Initial support for std::string_view (#633)

When PUGIXML_STRING_VIEW define is set and C++17 is available, add std::string_view support to a few functions. In the future, string view support will be enabled without the need for an extra define, but for now the support is opt-in to reduce compatibility risks.

PR is based on initial contribution by @brandl-muc.

.github/workflows/build.yml

@@ -12,7 +12,7 @@ jobs:
       matrix:
         os: [ubuntu, macos]
         compiler: [g++, clang++]
-        defines: [standard, PUGIXML_WCHAR_MODE, PUGIXML_COMPACT, PUGIXML_NO_EXCEPTIONS]
+        defines: [standard, PUGIXML_WCHAR_MODE, PUGIXML_COMPACT, PUGIXML_NO_EXCEPTIONS, PUGIXML_STRING_VIEW]
         exclude:
           - os: macos
             compiler: g++
@@ -25,6 +25,7 @@ jobs:
         export CXX=${{matrix.compiler}}
         make test cxxstd=c++11 defines=${{matrix.defines}} config=release -j2
         make test cxxstd=c++98 defines=${{matrix.defines}} config=debug -j2
+        make test cxxstd=c++17 defines=${{matrix.defines}} config=debug -j2
         make test defines=${{matrix.defines}} config=sanitize -j2
     - name: make coverage
       if: ${{!(matrix.os == 'ubuntu' && matrix.compiler == 'clang++')}} # linux/clang produces coverage info gcov can't parse
@@ -38,7 +39,7 @@ jobs:
     strategy:
       matrix:
         arch: [Win32, x64]
-        defines: [standard, PUGIXML_WCHAR_MODE, PUGIXML_COMPACT, PUGIXML_NO_EXCEPTIONS]
+        defines: [standard, PUGIXML_WCHAR_MODE, PUGIXML_COMPACT, PUGIXML_NO_EXCEPTIONS, PUGIXML_STRING_VIEW]
     steps:
     - uses: actions/checkout@v1
     - name: cmake configure
@@ -50,3 +51,10 @@ jobs:
         Debug/pugixml-check.exe
         cmake --build . -- -property:Configuration=Release -verbosity:minimal
         Release/pugixml-check.exe
+    - name: cmake configure (c++17)
+      run: cmake . -DPUGIXML_BUILD_TESTS=ON -DCMAKE_CXX_STANDARD=17 -D${{matrix.defines}}=ON -A ${{matrix.arch}}
+    - name: cmake test (c++17)
+      shell: bash # necessary for fail-fast
+      run: |
+        cmake --build . -- -property:Configuration=Debug -verbosity:minimal
+        Debug/pugixml-check.exe

CMakeLists.txt

@@ -48,14 +48,17 @@ option(PUGIXML_INSTALL "Enable installation rules" ON)
 option(PUGIXML_NO_XPATH "Disable XPath" OFF)
 option(PUGIXML_NO_STL "Disable STL" OFF)
 option(PUGIXML_NO_EXCEPTIONS "Disable Exceptions" OFF)
-mark_as_advanced(PUGIXML_NO_XPATH PUGIXML_NO_STL PUGIXML_NO_EXCEPTIONS)
+option(PUGIXML_STRING_VIEW "Enable std::string_view overloads" OFF) # requires C++17 and for PUGI_NO_STL to be OFF
+mark_as_advanced(PUGIXML_NO_XPATH PUGIXML_NO_STL PUGIXML_NO_EXCEPTIONS PUGIXML_STRING_VIEW)
 
 set(PUGIXML_PUBLIC_DEFINITIONS
   $<$<BOOL:${PUGIXML_WCHAR_MODE}>:PUGIXML_WCHAR_MODE>
   $<$<BOOL:${PUGIXML_COMPACT}>:PUGIXML_COMPACT>
   $<$<BOOL:${PUGIXML_NO_XPATH}>:PUGIXML_NO_XPATH>
   $<$<BOOL:${PUGIXML_NO_STL}>:PUGIXML_NO_STL>
-  $<$<BOOL:${PUGIXML_NO_EXCEPTIONS}>:PUGIXML_NO_EXCEPTIONS>)
+  $<$<BOOL:${PUGIXML_NO_EXCEPTIONS}>:PUGIXML_NO_EXCEPTIONS>
+  $<$<BOOL:${PUGIXML_STRING_VIEW}>:PUGIXML_STRING_VIEW>
+)
 
