added extractWithFormat in objc tracer

Author: mukesh-mt

Sources/Datadog/Tracing/Propagation/OpenTracing/HTTPHeadersReader.swift

@@ -6,19 +6,19 @@
 
 import Foundation
 
-internal class HTTPHeadersReader: OTHTTPHeadersReader, TracePropagationHeadersExtractor {
+public class HTTPHeadersReader: OTHTTPHeadersReader, TracePropagationHeadersExtractor {
     private let httpHeaderFields: [String: String]
     private var baggageItemQueue: DispatchQueue?
 
-    init(httpHeaderFields: [String: String]) {
+    public init(httpHeaderFields: [String: String]) {
         self.httpHeaderFields = httpHeaderFields
     }
 
-    func use(baggageItemQueue: DispatchQueue) {
+    public func use(baggageItemQueue: DispatchQueue) {
         self.baggageItemQueue = baggageItemQueue
     }
 
-    func extract() -> OTSpanContext? {
+    public func extract() -> OTSpanContext? {
         guard let baggageItemQueue = baggageItemQueue,
               let traceIDValue = httpHeaderFields[TracingHTTPHeaders.traceIDField],
               let spanIDValue = httpHeaderFields[TracingHTTPHeaders.parentSpanIDField],

Sources/DatadogObjc/OpenTracing/OTTracer+objc.swift

@@ -20,5 +20,5 @@ public protocol OTTracer {
     func startSpan(_ operationName: String, childOf parent: OTSpanContext?, tags: NSDictionary?) -> OTSpan
     func startSpan(_ operationName: String, childOf parent: OTSpanContext?, tags: NSDictionary?, startTime: Date?) -> OTSpan
     func inject(_ spanContext: OTSpanContext, format: String, carrier: Any) throws
-    func extractWithFormat(_ format: String, carrier: Any) throws
+    func extractWithFormat(_ format: String, carrier: Any) -> OTSpanContext?
 }

Sources/DatadogObjc/Tracer+objc.swift

@@ -10,6 +10,7 @@ import class Datadog.Tracer
 import protocol Datadog.OTTracer
 import struct Datadog.OTReference
 import class Datadog.HTTPHeadersWriter
+import class Datadog.HTTPHeadersReader
 
 @objc
 public class DDTracer: NSObject, DatadogObjc.OTTracer {
@@ -143,10 +144,17 @@ public class DDTracer: NSObject, DatadogObjc.OTTracer {
             throw error
         }
     }
-
+    
     @objc
-    public func extractWithFormat(_ format: String, carrier: Any) throws {
-        // TODO: RUMM-385 - we don't need to support it now
+    public func extractWithFormat(_ format: String, carrier: Any) -> OTSpanContext? {
+        if format == OT.formatTextMap, let headers = carrier as? [String: String] {
+            let reader = HTTPHeadersReader(httpHeaderFields: headers)
+            if let context =  swiftTracer.extract(reader: reader) {
+                return DDSpanContextObjc(swiftSpanContext: context)
+            }
+        }
+        
+        return nil
     }
 
     // MARK: - Private