zipatch-rs 1.4.0

/// All failures returned by parsing or applying a `ZiPatch` stream.
///
/// Both the parsing layer ([`crate::chunk`]) and the apply layer
/// ([`crate::apply`]) surface errors through this single enum, so callers
/// need only one error type in their `match` arms.
///
/// # Mapping from standard errors
///
/// - [`std::io::Error`] converts automatically via `#[from]` into [`ZiPatchError::Io`].
/// - [`std::string::FromUtf8Error`] converts automatically into [`ZiPatchError::Utf8Error`].
/// - [`binrw::Error`] converts automatically into [`ZiPatchError::BinrwError`].
///
/// # Example
///
/// ```rust
/// use zipatch_rs::ZiPatchError;
///
/// fn describe(e: &ZiPatchError) -> &'static str {
///     match e {
///         ZiPatchError::Io(_)               => "I/O error",
///         ZiPatchError::InvalidMagic        => "not a ZiPatch file",
///         ZiPatchError::UnknownChunkTag(_)  => "unrecognised chunk",
///         ZiPatchError::ChecksumMismatch {..}=> "corrupt chunk",
///         ZiPatchError::TruncatedPatch      => "download incomplete",
///         _                                 => "other error",
///     }
/// }
/// ```
#[non_exhaustive]
#[derive(Debug, thiserror::Error)]
pub enum ZiPatchError {
    /// Underlying I/O failure from the patch source or target filesystem.
    ///
    /// Raised by the parsing layer when reading from the patch stream fails
    /// (e.g. a network read error), and by the apply layer when any filesystem
    /// operation fails (open, seek, write, delete, create-dir).
    ///
    /// The wrapped [`std::io::Error`] carries the OS-level error code and kind.
    /// Use [`std::io::Error::kind`] to distinguish `NotFound`, `PermissionDenied`,
    /// and similar conditions.
    #[error("I/O error: {0}")]
    Io(#[from] std::io::Error),

    /// The 12-byte `ZiPatch` magic header was missing or did not match.
    ///
    /// Raised by [`ZiPatchReader::new`](crate::ZiPatchReader::new) and
    /// [`ZiPatchReader::from_path`](crate::ZiPatchReader::from_path) when
    /// the first 12 bytes of the source do not equal the expected magic
    /// sequence `\x91ZIPATCH\r\n\x1a\n`. Typically indicates the caller opened
    /// the wrong file, or the file is corrupted at the very start.
    #[error("invalid magic bytes")]
    InvalidMagic,

    /// A 4-byte chunk tag was not recognised by the parser.
    ///
    /// Raised by the chunk dispatcher in [`crate::chunk`] when a tag does not
    /// match any of `FHDR`, `APLY`, `APFS`, `ADIR`, `DELD`, `SQPK`, or
    /// `EOF_`. The raw tag bytes are preserved so callers can log them for
    /// diagnostic purposes.
    ///
    /// This can occur with genuinely new chunk types introduced by Square Enix
    /// in future patches. Upgrading the library or filing an issue is the
    /// appropriate response.
    #[error("unknown chunk tag: {0:?}")]
    UnknownChunkTag([u8; 4]),

    /// A SQPK sub-command byte was not recognised by the parser.
    ///
    /// Raised by the SQPK dispatcher in [`crate::chunk`] when the single-byte
    /// command code inside an `SQPK` chunk does not match any of the known
    /// values (`A`, `D`, `E`, `F`, `H`, `I`, `T`, `X`). The raw byte is
    /// preserved for diagnostics.
    #[error("unknown SQPK command: {0:#x}")]
    UnknownSqpkCommand(u8),

    /// A chunk's recorded CRC32 did not match the computed CRC32.
    ///
    /// Raised by the chunk framing code in [`crate::chunk`] when CRC32
    /// verification is enabled (the default) and the stored checksum in the
    /// patch stream does not match the checksum computed over `tag ++ body`.
    ///
    /// This indicates a corrupt or partially-written patch file. Disable
    /// verification with
    /// [`ZiPatchReader::skip_checksum_verification`](crate::ZiPatchReader::skip_checksum_verification)
    /// if the source has already been verified out-of-band.
    ///
    /// The `tag`, `expected`, and `actual` fields provide enough information
    /// to log a precise diagnostic message.
    #[error("CRC32 mismatch on chunk {tag:?}: expected {expected:#010x}, got {actual:#010x}")]
    ChecksumMismatch {
        /// Tag of the chunk whose checksum failed.
        tag: [u8; 4],
        /// CRC32 stored in the patch file.
        expected: u32,
        /// CRC32 computed over the actual chunk bytes.
        actual: u32,
    },

