From 1c1e1b1fb9bf9ca1c874beded0a0b97f8e98f7a4 Mon Sep 17 00:00:00 2001
From: Pavel Kirienko <pavel.kirienko@gmail.com>
Date: Fri, 28 Feb 2014 14:12:35 +0400
Subject: [PATCH] GDTR: much faster type signature computation

---
 libuavcan/src/global_data_type_registry.cpp  | 49 ++++++++------------
 libuavcan/test/global_data_type_registry.cpp |  8 ++++
 2 files changed, 28 insertions(+), 29 deletions(-)

diff --git a/libuavcan/src/global_data_type_registry.cpp b/libuavcan/src/global_data_type_registry.cpp
index 734f691367..18a26c423e 100644
--- a/libuavcan/src/global_data_type_registry.cpp
+++ b/libuavcan/src/global_data_type_registry.cpp
@@ -141,44 +141,35 @@ DataTypeSignature GlobalDataTypeRegistry::computeAggregateSignature(DataTypeKind
         return DataTypeSignature();
     }
 
+    int prev_dtid = -1;
     DataTypeSignature signature;
     bool signature_initialized = false;
-
-    for (int id = 0; id <= DataTypeDescriptor::MaxDataTypeID; id++)
+    Entry* p = list->get();
+    while (p)
     {
-        if (!inout_id_mask[id])
-            continue;
+        const DataTypeDescriptor& desc = p->descriptor;
 
-        // TODO: do it faster - no need to traverse the list on each iteration
-        const DataTypeDescriptor* desc = NULL;
-        {
-            Entry* p = list->get();
-            while (p)
-            {
-                if (p->descriptor.match(kind, id))
-                {
-                    desc = &p->descriptor;
-                    break;
-                }
-                p = p->getNextListNode();
-            }
-        }
-
-        if (desc)
+        if (inout_id_mask[desc.getID()])
         {
             if (signature_initialized)
-            {
-                signature.extend(desc->getSignature());
-            }
+                signature.extend(desc.getSignature());
             else
-            {
-                signature_initialized = true;
-                signature = DataTypeSignature(desc->getSignature());
-            }
+                signature = DataTypeSignature(desc.getSignature());
+            signature_initialized = true;
         }
-        else
-            inout_id_mask[id] = false;
+
+        assert(prev_dtid < desc.getID());  // Making sure that list is ordered properly
+        prev_dtid++;
+        while (prev_dtid < desc.getID())
+            inout_id_mask[prev_dtid++] = false; // Erasing bits for missing types
+        assert(prev_dtid == desc.getID());
+
+        p = p->getNextListNode();
     }
+    prev_dtid++;
+    while (prev_dtid <= DataTypeDescriptor::MaxDataTypeID)
+        inout_id_mask[prev_dtid++] = false;
+
     return signature;
 }
 
diff --git a/libuavcan/test/global_data_type_registry.cpp b/libuavcan/test/global_data_type_registry.cpp
index dbe12809c0..938136eee1 100644
--- a/libuavcan/test/global_data_type_registry.cpp
+++ b/libuavcan/test/global_data_type_registry.cpp
@@ -249,6 +249,14 @@ TEST(GlobalDataTypeRegistry, AggregateSignature)
         check_signature.extend(DataTypeB::getDataTypeSignature());
         ASSERT_EQ(check_signature, sign);
     }
+
+    // One
+    mask[1] = mask[43] = true;
+    sign = GlobalDataTypeRegistry::instance().computeAggregateSignature(uavcan::DataTypeKindService, mask);
+    ASSERT_TRUE(mask[43]);   // DataTypeD
+    mask[43] = false;
+    ASSERT_FALSE(mask.any());
+    ASSERT_EQ(DataTypeD::getDataTypeSignature(), sign);
 }