Enum DecodeError 

#[non_exhaustive]
pub enum DecodeError {
    UnexpectedEof,
    VarintTooLong,
    InvalidWireType(u32),
    InvalidFieldNumber,
    MessageTooLarge,
    WireTypeMismatch {
        field_number: u32,
        expected: u8,
        actual: u8,
    },
    InvalidUtf8,
    RecursionLimitExceeded,
    InvalidEndGroup(u32),
    InvalidMessageSet(&'static str),
    UnknownFieldLimitExceeded,
    ElementMemoryLimitExceeded,
    Custom(&'static str),
}

An error that occurred while decoding a protobuf message.

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

UnexpectedEof

The buffer ended before a complete value could be read.

VarintTooLong

A varint exceeded the maximum encoded length of 10 bytes.

InvalidWireType(u32)

The wire type in a tag was not a recognised protobuf wire type.

Carries the raw 3-bit value from the tag for diagnostic purposes.

InvalidFieldNumber

The field number decoded from a tag was zero, or the tag varint overflowed a u32 — both indicate a malformed message.

MessageTooLarge

The message or sub-message length exceeded the size limit.

By default, the limit is the 2 GiB protobuf maximum. Use DecodeOptions::with_max_message_size to set a lower limit for untrusted input. Fallible re-encode paths (OwnedView::from_owned) also surface an over-limit encode through this variant, mirroring EncodeError::MessageTooLarge.

WireTypeMismatch

The wire type of an incoming field did not match the type expected for that field number.

Carries the field number and the raw wire type values (as u8 to keep this type independent of the encoding module).

Fields

field_number: u32

expected: u8

actual: u8

InvalidUtf8

A string field contained bytes that are not valid UTF-8.

RecursionLimitExceeded

The message nesting depth exceeded the recursion limit.

InvalidEndGroup(u32)

An EndGroup tag was encountered with a field number that does not match the opening StartGroup tag, or an EndGroup was seen outside of a group.

InvalidMessageSet(&'static str)

A MessageSet Item group was malformed (missing or out-of-range type_id). Only occurs for messages declared with option message_set_wire_format = true.

UnknownFieldLimitExceeded

Decoding encountered more unknown fields than the configured limit.

Unknown fields can be far smaller on the wire than in memory (a 2-byte varint field occupies ~40 bytes as an UnknownField), so the decoder bounds how many it will materialize rather than trusting the input size. By default the limit is DEFAULT_UNKNOWN_FIELD_LIMIT (1,000,000 fields per decode); use DecodeOptions::with_unknown_field_limit to raise it for trusted inputs that legitimately carry very many unknown fields.

ElementMemoryLimitExceeded

A decode would materialize more memory in the elements of length-delimited containers — repeated message, string and bytes fields, and map entries — than its budget allows.

These elements cost far more decoded than encoded: an empty message element is two bytes on the wire and size_of::<T>() in the Vec it lands in, so a payload well inside DecodeOptions::with_max_message_size can still expand by two orders of magnitude. By default the budget is DEFAULT_ELEMENT_MEMORY_LIMIT (32 MiB per decode); use DecodeOptions::with_element_memory_limit to raise it for trusted inputs that legitimately decode into more.

Custom(&'static str)

A custom string/bytes representation rejected the decoded payload in its from_wire constructor — for example a length or domain check beyond UTF-8 validation. Carries a static reason for diagnostics (mirroring InvalidMessageSet).

Only produced by user-supplied ProtoString / ProtoBytes impls; the built-in representations never return it.

Trait Implementations

impl Clone for DecodeError

fn clone(&self) -> DecodeError

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for DecodeError

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

Formats the value using the given formatter.

impl Display for DecodeError

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

Formats the value using the given formatter.

impl Eq for DecodeError

impl Error for DecodeError

fn source(&self) -> Option<&(dyn Error + 'static)>

Returns the lower-level source of this error, if any.

fn description(&self) -> &str

👎Deprecated since 1.42.0:

use the Display impl or to_string()

fn cause(&self) -> Option<&dyn Error>

👎Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn provide<'a>(&'a self, request: &mut Request<'a>)

🔬This is a nightly-only experimental API. (error_generic_member_access)

Provides type-based access to context intended for error reports.

impl PartialEq for DecodeError

fn eq(&self, other: &DecodeError) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for DecodeError