xo-object2: + DString::from_view()

xo-object2/include/xo/object2/DString.hpp

@@ -72,6 +72,12 @@ namespace xo {
             static DString * from_cstr(obj<AAllocator> mm,
                                        const char * cstr);
 
+            /** create string containing a copy of @p sv.
+             *  Use memory from allocator @p mm
+             **/
+            static DString * from_view(obj<AAllocator> mm,
+                                       std::string_view sv);
+
             /** clone existing string **/
             static DString * clone(obj<AAllocator> mm,
                                    const DString * src);

xo-object2/src/object2/DString.cpp

@@ -57,6 +57,25 @@ namespace xo {
             return result;
         }
 
+        DString *
+        DString::from_view(obj<AAllocator> mm,
+                           std::string_view sv)
+        {
+            size_type len = sv.size();
+            size_type cap = len + 1;
+
+            void * mem = mm.alloc(typeseq::id<DString>(),
+                                  sizeof(DString) + cap);
+
+            DString * result = new (mem) DString();
+            result->capacity_ = cap;
+            result->size_ = len;
+            std::memcpy(result->chars_, sv.data(), len);
+            result->chars_[len] = '\0';
+
+            return result;
+        }
+
         DString *
         DString::clone(obj<AAllocator> mm, const DString * src)
         {

xo-object2/utest/DString.test.cpp

@@ -50,6 +50,31 @@ namespace xo {
             REQUIRE(std::strcmp(s->chars(), cstr) == 0);
         }
 
+        TEST_CASE("DString-from_view", "[object2][DString]")
+        {
+            ArenaConfig cfg { .name_ = "testarena",
+                              .size_ = 4*1024 };
+            DArena arena = DArena::map(cfg);
+            auto alloc = with_facet<AAllocator>::mkobj(&arena);
+
+            std::string_view sv = "hello world";
+            DString * s = DString::from_view(alloc, sv);
+
+            REQUIRE(s != nullptr);
+            REQUIRE(s->capacity() == 12);
+            REQUIRE(s->size() == 11);
+            REQUIRE(std::strcmp(s->chars(), "hello world") == 0);
+
+            // test with substring (not null-terminated)
+            std::string_view sub = sv.substr(0, 5);
+            DString * s2 = DString::from_view(alloc, sub);
+
+            REQUIRE(s2 != nullptr);
+            REQUIRE(s2->capacity() == 6);
+            REQUIRE(s2->size() == 5);
+            REQUIRE(std::strcmp(s2->chars(), "hello") == 0);
+        }
+
         TEST_CASE("DString-assign", "[object2][DString]")
         {
             ArenaConfig cfg { .name_ = "testarena",