UI: Add functions to create safe file names

Adds functions to generate safe file names from potentially unsafe
names.  Also a function to ensure that a particular filename isn't
duplicated.

obs/obs-app.cpp

@@ -17,6 +17,7 @@
 
 #include <time.h>
 #include <stdio.h>
+#include <wchar.h>
 #include <sstream>
 #include <util/bmem.h>
 #include <util/dstr.h>
@@ -847,6 +848,65 @@ char *GetConfigPathPtr(const char *name)
 	}
 }
 
+bool GetFileSafeName(const char *name, std::string &file)
+{
+	size_t base_len = strlen(name);
+	size_t len = os_utf8_to_wcs(name, base_len, nullptr, 0);
+	std::wstring wfile;
+
+	if (!len)
+		return false;
+
+	wfile.resize(len);
+	os_utf8_to_wcs(name, base_len, &wfile[0], len);
+
+	for (size_t i = wfile.size(); i > 0; i--) {
+		size_t im1 = i - 1;
+
+		if (iswspace(wfile[im1])) {
+			wfile[im1] = '_';
+		} else if (wfile[im1] != '_' && !iswalnum(wfile[im1])) {
+			wfile.erase(im1, 1);
+		}
+	}
+
+	if (wfile.size() == 0)
+		wfile = L"characters_only";
+
+	len = os_wcs_to_utf8(wfile.c_str(), wfile.size(), nullptr, 0);
+	if (!len)
+		return false;
+
+	file.resize(len);
+	os_wcs_to_utf8(wfile.c_str(), wfile.size(), &file[0], len);
+	return true;
+}
+
+bool GetClosestUnusedFileName(std::string &path, const char *extension)
+{
+	size_t len = path.size();
+	if (extension) {
+		path += ".";
+		path += extension;
+	}
+
+	if (!os_file_exists(path.c_str()))
+		return true;
+
+	int index = 1;
+
+	do {
+		path.resize(len);
+		path += std::to_string(++index);
+		if (extension) {
+			path += ".";
+			path += extension;
+		}
+	} while (os_file_exists(path.c_str()));
+
+	return true;
+}
+
 static inline bool arg_is(const char *arg,
 		const char *long_form, const char *short_form)
 {

obs/obs-app.hpp

@@ -112,3 +112,6 @@ inline config_t *GetGlobalConfig() {return App()->GlobalConfig();}
 std::vector<std::pair<std::string, std::string>> GetLocaleNames();
 inline const char *Str(const char *lookup) {return App()->GetString(lookup);}
 #define QTStr(lookupVal) QString::fromUtf8(Str(lookupVal))
+
+bool GetFileSafeName(const char *name, std::string &file);
+bool GetClosestUnusedFileName(std::string &path, const char *extension);