Struct EncoderDesc 

#[repr(C)]
pub struct EncoderDesc {
    pub name: &'static str,
    pub write_envelope: fn(&mut dyn Write, &Machine, &Envelope<'_>) -> Result<()>,
    pub write_error: fn(&mut dyn Write, &WireError) -> Result<()>,
    pub can_stream: fn() -> bool,
}

An encoding as a vtable: a name plus the three operations the wire contract needs. #[repr(C)] so codegen can reference a descriptor by address and entry.rs can read its fields after dereferencing the pointer from the capability table. A #[no_mangle] static of this type per encoding (PLG_ENC_TEXT, PLG_ENC_BSON) is what codegen’s @plg_caps table points at; encoders not listed there are unreferenced and get dead-stripped.

Fields

name: &'static str

The --format name this descriptor answers to (“text”, “bson”).

write_envelope: fn(&mut dyn Write, &Machine, &Envelope<'_>) -> Result<()>

write_error: fn(&mut dyn Write, &WireError) -> Result<()>

can_stream: fn() -> bool

False ⇒ the encoding can’t coexist with streamed write/1 bytes on the same stdout (binary formats), so the caller must run in capture mode.

Implementations

impl EncoderDesc

pub unsafe fn find( caps: *const *const EncoderDesc, len: usize, name: &str, ) -> Option<&'static EncoderDesc>

Find a descriptor by name in a capability table (codegen-baked pointers to #[no_mangle] static descriptors). Returns None when the name isn’t advertised — entry.rs maps that to a usage error (exit 2).

Safety

caps must point at len valid pointers to static descriptors.