlockTypeError {}
217
218impl core::fmt::Display for BlockTypeError {
219    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
220        match self {
221            BlockTypeError::InvalidBlocktypeNumber { num } => {
222                write!(
223                    f,
224                    "Invalid Blocktype number. Is: {num}. Should be one of: 0, 1, 2, 3 (3 is reserved).",
225                )
226            }
227        }
228    }
229}
230
231#[derive(Debug)]
232#[non_exhaustive]
233pub enum BlockSizeError {
234    BlockSizeTooLarge { size: u32 },
235}
236
237#[cfg(feature = "std")]
238impl std::error::Error for BlockSizeError {}
239
240impl core::fmt::Display for BlockSizeError {
241    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
242        match self {
243            BlockSizeError::BlockSizeTooLarge { size } => {
244                write!(
245                    f,
246                    "Blocksize was bigger than the absolute maximum {} (128kb). Is: {}",
247                    crate::common::MAX_BLOCK_SIZE,
248                    size,
249                )
250            }
251        }
252    }
253}
254
255#[derive(Debug)]
256#[non_exhaustive]
257pub enum DecompressBlockError {
258    BlockContentReadError(Error),
259    MalformedSectionHeader {
260        expected_len: usize,
261        remaining_bytes: usize,
262    },
263    DecompressLiteralsError(DecompressLiteralsError),
264    LiteralsSectionParseError(LiteralsSectionParseError),
265    SequencesHeaderParseError(SequencesHeaderParseError),
266    DecodeSequenceError(DecodeSequenceError),
267    ExecuteSequencesError(ExecuteSequencesError),
268}
269
270#[cfg(feature = "std")]
271impl std::error::Error for DecompressBlockError {
272    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
273        match self {
274            DecompressBlockError::BlockContentReadError(source) => Some(source),
275            DecompressBlockError::DecompressLiteralsError(source) => Some(source),
276            DecompressBlockError::LiteralsSectionParseError(source) => Some(source),
277            DecompressBlockError::SequencesHeaderParseError(source) => Some(source),
278            DecompressBlockError::DecodeSequenceError(source) => Some(source),
279            DecompressBlockError::ExecuteSequencesError(source) => Some(source),
280            _ => None,
281        }
282    }
283}
284
285impl core::fmt::Display for DecompressBlockError {
286    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
287        match self {
288            DecompressBlockError::BlockContentReadError(e) => {
289                write!(f, "Error while reading the block content: {e}")
290            }
291            DecompressBlockError::MalformedSectionHeader {
292                expected_len,
293                remaining_bytes,
294            } => {
295                write!(
296                    f,
297                    "Malformed section header. Says literals would be this long: {expected_len} but there are only {remaining_bytes} bytes left",
298                )
299            }
300            DecompressBlockError::DecompressLiteralsError(e) => write!(f, "{e:?}"),
301            DecompressBlockError::LiteralsSectionParseError(e) => write!(f, "{e:?}"),
302            DecompressBlockError::SequencesHeaderParseError(e) => write!(f, "{e:?}"),
303            DecompressBlockError::DecodeSequenceError(e) => write!(f, "{e:?}"),
304            DecompressBlockError::ExecuteSequencesError(e) => write!(f, "{e:?}"),
305        }
306    }
307}
308
309impl From<Error> for DecompressBlockError {
310    fn from(val: Error) -> Self {
311        Self::BlockContentReadError(val)
312    }
313}
314
315impl From<DecompressLiteralsError> for DecompressBlockError {
316    fn from(val: DecompressLiteralsError) -> Self {
317        Self::DecompressLiteralsError(val)
318    }
319}
320
321impl From<LiteralsSectionParseError> for DecompressBlockError {
322    fn from(val: LiteralsSectionParseError) -> Self {
323        Self::LiteralsSectionParseError(val)
324    }
325}
326
327impl From<SequencesHeaderParseError> for DecompressBlockError {
328    fn from(val: SequencesHeaderParseError) -> Self {
329        Self::SequencesHeaderParseError(val)
330    }
331}
332
333impl From<DecodeSequenceError> for DecompressBlockError {
334    fn from(val: DecodeSequenceError) -> Self {
335        Self::DecodeSequenceError(val)
336    }
337}
338
339impl From<ExecuteSequencesError> for DecompressBlockError {
340    fn from(val: ExecuteSequencesError) -> Self {
341        Self::ExecuteSequencesError(val)
342    }
343}
344
345#[derive(Debug)]
346#[non_exhaustive]
347pub enum DecodeBlockContentError {
348    DecoderStateIsFailed,
349    ExpectedHeaderOfPreviousBlock,
350    ReadError {
351        step: BlockType,
352        source: Error,
353    },
354    DecompressBlockError(DecompressBlockError),
355    /// The block's decompressed payload would not fit in the
356    /// caller-provided output buffer (only reachable via the
357    /// direct-decode path with a fixed-capacity backend). Internal
358    /// diagnostic variant — the frame-level decoder always
359    /// converts this into
360    /// `FrameDecoderError::FrameContentSizeMismatch` before
361    /// returning to the user, so external callers never observe
362    /// it. The `step: BlockType` field is kept for in-crate
363    /// debugging (which decode arm triggered the overshoot) but is
364    /// not part of any caller-visible distinction.
365    BackendOverflow {
366        step: BlockType,
367    },
368}
369
370#[cfg(feature = "std")]
371impl std::error::Error for DecodeBlockContentError {
372    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
373        match self {
374            DecodeBlockContentError::ReadError { step: _, source } => Some(source),
375            DecodeBlockContentError::DecompressBlockError(source) => Some(source),
376            _ => None,
377        }
378    }
379}
380
381impl core::fmt::Display for DecodeBlockContentError {
382    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
383        match self {
384            DecodeBlockContentError::DecoderStateIsFailed => {
385                write!(
386                    f,
387                    "Can't decode next block if failed along the way. Results will be nonsense",
388                )
389            }
390            DecodeBlockContentError::ExpectedHeaderOfPreviousBlock => {
391                write!(
392                    f,
393                    "Can't decode next block body, while expecting to decode the header of the previous block. Results will be nonsense",
394                )
395            }
396            DecodeBlockContentError::ReadError { step, source } => {
397                write!(f, "Error while reading bytes for {step}: {source}",)
398            }
399            DecodeBlockContentError::DecompressBlockError(e) => write!(f, "{e:?}"),
400            DecodeBlockContentError::BackendOverflow { step } => write!(
401                f,
402                "{step} block's decompressed payload exceeds the caller-provided output buffer",
403            ),
404        }
405    }
406}
407
408impl From<DecompressBlockError> for DecodeBlockContentError {
409    fn from(val: DecompressBlockError) -> Self {
410        Self::DecompressBlockError(val)
411    }
412}
413
414#[derive(Debug)]
415#[non_exhaustive]
416pub enum DecodeBufferError {
417    NotEnoughBytesInDictionary {
418        got: usize,
419        need: usize,
420    },
421    OffsetTooBig {
422        offset: usize,
423        buf_len: usize,
424    },
425    ZeroOffset,
426    /// Legacy unit variant kept for binary compatibility with earlier
427    /// snapshots of this enum. Not surfaced from any current
428    /// production path — `BufferBackend::try_extend` /
429    /// `try_extend_from_within` and the new `try_reserve` (used by
430    /// `DecodeBuffer::repeat`) carry their failures through the
431    /// richer [`Self::OutputBufferOverflow`] variant below, which
432    /// reports the offending `tail` / `requested` / `capacity`
433    /// triple. New code should pattern-match on
434    /// `OutputBufferOverflow`; this unit variant is retained to keep
435    /// the `#[non_exhaustive]` enum's existing discriminant set
436    /// stable.
