import { Context, TextMapGetter, TextMapSetter, TextMapPropagator } from '@opentelemetry/api';
/** The metadata key under which span context is stored as a binary value. */
export declare const GRPC_TRACE_KEY = "grpc-trace-bin";
/**
 * Propagator for the grpc-trace-bin header used by OpenCensus for
 * gRPC. Acts as a bridge between the TextMapPropagator interface and
 * the binary encoding/decoding that happens in the supporting
 * BinaryTraceContext class.
 */
export declare class GrpcCensusPropagator implements TextMapPropagator {
    /**
     * Injects trace propagation context into the carrier after encoding
     * in binary format
     *
     * @param context - Context to be injected
     * @param carrier - Carrier in which to inject (for gRPC this will
     *     be a grpc.Metadata object)
     * @param setter - setter function that sets the correct key in
     *     the carrier
     */
    inject(context: Context, carrier: unknown, setter: TextMapSetter): void;
    /**
     * Extracts trace propagation context from the carrier and decodes
     * from the binary format
     *
     * @param context - context to set extracted span context on
     * @param carrier - Carrier from which to extract (for gRPC this will
     *     be a grpc.Metadata object)
     * @param getter - getter function that gets value(s) for the correct
     *     key in the carrier
     * @returns Extracted context if successful, otherwise the input context
     */
    extract(context: Context, carrier: unknown, getter: TextMapGetter): Context;
    fields(): string[];
}