Add specialized constructors and safety checks to legate::Scalar (#736

)

* Add specialized constructors and safety checks to legate::Scalar

* Update src/core/data/scalar.h

Co-authored-by: Manolis Papadakis <manopapad@gmail.com>

---------

Co-authored-by: Manolis Papadakis <manopapad@gmail.com>

src/core/data/scalar.cc

@@ -15,16 +15,31 @@
  */
 
 #include "core/data/scalar.h"
-#include "core/utilities/dispatch.h"
 
 namespace legate {
 
 Scalar::Scalar(const Scalar& other) : own_(other.own_), type_(other.type_->clone()) { copy(other); }
 
+Scalar::Scalar(Scalar&& other) : own_(other.own_), type_(std::move(other.type_)), data_(other.data_)
+{
+  other.own_  = false;
+  other.type_ = nullptr;
+  other.data_ = nullptr;
+}
+
 Scalar::Scalar(std::unique_ptr<Type> type, const void* data) : type_(std::move(type)), data_(data)
 {
 }
 
+Scalar::Scalar(const std::string& string) : own_(true), type_(string_type())
+{
+  auto data_size                  = sizeof(char) * string.size();
+  auto buffer                     = malloc(sizeof(uint32_t) + data_size);
+  *static_cast<uint32_t*>(buffer) = string.size();
+  memcpy(static_cast<int8_t*>(buffer) + sizeof(uint32_t), string.data(), data_size);
+  data_ = buffer;
+}
+
 Scalar::~Scalar()
 {
   if (own_)

src/core/data/scalar.h

@@ -45,6 +45,8 @@ class Scalar {
  public:
   Scalar() = default;
   Scalar(const Scalar& other);
+  Scalar(Scalar&& other);
+
   /**
    * @brief Creates a shared `Scalar` with an existing allocation. The caller is responsible
    * for passing in a sufficiently big allocation.
@@ -65,6 +67,24 @@ class Scalar {
    */
   template <typename T>
   Scalar(T value);
+  /**
+   * @brief Creates an owned scalar of a specified type from a scalar value
+   *
+   * @tparam T The scalar type to wrap
+   *
+   * @param type The type of the scalar
+   * @param value A scalar value to create a `Scalar` with
+   */
+  template <typename T>
+  Scalar(T value, std::unique_ptr<Type> type);
+  /**
+   * @brief Creates an owned scalar from a string. The value from the
+   * original string will be copied.
+   *
+   * @param string A string to create a `Scalar` with
+   */
+  Scalar(const std::string& string);
+
   /**
    * @brief Creates an owned scalar from a tuple of scalars. The values in the input vector
    * will be copied.

src/core/data/scalar.inl

@@ -19,6 +19,22 @@ namespace legate {
 template <typename T>
 Scalar::Scalar(T value) : own_(true), type_(primitive_type(legate_type_code_of<T>))
 {
+  static_assert(legate_type_code_of<T> != Type::Code::FIXED_ARRAY);
+  static_assert(legate_type_code_of<T> != Type::Code::STRUCT);
+  static_assert(legate_type_code_of<T> != Type::Code::STRING);
+  static_assert(legate_type_code_of<T> != Type::Code::INVALID);
+  auto buffer = malloc(sizeof(T));
+  memcpy(buffer, &value, sizeof(T));
+  data_ = buffer;
+}
+
+template <typename T>
+Scalar::Scalar(T value, std::unique_ptr<Type> type) : own_(true), type_(std::move(type))
+{
+  if (type_->code == Type::Code::INVALID)
+    throw std::invalid_argument("Invalid type cannot be used");
+  if (type_->size() != sizeof(T))
+    throw std::invalid_argument("Size of the value doesn't match with the type");
   auto buffer = malloc(sizeof(T));
   memcpy(buffer, &value, sizeof(T));
   data_ = buffer;
@@ -37,12 +53,17 @@ Scalar::Scalar(const std::vector<T>& values)
 template <typename VAL>
 VAL Scalar::value() const
 {
+  if (sizeof(VAL) != type_->size())
+    throw std::invalid_argument("Size of the scalar is " + std::to_string(type_->size()) +
+                                ", but the requested type has size " + std::to_string(sizeof(VAL)));
   return *static_cast<const VAL*>(data_);
 }
 
 template <>
 inline std::string Scalar::value() const
 {
+  if (type_->code != Type::Code::STRING)
+    throw std::invalid_argument("Type of the scalar is not string");
   // Getting a span of a temporary scalar is illegal in general,
   // but we know this is safe as the span's pointer is held by this object.
   auto len          = *static_cast<const uint32_t*>(data_);
@@ -55,10 +76,21 @@ template <typename VAL>
 Span<const VAL> Scalar::values() const
 {
   if (type_->code == Type::Code::FIXED_ARRAY) {
-    auto size = static_cast<const FixedArrayType*>(type_.get())->num_elements();
+    auto arr_type         = static_cast<const FixedArrayType*>(type_.get());
+    const auto& elem_type = arr_type->element_type();
+    if (sizeof(VAL) != elem_type.size())
+      throw std::invalid_argument(
+        "The scalar's element type has size " + std::to_string(elem_type.size()) +
+        ", but the requested element type has size " + std::to_string(sizeof(VAL)));
+    auto size = arr_type->num_elements();
     return Span<const VAL>(reinterpret_cast<const VAL*>(data_), size);
-  } else
+  } else {
+    if (sizeof(VAL) != type_->size())
+      throw std::invalid_argument("Size of the scalar is " + std::to_string(type_->size()) +
+                                  ", but the requested element type has size " +
+                                  std::to_string(sizeof(VAL)));
     return Span<const VAL>(static_cast<const VAL*>(data_), 1);
+  }
 }
 
 template <>