[mc] Generalize AddressSpace::read<T>() to return a Remote<T>

[simgrid.git] / src / mc / AddressSpace.hpp

diff --git a/src/mc/AddressSpace.hpp b/src/mc/AddressSpace.hpp
index 0ff146a..18969aa 100644 (file)
--- a/src/mc/AddressSpace.hpp
+++ b/src/mc/AddressSpace.hpp
@@ -7,12 +7,14 @@
 #ifndef SIMGRID_MC_ADDRESS_SPACE_H
 #define SIMGRID_MC_ADDRESS_SPACE_H
 
+#include <cassert>
 #include <cstddef>
 #include <cstdint>
+#include <cstring>
 #include <type_traits>
 
 #include "src/mc/mc_forward.hpp"
-#include "src/mc/remote_ptr.hpp"
+#include "src/mc/RemotePtr.hpp"
 
 namespace simgrid {
 namespace mc {
@@ -90,6 +92,49 @@ public:
   static constexpr ReadOptions lazy() { return ReadOptions(1); }
 };
 
+/** A value from another process
+ *
+ *  This represents a value from another process:
+ *
+ *  * constructor/destructor are disabled;
+ *
+ *  * raw memory copy (std::memcpy) is used to copy Remote<T>;
+ *
+ *  * raw memory comparison is used to compare them;
+ *
+ *  * when T is a trivial type, Remote is convertible to a T.
+ *
+ *  We currently only handle the case where the type has the same layout
+ *  in the current process and in the target process: we don't handle
+ *  cross-architecture (such as 32-bit/64-bit access).
+ */
+template<class T>
+class Remote {
+private:
+  // If we use a union, it won't work with abstract types:
+  char buffer[sizeof(T)];
+public:
+  // HACK, some code currently cast this to T* which is **not** legal.
+  void*       data() { return buffer; }
+  const void* data() const { return buffer; }
+  constexpr std::size_t size() const { return sizeof(T); }
+  operator T() const {
+    static_assert(std::is_trivial<T>::value, "Cannot convert non trivial type");
+    T res;
+    std::memcpy(&res, buffer, sizeof(T));
+    return res;
+  }
+  Remote() {}
+  Remote(T const& x)
+  {
+    std::memcpy(&x, buffer, sizeof(T));
+  }
+  Remote& operator=(T const& x)
+  {
+    std::memcpy(&x, buffer, sizeof(T));
+  }
+};
+
 /** A given state of a given process (abstract base class)
  *
  *  Currently, this might either be:
@@ -116,23 +161,29 @@ public:
    *  @param options
    */
   virtual const void* read_bytes(void* buffer, std::size_t size,
-    remote_ptr<void> address, int process_index = ProcessIndexAny,
+    RemotePtr<void> address, int process_index = ProcessIndexAny,
     ReadOptions options = ReadOptions::none()) const = 0;
 
   /** Read a given data structure from the address space */
   template<class T> inline
-  void read(T *buffer, remote_ptr<T> ptr, int process_index = ProcessIndexAny)
+  void read(T *buffer, RemotePtr<T> ptr, int process_index = ProcessIndexAny)
   {
     this->read_bytes(buffer, sizeof(T), ptr, process_index);
   }
 
+  template<class T> inline
+  void read(Remote<T>& buffer, RemotePtr<T> ptr, int process_index = ProcessIndexAny)
+  {
+    this->read_bytes(buffer.data(), sizeof(T), ptr, process_index);
+  }
+
   /** Read a given data structure from the address space */
   template<class T> inline
-  T read(remote_ptr<T> ptr, int process_index = ProcessIndexMissing)
+  Remote<T> read(RemotePtr<T> ptr, int process_index = ProcessIndexMissing)
   {
-    static_assert(std::is_trivial<T>::value, "Cannot read a non-trivial type");
-    T res;
-    return *(T*)this->read_bytes(&res, sizeof(T), ptr, process_index);
+    Remote<T> res;
+    this->read_bytes(&res, sizeof(T), ptr, process_index);
+    return res;
   }
 };