Add ip-static.h

src/ip-static.h

@@ -0,0 +1,30 @@
+#pragma once
+
+#include <stdint.h>
+
+static inline int ip_get_version (const uint8_t *data, size_t size)
+{
+    if (size<20)   // XXX
+        return -1; // XXX
+
+    return data[0]>>4;
+}
+
+static inline void ip_set_size (uint8_t *data, size_t size)
+{
+    data[2] = 0xFF&(size>>8);
+    data[3] = 0xFF&(size);
+}
+
+static inline ssize_t ip_get_size (const uint8_t *data, size_t size)
+{
+    switch (ip_get_version(data, size)) {
+    case 4:
+        return (data[2]<<8)|data[3];
+    case -1:
+        return -1;
+    }
+
+    return 0;
+}
+