 # This is used to backport a CMake 3.15 feature, but is also forwards compatible
 if (NOT DEFINED CMAKE_MSVC_RUNTIME_LIBRARY)

src/pugiconfig.hpp

@@ -49,6 +49,11 @@
 // Uncomment this to enable long long support
 // #define PUGIXML_HAS_LONG_LONG
 
+// Uncomment this to enable support for std::string_view (requires c++17 and for PUGIXML_NO_STL to not be set)
+// Note: In a future version of pugixml this macro will become obsolete.
+//       Support will then be enabled automatically if the used C++ standard supports it.
+// #define PUGIXML_STRING_VIEW
+
 #endif
 
 /**

src/pugixml.cpp

@@ -5441,6 +5441,15 @@ namespace pugi
 		return impl::strcpy_insitu(_attr->name, _attr->header, impl::xml_memory_page_name_allocated_mask, rhs, size);
 	}
 
+#ifdef PUGIXML_HAS_STRING_VIEW
+	PUGI_IMPL_FN bool xml_attribute::set_name(string_view_t rhs)
+	{
+		if (!_attr) return false;
+
+		return impl::strcpy_insitu(_attr->name, _attr->header, impl::xml_memory_page_name_allocated_mask, rhs.data(), rhs.size());
+	}
+#endif
+
 	PUGI_IMPL_FN bool xml_attribute::set_value(const char_t* rhs)
 	{
 		if (!_attr) return false;
@@ -5455,6 +5464,15 @@ namespace pugi
 		return impl::strcpy_insitu(_attr->value, _attr->header, impl::xml_memory_page_value_allocated_mask, rhs, size);
 	}
 
+#ifdef PUGIXML_HAS_STRING_VIEW
+	PUGI_IMPL_FN bool xml_attribute::set_value(string_view_t rhs)
+	{
+		if (!_attr) return false;
+
+		return impl::strcpy_insitu(_attr->value, _attr->header, impl::xml_memory_page_value_allocated_mask, rhs.data(), rhs.size());
+	}
+#endif
+
 	PUGI_IMPL_FN bool xml_attribute::set_value(int rhs)
 	{
 		if (!_attr) return false;
@@ -5848,6 +5866,18 @@ namespace pugi
 		return impl::strcpy_insitu(_root->name, _root->header, impl::xml_memory_page_name_allocated_mask, rhs, size);
 	}
 
+#ifdef PUGIXML_HAS_STRING_VIEW
+	PUGI_IMPL_FN bool xml_node::set_name(string_view_t rhs)
+	{
+		xml_node_type type_ = _root ? PUGI_IMPL_NODETYPE(_root) : node_null;
+
+		if (type_ != node_element && type_ != node_pi && type_ != node_declaration)
+			return false;
+
+		return impl::strcpy_insitu(_root->name, _root->header, impl::xml_memory_page_name_allocated_mask, rhs.data(), rhs.size());
+	}
+#endif
+
 	PUGI_IMPL_FN bool xml_node::set_value(const char_t* rhs)
 	{
 		xml_node_type type_ = _root ? PUGI_IMPL_NODETYPE(_root) : node_null;
@@ -5868,6 +5898,18 @@ namespace pugi
 		return impl::strcpy_insitu(_root->value, _root->header, impl::xml_memory_page_value_allocated_mask, rhs, size);
 	}
 
