Override get_rcl_allocator for TLSF allocators.

This removes one more user of the broken generic version of
get_rcl_allocator, which is causing
ros2/rclcpp#1254.

tlsf_cpp/include/tlsf_cpp/tlsf.hpp

@@ -23,13 +23,16 @@
 #include <new>
 #include <stdexcept>
 
+#include "rcl/allocator.h"
+#include "rclcpp/allocator/allocator_common.hpp"
 #include "tlsf/tlsf.h"
 
 template<typename T, size_t DefaultPoolSize = 1024 * 1024>
 struct tlsf_heap_allocator
 {
   // Needed for std::allocator_traits
   using value_type = T;
+  static const bool is_tlsf_heap_allocator = true;
 
   explicit tlsf_heap_allocator(size_t size)
   : memory_pool(nullptr), pool_size(size)
@@ -137,4 +140,32 @@ constexpr bool operator!=(
   return a.memory_pool != b.memory_pool;
 }
 
+void* tlsf_rcl_allocate(size_t size, void*) {
+  return tlsf_malloc(size);
+}
+
+void tlsf_rcl_deallocate(void* pointer, void*) {
+  tlsf_free(pointer);
+}
+
+void* tlsf_reallocate(void* pointer, size_t size, void*) {
+  return tlsf_rcl_realloc(pointer, size);
+}
+
+void* tlsf_zero_allocate(size_t number_of_elements, size_t size_of_elements, void*) {
+  return tlsf_rcl_calloc(number_of_elements, size_of_elements);
+}
+
+template<typename T, size_t PoolSize>
+rcl_allocator_t get_rcl_allocator(tlsf_heap_allocator<T, PoolSize>& allocator)
+{
+  rcl_allocator_t rcl_allocator;
+  rcl_allocator.allocate = tlsf_allocate;
+  rcl_allocator.deallocate = tlsf_deallocate;
+  rcl_allocator.reallocate = tlsf_reallocate;
+  rcl_allocator.zero_allocate = tlsf_zero_allocate;
+  rcl_allocator.state = &allocator;
+  return rcl_allocator;
+}
+
 #endif  // TLSF_CPP__TLSF_HPP_