437    BackendOverflow,
438    /// Repeat-side match copy would write past the writable tail of
439    /// a fixed-capacity backend (`UserSliceBackend`). Surfaced by
440    /// [`super::decode_buffer::DecodeBuffer::repeat`] / `_lookahead`
441    /// when the new `BufferBackend::try_reserve` rejects the
442    /// pre-write capacity check — keeping the safe public decode
443    /// APIs error-returning instead of panicking via the per-call
444    /// `assert!` inside `extend_from_within_unchecked`. Growable
445    /// backends (`FlatBuf`, `RingBuffer`) never produce this; their
446    /// `try_reserve` falls through to infallible `reserve`.
447    OutputBufferOverflow {
448        tail: usize,
449        requested: usize,
450        capacity: usize,
451    },
452}
453
454#[cfg(feature = "std")]
455impl std::error::Error for DecodeBufferError {}
456
457impl core::fmt::Display for DecodeBufferError {
458    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
459        match self {
460            DecodeBufferError::NotEnoughBytesInDictionary { got, need } => {
461                write!(
462                    f,
463                    "Need {need} bytes from the dictionary but it is only {got} bytes long",
464                )
465            }
466            DecodeBufferError::OffsetTooBig { offset, buf_len } => {
467                write!(f, "offset: {offset} bigger than buffer: {buf_len}",)
468            }
469            DecodeBufferError::ZeroOffset => {
470                write!(f, "Illegal offset: 0 found")
471            }
472            DecodeBufferError::BackendOverflow => {
473                write!(
474                    f,
475                    "Match repeat would overflow the output buffer's fixed capacity"
476                )
477            }
478            DecodeBufferError::OutputBufferOverflow {
479                tail,
480                requested,
481                capacity,
482            } => {
483                write!(
484                    f,
485                    "Match repeat would write past fixed-capacity buffer: tail={tail}, requested={requested}, capacity={capacity}"
486                )
487            }
488        }
489    }
490}
491
492#[derive(Debug)]
493#[non_exhaustive]
494pub enum DictionaryDecodeError {
495    BadMagicNum { got: [u8; 4] },
496    DictionaryTooSmall { got: usize, need: usize },
497    ZeroDictionaryId,
498    ZeroRepeatOffsetInDictionary { index: u8 },
499    FSETableError(FSETableError),
500    HuffmanTableError(HuffmanTableError),
501}
502
503#[cfg(feature = "std")]
504impl std::error::Error for DictionaryDecodeError {
505    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
506        match self {
507            DictionaryDecodeError::FSETableError(source) => Some(source),
508            DictionaryDecodeError::HuffmanTableError(source) => Some(source),
509            _ => None,
510        }
511    }
512}
513
514impl core::fmt::Display for DictionaryDecodeError {
515    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
516        match self {
517            DictionaryDecodeError::BadMagicNum { got } => {
518                write!(
519                    f,
520                    "Bad magic_num at start of the dictionary; Got: {:#04X?}, Expected: {:#04x?}",
521                    got,
522                    crate::decoding::dictionary::MAGIC_NUM,
523                )
524            }
525            DictionaryDecodeError::DictionaryTooSmall { got, need } => {
526                write!(
527                    f,
528                    "Dictionary is too small: got {got} bytes, need at least {need} bytes",
529                )
530            }
531            DictionaryDecodeError::ZeroDictionaryId => {
532                write!(f, "Dictionary id must be non-zero")
533            }
534            DictionaryDecodeError::ZeroRepeatOffsetInDictionary { index } => {
535                write!(f, "Dictionary repeat offset rep{index} must be non-zero")
536            }
537            DictionaryDecodeError::FSETableError(e) => write!(f, "{e:?}"),
538            DictionaryDecodeError::HuffmanTableError(e) => write!(f, "{e:?}"),
539        }
540    }
541}
542
543impl From<FSETableError> for DictionaryDecodeError {
544    fn from(val: FSETableError) -> Self {
545        Self::FSETableError(val)
546    }
547}
548
549impl From<HuffmanTableError> for DictionaryDecodeError {
550    fn from(val: HuffmanTableError) -> Self {
551        Self::HuffmanTableError(val)
552    }
553}
554
555#[derive(Debug)]
556#[non_exhaustive]
557pub enum FrameDecoderError {
558    ReadFrameHeaderError(ReadFrameHeaderError),
559    FrameHeaderError(FrameHeaderError),
560    WindowSizeTooBig {
561        requested: u64,
562    },
563    DictionaryDecodeError(DictionaryDecodeError),
564    FailedToReadBlockHeader(BlockHeaderReadError),
565    FailedToReadBlockBody(DecodeBlockContentError),
566    FailedToReadChecksum(Error),
567    NotYetInitialized,
568    FailedToInitialize(FrameHeaderError),
569    FailedToDrainDecodebuffer(Error),
570    FailedToSkipFrame,
571    TargetTooSmall,
572    /// Decoded block sizes don't sum to the frame's declared
573    /// `frame_content_size` (either a block claims to expand past
574    /// FCS, or the stream ends before reaching FCS). Indicates a
575    /// malformed or corrupt frame — distinct from
576    /// [`Self::TargetTooSmall`] (which is the caller's
577    /// responsibility) so callers can tell decoder-side issues
578    /// apart from their own buffer sizing mistakes.
579    FrameContentSizeMismatch {
580        declared: u64,
581        produced: u64,
582    },
583    /// The frame carried a trailing XXH64 content checksum and the decoder
584    /// was set to [`ContentChecksum::Verify`](crate::decoding::ContentChecksum::Verify),
585    /// but the digest computed over the decompressed output did not match the
586    /// stored value. Indicates corruption in the compressed stream or its
587    /// trailing checksum. `expected` is the value read from the frame tail;
588    /// `calculated` is the digest the decoder computed (both low 32 bits).
589    ChecksumMismatch {
590        expected: u32,
591        calculated: u32,
592    },
593    DictNotProvided {
594        dict_id: u32,
595    },
596    DictIdMismatch {
597        expected: u32,
598        provided: u32,
599    },
600    DictAlreadyRegistered {
601        dict_id: u32,
602    },
603    /// Frame header's `dict_id` did not match the value pinned via
604    /// `FrameDecoder::expect_dict_id`. Returned BEFORE any block
605    /// decode and BEFORE any output is produced — no XXH64 init,
606    /// no partial output. Scratch buffer allocation / reservation
607    /// for the decode pipeline happens during frame-header parsing,
608    /// which is already complete when this validation fires, so
609    /// the cost of scratch sizing is paid even on a mismatched
610    /// header. `expected` is the pinned value (`Some(0)` is
611    /// treated as "no dictionary expected", matching a frame whose
612    /// header omits the optional `Dictionary_ID` field); `found`
613    /// reports what the frame actually carried (`None` when the
614    /// header omits the field, `Some(id)` when it does not).
615    #[cfg(feature = "lsm")]
616    UnexpectedDictId {
617        expected: Option<u32>,
618        found: Option<u32>,
619    },
620    /// Frame header's raw `Window_Descriptor` byte did not match
621    /// the value pinned via `FrameDecoder::expect_window_descriptor`.
622    /// Returned BEFORE any block decode work. Single-segment frames
623    /// (which omit the `Window_Descriptor` byte from the wire) are
624    /// reported via `found: None` so callers can distinguish
625    /// "wrong descriptor" from "no descriptor on the wire".
