[C++] Add ability to get a var data as a string_view. Issue #550.

real-logic · Feb 4, 2019 · c60ac3f · c60ac3f
1 parent 770c2b8
commit c60ac3f
Showing 1 changed file with 38 additions and 0 deletions.
diff --git a/sbe-tool/src/main/java/uk/co/real_logic/sbe/generation/cpp/CppGenerator.java b/sbe-tool/src/main/java/uk/co/real_logic/sbe/generation/cpp/CppGenerator.java
@@ -489,6 +489,29 @@ private CharSequence generateVarData(final String className, final List<Token> t
                 lengthByteOrderStr,
                 lengthCppType));
 
+            sb.append(String.format("\n" +
+                indent + "    #if __cplusplus >= 201703L\n" +
+                indent + "    const std::string_view get%1$sAsStringView()\n" +
+                indent + "    {\n" +
+                "%2$s" +
+                indent + "        std::uint64_t lengthOfLengthField = %3$d;\n" +
+                indent + "        std::uint64_t lengthPosition = sbePosition();\n" +
+                indent + "        sbePosition(lengthPosition + lengthOfLengthField);\n" +
+                indent + "        %5$s lengthFieldValue;\n" +
+                indent + "        std::memcpy(&lengthFieldValue, m_buffer + lengthPosition, sizeof(%5$s));\n" +
+                indent + "        std::uint64_t dataLength = %4$s(lengthFieldValue);\n" +
+                indent + "        std::uint64_t pos = sbePosition();\n" +
+                indent + "        const std::string_view result(m_buffer + pos, dataLength);\n" +
+                indent + "        sbePosition(pos + dataLength);\n" +
+                indent + "        return result;\n" +
+                indent + "    }\n" +
+                indent + "    #endif\n",
+                propertyName,
+                generateStringViewNotPresentCondition(token.version(), BASE_INDENT),
+                lengthOfLengthField,
+                lengthByteOrderStr,
+                lengthCppType));
+
             sb.append(String.format("\n" +
                 indent + "    %1$s &put%2$s(const std::string& str)\n" +
                 indent + "    {\n" +
@@ -844,6 +867,21 @@ private static CharSequence generateStringNotPresentCondition(final int sinceVer
             sinceVersion);
     }
 
+    private static CharSequence generateStringViewNotPresentCondition(final int sinceVersion, final String indent)
+    {
+        if (0 == sinceVersion)
+        {
+            return "";
+        }
+
+        return String.format(
+            indent + "        if (m_actingVersion < %1$d)\n" +
+            indent + "        {\n" +
+            indent + "            return std::string_view(\"\");\n" +
+            indent + "        }\n\n",
+            sinceVersion);
+    }
+
     private static CharSequence generateTypeFieldNotPresentCondition(final int sinceVersion, final String indent)
     {
         if (0 == sinceVersion)