    /// DEFLATE decompression of a `SqpkFile` block failed.
    ///
    /// Raised by the `SqpkFile` apply logic when `flate2` cannot decompress
    /// a compressed block payload inside an `AddFile` operation. The wrapped
    /// [`std::io::Error`] is the decompressor's error, not a filesystem error;
    /// it is stored as a `#[source]` rather than `#[from]` to keep it distinct
    /// from [`ZiPatchError::Io`].
    #[error("decompression error")]
    Decompress(#[source] std::io::Error),

    /// A field value failed a parser invariant (e.g. negative size).
    ///
    /// Raised by chunk-specific parsers in [`crate::chunk`] when a field
    /// value is syntactically valid (i.e. could be parsed) but violates a
    /// semantic constraint required by the format — for example, a length
    /// field that is negative, or a size that overflows the expected range.
    ///
    /// The `context` string names the specific field that failed its check,
    /// giving enough information to locate the offending position in the
    /// binary format documentation.
    #[error("invalid field: {context}")]
    InvalidField {
        /// Human-readable description of which field was invalid and why.
        context: &'static str,
    },

    /// A chunk declared a size larger than the parser's maximum (512 MiB).
    ///
    /// Raised by the chunk framing code in [`crate::chunk`] when the
    /// `body_len` field of a chunk frame exceeds 512 MiB. This guard prevents
    /// allocating an arbitrarily large buffer from a malformed or malicious
    /// patch stream. The preserved size value can be logged for diagnostics.
    #[error("chunk size {0} exceeds maximum")]
    OversizedChunk(usize),

    /// A `SqpkFile` operation byte was not recognised.
    ///
    /// Raised by the `SqpkFile` parser when the single-byte `operation` field
    /// does not match any of `A` (`AddFile`), `R` (`RemoveAll`), `D` (`DeleteFile`),
    /// or `M` (`MakeDirTree`). The raw byte is preserved for diagnostics.
    #[error("unknown SqpkFile operation: {0:#02x}")]
    UnknownFileOperation(u8),

    /// A UTF-8 decode failed when reading a path or name field.
    ///
    /// Raised by the parsing layer when a length-prefixed byte string (e.g. a
    /// directory name in an `ADIR` chunk or a file path in a `SqpkFile` chunk)
    /// is not valid UTF-8. FFXIV patch paths are documented as ASCII, so this
    /// error indicates either a corrupt patch file or an undocumented encoding
    /// extension.
    #[error("UTF-8 decode error")]
    Utf8Error(#[from] std::string::FromUtf8Error),

    /// A `binrw` parser produced an error; wraps the underlying cause.
    ///
    /// Several chunk types (notably those using `#[derive(BinRead)]`) delegate
    /// their parsing to `binrw`. When `binrw` encounters an unexpected byte
    /// pattern or short read, it returns a [`binrw::Error`] which is wrapped
    /// here via `#[from]`.
    ///
    /// The inner error message usually identifies the field name and byte
    /// offset where parsing failed.
    #[error("binrw parse error: {0}")]
    BinrwError(#[from] binrw::Error),

    /// A `SqpkFile` carried a negative `file_offset` that cannot be applied.
    ///
    /// Raised by the `AddFile` arm of the `SqpkFile` apply logic when
    /// `cmd.file_offset` is negative and therefore cannot be converted to a
    /// [`u64`] seek position. The wire format stores this field as `i64`;
    /// a non-negative value is the invariant required for correct application.
    ///
    /// The preserved `i64` value can be logged to report the exact field content.
    #[error("negative file_offset in SqpkFile: {0}")]
    NegativeFileOffset(i64),

    /// Stream ended without an `EOF_` chunk; download or copy was truncated.
    ///
    /// Raised by the chunk framing code when attempting to read the 4-byte
    /// `body_len` field of the next chunk returns an unexpected EOF. This
    /// indicates the patch stream ended before the mandatory `EOF_` terminator
    /// chunk was encountered — the patch file was likely incompletely
    /// downloaded or written to disk.
    ///
    /// Use [`ZiPatchReader::is_complete`](crate::ZiPatchReader::is_complete)
    /// after iteration to distinguish this case from a clean end of stream.
    #[error("patch file ended without EOF_ chunk (truncated download?)")]
    TruncatedPatch,

