diff --git a/aegisub/src/ass_file.cpp b/aegisub/src/ass_file.cpp
index 4cadbbb3d..99350b750 100644
--- a/aegisub/src/ass_file.cpp
+++ b/aegisub/src/ass_file.cpp
@@ -88,7 +88,7 @@ void AssFile::Load(const wxString &_filename,wxString charset,bool addToRecent)
 		}
 
 		// Get proper format reader
-		SubtitleFormat *reader = SubtitleFormat::GetReader(_filename);
+		const SubtitleFormat *reader = SubtitleFormat::GetReader(_filename);
 
 		if (!reader) {
 			wxMessageBox("Unknown file type","Error loading file",wxICON_ERROR | wxOK);
@@ -97,8 +97,7 @@ void AssFile::Load(const wxString &_filename,wxString charset,bool addToRecent)
 
 		// Read file
 		AssFile temp;
-		reader->SetTarget(&temp);
-		reader->ReadFile(_filename,charset);
+		reader->ReadFile(&temp, _filename, charset);
 		swap(temp);
 	}
 	catch (agi::UserCancelException const&) {
@@ -156,7 +155,7 @@ void AssFile::Load(const wxString &_filename,wxString charset,bool addToRecent)
 }
 
 void AssFile::Save(wxString filename, bool setfilename, bool addToRecent, wxString encoding) {
-	SubtitleFormat *writer = SubtitleFormat::GetWriter(filename);
+	const SubtitleFormat *writer = SubtitleFormat::GetWriter(filename);
 	if (!writer)
 		throw "Unknown file type.";
 
@@ -168,8 +167,7 @@ void AssFile::Save(wxString filename, bool setfilename, bool addToRecent, wxStri
 
 	FileSave();
 
-	writer->SetTarget(this);
-	writer->WriteFile(filename, encoding);
+	writer->WriteFile(this, filename, encoding);
 
 	if (addToRecent) {
 		AddToRecent(filename);
@@ -229,8 +227,7 @@ bool AssFile::CanSave() {
 	if (ext == ".txt") return false;
 
 	// Check if it's a known extension
-	SubtitleFormat *writer = SubtitleFormat::GetWriter(filename);
-	if (!writer) return false;
+	if (!SubtitleFormat::GetWriter(filename)) return false;
 
 	// Scan through the lines
 	AssStyle defstyle;
diff --git a/aegisub/src/subtitle_format.cpp b/aegisub/src/subtitle_format.cpp
index 8ea59c106..345208bd4 100644
--- a/aegisub/src/subtitle_format.cpp
+++ b/aegisub/src/subtitle_format.cpp
@@ -59,8 +59,6 @@ using namespace std::tr1::placeholders;
 
 SubtitleFormat::SubtitleFormat(wxString const& name)
 : name(name)
-, isCopy(0)
-, Line(0)
 {
 	formats.push_back(this);
 }
@@ -69,12 +67,6 @@ SubtitleFormat::~SubtitleFormat() {
 	formats.remove(this);
 }
 
-void SubtitleFormat::SetTarget(AssFile *file) {
-	ClearCopy();
-	Line = file ? &file->Line : 0;
-	assFile = file;
-}
-
 bool SubtitleFormat::CanReadFile(wxString const& filename) const {
 	return GetReadWildcards().Index(filename.AfterLast('.'), false) != wxNOT_FOUND;
 }
@@ -83,33 +75,8 @@ bool SubtitleFormat::CanWriteFile(wxString const& filename) const {
 	return GetWriteWildcards().Index(filename.AfterLast('.'), false) != wxNOT_FOUND;
 }
 
-void SubtitleFormat::CreateCopy() {
-	SetTarget(new AssFile(*assFile));
-	isCopy = true;
-}
-
-void SubtitleFormat::ClearCopy() {
-	if (isCopy) {
-		delete assFile;
-		assFile = NULL;
-		isCopy = false;
-	}
-}
-
-void SubtitleFormat::Clear() {
-	assFile->Clear();
-}
-
-void SubtitleFormat::LoadDefault(bool defline) {
-	assFile->LoadDefault(defline);
-}
-
-void SubtitleFormat::AddLine(wxString data, int *version, AssAttachment **attach) {
-	assFile->AddLine(data, version, attach);
-}
-
 /// @brief Ask the user to enter the FPS 
-FractionalTime SubtitleFormat::AskForFPS(bool showSMPTE) {
+FractionalTime SubtitleFormat::AskForFPS(bool showSMPTE) const {
 	wxArrayString choices;
 	bool drop = false;
 	
@@ -171,20 +138,16 @@ FractionalTime SubtitleFormat::AskForFPS(bool showSMPTE) {
 	return FractionalTime(fps, drop);
 }
 
-void SubtitleFormat::SortLines() {
-	AssFile::Sort(*Line);
-}
-
-void SubtitleFormat::StripTags() {
-	for (std::list<AssEntry*>::iterator cur = Line->begin(); cur != Line->end(); ++cur) {
+void SubtitleFormat::StripTags(LineList &lines) const {
+	for (LineList::iterator cur = lines.begin(); cur != lines.end(); ++cur) {
 		if (AssDialogue *current = dynamic_cast<AssDialogue*>(*cur)) {
 			current->StripTags();
 		}
 	}
 }
 
-void SubtitleFormat::ConvertNewlines(wxString const& newline, bool mergeLineBreaks) {
-	for (std::list<AssEntry*>::iterator cur = Line->begin(); cur != Line->end(); ++cur) {
+void SubtitleFormat::ConvertNewlines(LineList &lines, wxString const& newline, bool mergeLineBreaks) const {
+	for (LineList::iterator cur = lines.begin(); cur != lines.end(); ++cur) {
 		if (AssDialogue *current = dynamic_cast<AssDialogue*>(*cur)) {
 			current->Text.Replace("\\h", " ");
 			current->Text.Replace("\\n", newline);
@@ -196,25 +159,25 @@ void SubtitleFormat::ConvertNewlines(wxString const& newline, bool mergeLineBrea
 	}
 }
 
-void SubtitleFormat::StripComments() {
-	for (std::list<AssEntry*>::iterator it = Line->begin(); it != Line->end(); ) {
+void SubtitleFormat::StripComments(LineList &lines) const {
+	for (LineList::iterator it = lines.begin(); it != lines.end(); ) {
 		AssDialogue *diag = dynamic_cast<AssDialogue*>(*it);
 		if (!diag || (!diag->Comment && diag->Text.size()))
 			++it;
 		else {
 			delete *it;
-			Line->erase(it++);
+			lines.erase(it++);
 		}
 	}
 }
 
