Better output file handling

When -o is not specified in json2xom, derive the name of the output file
from the name of the input file by doing the following:

- Trim the filename at the last occurrence of ".json", if any.
- If the remaining filename already exists in the working directory,
append ".out"

I.e. save100.json becomes either 'save100' or 'save100.out' depending on
whether there is already a 'save100' in the working directory.

CMakeLists.txt

@@ -6,9 +6,14 @@ set (xcomsave_headers xcomio.h xcom.h util.h)
 
 # Linux-specific configuration
 if (UNIX)
-set (CMAKE_CXX_FLAGS ${CMAKE_CXX_FLAGS} -std=c++14)
+set (CMAKE_CXX_FLAGS ${CMAKE_CXX_FLAGS} -std=c++17)
 endif (UNIX)
 
+if (WIN32)
+set (CMAKE_CXX_FLAGS "-std:c++17 -EHsc")
+add_definitions(-D_CRT_SECURE_NO_WARNINGS -D_CRT_NONSTDC_NO_DEPRECATE)
+endif (WIN32)
+
 # External dependencies - json, lzo, zlib.
 # They're all fairly small and simple enough to statically link into
 # the project rather than adding them as cmake subdirectories. Zlib in
@@ -19,12 +24,6 @@ include_directories("minilzo-2.09" "json11" "zlib")
 add_definitions("-DSTDC -DNO_GZIP")
 file(GLOB zlib_sources zlib/*.c zlib/*.h)
 
-if (WIN32)
-add_definitions(-D_CRT_SECURE_NO_WARNINGS -D_CRT_NONSTDC_NO_DEPRECATE)
-set (CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} -EHsc")
-set (CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} -EHsc")
-endif (WIN32)
-
 add_library (xcomsave ${xcomsave_sources} ${zlib_sources} ${xcomsave_headers})
 set_target_properties(xcomsave PROPERTIES LINKER_LANGUAGE CXX)
 

json2xcom.cpp

@@ -6,10 +6,13 @@
 #include <cassert>
 #include <cstring>
 #include <string>
+#include <filesystem>
 
 using namespace json11;
 using namespace xcom;
 
+namespace fs = std::experimental::filesystem;
+
 struct property_dispatch
 {
     std::string name;
@@ -727,9 +730,12 @@ int main(int argc, char *argv[])
     }
 
     if (outfile.empty()) {
-        size_t pos = infile.find_last_of(".json");
+        size_t pos = infile.rfind(".json");
         if (pos != std::string::npos) {
             outfile = infile.substr(0, pos);
+            if (fs::exists(outfile)) {
+                outfile += ".out";
+            }
         }
         else {
             outfile = infile + ".out";