facebook-api: properly handle optional Thrift fields and scoping

The plugin is required to read Thrift data for the presence states of
contacts. The data which is being read has some optional fields, which
are rarely not supplied. This has led to this bug being undiscovered
for quite some time.

Not only was the plugin not properly accounting for optional fields,
but also did not account for field scoping. This is not really an issue
until a Thrift list is being read, which will cause the identifier to
grow with each field read, rather than reset. The field identifier is
only relevant to its local scope, nothing more. More importantly, the
identifier must be reset with each iteration of a list.

1 files changed, 15 insertions, 22 deletions

diff --git a/facebook/facebook-thrift.c b/facebook/facebook-thrift.c
index bde1eb1..9604e4d 100644
--- a/facebook/facebook-thrift.c
+++ b/facebook/facebook-thrift.c
@@ -26,7 +26,6 @@ struct _FbThriftPrivate
     guint offset;
     guint pos;
     guint lastbool;
-    gint16 lastid;
 };
 
 G_DEFINE_TYPE(FbThrift, fb_thrift, G_TYPE_OBJECT);
@@ -330,7 +329,8 @@ fb_thrift_read_str(FbThrift *thft, gchar **value)
 }
 
 gboolean
-fb_thrift_read_field(FbThrift *thft, FbThriftType *type, gint16 *id)
+fb_thrift_read_field(FbThrift *thft, FbThriftType *type, gint16 *id,
+                     gint16 lastid)
 {
     FbThriftPrivate *priv;
     gint16 i16;
@@ -338,6 +338,7 @@ fb_thrift_read_field(FbThrift *thft, FbThriftType *type, gint16 *id)
 
     g_return_val_if_fail(FB_IS_THRIFT(thft), FALSE);
     g_return_val_if_fail(type != NULL, FALSE);
+    g_return_val_if_fail(id != NULL, FALSE);
     priv = thft->priv;
 
     if (!fb_thrift_read_byte(thft, &byte)) {
@@ -352,29 +353,22 @@ fb_thrift_read_field(FbThrift *thft, FbThriftType *type, gint16 *id)
     *type = fb_thrift_ct2t(byte & 0x0F);
     i16 = (byte & 0xF0) >> 4;
 
-    if (*type == FB_THRIFT_TYPE_BOOL) {
-        priv->lastbool = 0x01;
-
-        if ((byte & 0x0F) == 0x01) {
-            priv->lastbool |= 0x01 << 2;
-        }
-
-        return TRUE;
-    }
-
     if (i16 == 0) {
-        if (!fb_thrift_read_i16(thft, &i16)) {
+        if (!fb_thrift_read_i16(thft, id)) {
             return FALSE;
         }
     } else {
-        i16 = priv->lastid + i16;
+        *id = lastid + i16;
     }
 
-    if (id != NULL) {
-        *id = i16;
+    if (*type == FB_THRIFT_TYPE_BOOL) {
+        priv->lastbool = 0x01;
+
+        if ((byte & 0x0F) == 0x01) {
+            priv->lastbool |= 0x01 << 2;
+        }
     }
 
-    priv->lastid = i16;
     return TRUE;
 }
 
@@ -585,7 +579,8 @@ fb_thrift_write_str(FbThrift *thft, const gchar *value)
 }
 
 void
-fb_thrift_write_field(FbThrift *thft, FbThriftType type, gint16 id)
+fb_thrift_write_field(FbThrift *thft, FbThriftType type, gint16 id,
+                      gint16 lastid)
 {
     FbThriftPrivate *priv;
     gint16 diff;
@@ -598,16 +593,14 @@ fb_thrift_write_field(FbThrift *thft, FbThriftType type, gint16 id)
     }
 
     type = fb_thrift_t2ct(type);
-    diff = id - priv->lastid;
+    diff = id - lastid;
 
-    if ((id <= priv->lastid) || (diff > 0x0F)) {
+    if ((id <= lastid) || (diff > 0x0F)) {
         fb_thrift_write_byte(thft, type);
         fb_thrift_write_i16(thft, id);
     } else {
         fb_thrift_write_byte(thft, (diff << 4) | type);
     }
-
-    priv->lastid = id;
 }
 
 void