-void SubtitleFormat::StripNonDialogue() {
-	for (std::list<AssEntry*>::iterator it = Line->begin(); it != Line->end(); ) {
+void SubtitleFormat::StripNonDialogue(LineList &lines) const {
+	for (LineList::iterator it = lines.begin(); it != lines.end(); ) {
 		if (dynamic_cast<AssDialogue*>(*it))
 			++it;
 		else {
 			delete *it;
-			Line->erase(it++);
+			lines.erase(it++);
 		}
 	}
 }
@@ -227,11 +190,11 @@ static bool dialog_start_lt(AssEntry *pos, AssDialogue *to_insert) {
 /// @brief Split and merge lines so there are no overlapping lines 
 ///
 /// Algorithm described at http://devel.aegisub.org/wiki/Technical/SplitMerge
-void SubtitleFormat::RecombineOverlaps() {
-	std::list<AssEntry*>::iterator cur, next = Line->begin();
+void SubtitleFormat::RecombineOverlaps(LineList &lines) const {
+	LineList::iterator cur, next = lines.begin();
 	cur = next++;
 
-	for (; next != Line->end(); cur = next++) {
+	for (; next != lines.end(); cur = next++) {
 		AssDialogue *prevdlg = dynamic_cast<AssDialogue*>(*cur);
 		AssDialogue *curdlg = dynamic_cast<AssDialogue*>(*next);
 
@@ -240,15 +203,15 @@ void SubtitleFormat::RecombineOverlaps() {
 
 		// Use names like in the algorithm description and prepare for erasing
 		// old dialogues from the list
-		std::list<AssEntry*>::iterator prev = cur;
+		LineList::iterator prev = cur;
 		cur = next;
 		next++;
 
 		// std::list::insert() inserts items before the given iterator, so
 		// we need 'next' for inserting. 'prev' and 'cur' can safely be erased
 		// from the list now.
-		Line->erase(prev);
-		Line->erase(cur);
+		lines.erase(prev);
+		lines.erase(cur);
 
 		//Is there an A part before the overlap?
 		if (curdlg->Start > prevdlg->Start) {
@@ -258,7 +221,7 @@ void SubtitleFormat::RecombineOverlaps() {
 			newdlg->End = curdlg->Start;
 			newdlg->Text = prevdlg->Text;
 
-			Line->insert(find_if(next, Line->end(), bind(dialog_start_lt, _1, newdlg)), newdlg);
+			lines.insert(find_if(next, lines.end(), bind(dialog_start_lt, _1, newdlg)), newdlg);
 		}
 
 		// Overlapping A+B part
@@ -269,7 +232,7 @@ void SubtitleFormat::RecombineOverlaps() {
 			// Put an ASS format hard linewrap between lines
 			newdlg->Text = curdlg->Text + "\\N" + prevdlg->Text;
 
-			Line->insert(find_if(next, Line->end(), bind(dialog_start_lt, _1, newdlg)), newdlg);
+			lines.insert(find_if(next, lines.end(), bind(dialog_start_lt, _1, newdlg)), newdlg);
 		}
 
 		// Is there an A part after the overlap?
@@ -280,7 +243,7 @@ void SubtitleFormat::RecombineOverlaps() {
 			newdlg->End = prevdlg->End;
 			newdlg->Text = prevdlg->Text;
 
-			Line->insert(find_if(next, Line->end(), bind(dialog_start_lt, _1, newdlg)), newdlg);
+			lines.insert(find_if(next, lines.end(), bind(dialog_start_lt, _1, newdlg)), newdlg);
 		}
 
 		// Is there a B part after the overlap?
@@ -291,7 +254,7 @@ void SubtitleFormat::RecombineOverlaps() {
 			newdlg->End = curdlg->End;
 			newdlg->Text = curdlg->Text;
 
-			Line->insert(find_if(next, Line->end(), bind(dialog_start_lt, _1, newdlg)), newdlg);
+			lines.insert(find_if(next, lines.end(), bind(dialog_start_lt, _1, newdlg)), newdlg);
 		}
 
 		next--;
@@ -299,11 +262,11 @@ void SubtitleFormat::RecombineOverlaps() {
 }
 
 /// @brief Merge identical lines that follow each other 
-void SubtitleFormat::MergeIdentical() {
-	std::list<AssEntry*>::iterator cur, next = Line->begin();
+void SubtitleFormat::MergeIdentical(LineList &lines) const {
+	LineList::iterator cur, next = lines.begin();
 	cur = next++;
 	
-	for (; next != Line->end(); cur = next++) {
+	for (; next != lines.end(); cur = next++) {
 		AssDialogue *curdlg = dynamic_cast<AssDialogue*>(*cur);
 		AssDialogue *nextdlg = dynamic_cast<AssDialogue*>(*next);
 		
@@ -314,7 +277,7 @@ void SubtitleFormat::MergeIdentical() {
 			
 			// Remove duplicate line
 			delete *cur;
-			Line->erase(cur);
+			lines.erase(cur);
 		}
 	}
 }
@@ -323,14 +286,14 @@ std::list<SubtitleFormat*> SubtitleFormat::formats;
 
 void SubtitleFormat::LoadFormats() {
 	if (formats.empty()) {
-		new ASSSubtitleFormat();
-		new EncoreSubtitleFormat();
-		new MKVSubtitleFormat();
-		new MicroDVDSubtitleFormat();
-		new SRTSubtitleFormat();
-		new TTXTSubtitleFormat();
-		new TXTSubtitleFormat();
-		new TranStationSubtitleFormat();
+		new ASSSubtitleFormat;
+		new EncoreSubtitleFormat;
+		new MKVSubtitleFormat;
+		new MicroDVDSubtitleFormat;
+		new SRTSubtitleFormat;
+		new TTXTSubtitleFormat;
+		new TXTSubtitleFormat;
+		new TranStationSubtitleFormat;
 	}
 }
 
@@ -347,12 +310,12 @@ SubtitleFormat *find_or_null(Cont &container, Pred pred) {
 	return *it;
 }
 
-SubtitleFormat *SubtitleFormat::GetReader(wxString const& filename) {
+const SubtitleFormat *SubtitleFormat::GetReader(wxString const& filename) {
 	LoadFormats();
 	return find_or_null(formats, bind(&SubtitleFormat::CanReadFile, _1, filename));
 }
 
-SubtitleFormat *SubtitleFormat::GetWriter(wxString const& filename) {
+const SubtitleFormat *SubtitleFormat::GetWriter(wxString const& filename) {
 	LoadFormats();
 	return find_or_null(formats, bind(&SubtitleFormat::CanWriteFile, _1, filename));
 }
diff --git a/aegisub/src/subtitle_format.h b/aegisub/src/subtitle_format.h
index 8a489b663..9c7262bfb 100644
--- a/aegisub/src/subtitle_format.h
+++ b/aegisub/src/subtitle_format.h
@@ -45,7 +45,6 @@
 
 #include <libaegisub/exception.h>
 
-class AssAttachment;
 class AssEntry;
 class AssFile;
 class FractionalTime;
@@ -57,8 +56,6 @@ class FractionalTime;
 /// DOCME
 class SubtitleFormat {
 	wxString name;
-	bool isCopy;
-	AssFile *assFile;
 