626    #[cfg(feature = "lsm")]
627    UnexpectedWindowDescriptor {
628        expected: u8,
629        found: Option<u8>,
630    },
631    /// Block-precise variant of [`Self::FailedToReadBlockHeader`]: a block
632    /// header read failed and the decoder captured WHERE. `block_index` is
633    /// the 0-based index of the failing block in the frame; `frame_offset`
634    /// is the frame-absolute byte offset of that block's `Block_Header`
635    /// (matches `FrameEmitInfo.blocks[block_index].offset_in_frame` from the
636    /// encode side). Lets per-block recovery (ECC repair) target the one bad
637    /// block instead of re-fetching the whole frame.
638    #[cfg(feature = "lsm")]
639    FailedToReadBlockHeaderAt {
640        source: BlockHeaderReadError,
641        block_index: u32,
642        frame_offset: u32,
643    },
644    /// Block-precise variant of [`Self::FailedToReadBlockBody`]: a block
645    /// body decode failed. Carries the same `block_index` / `frame_offset`
646    /// coordinates plus the failing block's structural metadata
647    /// ([`FrameBlock`]) reconstructed from its header, so a consumer can
648    /// locate and repair exactly this block.
649    ///
650    /// [`FrameBlock`]: crate::encoding::frame_emit_info::FrameBlock
651    #[cfg(feature = "lsm")]
652    FailedToReadBlockBodyAt {
653        source: DecodeBlockContentError,
654        block_index: u32,
655        frame_offset: u32,
656        block: crate::encoding::frame_emit_info::FrameBlock,
657    },
658    /// `FrameDecoder::decode_blocks_partial` was called with
659    /// `start_block > end_block` (the half-open block range is
660    /// empty-or-inverted and cannot describe a valid subset). API
661    /// misuse, surfaced as `Err` rather than a `PartialDecode`
662    /// outcome — distinct from a corrupt-frame stop, which is
663    /// reported via `PartialDecode::stopped_at`.
664    #[cfg(feature = "lsm")]
665    InvalidBlockRange {
666        start_block: u32,
667        end_block: u32,
668    },
669    /// A resuming [`FrameDecoder::decode_blocks_partial`] was given a
670    /// `window_prime` (via [`ResumeInput`]) shorter than the match window the
671    /// resume block can reach back into. The resumed decode would read past the
672    /// primed history and silently mis-resolve matches, so it is rejected up
673    /// front. `got` is the supplied prime length; `need` is the required
674    /// minimum (`min(window_size, output_offset)`).
675    ///
676    /// [`FrameDecoder::decode_blocks_partial`]: crate::decoding::FrameDecoder::decode_blocks_partial
677    /// [`ResumeInput`]: crate::decoding::ResumeInput
678    #[cfg(feature = "lsm")]
679    ResumeWindowTooShort {
680        got: usize,
681        need: usize,
682    },
683    /// A resuming [`FrameDecoder::decode_blocks_partial`] was given a
684    /// [`ResumeInput`] whose [`ResumeState`] was captured from a frame with a
685    /// different decode-relevant shape (window size, dictionary id,
686    /// single-segment flag, content-checksum flag, or magicless mode) than the
687    /// frame currently [`reset`](crate::decoding::FrameDecoder::reset) into the
688    /// decoder. Applying entropy/repcode state across mismatched frames would
689    /// yield byte-wrong output, so it is rejected up front.
690    ///
691    /// [`FrameDecoder::decode_blocks_partial`]: crate::decoding::FrameDecoder::decode_blocks_partial
692    /// [`ResumeInput`]: crate::decoding::ResumeInput
693    /// [`ResumeState`]: crate::decoding::ResumeState
694    #[cfg(feature = "lsm")]
695    ResumeFrameMismatch,
696}
697
698#[cfg(feature = "std")]
699impl StdError for FrameDecoderError {
700    fn source(&self) -> Option<&(dyn StdError + 'static)> {
701        match self {
702            FrameDecoderError::ReadFrameHeaderError(source) => Some(source),
703            FrameDecoderError::FrameHeaderError(source) => Some(source),
704            FrameDecoderError::DictionaryDecodeError(source) => Some(source),
705            FrameDecoderError::FailedToReadBlockHeader(source) => Some(source),
706            FrameDecoderError::FailedToReadBlockBody(source) => Some(source),
707            #[cfg(feature = "lsm")]
708            FrameDecoderError::FailedToReadBlockHeaderAt { source, .. } => Some(source),
709            #[cfg(feature = "lsm")]
710            FrameDecoderError::FailedToReadBlockBodyAt { source, .. } => Some(source),
711            FrameDecoderError::FailedToReadChecksum(source) => Some(source),
712            FrameDecoderError::FailedToInitialize(source) => Some(source),
713            FrameDecoderError::FailedToDrainDecodebuffer(source) => Some(source),
714            _ => None,
715        }
716    }
717}
718
719impl core::fmt::Display for FrameDecoderError {
720    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> ::core::fmt::Result {
721        match self {
722            FrameDecoderError::ReadFrameHeaderError(e) => {
723                write!(f, "{e:?}")
724            }
725            FrameDecoderError::FrameHeaderError(e) => {
726                write!(f, "{e:?}")
727            }
728            FrameDecoderError::WindowSizeTooBig { requested } => {
729                write!(
730                    f,
731                    "Specified window_size is too big; Requested: {}, Allowed: {}",
732                    requested,
733                    crate::common::MAXIMUM_ALLOWED_WINDOW_SIZE,
734                )
735            }
736            FrameDecoderError::DictionaryDecodeError(e) => {
737                write!(f, "{e:?}")
738            }
739            FrameDecoderError::FailedToReadBlockHeader(e) => {
740                write!(f, "Failed to parse/decode block body: {e}")
741            }
742            FrameDecoderError::FailedToReadBlockBody(e) => {
743                write!(f, "Failed to parse block header: {e}")
744            }
745            #[cfg(feature = "lsm")]
746            FrameDecoderError::FailedToReadBlockHeaderAt {
747                source,
748                block_index,
749                frame_offset,
750            } => {
751                write!(
752                    f,
753                    "Failed to read block header at block {block_index} (frame offset {frame_offset}): {source}"
754                )
755            }
756            #[cfg(feature = "lsm")]
757            FrameDecoderError::FailedToReadBlockBodyAt {
758                source,
759                block_index,
760                frame_offset,
761                ..
