Implement SP wire protocolsp

Implements the SP wire protocol, and infrastructure for legacy wire
protocol support.

Also added an XS_SERVICE_ID socket option to set the service id and renamed
the XS_PROTOCOL option to XS_PATTERN_VERSION.

The following pattern versions are supported:

PAIR:     v3
PUBSUB:   v1 (legacy), v4
REQREP:   v2
PIPELINE: v3
SURVEY:   v2

Note that all existing pattern versions have been bumped by 1 to allow for
use of legacy protocols (otherwise there would be no way to distinguish
between e.g. PUBSUB v3 and PUBSUB v3 using SP).

Signed-off-by: Martin Lucina <martin@lucina.net>

1 files changed, 43 insertions, 2 deletions

diff --git a/src/wire.hpp b/src/wire.hpp
index f840fce..014021b 100644
--- a/src/wire.hpp
+++ b/src/wire.hpp
@@ -24,11 +24,52 @@
 #include "stdint.hpp"
 
 //  Protocol-related constants.
-#define XS_CMD_SUBSCRIBE 1
-#define XS_CMD_UNSUBSCRIBE 2
+
+//  Protocol header.
+#define SP_HEADER_LENGTH 8
+
+//  Patterns.
+#define SP_PAIR 1
+#define SP_PUBSUB 2
+#define SP_REQREP 3
+#define SP_PIPELINE 4
+#define SP_SURVEY 5
+
+//  Roles.
+#define SP_PAIR_PAIR 1
+#define SP_PUBSUB_PUB 1
+#define SP_PUBSUB_SUB 2
+#define SP_REQREP_REQ 1
+#define SP_REQREP_REP 2
+#define SP_PIPELINE_PUSH 1
+#define SP_PIPELINE_PULL 2
+#define SP_SURVEY_SURVEYOR 1
+#define SP_SURVEY_RESPONDENT 2
+
+//  PUBSUB pattern commands.
+#define SP_PUBSUB_CMD_SUBSCRIBE 1
+#define SP_PUBSUB_CMD_UNSUBSCRIBE 2
 
 namespace xs
 {
+    //  Protocol header type.
+    typedef unsigned char sp_header_t [SP_HEADER_LENGTH];
+
+    //  Get the SP protocol header for the specified service, pattern, version
+    //  and role.
+    inline void sp_get_header (sp_header_t header_, int service_, int pattern_,
+        int version_, int role_)
+    {
+        header_ [0] = 0;                      //  Protocol identifier
+        header_ [1] = 'S';                    //  "
+        header_ [2] = 'P';                    //  "
+        header_ [3] = 0;                      //  Reserved, must be zero.
+        header_ [4] = (service_ >> 8) & 0xff; //  Service id high byte
+        header_ [5] = service_ & 0xff;        //  Service id low byte
+        header_ [6] = pattern_ & 0xff;        //  Pattern
+        header_ [7] = (version_ & 0xf) << 4;  //  Pattern version
+        header_ [7] |= role_ & 0xf;           //  Pattern role
+    }
 
     //  Helper functions to convert different integer types to/from network
     //  byte order.