Support Metacube metadata blocks, specifically timestamps.

[cubemap] / metacube2.cpp

diff --git a/metacube2.cpp b/metacube2.cpp
index 9473dced414b62fd5d93548d7d81b43745b81143..666355d16867524422b72de72853723725554e88 100644 (file)
--- a/metacube2.cpp
+++ b/metacube2.cpp
@@ -7,6 +7,8 @@
 
 #include "metacube2.h"
 
+#include <arpa/inet.h>
+
 /*
  * https://www.ece.cmu.edu/~koopman/pubs/KoopmanCRCWebinar9May2012.pdf
  * recommends this for messages as short as ours (see table at page 34).
@@ -24,7 +26,7 @@ uint16_t metacube2_compute_crc(const struct metacube2_block_header *hdr)
        uint16_t crc = METACUBE2_CRC_START;
        int i, j;
 
-       for (i = 0; i < data_len; ++i) {        
+       for (i = 0; i < data_len; ++i) {
                uint8_t c = data[i];
                for (j = 0; j < 8; j++) {
                        int bit = crc & 0x8000;
@@ -44,5 +46,14 @@ uint16_t metacube2_compute_crc(const struct metacube2_block_header *hdr)
                }
        }
 
+       /*
+        * Invert the checksum for metadata packets, so that clients that
+        * don't understand metadata will ignore it as broken. There will
+        * probably be logging, but apart from that, it's harmless.
+        */
+       if (ntohs(hdr->flags) & METACUBE_FLAGS_METADATA) {
+               crc ^= 0xffff;
+       }
+
        return crc;
 }