    /// `SqPack` path resolution refused to fall back to a default platform layout.
    ///
    /// Raised by the apply layer's internal `dat_path` and `index_path`
    /// resolvers when [`crate::apply::ApplyContext::platform`]
    /// is [`crate::Platform::Unknown`]: the parser tolerates unrecognised
    /// `platform_id` values from [`SqpkTargetInfo`](crate::chunk::SqpkTargetInfo)
    /// so that future platforms do not hard-fail parsing, but the apply layer
    /// refuses to resolve a `.dat`/`.index` path against a guessed-at platform —
    /// silently misrouting writes to e.g. the `win32` layout would corrupt the
    /// on-disk install. The wrapped `u16` is the raw `platform_id` carried by
    /// the offending `TargetInfo` chunk, so callers can surface it to users.
    ///
    /// Callers who legitimately know which platform layout to use can override
    /// the context after the `TargetInfo` chunk has been applied (which
    /// requires manual chunk iteration rather than
    /// [`ZiPatchReader::apply_to`](crate::ZiPatchReader::apply_to)) by setting
    /// [`crate::apply::ApplyContext::platform`] back to a concrete variant.
    #[error("unsupported platform id {0}: cannot resolve SqPack path")]
    UnsupportedPlatform(u16),

    /// Apply was cancelled by an [`ApplyObserver`](crate::ApplyObserver).
    ///
    /// Raised by [`ZiPatchReader::apply_to`](crate::ZiPatchReader::apply_to)
    /// when an observer returns
    /// [`std::ops::ControlFlow::Break`] from
    /// [`ApplyObserver::on_chunk_applied`](crate::ApplyObserver::on_chunk_applied),
    /// or when
    /// [`ApplyObserver::should_cancel`](crate::ApplyObserver::should_cancel)
    /// returns `true` during a long-running chunk (currently checked between
    /// blocks of an [`SqpkFile`](crate::chunk::sqpk::SqpkFile) `AddFile`
    /// operation).
    ///
    /// Cancellation is best-effort: filesystem changes already applied by
    /// previous chunks — or by previous blocks within the cancelled chunk —
    /// are **not** rolled back. The format provides no transactional semantics,
    /// so callers expecting clean cancellation must perform their own recovery
    /// at a higher level (e.g. by re-running the patch from scratch against a
    /// clean install snapshot).
    #[error("apply cancelled by observer")]
    Cancelled,

    /// An indexed-apply plan referenced a region whose source bytes are not
    /// reachable from the current applier.
    ///
    /// Raised by [`crate::index::IndexApplier`] when it encounters a
    /// [`crate::index::PartSource::Unavailable`] region. The builder does not
    /// emit this variant from any in-tree chunk parser, so reaching it
    /// typically means the plan was hand-constructed (or deserialized) with an
    /// explicit [`crate::index::PartSource::Unavailable`] region whose source
    /// bytes are not in the [`crate::index::PatchSource`] the applier was
    /// constructed with.
    #[error(
        "indexed apply: source bytes unavailable for region at target_offset {target_offset} length {length}"
    )]
    IndexSourceUnavailable {
        /// Target-file offset of the unavailable region.
        target_offset: u64,
        /// Length in bytes of the unavailable region.
        length: u32,
    },

    /// A [`crate::index::PatchSource::read`] call could not fill the requested
    /// buffer.
    ///
    /// Raised by [`crate::index::IndexApplier`] (via the built-in
    /// [`crate::index::FilePatchSource`] /
    /// [`crate::index::MemoryPatchSource`] implementations) when the source
    /// has fewer than `requested` bytes available at `offset` — i.e. the
    /// underlying file or buffer is shorter than the plan expected, or the
    /// caller passed an offset past the end. Indicates either a truncated
    /// patch source or a plan that does not match the source it is being
    /// applied against.
    #[error("patch source too short: offset {offset} requested {requested} bytes")]
    PatchSourceTooShort {
        /// Patch-file offset at which the read was attempted.
        offset: u64,
        /// Number of bytes the caller asked for.
        requested: usize,
    },