762            } => {
763                write!(
764                    f,
765                    "Failed to decode block body at block {block_index} (frame offset {frame_offset}): {source}"
766                )
767            }
768            FrameDecoderError::FailedToReadChecksum(e) => {
769                write!(f, "Failed to read checksum: {e}")
770            }
771            FrameDecoderError::NotYetInitialized => {
772                write!(f, "Decoder must initialized or reset before using it",)
773            }
774            FrameDecoderError::FailedToInitialize(e) => {
775                write!(f, "Decoder encountered error while initializing: {e}")
776            }
777            FrameDecoderError::FailedToDrainDecodebuffer(e) => {
778                write!(
779                    f,
780                    "Decoder encountered error while draining the decodebuffer: {e}",
781                )
782            }
783            FrameDecoderError::FailedToSkipFrame => {
784                write!(
785                    f,
786                    "Failed to skip bytes for the length given in the frame header"
787                )
788            }
789            FrameDecoderError::TargetTooSmall => {
790                write!(
791                    f,
792                    "Target must have at least as many bytes as the content size reported by the frame"
793                )
794            }
795            FrameDecoderError::FrameContentSizeMismatch { declared, produced } => {
796                write!(
797                    f,
798                    "Frame content size mismatch (corrupt frame): declared {declared} bytes, blocks summed to {produced} bytes"
799                )
800            }
801            FrameDecoderError::ChecksumMismatch {
802                expected,
803                calculated,
804            } => {
805                write!(
806                    f,
807                    "Content checksum mismatch (corrupt frame): frame stored 0x{expected:08X}, decoder calculated 0x{calculated:08X}"
808                )
809            }
810            FrameDecoderError::DictNotProvided { dict_id } => {
811                write!(
812                    f,
813                    "Frame header specified dictionary id 0x{dict_id:X} that wasn't provided via add_dict()/add_dict_from_bytes() (or add_dict_handle() on atomic targets) or reset_with_dict_handle()/decode_all_with_dict_handle()/decode_all_with_dict_bytes()"
814                )
815            }
816            FrameDecoderError::DictIdMismatch { expected, provided } => {
817                write!(
818                    f,
819                    "Frame header dictionary id 0x{expected:X} does not match provided dictionary id 0x{provided:X}"
820                )
821            }
822            FrameDecoderError::DictAlreadyRegistered { dict_id } => {
823                write!(
824                    f,
825                    "Dictionary id 0x{dict_id:X} already registered in decoder"
826                )
827            }
828            #[cfg(feature = "lsm")]
829            FrameDecoderError::UnexpectedDictId { expected, found } => {
830                write!(f, "Frame header dict_id mismatch: expected ")?;
831                match expected {
832                    Some(id) => write!(f, "0x{id:X}")?,
833                    None => write!(f, "<none>")?,
834                }
835                write!(f, ", found ")?;
836                match found {
837                    Some(id) => write!(f, "0x{id:X}"),
838                    None => write!(f, "<none>"),
839                }
840            }
841            #[cfg(feature = "lsm")]
842            FrameDecoderError::UnexpectedWindowDescriptor { expected, found } => {
843                write!(
844                    f,
845                    "Frame header window_descriptor mismatch: expected 0x{expected:02X}, found "
846                )?;
847                match found {
848                    Some(byte) => write!(f, "0x{byte:02X}"),
849                    None => write!(f, "<none> (single-segment frame omits window_descriptor)"),
850                }
851            }
852            #[cfg(feature = "lsm")]
853            FrameDecoderError::InvalidBlockRange {
854                start_block,
855                end_block,
856            } => {
857                write!(
858                    f,
859                    "Invalid block range for partial decode: start_block {start_block} > end_block {end_block}"
860                )
861            }
862            #[cfg(feature = "lsm")]
863            FrameDecoderError::ResumeWindowTooShort { got, need } => {
864                write!(
865                    f,
866                    "resume window_prime too short: got {got} bytes, need at least {need}"
867                )
868            }
869            #[cfg(feature = "lsm")]
870            FrameDecoderError::ResumeFrameMismatch => {
871                write!(
872                    f,
873                    "resume state was captured from a frame with a different decode shape than the current frame"
874                )
875            }
876        }
877    }
878}
879
880impl From<DictionaryDecodeError> for FrameDecoderError {
881    fn from(val: DictionaryDecodeError) -> Self {
882        Self::DictionaryDecodeError(val)
883    }
884}
885
886impl From<BlockHeaderReadError> for FrameDecoderError {
887    fn from(val: BlockHeaderReadError) -> Self {
888        Self::FailedToReadBlockHeader(val)
889    }
890}
891
892impl From<FrameHeaderError> for FrameDecoderError {
893    fn from(val: FrameHeaderError) -> Self {
894        Self::FrameHeaderError(val)
895    }
896}
897
898impl From<ReadFrameHeaderError> for FrameDecoderError {
899    fn from(val: ReadFrameHeaderError) -> Self {
900        Self::ReadFrameHeaderError(val)
901    }
902}
903
904#[derive(Debug)]
905#[non_exhaustive]
906pub enum DecompressLiteralsError {
907    MissingCompressedSize,
908    MissingNumStreams,
909    GetBitsError(GetBitsError),
910    HuffmanTableError(HuffmanTableError),
911    HuffmanDecoderError(HuffmanDecoderError),
912    UninitializedHuffmanTable,
913    MissingBytesForJumpHeader { got: usize },
914    MissingBytesForLiterals { got: usize, needed: usize },
915    ExtraPadding { skipped_bits: i32 },
916    BitstreamReadMismatch { read_til: isize, expected: isize },
917    DecodedLiteralCountMismatch { decoded: usize, expected: usize },
918}
919
920#[cfg(feature = "std")]
921impl std::error::Error for DecompressLiteralsError {
922    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
923        match self {
924            DecompressLiteralsError::GetBitsError(source) => Some(source),
925            DecompressLiteralsError::HuffmanTableError(source) => Some(source),
926            DecompressLiteralsError::HuffmanDecoderError(source) => Some(source),
927            _ => None,
928        }
929    }
930}
931impl core::fmt::Display for DecompressLiteralsError {
932    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
933        match self {
934            DecompressLiteralsError::MissingCompressedSize => {
935                write!(
936                    f,
937                    "compressed size was none even though it must be set to something for compressed literals",
938                )
939            }
940            DecompressLiteralsError::MissingNumStreams => {
941                write!(
942                    f,
943                    "num_streams was none even though it must be set to something (1 or 4) for compressed literals",
944                )
945            }
946            DecompressLiteralsError::GetBitsError(e) => write!(f, "{e:?}"),
947            DecompressLiteralsError::HuffmanTableError(e) => write!(f, "{e:?}"),
948            DecompressLiteralsError::HuffmanDecoderError(e) => write!(f, "{e:?}"),
949            DecompressLiteralsError::UninitializedHuffmanTable => {
950                write!(
951                    f,
952                    "Tried to reuse huffman table but it was never initialized",
953                )
954            }
955            DecompressLiteralsError::MissingBytesForJumpHeader { got } => {
956                write!(f, "Need 6 bytes to decode jump header, got {got} bytes",)
957            }
958            DecompressLiteralsError::MissingBytesForLiterals { got, needed } => {
959                write!(
960                    f,
961                    "Need at least {needed} bytes to decode literals. Have: {got} bytes",
962                )
963            }
964            DecompressLiteralsError::ExtraPadding { skipped_bits } => {
965                write!(
966                    f,
967                    "Padding at the end of the sequence_section was more than a byte long: {skipped_bits} bits. Probably caused by data corruption",
968                )
969            }
970            DecompressLiteralsError::BitstreamReadMismatch { read_til, expected } => {
971                write!(
972                    f,
973                    "Bitstream was read till: {read_til}, should have been: {expected}",
974                )
975            }
976            DecompressLiteralsError::DecodedLiteralCountMismatch { decoded, expected } => {
977                write!(
978                    f,
979                    "Did not decode enough literals: {decoded}, Should have been: {expected}",
980                )
981            }
982        }
983    }
984}
985
986impl From<HuffmanDecoderError> for DecompressLiteralsError {
987    fn from(val: HuffmanDecoderError) -> Self {
988        Self::HuffmanDecoderError(val)
989    }
990}
991
992impl From<GetBitsError> for DecompressLiteralsError {
993    fn from(val: GetBitsError) -> Self {
994        Self::GetBitsError(val)
995    }
996}
997
998impl From<HuffmanTableError> for DecompressLiteralsError {
999    fn from(val: HuffmanTableError) -> Self {
1000        Self::HuffmanTableError(val)
1001    }
1002}
1003
1004#[derive(Debug)]
1005#[non_exhaustive]
1006pub enum ExecuteSequencesError {
1007    DecodebufferError(DecodeBufferError),
1008    NotEnoughBytesForSequence {
1009        wanted: usize,
1010        have: usize,
1011    },
1012    ZeroOffset,
1013    /// A donor-shape inline sequence (`BufferBackend::exec_sequence_inline`)
1014    /// would have written past the writable tail of a fixed-size backend
1015    /// (`UserSliceBackend`). Indicates the frame is corrupt — its sequences
1016    /// expand past the declared `frame_content_size` plus the caller-supplied
1017    /// `WILDCOPY_OVERLENGTH` slack. The fast-path check is per-sequence; the
1018    /// post-block FCS overflow check would also catch the same shape, but the
1019    /// per-sequence guard is what keeps the unsafe write surface inside the
1020    /// user-provided slice on the way to the post-block check.
