SCI32: Fix handling of rewritable files opened with mode 1

In SSCI, all files opened through kFileIO are writable. Most of
the time this does not matter and the engine can get away with
using read-only streams, but when chase.dat is opened by Phant1
from the retry dialogue during the chase, it needs to be writable
because game code puts a '98' marker in the chase data. If this
write does not occur, the game gets stuck in a loop looking for
the marker.

3 files changed, 20 insertions, 11 deletions

diff --git a/engines/sci/engine/file.cpp b/engines/sci/engine/file.cpp
index a20fd7886d..da1d00f3bf 100644
--- a/engines/sci/engine/file.cpp
+++ b/engines/sci/engine/file.cpp
@@ -78,7 +78,7 @@ class SaveFileRewriteStream : public MemoryDynamicRWStream {
 public:
 	SaveFileRewriteStream(Common::String fileName,
 	                      Common::SeekableReadStream *inFile,
-	                      bool truncate, bool compress);
+	                      kFileOpenMode mode, bool compress);
 	virtual ~SaveFileRewriteStream();
 
 	virtual uint32 write(const void *dataPtr, uint32 dataSize) { _changed = true; return MemoryDynamicRWStream::write(dataPtr, dataSize); }
@@ -93,16 +93,21 @@ protected:
 
 SaveFileRewriteStream::SaveFileRewriteStream(Common::String fileName,
                                              Common::SeekableReadStream *inFile,
-                                             bool truncate,
+                                             kFileOpenMode mode,
                                              bool compress)
 : MemoryDynamicRWStream(DisposeAfterUse::YES),
   _fileName(fileName), _compress(compress)
 {
+	const bool truncate = mode == _K_FILE_MODE_CREATE;
+	const bool seekToEnd = mode == _K_FILE_MODE_OPEN_OR_CREATE;
+
 	if (!truncate && inFile) {
 		unsigned int s = inFile->size();
 		ensureCapacity(s);
 		inFile->read(_data, s);
-		seek(0, SEEK_END);
+		if (seekToEnd) {
+			seek(0, SEEK_END);
+		}
 		_changed = false;
 	} else {
 		_changed = true;
@@ -163,7 +168,7 @@ uint findFreeFileHandle(EngineState *s) {
  * for reading only.
  */
 
-reg_t file_open(EngineState *s, const Common::String &filename, int mode, bool unwrapFilename) {
+reg_t file_open(EngineState *s, const Common::String &filename, kFileOpenMode mode, bool unwrapFilename) {
 	Common::String englishName = g_sci->getSciLanguageString(filename, K_LANG_ENGLISH);
 	englishName.toLowercase();
 
@@ -200,9 +205,8 @@ reg_t file_open(EngineState *s, const Common::String &filename, int mode, bool u
 	}
 
 #ifdef ENABLE_SCI32
-	if (mode != _K_FILE_MODE_OPEN_OR_FAIL && (
-	    (g_sci->getGameId() == GID_PHANTASMAGORIA && (filename == "phantsg.dir" || filename == "chase.dat")) ||
-	    (g_sci->getGameId() == GID_PQSWAT && filename == "swat.dat"))) {
+	if ((g_sci->getGameId() == GID_PHANTASMAGORIA && (filename == "phantsg.dir" || filename == "chase.dat" || filename == "tmp.dat")) ||
+	    (g_sci->getGameId() == GID_PQSWAT && filename == "swat.dat")) {
 		debugC(kDebugLevelFile, "  -> file_open opening %s for rewriting", wrappedName.c_str());
 
 		inFile = saveFileMan->openForLoading(wrappedName);
@@ -211,8 +215,13 @@ reg_t file_open(EngineState *s, const Common::String &filename, int mode, bool u
 		if (!inFile)
 			inFile = SearchMan.createReadStreamForMember(englishName);
 
+		if (mode == _K_FILE_MODE_OPEN_OR_FAIL && !inFile) {
+			debugC(kDebugLevelFile, "  -> file_open(_K_FILE_MODE_OPEN_OR_FAIL): failed to open file '%s'", englishName.c_str());
+			return SIGNAL_REG;
+		}
+
 		SaveFileRewriteStream *stream;
-		stream = new SaveFileRewriteStream(wrappedName, inFile, mode == _K_FILE_MODE_CREATE, isCompressed);
+		stream = new SaveFileRewriteStream(wrappedName, inFile, mode, isCompressed);
 
 		delete inFile;
 
diff --git a/engines/sci/engine/file.h b/engines/sci/engine/file.h
index 0154338f6c..1c9a092063 100644
--- a/engines/sci/engine/file.h
+++ b/engines/sci/engine/file.h
@@ -28,7 +28,7 @@
 
 namespace Sci {
 
-enum {
+enum kFileOpenMode {
 	_K_FILE_MODE_OPEN_OR_CREATE = 0,
 	_K_FILE_MODE_OPEN_OR_FAIL = 1,
 	_K_FILE_MODE_CREATE = 2
diff --git a/engines/sci/engine/kfile.cpp b/engines/sci/engine/kfile.cpp
index 3454358afc..796eb08450 100644
--- a/engines/sci/engine/kfile.cpp
+++ b/engines/sci/engine/kfile.cpp
@@ -46,7 +46,7 @@
 
 namespace Sci {
 
-extern reg_t file_open(EngineState *s, const Common::String &filename, int mode, bool unwrapFilename);
+extern reg_t file_open(EngineState *s, const Common::String &filename, kFileOpenMode mode, bool unwrapFilename);
 extern FileHandle *getFileFromHandle(EngineState *s, uint handle);
 extern int fgets_wrapper(EngineState *s, char *dest, int maxsize, int handle);
 extern void listSavegames(Common::Array<SavegameDesc> &saves);
@@ -283,7 +283,7 @@ reg_t kFileIOOpen(EngineState *s, int argc, reg_t *argv) {
 		return SIGNAL_REG;
 	}
 
-	int mode = argv[1].toUint16();
+	kFileOpenMode mode = (kFileOpenMode)argv[1].toUint16();
 	bool unwrapFilename = true;
 
 	// SQ4 floppy prepends /\ to the filenames