sd-bus: change serialization of kdbus messages to qualify in their entirety as gvariant objects

Previously, we only minimally altered the dbus1 framing for kdbus, and
while the header and its fields where compliant Gvariant objects, and so
was the body, the entire message together was not.

As result of discussions with Ryan Lortie this is now changed, so that
the messages in there entirely are fully compliant GVariants. This
follows the framing description described here:

https://wiki.gnome.org/Projects/GLib/GDBus/Version2

Note that this change changes the framing of *all* messages sent via
kdbus, this means you have to reboot your kdbus system, after compiling
and installing this new version.

1 files changed, 60 insertions, 0 deletions

diff --git a/src/libsystemd/sd-bus/bus-gvariant.c b/src/libsystemd/sd-bus/bus-gvariant.c
index dc4000992..02b95cd13 100644
--- a/src/libsystemd/sd-bus/bus-gvariant.c
+++ b/src/libsystemd/sd-bus/bus-gvariant.c
@@ -247,3 +247,63 @@ int bus_gvariant_is_fixed_size(const char *signature) {
 
         return true;
 }
+
+size_t bus_gvariant_determine_word_size(size_t sz, size_t extra) {
+        if (sz + extra <= 0xFF)
+                return 1;
+        else if (sz + extra*2 <= 0xFFFF)
+                return 2;
+        else if (sz + extra*4 <= 0xFFFFFFFF)
+                return 4;
+        else
+                return 8;
+}
+
+size_t bus_gvariant_read_word_le(void *p, size_t sz) {
+        union {
+                uint16_t u16;
+                uint32_t u32;
+                uint64_t u64;
+        } x;
+
+        assert(p);
+
+        if (sz == 1)
+                return *(uint8_t*) p;
+
+        memcpy(&x, p, sz);
+
+        if (sz == 2)
+                return le16toh(x.u16);
+        else if (sz == 4)
+                return le32toh(x.u32);
+        else if (sz == 8)
+                return le64toh(x.u64);
+
+        assert_not_reached("unknown word width");
+}
+
+void bus_gvariant_write_word_le(void *p, size_t sz, size_t value) {
+        union {
+                uint16_t u16;
+                uint32_t u32;
+                uint64_t u64;
+        } x;
+
+        assert(p);
+        assert(sz == 8 || (value < (1ULL << (sz*8))));
+
+        if (sz == 1) {
+                *(uint8_t*) p = value;
+                return;
+        } else if (sz == 2)
+                x.u16 = htole16((uint16_t) value);
+        else if (sz == 4)
+                x.u32 = htole32((uint32_t) value);
+        else if (sz == 8)
+                x.u64 = htole64((uint64_t) value);
+        else
+                assert_not_reached("unknown word width");
+
+        memcpy(p, &x, sz);
+}