Trait LengthResolver 

pub trait LengthResolver {
    // Required method
    fn resolve_length(&mut self, length_ref: ObjectId) -> Result<i64, PdfError>;
}

Caller-supplied hook that resolves an indirect /Length reference on a stream dictionary to the underlying integer.

ISO 32000-1 §7.3.10 Example 3 makes indirect /Length normative on stream objects: a one-pass writer that doesn’t know the encoded stream size up front emits << /Length 8 0 R >> and writes the length-carrying integer object after the stream. A reader walking such a PDF needs the xref table to fetch the integer.

The trait receives the ObjectId from the reference and is expected to return the resolved integer (or a PdfError when the target is missing / not an integer / a cycle is detected). Using a trait (rather than a free FnMut) sidesteps the lifetime gymnastics needed to thread an Option<&mut dyn FnMut> through multiple recursive parse helpers — implementers just write a tiny struct holding the borrowed state they need.

When the resolver is the unit no-op NoLengthResolver (the Parser::parse_indirect / Parser::parse_object entry points), an indirect /Length is rejected — that path is reserved for xref-stream parsing, where the xref isn’t built yet and the spec (§7.5.8) effectively requires the direct-integer form anyway.

Required Methods

fn resolve_length(&mut self, length_ref: ObjectId) -> Result<i64, PdfError>

Resolve the integer carried by the indirect object at length_ref. Returning Err(_) flows up the parse stack and aborts the stream-object decode.

Dyn Compatibility

This trait is dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementors

impl LengthResolver for NoLengthResolver

impl<F> LengthResolver for F

where F: FnMut(ObjectId) -> Result<i64, PdfError>,

Blanket impl so closures with the same signature work as LengthResolvers without writing a struct.