Adding a couple of string tests. (#1935)

* Adding a couple of string tests.

doc/basics.md

@@ -41,7 +41,7 @@ Requirements
 - Visual Studio 2017 or better under 64-bit Windows. Users should target a 64-bit build (x64) instead of a 32-bit build (x86). We support the LLVM clang compiler under Visual Studio (clangcl) as well as as the regular Visual Studio compiler. We also support MinGW 64-bit under Windows.
 
 
-Support for AVX-512 require a processor with AVX512-VBMI2 support (Ice Lake or better) under a 64-bit system and a recent compiler (LLVM clang 6 or better, GCC 8 or better, Visual Studio 2019 or better). You need a correspondingly recent assembler such as gas (2.30+) or nasm (2.14+): recent compilers usually come with recent assemblers. If you mix a recent compiler with an incompatible/old assembler (e.g., when using a recent compiler with an old Linux distribution), you may get errors at build time because the compiler produces instructions that the assembler does not recognize: you should update your assembler to match your compiler (e.g., upgrade binutils to version 2.30 or better under Linux) or use an older compiler matching the capabilities of your assembler. 
+Support for AVX-512 require a processor with AVX512-VBMI2 support (Ice Lake or better) under a 64-bit system and a recent compiler (LLVM clang 6 or better, GCC 8 or better, Visual Studio 2019 or better). You need a correspondingly recent assembler such as gas (2.30+) or nasm (2.14+): recent compilers usually come with recent assemblers. If you mix a recent compiler with an incompatible/old assembler (e.g., when using a recent compiler with an old Linux distribution), you may get errors at build time because the compiler produces instructions that the assembler does not recognize: you should update your assembler to match your compiler (e.g., upgrade binutils to version 2.30 or better under Linux) or use an older compiler matching the capabilities of your assembler.
 
 Including simdjson
 ------------------
@@ -297,7 +297,8 @@ support for users who avoid exceptions. See [the simdjson error handling documen
   ondemand::object and ondemand::array. We also have explicit methods such as `get_string()`, `get_double()`,
   `get_uint64()`, `get_int64()`, `get_bool()`, `get_object()` and `get_array()`. After a cast or an explicit method,
   the number, string or boolean will be parsed, or the initial `[` or `{` will be verified. An exception is thrown if
-  the cast is not possible.
+  the cast is not possible. The `get_string()` returns a valid UTF-8 string, after
+  unescaping characters as needed: unmatched surrogate pairs are treated as an error. When calling `get_uint64()` and `get_int64()`, if the number does not fit in a corresponding 64-bit integer type, it is also considered an error.
 
   > IMPORTANT NOTE: values can only be parsed once. Since documents are *iterators*, once you have
   > parsed a value (such as by casting to double), you cannot get at it again. It is an error to call

doc/dom.md

@@ -65,7 +65,7 @@ Once you have an element, you can navigate it with idiomatic C++ iterators, oper
 * **Extracting Values (with exceptions):** You can cast a JSON element to a native type: `double(element)` or
   `double x = json_element`. This works for double, uint64_t, int64_t, bool,
   dom::object and dom::array. An exception (`simdjson::simdjson_error`) is thrown if the cast is not possible.
-* **Extracting Values (without exceptions):** You can use a variant usage of `get()` with error codes to avoid exceptions. You first declare the variable of the appropriate type (`double`, `uint64_t`, `int64_t`, `bool`,
+* **Extracting Values (without exceptions):** You can use a variant usage of `get()` with error codes to avoid exceptions. You first declare the variable of the appropriate type (`double`, `uint64_t`, `int64_t`, `bool`, `std::string_view`,
   `dom::object` and `dom::array`) and pass it by reference to `get()` which gives you back an error code: e.g.,
   ```c++
   simdjson::error_code error;
@@ -76,6 +76,7 @@ Once you have an element, you can navigate it with idiomatic C++ iterators, oper
   if (error) { std::cerr << error << std::endl; return EXIT_FAILURE; }
   std::cout << "I parsed " << value << " from " << numberstring.data() << std::endl;
   ```
+  The strings contain unescaped valid UTF-8 strings: no unmatched surrogate is allowed.
 * **Field Access:** To get the value of the "foo" field in an object, use `object["foo"]`.
 * **Array Iteration:** To iterate through an array, use `for (auto value : array) { ... }`. If you
   know the type of the value, you can cast it right there, too! `for (double value : array) { ... }`
@@ -88,7 +89,7 @@ Once you have an element, you can navigate it with idiomatic C++ iterators, oper
 * **Array and Object size** Given an array or an object, you can get its size (number of elements or keys)
   with the `size()` method.
 * **Checking an Element Type:** You can check an element's type with `element.type()`. It
-  returns an `element_type` with values such as `simdjson::dom::element_type::ARRAY`, `simdjson::dom::element_type::OBJECT`, `simdjson::dom::element_type::INT64`,  `simdjson::dom::element_type::UINT64`,`simdjson::dom::element_type::DOUBLE`, `simdjson::dom::element_type::BOOL` or, `simdjson::dom::element_type::NULL_VALUE`.
+  returns an `element_type` with values such as `simdjson::dom::element_type::ARRAY`, `simdjson::dom::element_type::OBJECT`, `simdjson::dom::element_type::INT64`,  `simdjson::dom::element_type::UINT64`,`simdjson::dom::element_type::DOUBLE`, `simdjson::dom::element_type::STRING`, `simdjson::dom::element_type::BOOL` or, `simdjson::dom::element_type::NULL_VALUE`.
 * **Output to streams and strings:** Given a document or an element (or node) out of a JSON document, you can output a minified string version using the C++ stream idiom (`out << element`). You can also request the construction of a minified string version (`simdjson::minify(element)`). Numbers are serialized as 64-bit floating-point numbers (`double`).
 
 ### Examples
@@ -436,7 +437,7 @@ bool parse_double(const char *j, double &d) {
 
 bool parse_string(const char *j, std::string &s) {
   std::string_view answer;
-  auto error = parser.parse(j,strlen(j))
+  auto error = parser.parse(j, strlen(j))
         .at(0)
         .get(answer, error);
   if (error) { return false; }

tests/ondemand/ondemand_misc_tests.cpp

@@ -52,6 +52,30 @@ namespace misc_tests {
     TEST_SUCCEED();
   }
 
+  bool issue_uffff() {
+    TEST_START();
+    ondemand::parser parser;
+    auto json = R"(   "wow:\uFFFF"   )"_padded;
+    ondemand::document doc;
+    ASSERT_SUCCESS(parser.iterate(json).get(doc));
+    std::string_view view;
+    ASSERT_SUCCESS( doc.get_string().get(view));
+    ASSERT_EQUAL(view, u8"wow:\uFFFF");
+    TEST_SUCCEED();
+  }
+
+  bool issue_backslash() {
+    TEST_START();
+    ondemand::parser parser;
+    auto json = R"(   "sc:\\./"   )"_padded;
+    ondemand::document doc;
+    ASSERT_SUCCESS(parser.iterate(json).get(doc));
+    std::string_view view;
+    ASSERT_SUCCESS( doc.get_string().get(view));
+    ASSERT_EQUAL(view, "sc:\\./");
+    TEST_SUCCEED();
+  }
+
   bool issue1870() {
     TEST_START();
     ondemand::parser parser;
@@ -496,6 +520,8 @@ namespace misc_tests {
 
   bool run() {
     return
+           issue_uffff() &&
+           issue_backslash() &&
            issue1870() &&
            issue1894() &&
            issue1894toolarge() &&