integrating the existing state of TON Storage / TON Payments / CPS Fift development branches

tdutils/td/utils/Span.h

@@ -86,6 +86,26 @@ class SpanImpl {
     return data_[i];
   }
 
+  InnerT &back() {
+    DCHECK(!empty());
+    return data_[size() - 1];
+  }
+
+  const InnerT &back() const {
+    DCHECK(!empty());
+    return data_[size() - 1];
+  }
+
+  InnerT &front() {
+    DCHECK(!empty());
+    return data_[0];
+  }
+
+  const InnerT &front() const {
+    DCHECK(!empty());
+    return data_[0];
+  }
+
   InnerT *data() const {
     return data_;
   }
@@ -109,8 +129,9 @@ class SpanImpl {
   }
 
   SpanImpl &truncate(size_t size) {
-    CHECK(size <= size_);
-    size_ = size;
+    if (size < size_) {
+      size_ = size;
+    }
     return *this;
   }
 
@@ -136,9 +157,45 @@ template <class T>
 Span<T> span(const T *ptr, size_t size) {
   return Span<T>(ptr, size);
 }
+template <class T>
+Span<T> span(const std::vector<T> &vec) {
+  return Span<T>(vec);
+}
+
 template <class T>
 MutableSpan<T> mutable_span(T *ptr, size_t size) {
   return MutableSpan<T>(ptr, size);
 }
+template <class T>
+MutableSpan<T> mutable_span(std::vector<T> &vec) {
+  return MutableSpan<T>(vec);
+}
+
+template <class T>
+Span<T> span_one(const T &value) {
+  return td::Span<T>(&value, 1);
+}
+template <class T>
+MutableSpan<T> mutable_span_one(T &value) {
+  return td::MutableSpan<T>(&value, 1);
+}
+
+template <class T>
+Span<T> as_span(Span<T> span) {
+  return span;
+}
+template <class T>
+Span<T> as_span(const std::vector<T> &vec) {
+  return Span<T>(vec);
+}
+
+template <class T>
+MutableSpan<T> as_mutable_span(MutableSpan<T> span) {
+  return span;
+}
+template <class T>
+MutableSpan<T> as_mutable_span(std::vector<T> &vec) {
+  return MutableSpan<T>(vec);
+}
 
 }  // namespace td