Opentracing support

vendor/github.com/Shopify/sarama/packet_decoder.go

@@ -0,0 +1,45 @@
+package sarama
+
+// PacketDecoder is the interface providing helpers for reading with Kafka's encoding rules.
+// Types implementing Decoder only need to worry about calling methods like GetString,
+// not about how a string is represented in Kafka.
+type packetDecoder interface {
+	// Primitives
+	getInt8() (int8, error)
+	getInt16() (int16, error)
+	getInt32() (int32, error)
+	getInt64() (int64, error)
+	getArrayLength() (int, error)
+
+	// Collections
+	getBytes() ([]byte, error)
+	getString() (string, error)
+	getInt32Array() ([]int32, error)
+	getInt64Array() ([]int64, error)
+	getStringArray() ([]string, error)
+
+	// Subsets
+	remaining() int
+	getSubset(length int) (packetDecoder, error)
+
+	// Stacks, see PushDecoder
+	push(in pushDecoder) error
+	pop() error
+}
+
+// PushDecoder is the interface for decoding fields like CRCs and lengths where the validity
+// of the field depends on what is after it in the packet. Start them with PacketDecoder.Push() where
+// the actual value is located in the packet, then PacketDecoder.Pop() them when all the bytes they
+// depend upon have been decoded.
+type pushDecoder interface {
+	// Saves the offset into the input buffer as the location to actually read the calculated value when able.
+	saveOffset(in int)
+
+	// Returns the length of data to reserve for the input of this encoder (eg 4 bytes for a CRC32).
+	reserveLength() int
+
+	// Indicates that all required data is now available to calculate and check the field.
+	// SaveOffset is guaranteed to have been called first. The implementation should read ReserveLength() bytes
+	// of data from the saved offset, and verify it based on the data between the saved offset and curOffset.
+	check(curOffset int, buf []byte) error
+}