1021    OutputBufferOverflow {
1022        tail: usize,
1023        requested: usize,
1024        capacity: usize,
1025    },
1026}
1027
1028impl core::fmt::Display for ExecuteSequencesError {
1029    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
1030        match self {
1031            ExecuteSequencesError::DecodebufferError(e) => {
1032                write!(f, "{e:?}")
1033            }
1034            ExecuteSequencesError::NotEnoughBytesForSequence { wanted, have } => {
1035                write!(
1036                    f,
1037                    "Sequence wants to copy up to byte {wanted}. Bytes in literalsbuffer: {have}"
1038                )
1039            }
1040            ExecuteSequencesError::ZeroOffset => {
1041                write!(f, "Illegal offset: 0 found")
1042            }
1043            ExecuteSequencesError::OutputBufferOverflow {
1044                tail,
1045                requested,
1046                capacity,
1047            } => {
1048                write!(
1049                    f,
1050                    "Donor-path sequence would write past fixed-size buffer: tail={tail}, requested={requested}, capacity={capacity}"
1051                )
1052            }
1053        }
1054    }
1055}
1056
1057#[cfg(feature = "std")]
1058impl std::error::Error for ExecuteSequencesError {
1059    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
1060        match self {
1061            ExecuteSequencesError::DecodebufferError(source) => Some(source),
1062            _ => None,
1063        }
1064    }
1065}
1066
1067impl From<DecodeBufferError> for ExecuteSequencesError {
1068    fn from(val: DecodeBufferError) -> Self {
1069        Self::DecodebufferError(val)
1070    }
1071}
1072
1073impl From<crate::decoding::buffer_backend::BackendOverflow> for ExecuteSequencesError {
1074    fn from(val: crate::decoding::buffer_backend::BackendOverflow) -> Self {
1075        Self::OutputBufferOverflow {
1076            tail: val.tail,
1077            requested: val.requested,
1078            capacity: val.capacity,
1079        }
1080    }
1081}
1082
1083impl ExecuteSequencesError {
1084    /// `Some(requested)` when this error is a fixed-capacity output-buffer
1085    /// overshoot from the Compressed-block sequence executor — either the
1086    /// donor-inline path ([`Self::OutputBufferOverflow`]) or the
1087    /// match-repeat fallback ([`DecodeBufferError::OutputBufferOverflow`]
1088    /// wrapped in [`Self::DecodebufferError`]). `requested` is the byte
1089    /// count the failing write tried to append past the slice end.
1090    ///
1091    /// `None` for every non-overflow variant. Used by
1092    /// `FrameDecoder::run_direct_decode` to fold an in-block Compressed
1093    /// overshoot into the same `FrameContentSizeMismatch` contract the
1094    /// Raw/RLE [`DecodeBlockContentError::BackendOverflow`] arm already
1095    /// produces — both mean "the frame's content expands past the
1096    /// declared `frame_content_size`".
1097    pub(crate) fn output_overflow_requested(&self) -> Option<usize> {
1098        match self {
1099            ExecuteSequencesError::OutputBufferOverflow { requested, .. } => Some(*requested),
1100            ExecuteSequencesError::DecodebufferError(DecodeBufferError::OutputBufferOverflow {
1101                requested,
1102                ..
1103            }) => Some(*requested),
1104            _ => None,
1105        }
1106    }
1107}
1108
1109#[derive(Debug)]
1110#[non_exhaustive]
1111pub enum DecodeSequenceError {
1112    GetBitsError(GetBitsError),
1113    FSEDecoderError(FSEDecoderError),
1114    FSETableError(FSETableError),
1115    ExtraPadding {
1116        skipped_bits: i32,
1117    },
1118    UnsupportedOffset {
1119        offset_code: u8,
1120    },
1121    ZeroOffset,
1122    NotEnoughBytesForNumSequences,
1123    ExtraBits {
1124        bits_remaining: isize,
1125    },
1126    MissingCompressionMode,
1127    MissingByteForRleLlTable,
1128    MissingByteForRleOfTable,
1129    MissingByteForRleMlTable,
1130    /// An RLE-mode sequence table's single symbol code is out of range
1131    /// for its axis (LL/ML/OF). `axis` names the axis; `code` is the
1132    /// offending value read from the stream.
1133    InvalidRleCode {
1134        axis: &'static str,
1135        code: u8,
1136    },
1137}
1138
1139#[cfg(feature = "std")]
1140impl std::error::Error for DecodeSequenceError {
1141    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
1142        match self {
1143            DecodeSequenceError::GetBitsError(source) => Some(source),
1144            DecodeSequenceError::FSEDecoderError(source) => Some(source),
1145            DecodeSequenceError::FSETableError(source) => Some(source),
1146            _ => None,
1147        }
1148    }
1149}
1150
1151impl core::fmt::Display for DecodeSequenceError {
1152    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
1153        match self {
1154            DecodeSequenceError::GetBitsError(e) => write!(f, "{e:?}"),
1155            DecodeSequenceError::FSEDecoderError(e) => write!(f, "{e:?}"),
1156            DecodeSequenceError::FSETableError(e) => write!(f, "{e:?}"),
1157            DecodeSequenceError::ExtraPadding { skipped_bits } => {
1158                write!(
1159                    f,
1160                    "Padding at the end of the sequence_section was more than a byte long: {skipped_bits} bits. Probably caused by data corruption",
1161                )
1162            }
1163            DecodeSequenceError::UnsupportedOffset { offset_code } => {
1164                write!(
1165                    f,
1166                    "Do not support offsets bigger than 1<<32; got: {offset_code}",
1167                )
1168            }
1169            DecodeSequenceError::ZeroOffset => write!(
1170                f,
1171                "Read an offset == 0. That is an illegal value for offsets"
1172            ),
1173            DecodeSequenceError::NotEnoughBytesForNumSequences => write!(
1174                f,
1175                "Bytestream did not contain enough bytes to decode num_sequences"
1176            ),
1177            DecodeSequenceError::ExtraBits { bits_remaining } => write!(f, "{bits_remaining}"),
1178            DecodeSequenceError::MissingCompressionMode => write!(
1179                f,
1180                "compression modes are none but they must be set to something"
1181            ),
1182            DecodeSequenceError::MissingByteForRleLlTable => {
1183                write!(f, "Need a byte to read for RLE ll table")
1184            }
1185            DecodeSequenceError::MissingByteForRleOfTable => {
1186                write!(f, "Need a byte to read for RLE of table")
1187            }
1188            DecodeSequenceError::MissingByteForRleMlTable => {
1189                write!(f, "Need a byte to read for RLE ml table")
1190            }
1191            DecodeSequenceError::InvalidRleCode { axis, code } => {
1192                write!(f, "RLE {axis} table code {code} is out of range")
1193            }
1194        }
1195    }
1196}
1197
1198impl From<GetBitsError> for DecodeSequenceError {
1199    fn from(val: GetBitsError) -> Self {
1200        Self::GetBitsError(val)
1201    }
1202}
1203
1204impl From<FSETableError> for DecodeSequenceError {
1205    fn from(val: FSETableError) -> Self {
1206        Self::FSETableError(val)
1207    }
