Documenting how one can check for the end of the document. (#1907)

doc/basics.md

@@ -1110,6 +1110,8 @@ for (auto val : doc) {
 std::cout << doc.current_location() << std::endl;   // Throws OUT_OF_BOUNDS
 ```
 
+Conversely, if `doc.current_location()` succeeds, then the document has more content.
+
 Finally, the `current_location()` method may also be used even when no exceptions/errors
 are thrown. This can be helpful for users that want to know the current state of iteration during parsing. For example:
 

tools/json2json.cpp

@@ -64,6 +64,16 @@ int main(int argc, const char *argv[]) {
     error = parser.iterate(docdata).get(doc);
     if(error != simdjson::SUCCESS) { std::cout << error << std::endl; return EXIT_FAILURE; }
     std::cout << doc;
+    // check if there is more content
+    const char * endofstream;
+    if(doc.current_location().get(endofstream) == simdjson::SUCCESS) {
+      // there is more content !
+      // let us find what it is:
+      size_t len = docdata.data() + docdata.size() - endofstream;
+      std::string_view content{endofstream, len};
+      std::cerr << "\nThere is leftover content: '" << content << "'" << std::endl;
+      return EXIT_FAILURE;
+    }
     return EXIT_SUCCESS;
   }
   simdjson::dom::parser parser;