Add getBuffer() methods to protocol classes

Most of the classes contains a convenience method
named getBuffer() which allows the user to get a
"blob" containing the encoded data. This patch
adds the method to those classes which didn't
have the method.

Change-Id: I1cc1921e3afe58ee2e426dafc9b734cd534e1996
Reviewed-on: http://review.couchbase.org/c/kv_engine/+/138032
Tested-by: Build Bot <[email protected]>
Reviewed-by: Dave Rigby <[email protected]>

Author: trondn

include/memcached/protocol_binary.h

@@ -612,6 +612,10 @@ class DcpOpenPayload {
      */
     static const uint32_t IncludeDeletedUserXattrs = 256;
 
+    cb::const_byte_buffer getBuffer() const {
+        return {reinterpret_cast<const uint8_t*>(this), sizeof(*this)};
+    }
+
 protected:
     uint32_t seqno = 0;
     uint32_t flags = 0;
@@ -728,6 +732,10 @@ class DcpStreamReqPayload {
         DcpStreamReqPayload::snap_end_seqno = htonll(snap_end_seqno);
     }
 
+    cb::const_byte_buffer getBuffer() const {
+        return {reinterpret_cast<const uint8_t*>(this), sizeof(*this)};
+    }
+
 protected:
     uint32_t flags = 0;
     uint32_t reserved = 0;
@@ -748,6 +756,10 @@ class DcpStreamEndPayload {
         DcpStreamEndPayload::status = htonl(uint32_t(status));
     }
 
+    cb::const_byte_buffer getBuffer() const {
+        return {reinterpret_cast<const uint8_t*>(this), sizeof(*this)};
+    }
+
 protected:
     /**
      * Note the following is maintained in network/big endian
@@ -1671,6 +1683,10 @@ struct GetMetaResponse {
           seqno(seqno),
           datatype(datatype) {
     }
+
+    cb::const_byte_buffer getBuffer() const {
+        return {reinterpret_cast<const uint8_t*>(this), sizeof(*this)};
+    }
 };
 
 #pragma pack()
@@ -1716,6 +1732,10 @@ class ReturnMetaPayload {
         ReturnMetaPayload::expiration = htonl(expiration);
     }
 
+    cb::const_byte_buffer getBuffer() const {
+        return {reinterpret_cast<const uint8_t*>(this), sizeof(*this)};
+    }
+
 protected:
     uint32_t mutation_type = 0;
     uint32_t flags = 0;
@@ -1783,6 +1803,10 @@ class CompactDbPayload {
         return align_pad1 == 0 && align_pad3 == 0;
     }
 
+    cb::const_byte_buffer getBuffer() const {
+        return {reinterpret_cast<const uint8_t*>(this), sizeof(*this)};
+    }
+
 protected:
     uint64_t purge_before_ts = 0;
     uint64_t purge_before_seq = 0;