Use RapidJSON instead of Casablanca to parse JSON data

This increases the host startup performance by a few milliseconds (at
the order of 5ms) at the same time that the host libraries are reduced
by almost 80KiB in size on a release build for x86-64/Linux.

For comparison, these are the sizes with RapidJSON (release mode, Linux,
x86-64, stripped):

     text	   data	    bss	    dec	    hex	filename
   306034	   2292	   1056	 309382	  4b886	libhostfxr.so
   258763	   2612	    800	 262175	  4001f	libhostpolicy.so

And these are the sizes with Casablanca (release mode, Linux, x86-64,
stripped):

     text	   data	    bss	    dec	    hex	filename
   340175	   4340	   1088	 345603	  54603	libhostfxr.so
   294478	   4636	    840	 299954	  493b2	libhostpolicy.so

RapidJSON is based off of commit d87b698d0fcc10a5f632ecbc80a9cb2a8fa094a5.

THIRD-PARTY-NOTICES.TXT

@@ -629,3 +629,22 @@ AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 SOFTWARE.
+
+
+License notice for RapidJSON
+----------------------------
+
+Tencent is pleased to support the open source community by making RapidJSON available.
+
+Copyright (C) 2015 THL A29 Limited, a Tencent company, and Milo Yip. All rights reserved.
+
+Licensed under the MIT License (the "License"); you may not use this file except
+in compliance with the License. You may obtain a copy of the License at
+
+http://opensource.org/licenses/MIT
+
+Unless required by applicable law or agreed to in writing, software distributed
+under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
+CONDITIONS OF ANY KIND, either express or implied. See the License for the
+specific language governing permissions and limitations under the License.
+

src/corehost/cli/comhost/CMakeLists.txt

@@ -9,7 +9,7 @@ set(DOTNET_PROJECT_NAME "comhost")
 
 # Include directories
 include_directories(../fxr)
-include_directories(../json/casablanca/include)
+include_directories(../json)
 
 # CMake does not recommend using globbing since it messes with the freshness checks
 set(SOURCES
@@ -18,16 +18,13 @@ set(SOURCES
     clsidmap.cpp
     ../redirected_error_writer.cpp
     ../fxr/fx_ver.cpp
-    ../json/casablanca/src/json/json.cpp
-    ../json/casablanca/src/json/json_parsing.cpp
-    ../json/casablanca/src/json/json_serialization.cpp
-    ../json/casablanca/src/utilities/asyncrt_utils.cpp
+    ../json_parser.cpp
 )
 
 set(HEADERS
     comhost.h
     ../fxr/fx_ver.h
-    ../json/casablanca/include/cpprest/json.h
+    ../json_parser.h
 )
 
 if(WIN32)

src/corehost/cli/comhost/clsidmap.cpp

@@ -12,8 +12,9 @@
 #include <wintrust.h>
 #include <Softpub.h>
 
-#include <cpprest/json.h>
-using namespace web;
+#include "rapidjson/document.h"
+#include "rapidjson/istreamwrapper.h"
+#include "json_parser.h"
 
 using comhost::clsid_map_entry;
 using comhost::clsid_map;
@@ -45,29 +46,21 @@ namespace
 
     clsid_map parse_stream(_Inout_ pal::istream_t &json_map_raw)
     {
-        skip_utf8_bom(&json_map_raw);
+        json_parser_t json;
 
-        // Parse JSON
-        json::value json_map;
-        try
-        {
-            json_map = json::value::parse(json_map_raw);
-        }
-        catch (const json::json_exception&)
+        if (!json.parse_stream(json_map_raw, _X("<embedded .clsidmap>")))
         {
             trace::error(_X("Embedded .clsidmap format is invalid"));
             throw HResultException{ StatusCode::InvalidConfigFile };
         }
 
-        json::object &json_obj = json_map.as_object();
-
         // Process JSON and construct a map
         HRESULT hr;
         clsid_map mapping;
-        for (std::pair<utility::string_t, json::value> &prop : json_obj)
+        for (const auto &prop : json.document().GetObject())
         {
             CLSID clsidMaybe;
-            hr = string_to_clsid(prop.first, clsidMaybe);
+            hr = string_to_clsid(prop.name.GetString(), clsidMaybe);
             if (FAILED(hr))
             {
                 assert(false && "Invalid CLSID");
@@ -79,14 +72,14 @@ namespace
 
             e.clsid = clsidMaybe;
 
-            json::object &val = prop.second.as_object();
-            e.assembly = val.at(_X("assembly")).as_string();
-            e.type = val.at(_X("type")).as_string();
+            const auto &val = prop.value.GetObject();
+            e.assembly = val[_X("assembly")].GetString();
+            e.type = val[_X("type")].GetString();
 
             // Check if a ProgID was defined.
-            auto prodIdMaybe = val.find(_X("progid"));
-            if (prodIdMaybe != val.cend())
-                e.progid = prodIdMaybe->second.as_string();
+            const auto &prodIdMaybe = val.FindMember(_X("progid"));
+            if (prodIdMaybe != val.MemberEnd())
+                e.progid = prodIdMaybe->value.GetString();
 
             mapping[clsidMaybe] = std::move(e);
         }