 	/// Get this format's wildcards for a load dialog
 	virtual wxArrayString GetReadWildcards() const { return wxArrayString(); }
@@ -69,47 +66,28 @@ class SubtitleFormat {
 	static std::list<SubtitleFormat*> formats;
 
 protected:
-	std::list<AssEntry*> *Line;
+	typedef std::list<AssEntry*> LineList;
 
-	/// Copy the input subtitles file; must be called before making any changes
-	void CreateCopy();
-	/// Delete the subtitle file if we own it; should be called after processing
-	/// if CreateCopy was used
-	void ClearCopy();
-	/// Sort the lines by start time
-	void SortLines();
 	/// Strip override tags
-	void StripTags();
+	void StripTags(LineList &lines) const;
 	/// Convert newlines to the specified character(s)
 	/// @param lineEnd newline character(s)
 	/// @param mergeLineBreaks Should multiple consecutive line breaks be merged into one?
-	void ConvertNewlines(wxString const& newline, bool mergeLineBreaks = true);
+	void ConvertNewlines(LineList &lines, wxString const& newline, bool mergeLineBreaks = true) const;
 	/// Remove All commented and empty lines
-	void StripComments();
+	void StripComments(LineList &lines) const;
 	/// Remove everything but the dialogue lines
-	void StripNonDialogue();
+	void StripNonDialogue(LineList &lines) const;
 	/// @brief Split and merge lines so there are no overlapping lines
 	///
 	/// Algorithm described at http://devel.aegisub.org/wiki/Technical/SplitMerge
-	void RecombineOverlaps();
+	void RecombineOverlaps(LineList &lines) const;
 	/// Merge sequential identical lines
-	void MergeIdentical();
+	void MergeIdentical(LineList &lines) const;
 
-	/// Clear the subtitle file
-	void Clear();
-	/// Load the default file
-	/// @param defline Add a blank line?
-	void LoadDefault(bool defline=true);
-
-	AssFile *GetAssFile() { return assFile; }
-	/// Add a line to the output file
-	/// @param data Full text of ASS line
-	/// @param[in,out] version ASS version the line was parsed as
-	/// @param[in,out] attach Accumulator for attachment parsing
-	void AddLine(wxString data, int *version, AssAttachment **attach);
 	/// Prompt the user for a framerate to use
 	/// @param showSMPTE Include SMPTE as an option?
-	FractionalTime AskForFPS(bool showSMPTE=false);
+	FractionalTime AskForFPS(bool showSMPTE=false) const;
 
 public:
 	/// Constructor
@@ -120,42 +98,41 @@ public:
 	/// @note Automatically unregisters the format
 	virtual ~SubtitleFormat();
 
-	/// Set the target file to write
-	void SetTarget(AssFile *file);
-
 	/// Get this format's name
 	wxString GetName() const { return name; }
 
 	/// @brief Check if the given file can be read by this format
 	///
-	/// Default implemention simply checks if the file's extension is in the
+	/// Default implement ion simply checks if the file's extension is in the
 	/// format's wildcard list
 	virtual bool CanReadFile(wxString const& filename) const;
 
 	/// @brief Check if the given file can be written by this format
 	///
-	/// Default implemention simply checks if the file's extension is in the
+	/// Default implement ion simply checks if the file's extension is in the
 	/// format's wildcard list
 	virtual bool CanWriteFile(wxString const& filename) const;
 
 	/// Load a subtitle file
+	/// @param[out] target Destination to read lines into
 	/// @param filename File to load
 	/// @param forceEncoding Encoding to use or empty string for default
-	virtual void ReadFile(wxString const& filename, wxString const& forceEncoding="") { }
+	virtual void ReadFile(AssFile *target, wxString const& filename, wxString const& forceEncoding="") const { }
 
 	/// Save a subtitle file
+	/// @param src Data to write
 	/// @param filename File to write to
 	/// @param forceEncoding Encoding to use or empty string for default
-	virtual void WriteFile(wxString const& filename, wxString const& encoding="") { }
+	virtual void WriteFile(const AssFile *src, wxString const& filename, wxString const& encoding="") const { }
 
 	/// Get the wildcards for a save or load dialog
 	/// @param mode 0: load 1: save
 	static wxString GetWildcards(int mode);
 
 	/// Get a subtitle format that can read the given file or NULL if none can
-	static SubtitleFormat *GetReader(wxString const& filename);
+	static const SubtitleFormat *GetReader(wxString const& filename);
 	/// Get a subtitle format that can write the given file or NULL if none can
-	static SubtitleFormat *GetWriter(wxString const& filename);
+	static const SubtitleFormat *GetWriter(wxString const& filename);
 	/// Initialize subtitle formats
 	static void LoadFormats();
 	/// Deinitialize subtitle formats
diff --git a/aegisub/src/subtitle_format_ass.cpp b/aegisub/src/subtitle_format_ass.cpp
index 465c7734a..ed5aa8857 100644
--- a/aegisub/src/subtitle_format_ass.cpp
+++ b/aegisub/src/subtitle_format_ass.cpp
@@ -39,6 +39,7 @@
 #include "subtitle_format_ass.h"
 
 #include "ass_dialogue.h"
+#include "ass_file.h"
 #include "compat.h"
 #include "text_file_reader.h"
 #include "text_file_writer.h"
@@ -64,9 +65,11 @@ wxArrayString ASSSubtitleFormat::GetWriteWildcards() const {
 	return formats;
 }
 
-void ASSSubtitleFormat::ReadFile(wxString const& filename, wxString const& encoding) {
+void ASSSubtitleFormat::ReadFile(AssFile *target, wxString const& filename, wxString const& encoding) const {
 	using namespace std;
 
+	target->Clear();
+
 	TextFileReader file(filename, encoding);
 	int version = filename.Right(4).Lower() != ".ssa";
 	AssAttachment *attach = 0;
@@ -74,22 +77,22 @@ void ASSSubtitleFormat::ReadFile(wxString const& filename, wxString const& encod
 	while (file.HasMoreLines()) {
 		wxString line = file.ReadLineFromFile();
 		try {
-			AddLine(line, &version, &attach);
+			target->AddLine(line, &version, &attach);
 		}
 		catch (const char *err) {
-			Clear();
+			target->Clear();
 			throw AssParseError("Error processing line: " + STD_STR(line) + ": " + err, 0);
 		}
 	}
 }
 
-void ASSSubtitleFormat::WriteFile(wxString const& filename, wxString const& encoding) {
+void ASSSubtitleFormat::WriteFile(const AssFile *src, wxString const& filename, wxString const& encoding) const {
 	TextFileWriter file(filename, encoding);
 	bool ssa = filename.Right(4).Lower() == ".ssa";
 