1208}
1209
1210impl From<FSEDecoderError> for DecodeSequenceError {
1211    fn from(val: FSEDecoderError) -> Self {
1212        Self::FSEDecoderError(val)
1213    }
1214}
1215
1216#[derive(Debug)]
1217#[non_exhaustive]
1218pub enum LiteralsSectionParseError {
1219    IllegalLiteralSectionType { got: u8 },
1220    GetBitsError(GetBitsError),
1221    NotEnoughBytes { have: usize, need: u8 },
1222}
1223
1224#[cfg(feature = "std")]
1225impl std::error::Error for LiteralsSectionParseError {
1226    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
1227        match self {
1228            LiteralsSectionParseError::GetBitsError(source) => Some(source),
1229            _ => None,
1230        }
1231    }
1232}
1233impl core::fmt::Display for LiteralsSectionParseError {
1234    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
1235        match self {
1236            LiteralsSectionParseError::IllegalLiteralSectionType { got } => {
1237                write!(
1238                    f,
1239                    "Illegal literalssectiontype. Is: {got}, must be in: 0, 1, 2, 3"
1240                )
1241            }
1242            LiteralsSectionParseError::GetBitsError(e) => write!(f, "{e:?}"),
1243            LiteralsSectionParseError::NotEnoughBytes { have, need } => {
1244                write!(
1245                    f,
1246                    "Not enough byte to parse the literals section header. Have: {have}, Need: {need}",
1247                )
1248            }
1249        }
1250    }
1251}
1252
1253impl From<GetBitsError> for LiteralsSectionParseError {
1254    fn from(val: GetBitsError) -> Self {
1255        Self::GetBitsError(val)
1256    }
1257}
1258
1259impl core::fmt::Display for LiteralsSectionType {
1260    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> Result<(), core::fmt::Error> {
1261        match self {
1262            LiteralsSectionType::Compressed => write!(f, "Compressed"),
1263            LiteralsSectionType::Raw => write!(f, "Raw"),
1264            LiteralsSectionType::RLE => write!(f, "RLE"),
1265            LiteralsSectionType::Treeless => write!(f, "Treeless"),
1266        }
1267    }
1268}
1269
1270#[derive(Debug)]
1271#[non_exhaustive]
1272pub enum SequencesHeaderParseError {
1273    NotEnoughBytes { need_at_least: u8, got: usize },
1274}
1275
1276#[cfg(feature = "std")]
1277impl std::error::Error for SequencesHeaderParseError {}
1278
1279impl core::fmt::Display for SequencesHeaderParseError {
1280    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
1281        match self {
1282            SequencesHeaderParseError::NotEnoughBytes { need_at_least, got } => {
1283                write!(
1284                    f,
1285                    "source must have at least {need_at_least} bytes to parse header; got {got} bytes",
1286                )
1287            }
1288        }
1289    }
1290}
1291
1292#[derive(Debug)]
1293#[non_exhaustive]
1294pub enum FSETableError {
1295    AccLogIsZero,
1296    AccLogTooBig {
1297        got: u8,
1298        max: u8,
1299    },
1300    GetBitsError(GetBitsError),
1301    ProbabilityCounterMismatch {
1302        got: u32,
1303        expected_sum: u32,
1304        symbol_probabilities: Vec<i32>,
1305    },
1306    TooManySymbols {
1307        got: usize,
1308    },
1309    /// Probability value outside the RFC 8878 §4.1.1 allowed set
1310    /// `{-1, 0, 1..=table_size}`. Carries the violating value, the
1311    /// table size (`1 << accuracy_log`) and `accuracy_log` so the
1312    /// caller can pinpoint the failure without re-deriving the bound.
1313    InvalidProbability {
1314        value: i32,
1315        table_size: u32,
1316        accuracy_log: u8,
1317    },
1318    /// `calc_baseline_and_numbits` produced a state-entry whose bit
1319    /// width exceeds the table's accuracy log, violating the
1320    /// `new_state + (1 << num_bits) - 1 < table_size` invariant that
1321    /// the unchecked `read_entry` decode hot path relies on. The
1322    /// triggering probability is in-range per RFC 8878 §4.1.1; the
1323    /// failure is an internal table-shape inconsistency surfaced
1324    /// against the public `build_from_probabilities` API.
1325    TableInvariantViolation {
1326        prob: i32,
1327        symbol: u8,
1328        num_bits: u8,
1329        accuracy_log: u8,
1330    },
1331}
1332
1333#[cfg(feature = "std")]
1334impl std::error::Error for FSETableError {
1335    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
1336        match self {
1337            FSETableError::GetBitsError(source) => Some(source),
1338            _ => None,
1339        }
1340    }
1341}
1342
1343impl core::fmt::Display for FSETableError {
1344    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
1345        match self {
1346            FSETableError::AccLogIsZero => write!(f, "Acclog must be at least 1"),
1347            FSETableError::AccLogTooBig { got, max } => {
1348                write!(
1349                    f,
1350                    "Found FSE acc_log: {got} bigger than allowed maximum in this case: {max}"
1351                )
1352            }
1353            FSETableError::GetBitsError(e) => write!(f, "{e:?}"),
1354            FSETableError::ProbabilityCounterMismatch {
1355                got,
1356                expected_sum,
1357                symbol_probabilities,
1358            } => {
1359                write!(
1360                    f,
1361                    "FSE probability sum mismatch: got {got}, expected {expected_sum}. Indicates corrupted data or an invalid distribution\n {symbol_probabilities:?}",
1362                )
1363            }
1364            FSETableError::TooManySymbols { got } => {
1365                write!(
1366                    f,
1367                    "There are too many symbols in this distribution: {got}. Max: 256",
1368                )
1369            }
1370            FSETableError::InvalidProbability {
1371                value,
1372                table_size,
1373                accuracy_log,
1374            } => {
1375                write!(
1376                    f,
1377                    "FSE probability value {value} is outside the RFC 8878 allowed set (must be -1, 0, or in 1..={table_size}; accuracy_log={accuracy_log})",
1378                )
1379            }
1380            FSETableError::TableInvariantViolation {
1381                prob,
1382                symbol,
1383                num_bits,
1384                accuracy_log,
1385            } => {
1386                write!(
1387                    f,
1388                    "FSE table invariant violation: symbol {symbol} (prob {prob}) produced num_bits {num_bits} > accuracy_log {accuracy_log}",
1389                )
1390            }
1391        }
1392    }
1393}
1394
1395impl From<GetBitsError> for FSETableError {
1396    fn from(val: GetBitsError) -> Self {
1397        Self::GetBitsError(val)
1398    }
1399}
1400
1401#[derive(Debug)]
1402#[non_exhaustive]
1403pub enum FSEDecoderError {
1404    GetBitsError(GetBitsError),
1405    TableIsUninitialized,
1406    /// Externally constructed `FSETable` violates the
1407    /// `decode.len() == 1 << accuracy_log` shape invariant. Only
1408    /// reachable under `feature = "fuzz_exports"`, where fuzz
1409    /// harnesses can set the `FSETable.decode` / `accuracy_log`
1410    /// fields directly and skip `build_decoding_table`.
