W3CTraceContextPropagator.php

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<?php
namespace Wikimedia\Telemetry;
 
class W3CTraceContextPropagator implements ContextPropagatorInterface {
    public function inject( ?SpanContext $spanContext, array $carrier ): array {
        if ( $spanContext === null ) {
            return $carrier;
        }
        $traceId = $spanContext->getTraceId();
        $spanId = $spanContext->getSpanId();
        $sampled = $spanContext->isSampled() ? '01' : '00';
        if ( strlen( $traceId ) === 32 && strlen( $spanId ) === 16 ) {
            $carrier['traceparent'] = "00-{$traceId}-{$spanId}-{$sampled}";
        }
 
        return $carrier;
    }
 
    public function extract( array $carrier ): ?SpanContext {
        $carrier = array_change_key_case( $carrier, CASE_LOWER );
        if ( !isset( $carrier['traceparent'] ) ) {
            return null;
        }
        $matches = [];
        if ( !preg_match( '/^00-([0-9a-f]{32})-([0-9a-f]{16})-([0-9a-f]{2})$/', $carrier['traceparent'], $matches ) ) {
            return null;
        }
        return new SpanContext(
            $matches[1],
            $matches[2],
            null,
            '',
            ( hexdec( $matches[3] ) & 1 ) === 1
        );
    }
}