-	std::list<AssEntry*>::iterator last = Line->end(); --last;
-	wxString group = Line->front()->group;
-	for (std::list<AssEntry*>::iterator cur=Line->begin(); cur!=Line->end(); ++cur) {
+	LineList::const_iterator last = src->Line.end(); --last;
+	wxString group = src->Line.front()->group;
+	for (LineList::const_iterator cur = src->Line.begin(); cur != src->Line.end(); ++cur) {
 		// Add a blank line between each group
 		if ((*cur)->group != group) {
 			file.WriteLineToFile("");
diff --git a/aegisub/src/subtitle_format_ass.h b/aegisub/src/subtitle_format_ass.h
index 53317ebca..a0eb82af1 100644
--- a/aegisub/src/subtitle_format_ass.h
+++ b/aegisub/src/subtitle_format_ass.h
@@ -48,6 +48,6 @@ public:
 	wxArrayString GetReadWildcards() const;
 	wxArrayString GetWriteWildcards() const;
 
-	void ReadFile(wxString const& filename, wxString const& forceEncoding);
-	void WriteFile(wxString const& filename, wxString const& encoding);
+	void ReadFile(AssFile *target, wxString const& filename, wxString const& forceEncoding) const;
+	void WriteFile(const AssFile *src, wxString const& filename, wxString const& encoding) const;
 };
diff --git a/aegisub/src/subtitle_format_encore.cpp b/aegisub/src/subtitle_format_encore.cpp
index 3641f92dc..d1f1ed76b 100644
--- a/aegisub/src/subtitle_format_encore.cpp
+++ b/aegisub/src/subtitle_format_encore.cpp
@@ -39,6 +39,7 @@
 #include "subtitle_format_encore.h"
 
 #include "ass_dialogue.h"
+#include "ass_file.h"
 #include "text_file_writer.h"
 
 EncoreSubtitleFormat::EncoreSubtitleFormat()
@@ -52,20 +53,20 @@ wxArrayString EncoreSubtitleFormat::GetWriteWildcards() const {
 	return formats;
 }
 
-void EncoreSubtitleFormat::WriteFile(wxString const& filename, wxString const& encoding) {
+void EncoreSubtitleFormat::WriteFile(const AssFile *src, wxString const& filename, wxString const& encoding) const {
 	FractionalTime ft = AskForFPS(true);
 	if (!ft.FPS().IsLoaded()) return;
 
 	TextFileWriter file(filename, encoding);
 
 	// Convert to encore
-	CreateCopy();
-	SortLines();
-	StripComments();
-	RecombineOverlaps();
-	MergeIdentical();
-	StripTags();
-	ConvertNewlines("\r\n");
+	AssFile copy(*src);
+	copy.Sort();
+	StripComments(copy.Line);
+	RecombineOverlaps(copy.Line);
+	MergeIdentical(copy.Line);
+	StripTags(copy.Line);
+	ConvertNewlines(copy.Line, "\r\n");
 
 	// Write lines
 	int i = 0;
@@ -73,12 +74,10 @@ void EncoreSubtitleFormat::WriteFile(wxString const& filename, wxString const& e
 	// Encore wants ; instead of : if we're dealing with NTSC dropframe stuff
 	char sep = ft.IsDrop() ? ';' : ':';
 
-	for (std::list<AssEntry*>::iterator cur=Line->begin();cur!=Line->end();cur++) {
+	for (LineList::const_iterator cur = copy.Line.begin(); cur != copy.Line.end(); ++cur) {
 		if (AssDialogue *current = dynamic_cast<AssDialogue*>(*cur)) {
 			++i;
 			file.WriteLineToFile(wxString::Format("%i %s %s %s", i, ft.ToSMPTE(current->Start, sep), ft.ToSMPTE(current->End, sep), current->Text));
 		}
 	}
-
-	ClearCopy();
 }
diff --git a/aegisub/src/subtitle_format_encore.h b/aegisub/src/subtitle_format_encore.h
index 06c8a81ad..552297405 100644
--- a/aegisub/src/subtitle_format_encore.h
+++ b/aegisub/src/subtitle_format_encore.h
@@ -46,5 +46,5 @@ class EncoreSubtitleFormat : public SubtitleFormat {
 public:
 	EncoreSubtitleFormat();
 	wxArrayString GetWriteWildcards() const;
-	void WriteFile(wxString const& filename, wxString const& encoding);
+	void WriteFile(const AssFile *src, wxString const& filename, wxString const& encoding) const;
 };
diff --git a/aegisub/src/subtitle_format_microdvd.cpp b/aegisub/src/subtitle_format_microdvd.cpp
index 593cb224e..a78c38422 100644
--- a/aegisub/src/subtitle_format_microdvd.cpp
+++ b/aegisub/src/subtitle_format_microdvd.cpp
@@ -36,13 +36,15 @@
 
 #include "config.h"
 
+#include "subtitle_format_microdvd.h"
+
 #ifndef AGI_PRE
 #include <wx/regex.h>
 #endif
 
 #include "ass_dialogue.h"
+#include "ass_file.h"
 #include "ass_time.h"
-#include "subtitle_format_microdvd.h"
 #include "text_file_reader.h"
 #include "text_file_writer.h"
 #include "video_context.h"
@@ -76,11 +78,11 @@ bool MicroDVDSubtitleFormat::CanReadFile(wxString const& filename) const {
 	return false;
 }
 
-void MicroDVDSubtitleFormat::ReadFile(wxString const& filename, wxString const& forceEncoding) {
+void MicroDVDSubtitleFormat::ReadFile(AssFile *target, wxString const& filename, wxString const& encoding) const {
 	TextFileReader file(filename);
 	wxRegEx exp("^[\\{\\[]([0-9]+)[\\}\\]][\\{\\[]([0-9]+)[\\}\\]](.*)$", wxRE_ADVANCED);
 
-	LoadDefault(false);
+	target->LoadDefault(false);
 
 	agi::vfr::Framerate fps;
 
@@ -117,22 +119,22 @@ void MicroDVDSubtitleFormat::ReadFile(wxString const& filename, wxString const&
 			diag->Start = fps.TimeAtFrame(f1, agi::vfr::START);
 			diag->End = fps.TimeAtFrame(f2, agi::vfr::END);
 			diag->Text = text;
-			Line->push_back(diag);
+			target->Line.push_back(diag);
 		}
 	}
 }
 
-void MicroDVDSubtitleFormat::WriteFile(wxString const& filename, wxString const& encoding) {
+void MicroDVDSubtitleFormat::WriteFile(const AssFile *src, wxString const& filename, wxString const& encoding) const {
 	agi::vfr::Framerate fps = AskForFPS().FPS();
 	if (!fps.IsLoaded()) return;
 
-	CreateCopy();
-	SortLines();
-	StripComments();
-	RecombineOverlaps();
-	MergeIdentical();
-	StripTags();
-	ConvertNewlines("|");
+	AssFile copy(*src);
+	copy.Sort();
+	StripComments(copy.Line);
+	RecombineOverlaps(copy.Line);
+	MergeIdentical(copy.Line);
+	StripTags(copy.Line);
+	ConvertNewlines(copy.Line, "|");
 
