Struct AttributeEntry 

pub struct AttributeEntry { /* private fields */ }

One attribute as an object header holds it: the message, plus the creation index the file records for it.

AttributeMessage::decode fails on a payload this crate cannot model — an object-reference datatype, say — but the name sits ahead of the datatype in the message, so such an attribute is still identifiable. Carrying the unreadable case in the same list is what lets a listing answer “this object has an attribute named X that I cannot read” instead of answering as though X were not there.

The creation index is a property of the attribute, exactly as its name is — H5A_shared_t::crt_idx, stored in the object header message envelope when the set is compact and in the index records when it is dense. Keeping it here is what stops a rewrite from re-deriving it from the position an attribute happens to occupy in a list: a dense set is read back in name-hash order, so a position-derived index re-stamps the whole set with the order the hash walk took.

Implementations

impl AttributeEntry

pub fn parse(buf: &[u8], ctx: &FormatContext) -> FormatResult<Self>

Parse one attribute message. The entry carries no creation index — only the envelope or index record it came out of knows one, so the caller that has it attaches it with with_creation_index.

Total over every message whose envelope and name parse: a payload this crate cannot decode is named, never an absence. Only a message too damaged to yield a name at all is an error, because there is then no name to report.

pub fn with_creation_index(self, creation_index: Option<u16>) -> Self

This entry with creation_index attached.

pub fn set_creation_index(&mut self, creation_index: Option<u16>)

Attach creation_index in place.

pub fn creation_index(&self) -> Option<u16>

The index this attribute was created with, or None when its object does not track creation order.

pub fn name(&self) -> &str

The attribute’s name, whether or not its payload decoded.

pub fn decoded(&self) -> Result<&AttributeMessage, &str>

The decoded message, or the reason there is none — exactly one of the two, so a caller reporting the failure never needs a branch for an attribute that is neither.

pub fn readable(&self) -> Option<&AttributeMessage>

The decoded message, or None when only the name is known.

pub fn unreadable_reason(&self) -> Option<&str>

Why this attribute cannot be read, or None when it can be.

pub fn encode(&self, ctx: &FormatContext) -> Vec<u8>

The message payload to write back into an object header.

An unreadable attribute returns the bytes it was read from: re-encoding is impossible without a decoded form, and dropping it would delete an attribute the caller never asked to change.

pub fn encode_at(&self, ctx: &FormatContext, libver: LibverBound) -> Vec<u8>

The same, for a file whose low libver bound is libver: the datatype message inside a readable attribute follows it. An unreadable one is bytes, and bytes have no version to choose.

pub fn encode_for( &self, ctx: &FormatContext, libver: LibverBound, format: ObjectFormat, ) -> Vec<u8>

The same, at the message version format calls for.

Trait Implementations

impl Clone for AttributeEntry

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for AttributeEntry

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

Formats the value using the given formatter.

impl From<AttributeMessage> for AttributeEntry

fn from(attr: AttributeMessage) -> Self

Converts to this type from the input type.

impl PartialEq for AttributeEntry

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

Equality operator ==.

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

Inequality operator !=.

impl StructuralPartialEq for AttributeEntry