    /// A [`crate::index::PatchSource::read`] call asked for a patch index
    /// outside the source's configured chain.
    ///
    /// Raised by [`crate::index::FilePatchSource`] /
    /// [`crate::index::MemoryPatchSource`] when the applier passes a
    /// `patch: u32` value `>= count`. Indicates either a stale plan referring
    /// to a patch the source no longer carries, or an off-by-one in a
    /// hand-built chain source.
    #[error("patch index {patch} out of range: source carries {count} patches")]
    PatchIndexOutOfRange {
        /// Index that was requested.
        patch: u32,
        /// Total number of patches the source was constructed with.
        count: usize,
    },

    /// An indexed-plan target or filesystem-op carried a path that escapes the
    /// install root.
    ///
    /// Raised by [`crate::index::PlanBuilder`] when a chunk carries a relative
    /// path that contains a `..` component, starts with `/` (absolute Unix
    /// path), or starts with a Windows drive-letter prefix (e.g. `C:\`). The
    /// indexed builder is a natural choke point for this check; the sequential
    /// apply path does not currently reject these paths (writes would land
    /// outside the install root if a malicious patch supplied one), but the
    /// indexed builder refuses to construct the plan rather than building one
    /// that would point at the wrong filesystem location. `SqPack`-encoded
    /// targets ([`crate::index::TargetPath::SqpackDat`] /
    /// [`crate::index::TargetPath::SqpackIndex`]) are structurally constrained
    /// by their numeric `(main_id, sub_id, file_id)` triple and are not subject
    /// to this check.
    #[error("unsafe target path rejected by index builder: {0:?}")]
    UnsafeTargetPath(String),

    /// A serialized type carrying a `schema_version` field was decoded with a
    /// version this build cannot represent.
    ///
    /// Raised by [`crate::index::Plan::check_schema_version`] and by the
    /// resume side of the apply-checkpoint surface when a persisted record's
    /// `schema_version` does not equal the constant this build pins. Older
    /// readers refuse to silently drop fields they cannot understand rather
    /// than risk an apply against a partial decode.
    ///
    /// The `kind` field is a `&'static str` naming which type's schema the
    /// mismatch refers to (`"plan"` for [`crate::index::Plan`], future kinds
    /// for the checkpoint structs). `found` is the persisted version,
    /// `expected` the constant this build supports.
    #[error("{kind} schema version mismatch: persisted {found}, this build expects {expected}")]
    SchemaVersionMismatch {
        /// Type name whose schema the mismatch refers to (e.g. `"plan"`).
        kind: &'static str,
        /// `schema_version` field stored on the persisted record.
        found: u32,
        /// `schema_version` this build supports.
        expected: u32,
    },

    /// Two patches in the same chain shared a `name`.
    ///
    /// Raised by [`crate::index::PlanBuilder::add_patch`] (and the freestanding
    /// [`crate::index::build_plan_chain`]) when a patch with the same `name`
    /// has already been added to this builder. The chain protocol is
    /// order-sensitive — re-adding the same patch almost always indicates a
    /// caller accidentally fed the same source into the chain twice, which
    /// would produce a `Plan` whose `patches` vector carries duplicate entries
    /// and whose region timelines reapply the same bytes. The builder refuses
    /// to construct the plan rather than silently letting this slip through.
    /// The duplicate `name` is preserved so callers can log it.
    #[error("duplicate patch in chain: {name:?}")]
    DuplicatePatch {
        /// The patch name that was added twice.
        name: String,
    },

    /// A region's post-write CRC32 did not match the expected value.
    ///
    /// Reserved for content-CRC verification flows that operate on plans
    /// populated by [`crate::index::Plan::compute_crc32`]. The default builder
    /// only emits [`crate::index::PartExpected::SizeOnly`] / `Zeros` /
    /// `EmptyBlock`, so this variant is only reached once a plan has had
    /// CRC32 expectations populated and a downstream check compares observed
    /// bytes against them.
    #[error(
        "CRC32 mismatch at target_offset {target_offset}: expected {expected:#010x}, got {actual:#010x}"
    )]
    Crc32Mismatch {
        /// Target-file offset of the mismatched region.
        target_offset: u64,
        /// CRC32 declared by the plan's [`crate::index::PartExpected::Crc32`].
        expected: u32,
        /// CRC32 computed over the bytes the applier wrote.
        actual: u32,
    },
}