 	TextFileWriter file(filename, encoding);
 
@@ -142,7 +144,7 @@ void MicroDVDSubtitleFormat::WriteFile(wxString const& filename, wxString const&
 	}
 
 	// Write lines
-	for (std::list<AssEntry*>::iterator cur=Line->begin();cur!=Line->end();cur++) {
+	for (LineList::const_iterator cur = copy.Line.begin(); cur != copy.Line.end(); ++cur) {
 		if (AssDialogue *current = dynamic_cast<AssDialogue*>(*cur)) {
 			int start = fps.FrameAtTime(current->Start, agi::vfr::START);
 			int end = fps.FrameAtTime(current->End, agi::vfr::END);
@@ -150,6 +152,4 @@ void MicroDVDSubtitleFormat::WriteFile(wxString const& filename, wxString const&
 			file.WriteLineToFile(wxString::Format("{%i}{%i}%s", start, end, current->Text));
 		}
 	}
-
-	ClearCopy();
 }
diff --git a/aegisub/src/subtitle_format_microdvd.h b/aegisub/src/subtitle_format_microdvd.h
index 7e311c115..f6709449b 100644
--- a/aegisub/src/subtitle_format_microdvd.h
+++ b/aegisub/src/subtitle_format_microdvd.h
@@ -49,7 +49,7 @@ public:
 	wxArrayString GetWriteWildcards() const;
 
 	bool CanReadFile(wxString const& filename) const;
-	void ReadFile(wxString const& filename, wxString const& forceEncoding);
+	void ReadFile(AssFile *target, wxString const& filename, wxString const& forceEncoding) const;
 
-	void WriteFile(wxString const& filename, wxString const& encoding);
+	void WriteFile(const AssFile *src, wxString const& filename, wxString const& encoding) const;
 };
diff --git a/aegisub/src/subtitle_format_mkv.cpp b/aegisub/src/subtitle_format_mkv.cpp
index 0babc37a2..2d04e3b7e 100644
--- a/aegisub/src/subtitle_format_mkv.cpp
+++ b/aegisub/src/subtitle_format_mkv.cpp
@@ -53,6 +53,6 @@ wxArrayString MKVSubtitleFormat::GetReadWildcards() const {
 	return formats;
 }
 
-void MKVSubtitleFormat::ReadFile(wxString const& filename, wxString const&) {
-	MatroskaWrapper::GetSubtitles(filename, GetAssFile());
+void MKVSubtitleFormat::ReadFile(AssFile *target, wxString const& filename, wxString const&) const {
+	MatroskaWrapper::GetSubtitles(filename, target);
 }
diff --git a/aegisub/src/subtitle_format_mkv.h b/aegisub/src/subtitle_format_mkv.h
index cb6957fb9..6042e1369 100644
--- a/aegisub/src/subtitle_format_mkv.h
+++ b/aegisub/src/subtitle_format_mkv.h
@@ -46,5 +46,5 @@ public:
 	MKVSubtitleFormat();
 	wxArrayString GetReadWildcards() const;
 
-	void ReadFile(wxString const& filename, wxString const& forceEncoding);
+	void ReadFile(AssFile *target, wxString const& filename, wxString const& forceEncoding) const;
 };
diff --git a/aegisub/src/subtitle_format_srt.cpp b/aegisub/src/subtitle_format_srt.cpp
index 45564ad47..2d99f1376 100644
--- a/aegisub/src/subtitle_format_srt.cpp
+++ b/aegisub/src/subtitle_format_srt.cpp
@@ -375,11 +375,11 @@ wxArrayString SRTSubtitleFormat::GetWriteWildcards() const {
 	return GetReadWildcards();
 }
 
-void SRTSubtitleFormat::ReadFile(wxString const& filename, wxString const& encoding) {
+void SRTSubtitleFormat::ReadFile(AssFile *target, wxString const& filename, wxString const& encoding) const {
 	using namespace std;
 
 	TextFileReader file(filename, encoding);
-	LoadDefault(false);
+	target->LoadDefault(false);
 
 	// See parsing algorithm at <http://devel.aegisub.org/wiki/SubtitleFormats/SRT>
 
@@ -433,7 +433,7 @@ found_timestamps:
 				line->Start = ReadSRTTime(timestamp_regex.GetMatch(text_line, 1));
 				line->End = ReadSRTTime(timestamp_regex.GetMatch(text_line, 2));
 				// store pointer to subtitle, we'll continue working on it
-				Line->push_back(line);
+				target->Line.push_back(line);
 				// next we're reading the text
 				state = 3;
 				break;
@@ -496,20 +496,20 @@ found_timestamps:
 		line->Text = tag_parser.ToAss(line->Text);
 }
 
-void SRTSubtitleFormat::WriteFile(wxString const& filename, wxString const& encoding) {
-	TextFileWriter file(filename,encoding);
+void SRTSubtitleFormat::WriteFile(const AssFile *src, wxString const& filename, wxString const& encoding) const {
+	TextFileWriter file(filename, encoding);
 
 	// Convert to SRT
-	CreateCopy();
-	SortLines();
-	StripComments();
-	RecombineOverlaps();
-	MergeIdentical();
-	ConvertNewlines("\r\n", false);
+	AssFile copy(*src);
+	copy.Sort();
+	StripComments(copy.Line);
+	RecombineOverlaps(copy.Line);
+	MergeIdentical(copy.Line);
+	ConvertNewlines(copy.Line, "\r\n", false);
 
 	// Write lines
 	int i=1;
-	for (std::list<AssEntry*>::iterator cur = Line->begin(); cur != Line->end(); ++cur) {
+	for (LineList::const_iterator cur = copy.Line.begin(); cur != copy.Line.end(); ++cur) {
 		if (AssDialogue *current = dynamic_cast<AssDialogue*>(*cur)) {
 			file.WriteLineToFile(wxString::Format("%d", i++));
 			file.WriteLineToFile(WriteSRTTime(current->Start) + " --> " + WriteSRTTime(current->End));
@@ -517,11 +517,9 @@ void SRTSubtitleFormat::WriteFile(wxString const& filename, wxString const& enco
 			file.WriteLineToFile("");
 		}
 	}
-
-	ClearCopy();
 }
 
-wxString SRTSubtitleFormat::ConvertTags(AssDialogue *diag) {
+wxString SRTSubtitleFormat::ConvertTags(AssDialogue *diag) const {
 	wxString final;
 	std::map<char, bool> tag_states;
 	tag_states['i'] = false;
diff --git a/aegisub/src/subtitle_format_srt.h b/aegisub/src/subtitle_format_srt.h
index c7c1f13ae..dc6254cbe 100644
--- a/aegisub/src/subtitle_format_srt.h
+++ b/aegisub/src/subtitle_format_srt.h
@@ -42,12 +42,12 @@
 ///
 /// DOCME
 class SRTSubtitleFormat : public SubtitleFormat {
-	wxString ConvertTags(AssDialogue *diag);
+	wxString ConvertTags(AssDialogue *diag) const;
 public:
 	SRTSubtitleFormat();
 	wxArrayString GetReadWildcards() const;
 	wxArrayString GetWriteWildcards() const;
 
