Struct Encoder 

pub struct Encoder { /* private fields */ }

A protobuf message under construction.

Sub-messages are built as their own Encoder and then handed to Encoder::message, because a length-delimited field has to know its length before it writes its body and the only honest way to know that is to have encoded the body already.

Implementations

impl Encoder

pub fn new() -> Self

pub fn into_bytes(self) -> Vec<u8>

pub fn as_bytes(&self) -> &[u8]

pub fn len(&self) -> usize

pub fn is_empty(&self) -> bool

pub fn uint64(&mut self, field: u32, value: u64)

A uint32/uint64 field. Zero is proto3’s default for these, and a field left out decodes back to the default, so writing it would only make the payload bigger.

pub fn uint32(&mut self, field: u32, value: u32)

pub fn int64(&mut self, field: u32, value: i64)

An int64 field. Negative values sign-extend to a full 64 bits, which is why protobuf spends ten bytes on -1 — sint64 is the zig-zag alternative, and OTLP does not use it anywhere this crate encodes.

pub fn bool(&mut self, field: u32, value: bool)

pub fn bool_present(&mut self, field: u32, value: bool)

Fields inside a oneof have explicit presence, so their default value still has to be written.

This is not a micro-optimisation in reverse — it is the difference between an attribute arriving as false and arriving as nothing at all. A decoder tracks which arm of a oneof is set by which tag it saw, so omitting bool_value = false sets no arm and the collector prints Empty(). OTLP’s AnyValue and NumberDataPoint.value are both oneofs, and a real collector is where this was caught.

pub fn int64_present(&mut self, field: u32, value: i64)

See Encoder::bool_present — AnyValue.int_value.

pub fn string_present(&mut self, field: u32, value: &str)

See Encoder::bool_present — AnyValue.string_value.

pub fn sfixed64_present(&mut self, field: u32, value: i64)

See Encoder::bool_present — NumberDataPoint.as_int.

pub fn enumeration(&mut self, field: u32, value: i32)

An enum field. Enums travel as varints, and every OTLP enum reserves zero for “unspecified”, so omitting zero is right here too.

pub fn fixed64(&mut self, field: u32, value: u64)

A fixed64 field: eight little-endian bytes, no varint compression. OTLP uses it for timestamps, where the values are large enough that a varint would cost more than eight bytes anyway.

pub fn fixed32(&mut self, field: u32, value: u32)

A fixed32 field: four little-endian bytes. LogRecord.flags is the one user here, carrying the W3C trace flags.

pub fn sfixed64(&mut self, field: u32, value: i64)

A sfixed64 field — NumberDataPoint.as_int, and nothing else here.

pub fn double(&mut self, field: u32, value: f64)

A double field, IEEE 754 little-endian.

pub fn present_double(&mut self, field: u32, value: f64)

A double field that is written even when it holds the default.

Proto3 optional double has explicit presence, and OTLP uses it for HistogramDataPoint.sum, min and max. There, absent means “this histogram does not report a sum” while zero means “the sum is zero” — two different facts that the default-skipping Encoder::double would collapse into one.

pub fn string(&mut self, field: u32, value: &str)

A string field: length-delimited UTF-8.

pub fn bytes_field(&mut self, field: u32, value: &[u8])

A bytes field. Named to leave bytes free for the buffer itself.

pub fn message(&mut self, field: u32, message: &Encoder)

A nested message.

Written even when the sub-message encoded to nothing: message fields have explicit presence in proto3, so an empty Status still says “this span carries a status” rather than “no status was set”. Callers that mean the second one simply do not call this.

pub fn packed_fixed64(&mut self, field: u32, values: &[u64])

A packed repeated fixed64 — HistogramDataPoint.bucket_counts.

Packed means one length-delimited field holding every element back to back, rather than one tag per element. Proto3 packs repeated scalars by default, so a collector expects exactly this.

pub fn packed_double(&mut self, field: u32, values: &[f64])

A packed repeated double — HistogramDataPoint.explicit_bounds.

Trait Implementations

impl Clone for Encoder

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 Encoder

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

Formats the value using the given formatter.

impl Default for Encoder

fn default() -> Self

Returns the “default value” for a type.