Implement command-line playtesting (#163)

desktop_version/src/FileSystemUtils.cpp

@@ -7,6 +7,10 @@
 #include <stdlib.h>
 #include <string.h>
 
+#include <iterator>
+#include <algorithm>
+#include <iostream>
+
 #include <SDL.h>
 #include <physfs.h>
 
@@ -144,6 +148,28 @@ char *FILESYSTEM_getUserLevelDirectory()
 void FILESYSTEM_loadFileToMemory(const char *name, unsigned char **mem,
                                  size_t *len, bool addnull)
 {
+	if (strcmp(name, "levels/special/stdin.vvvvvv") == 0) {
+		// this isn't *technically* necessary when piping directly from a file, but checking for that is annoying
+		static std::vector<char> STDIN_BUFFER;
+		static bool STDIN_LOADED = false;
+		if (!STDIN_LOADED) {
+			std::istreambuf_iterator<char> begin(std::cin), end;
+			STDIN_BUFFER.assign(begin, end);
+			STDIN_BUFFER.push_back(0); // there's no observable change in behavior if addnull is always true, but not vice versa
+			STDIN_LOADED = true;
+		}
+
+		size_t length = STDIN_BUFFER.size() - 1;
+		if (len != NULL) {
+			*len = length;
+		}
+
+		++length;
+		*mem = static_cast<unsigned char*>(malloc(length)); // STDIN_BUFFER.data() causes double-free
+		std::copy(STDIN_BUFFER.begin(), STDIN_BUFFER.end(), reinterpret_cast<char*>(*mem));
+		return;
+	}
+
 	PHYSFS_File *handle = PHYSFS_openRead(name);
 	if (handle == NULL)
 	{