+#ifdef PUGIXML_HAS_STRING_VIEW
+	PUGI_IMPL_FN bool xml_node::set_value(string_view_t rhs)
+	{
+		xml_node_type type_ = _root ? PUGI_IMPL_NODETYPE(_root) : node_null;
+
+		if (type_ != node_pcdata && type_ != node_cdata && type_ != node_comment && type_ != node_pi && type_ != node_doctype)
+			return false;
+
+		return impl::strcpy_insitu(_root->value, _root->header, impl::xml_memory_page_value_allocated_mask, rhs.data(), rhs.size());
+	}
+#endif
+
 	PUGI_IMPL_FN xml_attribute xml_node::append_attribute(const char_t* name_)
 	{
 		if (!impl::allow_insert_attribute(type())) return xml_attribute();
@@ -6757,6 +6799,15 @@ namespace pugi
 		return dn ? impl::strcpy_insitu(dn->value, dn->header, impl::xml_memory_page_value_allocated_mask, rhs, size) : false;
 	}
 
+#ifdef PUGIXML_HAS_STRING_VIEW
+	PUGI_IMPL_FN bool xml_text::set(string_view_t rhs)
+	{
+		xml_node_struct* dn = _data_new();
+
+		return dn ? impl::strcpy_insitu(dn->value, dn->header, impl::xml_memory_page_value_allocated_mask, rhs.data(), rhs.size()) : false;
+	}
+#endif
+
 	PUGI_IMPL_FN bool xml_text::set(int rhs)
 	{
 		xml_node_struct* dn = _data_new();

src/pugixml.hpp

@@ -38,6 +38,20 @@
 #	include <string>
 #endif
 
+// Check if std::string_view is both requested and available
+#if defined(PUGIXML_STRING_VIEW) && !defined(PUGIXML_NO_STL)
+#	if __cplusplus >= 201703L
+#		define PUGIXML_HAS_STRING_VIEW
+#	elif defined(_MSVC_LANG) && _MSVC_LANG >= 201703L
+#		define PUGIXML_HAS_STRING_VIEW
+#	endif
+#endif
+
+// Include string_view if appropriate
+#ifdef PUGIXML_HAS_STRING_VIEW
+#	include <string_view>
+#endif
+
 // Macro for deprecated features
 #ifndef PUGIXML_DEPRECATED
 #	if defined(__GNUC__)
@@ -140,6 +154,11 @@ namespace pugi
 	// String type used for operations that work with STL string; depends on PUGIXML_WCHAR_MODE
 	typedef std::basic_string<PUGIXML_CHAR> string_t;
 #endif
+
+#ifdef PUGIXML_HAS_STRING_VIEW
+	// String view type used for operations that can work with a length delimited string; depends on PUGIXML_WCHAR_MODE
+	typedef std::basic_string_view<PUGIXML_CHAR> string_view_t;
+#endif
 }
 
 // The PugiXML namespace
@@ -423,8 +442,14 @@ namespace pugi
 		// Set attribute name/value (returns false if attribute is empty or there is not enough memory)
 		bool set_name(const char_t* rhs);
 		bool set_name(const char_t* rhs, size_t size);
+	#ifdef PUGIXML_HAS_STRING_VIEW
+		bool set_name(string_view_t rhs);
+	#endif
 		bool set_value(const char_t* rhs);
 		bool set_value(const char_t* rhs, size_t size);
+	#ifdef PUGIXML_HAS_STRING_VIEW
+		bool set_value(string_view_t rhs);
+	#endif
 
 		// Set attribute value with type conversion (numbers are converted to strings, boolean is converted to "true"/"false")
 		bool set_value(int rhs);
@@ -559,8 +584,14 @@ namespace pugi
 		// Set node name/value (returns false if node is empty, there is not enough memory, or node can not have name/value)
 		bool set_name(const char_t* rhs);
 		bool set_name(const char_t* rhs, size_t size);
+	#ifdef PUGIXML_HAS_STRING_VIEW
+		bool set_name(string_view_t rhs);
+	#endif
 		bool set_value(const char_t* rhs);
 		bool set_value(const char_t* rhs, size_t size);
+	#ifdef PUGIXML_HAS_STRING_VIEW
+		bool set_value(string_view_t rhs);
+	#endif
 
 		// Add attribute with specified name. Returns added attribute, or empty attribute on errors.
 		xml_attribute append_attribute(const char_t* name);
@@ -790,6 +821,9 @@ namespace pugi
 		// Set text (returns false if object is empty or there is not enough memory)
 		bool set(const char_t* rhs);
 		bool set(const char_t* rhs, size_t size);
+	#ifdef PUGIXML_HAS_STRING_VIEW
+		bool set(string_view_t rhs);
+	#endif
 
