multifd: Make no compression operations into its own structure

It will be used later.

Signed-off-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

---

No comp value needs to be zero.
diff --git a/migration/multifd.h b/migration/multifd.h
index d8b0205..54075ff 100644
--- a/migration/multifd.h
+++ b/migration/multifd.h
@@ -25,6 +25,11 @@
 
 #define MULTIFD_FLAG_SYNC (1 << 0)
 
+/* We reserve 3 bits for compression methods */
+#define MULTIFD_FLAG_COMPRESSION_MASK (7 << 1)
+/* we need to be compatible. Before compression value was 0 */
+#define MULTIFD_FLAG_NOCOMP (0 << 1)
+
 /* This value needs to be a multiple of qemu_target_page_size() */
 #define MULTIFD_PACKET_SIZE (512 * 1024)
 
@@ -96,6 +101,8 @@
     uint64_t num_pages;
     /* syncs main thread and channels */
     QemuSemaphore sem_sync;
+    /* used for compression methods */
+    void *data;
 }  MultiFDSendParams;
 
 typedef struct {
@@ -133,7 +140,26 @@
     uint64_t num_pages;
     /* syncs main thread and channels */
     QemuSemaphore sem_sync;
+    /* used for de-compression methods */
+    void *data;
 } MultiFDRecvParams;
 
+typedef struct {
+    /* Setup for sending side */
+    int (*send_setup)(MultiFDSendParams *p, Error **errp);
+    /* Cleanup for sending side */
+    void (*send_cleanup)(MultiFDSendParams *p, Error **errp);
+    /* Prepare the send packet */
+    int (*send_prepare)(MultiFDSendParams *p, uint32_t used, Error **errp);
+    /* Write the send packet */
+    int (*send_write)(MultiFDSendParams *p, uint32_t used, Error **errp);
+    /* Setup for receiving side */
+    int (*recv_setup)(MultiFDRecvParams *p, Error **errp);
+    /* Cleanup for receiving side */
+    void (*recv_cleanup)(MultiFDRecvParams *p);
+    /* Read all pages */
+    int (*recv_pages)(MultiFDRecvParams *p, uint32_t used, Error **errp);
+} MultiFDMethods;
+
 #endif