-	void ReadFile(wxString const& filename, wxString const& forceEncoding);
-	void WriteFile(wxString const& filename, wxString const& encoding);
+	void ReadFile(AssFile *target, wxString const& filename, wxString const& forceEncoding) const;
+	void WriteFile(const AssFile *src, wxString const& filename, wxString const& encoding) const;
 };
diff --git a/aegisub/src/subtitle_format_transtation.cpp b/aegisub/src/subtitle_format_transtation.cpp
index d843e40e4..235ef149c 100644
--- a/aegisub/src/subtitle_format_transtation.cpp
+++ b/aegisub/src/subtitle_format_transtation.cpp
@@ -59,25 +59,25 @@ wxArrayString TranStationSubtitleFormat::GetWriteWildcards() const {
 	return formats;
 }
 
-void TranStationSubtitleFormat::WriteFile(wxString const& filename, wxString const& encoding) {
+void TranStationSubtitleFormat::WriteFile(const AssFile *src, wxString const& filename, wxString const& encoding) const {
 	FractionalTime ft = AskForFPS(true);
 	if (!ft.FPS().IsLoaded()) return;
 
 	TextFileWriter file(filename, encoding);
 
 	// Convert to TranStation
-	CreateCopy();
-	SortLines();
-	StripComments();
-	RecombineOverlaps();
-	MergeIdentical();
+	AssFile copy(*src);
+	copy.Sort();
+	StripComments(copy.Line);
+	RecombineOverlaps(copy.Line);
+	MergeIdentical(copy.Line);
 
 	AssDialogue *prev = 0;
-	for (std::list<AssEntry*>::iterator it = Line->begin(); it != Line->end(); ++it) {
+	for (std::list<AssEntry*>::iterator it = copy.Line.begin(); it != copy.Line.end(); ++it) {
 		AssDialogue *cur = dynamic_cast<AssDialogue*>(*it);
 
 		if (prev && cur) {
-			file.WriteLineToFile(ConvertLine(prev, &ft, cur->Start));
+			file.WriteLineToFile(ConvertLine(&copy, prev, &ft, cur->Start));
 			file.WriteLineToFile("");
 		}
 
@@ -87,19 +87,17 @@ void TranStationSubtitleFormat::WriteFile(wxString const& filename, wxString con
 
 	// flush last line
 	if (prev)
-		file.WriteLineToFile(ConvertLine(prev, &ft, -1));
+		file.WriteLineToFile(ConvertLine(&copy, prev, &ft, -1));
 
 	// Every file must end with this line
 	file.WriteLineToFile("SUB[");
-
-	ClearCopy();
 }
 
-wxString TranStationSubtitleFormat::ConvertLine(AssDialogue *current, FractionalTime *ft, int nextl_start) {
+wxString TranStationSubtitleFormat::ConvertLine(AssFile *file, AssDialogue *current, FractionalTime *ft, int nextl_start) const {
 	int valign = 0;
 	const char *halign = " "; // default is centered
 	const char *type = "N"; // no special style
-	if (AssStyle *style = GetAssFile()->GetStyle(current->Style)) {
+	if (AssStyle *style = file->GetStyle(current->Style)) {
 		if (style->alignment >= 4) valign = 4;
 		if (style->alignment >= 7) valign = 9;
 		if (style->alignment == 1 || style->alignment == 4 || style->alignment == 7) halign = "L";
diff --git a/aegisub/src/subtitle_format_transtation.h b/aegisub/src/subtitle_format_transtation.h
index 122a2cea5..c253d3395 100644
--- a/aegisub/src/subtitle_format_transtation.h
+++ b/aegisub/src/subtitle_format_transtation.h
@@ -44,10 +44,10 @@ class AssDialogue;
 ///
 /// DOCME
 class TranStationSubtitleFormat : public SubtitleFormat {
-	wxString ConvertLine(AssDialogue *line, FractionalTime *ft, int nextl_start);
+	wxString ConvertLine(AssFile *file, AssDialogue *line, FractionalTime *ft, int nextl_start) const;
 
 public:
 	TranStationSubtitleFormat();
 	wxArrayString GetWriteWildcards() const;
-	void WriteFile(wxString const& filename, wxString const& encoding);
+	void WriteFile(const AssFile *src, wxString const& filename, wxString const& encoding) const;
 };
diff --git a/aegisub/src/subtitle_format_ttxt.cpp b/aegisub/src/subtitle_format_ttxt.cpp
index ed224baf9..e897140c3 100644
--- a/aegisub/src/subtitle_format_ttxt.cpp
+++ b/aegisub/src/subtitle_format_ttxt.cpp
@@ -38,6 +38,10 @@
 
 #include "subtitle_format_ttxt.h"
 
+#ifndef AGI_PRE
+#include <wx/xml/xml.h>
+#endif
+
 #include "ass_dialogue.h"
 #include "ass_file.h"
 #include "ass_time.h"
@@ -61,8 +65,8 @@ wxArrayString TTXTSubtitleFormat::GetWriteWildcards() const {
 	return GetReadWildcards();
 }
 
-void TTXTSubtitleFormat::ReadFile(wxString const& filename, wxString const& forceEncoding) {
-	LoadDefault(false);
+void TTXTSubtitleFormat::ReadFile(AssFile *target, wxString const& filename, wxString const& encoding) const {
+	target->LoadDefault(false);
 
 	// Load XML document
 	wxXmlDocument doc;
@@ -73,106 +77,96 @@ void TTXTSubtitleFormat::ReadFile(wxString const& filename, wxString const& forc
 
 	// Check version
 	wxString verStr = doc.GetRoot()->GetAttribute("version", "");
-	version = -1;
-	if (verStr == "1.0") version = 0;
-	else if (verStr == "1.1") version = 1;
-	else throw TTXTParseError("Unknown TTXT version: " + STD_STR(verStr), 0);
+	int version = -1;
+	if (verStr == "1.0")
+		version = 0;
+	else if (verStr == "1.1")
+		version = 1;
+	else
+		throw TTXTParseError("Unknown TTXT version: " + STD_STR(verStr), 0);
 
 	// Get children
-	diag = NULL;
-	wxXmlNode *child = doc.GetRoot()->GetChildren();
+	AssDialogue *diag = 0;
 	int lines = 0;
-	while (child) {
+	for (wxXmlNode *child = doc.GetRoot()->GetChildren(); child; child = child->GetNext()) {
 		// Line
 		if (child->GetName() == "TextSample") {
-			if (ProcessLine(child)) lines++;
+			if (diag = ProcessLine(child, diag, version)) {
+				lines++;
+				target->Line.push_back(diag);
+			}
 		}
-
 		// Header
 		else if (child->GetName() == "TextStreamHeader") {
 			ProcessHeader(child);
 		}
-
-		// Proceed to next child
-		child = child->GetNext();
 	}
 