1411    InvalidTableShape {
1412        decode_len: usize,
1413        accuracy_log: u8,
1414    },
1415}
1416
1417#[cfg(feature = "std")]
1418impl std::error::Error for FSEDecoderError {
1419    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
1420        match self {
1421            FSEDecoderError::GetBitsError(source) => Some(source),
1422            _ => None,
1423        }
1424    }
1425}
1426
1427impl core::fmt::Display for FSEDecoderError {
1428    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
1429        match self {
1430            FSEDecoderError::GetBitsError(e) => write!(f, "{e:?}"),
1431            FSEDecoderError::TableIsUninitialized => {
1432                write!(f, "Tried to use an uninitialized table!")
1433            }
1434            FSEDecoderError::InvalidTableShape {
1435                decode_len,
1436                accuracy_log,
1437            } => match 1usize.checked_shl((*accuracy_log).into()) {
1438                Some(expected) => write!(
1439                    f,
1440                    "FSETable shape invariant violated: decode.len() = {decode_len}, expected 1 << accuracy_log = {expected} (accuracy_log = {accuracy_log})",
1441                ),
1442                None => write!(
1443                    f,
1444                    "FSETable shape invariant violated: decode.len() = {decode_len}, accuracy_log = {accuracy_log} overflows 1 << accuracy_log for usize",
1445                ),
1446            },
1447        }
1448    }
1449}
1450
1451impl From<GetBitsError> for FSEDecoderError {
1452    fn from(val: GetBitsError) -> Self {
1453        Self::GetBitsError(val)
1454    }
1455}
1456
1457#[derive(Debug)]
1458#[non_exhaustive]
1459pub enum HuffmanTableError {
1460    GetBitsError(GetBitsError),
1461    FSEDecoderError(FSEDecoderError),
1462    FSETableError(FSETableError),
1463    SourceIsEmpty,
1464    NotEnoughBytesForWeights {
1465        got_bytes: usize,
1466        expected_bytes: u8,
1467    },
1468    ExtraPadding {
1469        skipped_bits: i32,
1470    },
1471    TooManyWeights {
1472        got: usize,
1473    },
1474    MissingWeights,
1475    LeftoverIsNotAPowerOf2 {
1476        got: u32,
1477    },
1478    NotEnoughBytesToDecompressWeights {
1479        have: usize,
1480        need: usize,
1481    },
1482    FSETableUsedTooManyBytes {
1483        used: usize,
1484        available_bytes: u8,
1485    },
1486    NotEnoughBytesInSource {
1487        got: usize,
1488        need: usize,
1489    },
1490    WeightBiggerThanMaxNumBits {
1491        got: u8,
1492    },
1493    MaxBitsTooHigh {
1494        got: u8,
1495    },
1496}
1497
1498#[cfg(feature = "std")]
1499impl StdError for HuffmanTableError {
1500    fn source(&self) -> Option<&(dyn StdError + 'static)> {
1501        match self {
1502            HuffmanTableError::GetBitsError(source) => Some(source),
1503            HuffmanTableError::FSEDecoderError(source) => Some(source),
1504            HuffmanTableError::FSETableError(source) => Some(source),
1505            _ => None,
1506        }
1507    }
1508}
1509
1510impl core::fmt::Display for HuffmanTableError {
1511    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> ::core::fmt::Result {
1512        match self {
1513            HuffmanTableError::GetBitsError(e) => write!(f, "{e:?}"),
1514            HuffmanTableError::FSEDecoderError(e) => write!(f, "{e:?}"),
1515            HuffmanTableError::FSETableError(e) => write!(f, "{e:?}"),
1516            HuffmanTableError::SourceIsEmpty => write!(f, "Source needs to have at least one byte"),
1517            HuffmanTableError::NotEnoughBytesForWeights {
1518                got_bytes,
1519                expected_bytes,
1520            } => {
1521                write!(
1522                    f,
1523                    "Header says there should be {expected_bytes} bytes for the weights but there are only {got_bytes} bytes in the stream"
1524                )
1525            }
1526            HuffmanTableError::ExtraPadding { skipped_bits } => {
1527                write!(
1528                    f,
1529                    "Padding at the end of the sequence_section was more than a byte long: {skipped_bits} bits. Probably caused by data corruption",
1530                )
1531            }
1532            HuffmanTableError::TooManyWeights { got } => {
1533                write!(
1534                    f,
1535                    "More than 255 weights decoded (got {got} weights). Stream is probably corrupted",
1536                )
1537            }
1538            HuffmanTableError::MissingWeights => {
1539                write!(f, "Can\'t build huffman table without any weights")
1540            }
1541            HuffmanTableError::LeftoverIsNotAPowerOf2 { got } => {
1542                write!(f, "Leftover must be power of two but is: {got}")
1543            }
1544            HuffmanTableError::NotEnoughBytesToDecompressWeights { have, need } => {
1545                write!(
1546                    f,
1547                    "Not enough bytes in stream to decompress weights. Is: {have}, Should be: {need}",
1548                )
1549            }
1550            HuffmanTableError::FSETableUsedTooManyBytes {
1551                used,
1552                available_bytes,
1553            } => {
1554                write!(
1555                    f,
1556                    "FSE table used more bytes: {used} than were meant to be used for the whole stream of huffman weights ({available_bytes})",
1557                )
1558            }
1559            HuffmanTableError::NotEnoughBytesInSource { got, need } => {
1560                write!(f, "Source needs to have at least {need} bytes, got: {got}",)
1561            }
1562            HuffmanTableError::WeightBiggerThanMaxNumBits { got } => {
1563                write!(
1564                    f,
1565                    "Cant have weight: {} bigger than max_num_bits: {}",
1566                    got,
1567                    crate::huff0::MAX_MAX_NUM_BITS,
1568                )
1569            }
1570            HuffmanTableError::MaxBitsTooHigh { got } => {
1571                write!(
1572                    f,
1573                    "max_bits derived from weights is: {} should be lower than: {}",
1574                    got,
1575                    crate::huff0::MAX_MAX_NUM_BITS,
1576                )
1577            }
1578        }
1579    }
1580}
1581
1582impl From<GetBitsError> for HuffmanTableError {
1583    fn from(val: GetBitsError) -> Self {
1584        Self::GetBitsError(val)
1585    }
1586}
1587
1588impl From<FSEDecoderError> for HuffmanTableError {
1589    fn from(val: FSEDecoderError) -> Self {
1590        Self::FSEDecoderError(val)
1591    }
1592}
1593
1594impl From<FSETableError> for HuffmanTableError {
1595    fn from(val: FSETableError) -> Self {
1596        Self::FSETableError(val)
1597    }
1598}
1599
1600#[derive(Debug)]
1601#[non_exhaustive]
1602pub enum HuffmanDecoderError {
1603    GetBitsError(GetBitsError),
1604}
1605
1606impl core::fmt::Display for HuffmanDecoderError {
1607    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
1608        match self {
1609            HuffmanDecoderError::GetBitsError(e) => write!(f, "{e:?}"),
1610        }
1611    }
1612}
1613
1614#[cfg(feature = "std")]
1615impl StdError for HuffmanDecoderError {
1616    fn source(&self) -> Option<&(dyn StdError + 'static)> {
1617        match self {
1618            HuffmanDecoderError::GetBitsError(source) => Some(source),
1619        }
1620    }
1621}
1622
1623impl From<GetBitsError> for HuffmanDecoderError {
1624    fn from(val: GetBitsError) -> Self {
1625        Self::GetBitsError(val)
1626    }
1627}
1628
1629#[cfg(test)]
1630mod tests {
1631    use alloc::{string::ToString, vec};
1632
1633    use super::{
1634        BlockTypeError, DecodeBlockContentError, DecodeBufferError, DecodeSequenceError,
1635        DecompressBlockError, DecompressLiteralsError, ExecuteSequencesError, FSETableError,
1636        FrameDecoderError, HuffmanTableError,
1637    };
1638
1639    #[test]
1640    fn execute_sequences_output_overflow_requested_covers_all_arms() {
1641        // #246: `run_direct_decode` folds a Compressed-block overshoot into
1642        // `FrameContentSizeMismatch` by reading `requested` from whichever
1643        // overflow shape the executor produced. Cover all three arms:
1644        //   1. donor-inline path -> `OutputBufferOverflow` directly,
1645        //   2. match-repeat path -> `DecodebufferError(OutputBufferOverflow)`,
1646        //   3. any other variant -> None (no fold).
