From f91d8090c9506a64c2496aa6ed236b6537ea57fa Mon Sep 17 00:00:00 2001
From: Pavel Kirienko <pavel.kirienko@gmail.com>
Date: Tue, 4 Feb 2014 20:12:27 +0400
Subject: [PATCH] Globally defined and statically checked block size for pool
 allocator

---
 .../uavcan/internal/impl_constants.hpp        | 33 +++++++++++++++++++
 .../include/uavcan/internal/static_assert.hpp |  7 +++-
 .../uavcan/internal/transport/can_io.hpp      |  8 ++---
 .../transport/transfer_id_registry.hpp        |  6 ++--
 .../test/transport/transfer_id_registry.cpp   |  4 +--
 5 files changed, 47 insertions(+), 11 deletions(-)
 create mode 100644 libuavcan/include/uavcan/internal/impl_constants.hpp

diff --git a/libuavcan/include/uavcan/internal/impl_constants.hpp b/libuavcan/include/uavcan/internal/impl_constants.hpp
new file mode 100644
index 0000000000..d198fe5b90
--- /dev/null
+++ b/libuavcan/include/uavcan/internal/impl_constants.hpp
@@ -0,0 +1,33 @@
+/*
+ * Copyright (C) 2014 Pavel Kirienko <pavel.kirienko@gmail.com>
+ */
+
+#pragma once
+
+#include <uavcan/internal/static_assert.hpp>
+
+namespace uavcan
+{
+
+/**
+ * Should be OK for any target arch up to AMD64 and any compiler.
+ * The library leverages compile-time checks to ensure that all types that are subject to dynamic allocation
+ * fit this size; otherwise compilation fails.
+ */
+#if UAVCAN_MEM_POOL_BLOCK_SIZE
+enum { MEM_POOL_BLOCK_SIZE = UAVCAN_MEM_POOL_BLOCK_SIZE };
+#else
+enum { MEM_POOL_BLOCK_SIZE = 48 };
+#endif
+
+enum { MEM_POOL_ALIGNMENT = 8 };
+
+typedef char _alignment_check_for_MEM_POOL_BLOCK_SIZE[((MEM_POOL_BLOCK_SIZE & (MEM_POOL_ALIGNMENT - 1)) == 0) ? 1 : -1];
+
+template <typename T>
+struct AssertDynamicallyAllocatable
+{
+    static void check() { StaticAssert<sizeof(T) <= MEM_POOL_BLOCK_SIZE>::check(); }
+};
+
+}
diff --git a/libuavcan/include/uavcan/internal/static_assert.hpp b/libuavcan/include/uavcan/internal/static_assert.hpp
index 85a707acf2..10964b640d 100644
--- a/libuavcan/include/uavcan/internal/static_assert.hpp
+++ b/libuavcan/include/uavcan/internal/static_assert.hpp
@@ -8,7 +8,6 @@
 
 namespace uavcan
 {
-
 /**
  * Usage:
  *  StaticAssert<expression>::check();
@@ -27,4 +26,10 @@ struct StaticAssert<true>
     static void check() { }
 };
 
+/**
+ * Usage:
+ *  ShowIntegerAsError<integer_expression>::foobar();
+ */
+template<long N> struct ShowIntegerAsError;
+
 }
diff --git a/libuavcan/include/uavcan/internal/transport/can_io.hpp b/libuavcan/include/uavcan/internal/transport/can_io.hpp
index a0d6916a88..353bced9d4 100644
--- a/libuavcan/include/uavcan/internal/transport/can_io.hpp
+++ b/libuavcan/include/uavcan/internal/transport/can_io.hpp
@@ -9,7 +9,7 @@
 #include <stdint.h>
 #include <uavcan/internal/linked_list.hpp>
 #include <uavcan/internal/dynamic_memory.hpp>
-#include <uavcan/internal/static_assert.hpp>
+#include <uavcan/internal/impl_constants.hpp>
 #include <uavcan/can_driver.hpp>
 #include <uavcan/system_clock.hpp>
 
@@ -33,8 +33,7 @@ class CanTxQueue
 public:
     enum Qos { VOLATILE, PERSISTENT };
 
-#pragma pack(push, 1)
-    struct Entry : public LinkedListNode<Entry>
+    struct Entry : public LinkedListNode<Entry>  // Not required to be packed - fits the block in any case
     {
         uint64_t monotonic_deadline;
         CanFrame frame;
@@ -46,7 +45,7 @@ public:
         , qos(uint8_t(qos))
         {
             assert(qos == VOLATILE || qos == PERSISTENT);
-            StaticAssert<sizeof(Entry) <= 32>::check();
+            AssertDynamicallyAllocatable<Entry>::check();
         }
 
         bool isExpired(uint64_t monotonic_timestamp) const { return monotonic_timestamp > monotonic_deadline; }
@@ -58,7 +57,6 @@ public:
 
         std::string toString() const;
     };
-#pragma pack(pop)
 
 private:
     class PriorityInsertionComparator
diff --git a/libuavcan/include/uavcan/internal/transport/transfer_id_registry.hpp b/libuavcan/include/uavcan/internal/transport/transfer_id_registry.hpp
index 1ae06071ef..d621b12faf 100644
--- a/libuavcan/include/uavcan/internal/transport/transfer_id_registry.hpp
+++ b/libuavcan/include/uavcan/internal/transport/transfer_id_registry.hpp
@@ -8,7 +8,7 @@
 #include <stdint.h>
 #include <uavcan/internal/transport/transfer.hpp>
 #include <uavcan/internal/linked_list.hpp>
-#include <uavcan/internal/static_assert.hpp>
+#include <uavcan/internal/impl_constants.hpp>
 #include <uavcan/internal/dynamic_memory.hpp>
 
 namespace uavcan
@@ -81,13 +81,13 @@ private:
     {
         enum
         {
-            NUM_ENTRIES = (32 - sizeof(LinkedListNode<StorageEntryGroup>)) / sizeof(StorageEntry)
+            NUM_ENTRIES = (MEM_POOL_BLOCK_SIZE - sizeof(LinkedListNode<StorageEntryGroup>)) / sizeof(StorageEntry)
         };
         StorageEntry entries[NUM_ENTRIES];
 
         StorageEntryGroup()
         {
-            StaticAssert<sizeof(StorageEntryGroup) <= 32>::check();
+            AssertDynamicallyAllocatable<StorageEntryGroup>::check();
             StaticAssert<NUM_ENTRIES >= 2>::check();
         }
     };
diff --git a/libuavcan/test/transport/transfer_id_registry.cpp b/libuavcan/test/transport/transfer_id_registry.cpp
index e83c51b853..75ce7d0a05 100644
--- a/libuavcan/test/transport/transfer_id_registry.cpp
+++ b/libuavcan/test/transport/transfer_id_registry.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2014 <pavel.kirienko@gmail.com>
+ * Copyright (C) 2014 Pavel Kirienko <pavel.kirienko@gmail.com>
  */
 
 #include <gtest/gtest.h>
@@ -26,7 +26,7 @@ TEST(TransferIDRegistry, Basic)
     typedef TransferIDRegistry::Entry Entry;
 
     static const int POOL_BLOCKS = 8;
-    uavcan::PoolAllocator<32 * POOL_BLOCKS, 32> pool;
+    uavcan::PoolAllocator<uavcan::MEM_POOL_BLOCK_SIZE * POOL_BLOCKS, uavcan::MEM_POOL_BLOCK_SIZE> pool;
     uavcan::PoolManager<2> poolmgr;
     poolmgr.addPool(&pool);