 		// Set text with type conversion (numbers are converted to strings, boolean is converted to "true"/"false")
 		bool set(int rhs);

tests/test_dom_modify.cpp

@@ -56,6 +56,23 @@ TEST_XML(dom_attr_set_name_with_size, "<node attr='value' />")
 	CHECK_NODE(doc, STR("<node n=\"value\"/>"));
 }
 
+#ifdef PUGIXML_HAS_STRING_VIEW
+TEST_XML(dom_attr_set_name_with_string_view, "<node attr='value' />")
+{
+	xml_attribute attr = doc.child(STR("node")).attribute(STR("attr"));
+
+	CHECK(attr.set_name(string_view_t()));
+	CHECK(!xml_attribute().set_name(string_view_t()));
+
+	CHECK_NODE(doc, STR("<node :anonymous=\"value\"/>"));
+
+	CHECK(attr.set_name(string_view_t(STR("n1234"), 1)));
+	CHECK(!xml_attribute().set_name(string_view_t(STR("nfail"), 1)));
+
+	CHECK_NODE(doc, STR("<node n=\"value\"/>"));
+}
+#endif
+
 TEST_XML(dom_attr_set_value, "<node/>")
 {
 	xml_node node = doc.child(STR("node"));
@@ -225,6 +242,25 @@ TEST_XML(dom_node_set_name_with_size, "<node>text</node>")
 	CHECK_NODE(doc, STR("<n>text</n>"));
 }
 
+#ifdef PUGIXML_HAS_STRING_VIEW
+TEST_XML(dom_node_set_name_with_string_view, "<node>text</node>")
+{
+	xml_node node = doc.child(STR("node"));
+
+	CHECK(node.set_name(string_view_t()));
+	CHECK(!node.first_child().set_name(string_view_t(STR("n42"), 1)));
+	CHECK(!xml_node().set_name(string_view_t(STR("nanothername"), 1)));
+
+	CHECK_NODE(doc, STR("<:anonymous>text</:anonymous>"));
+
+	CHECK(node.set_name(string_view_t(STR("nlongname"), 1)));
+	CHECK(!doc.child(STR("node")).first_child().set_name(string_view_t(STR("n42"), 1)));
+	CHECK(!xml_node().set_name(string_view_t(STR("nanothername"), 1)));
+
+	CHECK_NODE(doc, STR("<n>text</n>"));
+}
+#endif
+
 TEST_XML(dom_node_set_value, "<node>text</node>")
 {
 	CHECK(doc.child(STR("node")).first_child().set_value(STR("no text")));
@@ -252,6 +288,26 @@ TEST_XML(dom_node_set_value_with_size, "<node>text</node>")
 	CHECK_NODE(doc, STR("<node>no text</node>"));
 }
 
+#ifdef PUGIXML_HAS_STRING_VIEW
+TEST_XML(dom_node_set_value_partially_with_string_view, "<node>text</node>")
+{
+	CHECK(doc.child(STR("node")).first_child().set_value(string_view_t(STR("no text"), 2)));
+	CHECK(!doc.child(STR("node")).set_value(string_view_t(STR("no text"), 2)));
+	CHECK(!xml_node().set_value(string_view_t(STR("no text"), 2)));
+
+	CHECK_NODE(doc, STR("<node>no</node>"));
+}
+
+TEST_XML(dom_node_set_value_with_string_view, "<node>text</node>")
+{
+	CHECK(doc.child(STR("node")).first_child().set_value(string_view_t(STR("no text"), 7)));
+	CHECK(!doc.child(STR("node")).set_value(string_view_t(STR("no text"), 7)));
+	CHECK(!xml_node().set_value(string_view_t(STR("no text"), 7)));
+
+	CHECK_NODE(doc, STR("<node>no text</node>"));
+}
+#endif
+
 TEST_XML(dom_node_set_value_allocated, "<node>text</node>")
 {
 	CHECK(doc.child(STR("node")).first_child().set_value(STR("no text")));