1647        let inline = ExecuteSequencesError::OutputBufferOverflow {
1648            tail: 10,
1649            requested: 7,
1650            capacity: 12,
1651        };
1652        assert_eq!(inline.output_overflow_requested(), Some(7));
1653
1654        let repeat =
1655            ExecuteSequencesError::DecodebufferError(DecodeBufferError::OutputBufferOverflow {
1656                tail: 3,
1657                requested: 99,
1658                capacity: 4,
1659            });
1660        assert_eq!(repeat.output_overflow_requested(), Some(99));
1661
1662        // Non-overflow variants (and non-overflow DecodeBufferError) -> None.
1663        assert_eq!(
1664            ExecuteSequencesError::ZeroOffset.output_overflow_requested(),
1665            None
1666        );
1667        assert_eq!(
1668            ExecuteSequencesError::DecodebufferError(DecodeBufferError::ZeroOffset)
1669                .output_overflow_requested(),
1670            None
1671        );
1672    }
1673
1674    #[test]
1675    fn block_and_sequence_display_messages_are_specific() {
1676        assert_eq!(
1677            BlockTypeError::InvalidBlocktypeNumber { num: 7 }.to_string(),
1678            "Invalid Blocktype number. Is: 7. Should be one of: 0, 1, 2, 3 (3 is reserved)."
1679        );
1680        assert_eq!(
1681            DecompressBlockError::MalformedSectionHeader {
1682                expected_len: 12,
1683                remaining_bytes: 3,
1684            }
1685            .to_string(),
1686            "Malformed section header. Says literals would be this long: 12 but there are only 3 bytes left"
1687        );
1688        assert_eq!(
1689            DecodeBlockContentError::ExpectedHeaderOfPreviousBlock.to_string(),
1690            "Can't decode next block body, while expecting to decode the header of the previous block. Results will be nonsense"
1691        );
1692        assert_eq!(
1693            DecodeSequenceError::ExtraPadding { skipped_bits: 11 }.to_string(),
1694            "Padding at the end of the sequence_section was more than a byte long: 11 bits. Probably caused by data corruption"
1695        );
1696    }
1697
1698    #[test]
1699    fn frame_decoder_display_messages_are_specific() {
1700        assert_eq!(
1701            FrameDecoderError::TargetTooSmall.to_string(),
1702            "Target must have at least as many bytes as the content size reported by the frame"
1703        );
1704        assert_eq!(
1705            FrameDecoderError::DictNotProvided { dict_id: 0xABCD }.to_string(),
1706            "Frame header specified dictionary id 0xABCD that wasn't provided via add_dict()/add_dict_from_bytes() (or add_dict_handle() on atomic targets) or reset_with_dict_handle()/decode_all_with_dict_handle()/decode_all_with_dict_bytes()"
1707        );
1708        assert_eq!(
1709            FrameDecoderError::DictIdMismatch {
1710                expected: 0xABCD,
1711                provided: 0x1234
1712            }
1713            .to_string(),
1714            "Frame header dictionary id 0xABCD does not match provided dictionary id 0x1234"
1715        );
1716        assert_eq!(
1717            FrameDecoderError::DictAlreadyRegistered { dict_id: 0xABCD }.to_string(),
1718            "Dictionary id 0xABCD already registered in decoder"
1719        );
1720        assert_eq!(
1721            FrameDecoderError::FrameContentSizeMismatch {
1722                declared: 100,
1723                produced: 87,
1724            }
1725            .to_string(),
1726            "Frame content size mismatch (corrupt frame): declared 100 bytes, blocks summed to 87 bytes"
1727        );
1728        // Locks the wasm-exposed checksum-mismatch contract (exact string).
1729        assert_eq!(
1730            FrameDecoderError::ChecksumMismatch {
1731                expected: 0xDEAD_BEEF,
1732                calculated: 0x0BAD_F00D,
1733            }
1734            .to_string(),
1735            "Content checksum mismatch (corrupt frame): frame stored 0xDEADBEEF, decoder calculated 0x0BADF00D"
1736        );
1737    }
1738
1739    #[test]
1740    fn decode_block_content_backend_overflow_display_names_the_step() {
1741        use crate::blocks::block::BlockType;
1742        assert_eq!(
1743            DecodeBlockContentError::BackendOverflow {
1744                step: BlockType::RLE
1745            }
1746            .to_string(),
1747            "RLE block's decompressed payload exceeds the caller-provided output buffer"
1748        );
1749        assert_eq!(
1750            DecodeBlockContentError::BackendOverflow {
1751                step: BlockType::Raw
1752            }
1753            .to_string(),
1754            "Raw block's decompressed payload exceeds the caller-provided output buffer"
1755        );
1756    }
1757
1758    #[test]
1759    fn literal_display_messages_are_specific() {
1760        assert_eq!(
1761            DecompressLiteralsError::MissingCompressedSize.to_string(),
1762            "compressed size was none even though it must be set to something for compressed literals"
1763        );
1764        assert_eq!(
1765            DecompressLiteralsError::MissingNumStreams.to_string(),
1766            "num_streams was none even though it must be set to something (1 or 4) for compressed literals"
1767        );
1768        assert_eq!(
1769            DecompressLiteralsError::ExtraPadding { skipped_bits: 9 }.to_string(),
1770            "Padding at the end of the sequence_section was more than a byte long: 9 bits. Probably caused by data corruption"
1771        );
1772    }
1773
1774    #[test]
1775    fn fse_and_huffman_display_messages_are_specific() {
1776        assert_eq!(
1777            FSETableError::ProbabilityCounterMismatch {
1778                got: 4,
1779                expected_sum: 3,
1780                symbol_probabilities: vec![1, -1],
1781            }
1782            .to_string(),
1783            "FSE probability sum mismatch: got 4, expected 3. Indicates corrupted data or an invalid distribution\n [1, -1]"
1784        );
1785        assert_eq!(
1786            HuffmanTableError::NotEnoughBytesForWeights {
1787                got_bytes: 2,
1788                expected_bytes: 5,
1789            }
1790            .to_string(),
1791            "Header says there should be 5 bytes for the weights but there are only 2 bytes in the stream"
1792        );
1793        assert_eq!(
1794            HuffmanTableError::ExtraPadding { skipped_bits: 13 }.to_string(),
1795            "Padding at the end of the sequence_section was more than a byte long: 13 bits. Probably caused by data corruption"
1796        );
1797        assert_eq!(
1798            HuffmanTableError::FSETableUsedTooManyBytes {
1799                used: 7,
1800                available_bytes: 6,
1801            }
1802            .to_string(),
1803            "FSE table used more bytes: 7 than were meant to be used for the whole stream of huffman weights (6)"
1804        );
1805    }
1806}
structured_zstd/decoding/errors.rs

structured_zstd/decoding/
errors.rs