 	// No lines?
-	if (lines == 0) {
-		AssDialogue *line = new AssDialogue();
-		line->group = "[Events]";
-		line->Style = "Default";
-		line->Start = 0;
-		line->End = 5000;
-		Line->push_back(line);
-	}
+	if (lines == 0)
+		target->Line.push_back(new AssDialogue);
 }
 
-bool TTXTSubtitleFormat::ProcessLine(wxXmlNode *node) {
+AssDialogue *TTXTSubtitleFormat::ProcessLine(wxXmlNode *node, AssDialogue *prev, int version) const {
 	// Get time
 	wxString sampleTime = node->GetAttribute("sampleTime", "00:00:00.000");
 	AssTime time;
 	time.ParseASS(sampleTime);
 
 	// Set end time of last line
-	if (diag) diag->End = time;
-	diag = NULL;
+	if (prev)
+		prev->End = time;
 
 	// Get text
 	wxString text;
-	if (version == 0) text = node->GetAttribute("text", "");
-	else text = node->GetNodeContent();
+	if (version == 0)
+		text = node->GetAttribute("text", "");
+	else
+		text = node->GetNodeContent();
 
 	// Create line
-	if (!text.IsEmpty()) {
-		// Create dialogue
-		diag = new AssDialogue();
-		diag->Start = time;
-		diag->End = 36000000-10;
-		diag->group = "[Events]";
-		diag->Style = "Default";
-		diag->Comment = false;
+	if (text.empty()) return 0;
 
-		// Process text for 1.0
-		if (version == 0) {
-			wxString finalText;
-			finalText.Alloc(text.Length());
-			bool in = false;
-			bool first = true;
-			for (size_t i=0;i<text.Length();i++) {
-				if (text[i] == '\'') {
-					if (!in && !first) finalText += "\\N";
-					first = false;
-					in = !in;
-				}
-				else if (in) finalText += text[i];
+	// Create dialogue
+	AssDialogue *diag = new AssDialogue;
+	diag->Start = time;
+	diag->End = 36000000-10;
+
+	// Process text for 1.0
+	if (version == 0) {
+		wxString finalText;
+		finalText.reserve(text.size());
+		bool in = false;
+		bool first = true;
+		for (size_t i = 0; i < text.size(); ++i) {
+			if (text[i] == '\'') {
+				if (!in && !first) finalText += "\\N";
+				first = false;
+				in = !in;
 			}
-			diag->Text = finalText;
+			else if (in) finalText += text[i];
 		}
-
-		// Process text for 1.1
-		else {
-			text.Replace("\r", "");
-			text.Replace("\n", "\\N");
-			diag->Text = text;
-		}
-
-		// Insert dialogue
-		Line->push_back(diag);
-		return true;
+		diag->Text = finalText;
 	}
 
-	else return false;
+	// Process text for 1.1
+	else {
+		text.Replace("\r", "");
+		text.Replace("\n", "\\N");
+		diag->Text = text;
+	}
+
+	return diag;
 }
 
-void TTXTSubtitleFormat::ProcessHeader(wxXmlNode *node) {
+void TTXTSubtitleFormat::ProcessHeader(wxXmlNode *node) const {
 	// TODO
 }
 
-void TTXTSubtitleFormat::WriteFile(wxString const& filename, wxString const& encoding) {
+void TTXTSubtitleFormat::WriteFile(const AssFile *src, wxString const& filename, wxString const& encoding) const {
 	// Convert to TTXT
-	CreateCopy();
-	ConvertToTTXT();
+	AssFile copy(*src);
+	ConvertToTTXT(copy);
 
 	// Create XML structure
 	wxXmlDocument doc;
@@ -184,28 +178,22 @@ void TTXTSubtitleFormat::WriteFile(wxString const& filename, wxString const& enc
 	WriteHeader(root);
 
 	// Create lines
-	int i=1;
-	using std::list;
-	prev = NULL;
-	for (list<AssEntry*>::iterator cur=Line->begin();cur!=Line->end();cur++) {
+	AssDialogue *prev = 0;
+	for (LineList::iterator cur = copy.Line.begin(); cur != copy.Line.end(); ++cur) {
 		AssDialogue *current = dynamic_cast<AssDialogue*>(*cur);
 		if (current && !current->Comment) {
-			WriteLine(root, current);
-			i++;
+			WriteLine(root, prev, current);
+			prev = current;
 		}
 		else
 			throw TTXTParseError("Unexpected line type in TTXT file", 0);
 	}
 
 	// Save XML
-	//prevNode->SetNext(NULL);
 	doc.Save(filename);
-
-	// Clear
-	ClearCopy();
 }
 
-void TTXTSubtitleFormat::WriteHeader(wxXmlNode *root) {
+void TTXTSubtitleFormat::WriteHeader(wxXmlNode *root) const {
 	// Write stream header
 	wxXmlNode *node = new wxXmlNode(wxXML_ELEMENT_NODE, "TextStreamHeader");
 	node->AddAttribute("width", "400");
@@ -255,7 +243,7 @@ void TTXTSubtitleFormat::WriteHeader(wxXmlNode *root) {
 	root->AddChild(node);
 }
 
-void TTXTSubtitleFormat::WriteLine(wxXmlNode *root, AssDialogue *line) {
+void TTXTSubtitleFormat::WriteLine(wxXmlNode *root, AssDialogue *prev, AssDialogue *line) const {
 	// If it doesn't start at the end of previous, add blank
 	if (prev && prev->End != line->Start) {
 		wxXmlNode *node = new wxXmlNode(wxXML_ELEMENT_NODE, "TextSample");
@@ -271,22 +259,19 @@ void TTXTSubtitleFormat::WriteLine(wxXmlNode *root, AssDialogue *line) {
 	node->AddAttribute("xml:space", "preserve");
 	root->AddChild(node);
 	node->AddChild(new wxXmlNode(wxXML_TEXT_NODE, "", line->Text));
-
-	// Set as previous
-	prev = line;
 }
 
-void TTXTSubtitleFormat::ConvertToTTXT () {
-	SortLines();
-	StripComments();
-	RecombineOverlaps();
-	MergeIdentical();
-	StripTags();
-	ConvertNewlines("\r\n");
+void TTXTSubtitleFormat::ConvertToTTXT(AssFile &file) const {
+	file.Sort();
+	StripComments(file.Line);
+	RecombineOverlaps(file.Line);
+	MergeIdentical(file.Line);
+	StripTags(file.Line);
+	ConvertNewlines(file.Line, "\r\n");
 
 	// Find last line
 	AssTime lastTime;
-	for (std::list<AssEntry*>::reverse_iterator cur=Line->rbegin();cur!=Line->rend();cur++) {
+	for (LineList::reverse_iterator cur = file.Line.rbegin(); cur != file.Line.rend(); ++cur) {
 		if (AssDialogue *prev = dynamic_cast<AssDialogue*>(*cur)) {
 			lastTime = prev->End;
 			break;
@@ -294,11 +279,11 @@ void TTXTSubtitleFormat::ConvertToTTXT () {
 	}
 
