Opentracing support

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

@@ -0,0 +1,50 @@
+package sarama
+
+import "github.com/rcrowley/go-metrics"
+
+// PacketEncoder is the interface providing helpers for writing with Kafka's encoding rules.
+// Types implementing Encoder only need to worry about calling methods like PutString,
+// not about how a string is represented in Kafka.
+type packetEncoder interface {
+	// Primitives
+	putInt8(in int8)
+	putInt16(in int16)
+	putInt32(in int32)
+	putInt64(in int64)
+	putArrayLength(in int) error
+
+	// Collections
+	putBytes(in []byte) error
+	putRawBytes(in []byte) error
+	putString(in string) error
+	putStringArray(in []string) error
+	putInt32Array(in []int32) error
+	putInt64Array(in []int64) error
+
+	// Provide the current offset to record the batch size metric
+	offset() int
+
+	// Stacks, see PushEncoder
+	push(in pushEncoder)
+	pop() error
+
+	// To record metrics when provided
+	metricRegistry() metrics.Registry
+}
+
+// PushEncoder is the interface for encoding fields like CRCs and lengths where the value
+// of the field depends on what is encoded after it in the packet. Start them with PacketEncoder.Push() where
+// the actual value is located in the packet, then PacketEncoder.Pop() them when all the bytes they
+// depend upon have been written.
+type pushEncoder interface {
+	// Saves the offset into the input buffer as the location to actually write the calculated value when able.
+	saveOffset(in int)
+
+	// Returns the length of data to reserve for the output of this encoder (eg 4 bytes for a CRC32).
+	reserveLength() int
+
+	// Indicates that all required data is now available to calculate and write the field.
+	// SaveOffset is guaranteed to have been called first. The implementation should write ReserveLength() bytes
+	// of data to the saved offset, based on the data between the saved offset and curOffset.
+	run(curOffset int, buf []byte) error
+}