+/** Options for read operations
+ *
+ * This is a set of flags managed with bitwise operators. Only the
+ * meaningful operations are defined: addition, conversions to/from
+ * integers are not allowed.
+ */
+class ReadOptions {
+ std::uint32_t value_;
+ constexpr explicit ReadOptions(std::uint32_t value) : value_(value) {}
+public:
+ constexpr ReadOptions() : value_(0) {}
+
+ constexpr operator bool() const { return value_ != 0; }
+ constexpr bool operator!() const { return value_ == 0; }
+
+ constexpr ReadOptions operator|(ReadOptions const& that) const
+ {
+ return ReadOptions(value_ | that.value_);
+ }
+ constexpr ReadOptions operator&(ReadOptions const& that) const
+ {
+ return ReadOptions(value_ & that.value_);
+ }
+ constexpr ReadOptions operator^(ReadOptions const& that) const
+ {
+ return ReadOptions(value_ ^ that.value_);
+ }
+ constexpr ReadOptions operator~() const
+ {
+ return ReadOptions(~value_);
+ }
+
+ ReadOptions& operator|=(ReadOptions const& that)
+ {
+ value_ |= that.value_;
+ return *this;
+ }
+ ReadOptions& operator&=(ReadOptions const& that)
+ {
+ value_ &= that.value_;
+ return *this;
+ }
+ ReadOptions& operator^=(ReadOptions const& that)
+ {
+ value_ &= that.value_;
+ return *this;
+ }
+
+ /** Copy the data to the given buffer */
+ static constexpr ReadOptions none() { return ReadOptions(0); }
+
+ /** Allows to return a pointer to another buffer where the data is
+ * available instead of copying the data into the buffer
+ */
+ 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:
+ *
+ * * the current state of an existing process;
+ *
+ * * a snapshot.
+ */