 	// Insert blank line at the end
-	AssDialogue *diag = new AssDialogue();
+	AssDialogue *diag = new AssDialogue;
 	diag->Start = lastTime;
 	diag->End = lastTime+OPT_GET("Timing/Default Duration")->GetInt();
 	diag->group = "[Events]";
 	diag->Style = "Default";
 	diag->Comment = false;
-	Line->push_back(diag);
+	file.Line.push_back(diag);
 }
diff --git a/aegisub/src/subtitle_format_ttxt.h b/aegisub/src/subtitle_format_ttxt.h
index d1819433b..7a20095be 100644
--- a/aegisub/src/subtitle_format_ttxt.h
+++ b/aegisub/src/subtitle_format_ttxt.h
@@ -34,14 +34,10 @@
 /// @ingroup subtitle_io
 ///
 
-#ifndef AGI_PRE
-#include <wx/xml/xml.h>
-#endif
-
 #include "subtitle_format.h"
 
 class AssDialogue;
-
+class wxXmlNode;
 
 /// DOCME
 /// @class TTXTSubtitleFormat
@@ -49,28 +45,19 @@ class AssDialogue;
 ///
 /// DOCME
 class TTXTSubtitleFormat : public SubtitleFormat {
-	/// DOCME
-	int version;
+	AssDialogue *ProcessLine(wxXmlNode *node, AssDialogue *prev, int version) const;
+	void ProcessHeader(wxXmlNode *node) const;
 
-	/// DOCME
-	AssDialogue *diag;
+	void WriteHeader(wxXmlNode *root) const;
+	void WriteLine(wxXmlNode *root, AssDialogue *prev, AssDialogue *line) const;
 
-	/// DOCME
-	AssDialogue *prev;
-
-	bool ProcessLine(wxXmlNode *node);
-	void ProcessHeader(wxXmlNode *node);
-
-	void WriteHeader(wxXmlNode *root);
-	void WriteLine(wxXmlNode *root, AssDialogue *line);
-
-	void ConvertToTTXT();
+	void ConvertToTTXT(AssFile &file) const;
 
 public:
 	TTXTSubtitleFormat();
 	wxArrayString GetReadWildcards() const;
 	wxArrayString GetWriteWildcards() const;
 
-	void ReadFile(wxString const& filename, wxString const& forceEncoding);
-	void WriteFile(wxString const& filename, wxString const& encoding);
+	void ReadFile(AssFile *target, wxString const& filename, wxString const& forceEncoding) const;
+	void WriteFile(const AssFile *src, wxString const& filename, wxString const& encoding) const;
 };
diff --git a/aegisub/src/subtitle_format_txt.cpp b/aegisub/src/subtitle_format_txt.cpp
index 408fd6ae7..445547c03 100644
--- a/aegisub/src/subtitle_format_txt.cpp
+++ b/aegisub/src/subtitle_format_txt.cpp
@@ -39,6 +39,7 @@
 #include "subtitle_format_txt.h"
 
 #include "ass_dialogue.h"
+#include "ass_file.h"
 #include "compat.h"
 #include "dialog_text_import.h"
 #include "main.h"
@@ -66,14 +67,14 @@ bool TXTSubtitleFormat::CanWriteFile(wxString const& filename) const {
 	return (filename.Right(4).Lower() == ".txt" && filename.Right(11).Lower() != ".encore.txt" && filename.Right(16).Lower() != ".transtation.txt");
 }
 
-void TXTSubtitleFormat::ReadFile(wxString const& filename, wxString const& encoding) {
+void TXTSubtitleFormat::ReadFile(AssFile *target, wxString const& filename, wxString const& encoding) const {
 	using namespace std;
 	DialogTextImport dlg;
 	if (dlg.ShowModal() == wxID_CANCEL) return;
 
 	TextFileReader file(filename, encoding, false);
 
-	LoadDefault(false);
+	target->LoadDefault(false);
 
 	wxString actor;
 	wxString separator = lagi_wxString(OPT_GET("Tool/Import/Text/Actor Separator")->GetString());
@@ -123,7 +124,7 @@ void TXTSubtitleFormat::ReadFile(wxString const& filename, wxString const& encod
 		line->End = 0;
 
 		// Adds line
-		Line->push_back(line);
+		target->Line.push_back(line);
 		lines++;
 	}
 
@@ -131,15 +132,15 @@ void TXTSubtitleFormat::ReadFile(wxString const& filename, wxString const& encod
 	if (lines == 0) {
 		AssDialogue *line = new AssDialogue;
 		line->End = OPT_GET("Timing/Default Duration")->GetInt();
-		Line->push_back(line);
+		target->Line.push_back(line);
 	}
 }
 
-void TXTSubtitleFormat::WriteFile(wxString const& filename, wxString const& encoding) {
+void TXTSubtitleFormat::WriteFile(const AssFile *src, wxString const& filename, wxString const& encoding) const {
 	size_t num_actor_names = 0, num_dialogue_lines = 0;
 
 	// Detect number of lines with Actor field filled out
-	for (std::list<AssEntry*>::iterator l = Line->begin(); l != Line->end(); ++l) {
+	for (LineList::const_iterator l = src->Line.begin(); l != src->Line.end(); ++l) {
 		AssDialogue *dia = dynamic_cast<AssDialogue*>(*l);
 		if (dia && !dia->Comment) {
 			num_dialogue_lines++;
@@ -156,7 +157,7 @@ void TXTSubtitleFormat::WriteFile(wxString const& filename, wxString const& enco
 	file.WriteLineToFile(wxString("# Exported by Aegisub ") + GetAegisubShortVersionString());
 
 	// Write the file
-	for (std::list<AssEntry*>::iterator l = Line->begin(); l != Line->end(); ++l) {
+	for (LineList::const_iterator l = src->Line.begin(); l != src->Line.end(); ++l) {
 		AssDialogue *dia = dynamic_cast<AssDialogue*>(*l);
 
 		if (dia) {
diff --git a/aegisub/src/subtitle_format_txt.h b/aegisub/src/subtitle_format_txt.h
index c8431fa20..f6cd22e03 100644
--- a/aegisub/src/subtitle_format_txt.h
+++ b/aegisub/src/subtitle_format_txt.h
@@ -48,6 +48,6 @@ public:
 	wxArrayString GetWriteWildcards() const;
 
 	bool CanWriteFile(wxString const& filename) const;
-	void ReadFile(wxString const& filename, wxString const& forceEncoding);
-	void WriteFile(wxString const& filename, wxString const& encoding);
+	void ReadFile(AssFile *target, wxString const& filename, wxString const& forceEncoding) const;
+	void WriteFile(const AssFile *src, wxString const& filename, wxString const& encoding) const;
 };