GLK: FROTZ: Implemented Quetzal class for savegames

9 files changed, 648 insertions, 19 deletions

diff --git a/engines/gargoyle/frotz/err.h b/engines/gargoyle/frotz/err.h
index e71c9881e8..090ce3f7df 100644
--- a/engines/gargoyle/frotz/err.h
+++ b/engines/gargoyle/frotz/err.h
@@ -96,7 +96,7 @@ protected:
 	/**
 	 * Get the PC. Is implemented by the Processor class, which derives from Errors
 	 */
-	virtual zword getPC() const = 0;
+	virtual uint getPC() const = 0;
 public:
 	/**
 	 * Constructor
diff --git a/engines/gargoyle/frotz/mem.cpp b/engines/gargoyle/frotz/mem.cpp
index ad60b89bbb..e327fbaecf 100644
--- a/engines/gargoyle/frotz/mem.cpp
+++ b/engines/gargoyle/frotz/mem.cpp
@@ -129,14 +129,11 @@ void Mem::initialize() {
 
 	// Load story file in chunks of 32KB
 	uint n = 0x8000;
-
 	for (uint size = 64; size < story_size; size += n) {
 		if (story_size - size < 0x8000)
 			n = story_size - size;
 
-		SET_PC(size);
-
-		if (story_fp->read(pcp, n) != n)
+		if (story_fp->read(zmp + size, n) != n)
 			error("Story file read error");
 	}
 
diff --git a/engines/gargoyle/frotz/processor.h b/engines/gargoyle/frotz/processor.h
index 6a28121512..0f7ecc06b4 100644
--- a/engines/gargoyle/frotz/processor.h
+++ b/engines/gargoyle/frotz/processor.h
@@ -32,25 +32,27 @@
 namespace Gargoyle {
 namespace Frotz {
 
-#define CODE_BYTE(v)	   v = *pcp++
-#define CODE_WORD(v)       v = READ_BE_UINT16(pcp += 2)
-#define CODE_IDX_WORD(v,i) v = READ_BE_UINT16(pcp + i)
-#define GET_PC(v)          v = pcp - zmp
-#define SET_PC(v)          pcp = zmp + v
-
 #define TEXT_BUFFER_SIZE 200
 
+#define CODE_BYTE(v)	   v = codeByte()
+#define CODE_WORD(v)       v = codeWord()
+#define CODE_IDX_WORD(v,i) v = codeWordIdx(i)
+#define GET_PC(v)          v = getPC()
+#define SET_PC(v)          setPC(v)
+
 enum string_type {
 	LOW_STRING, ABBREVIATION, HIGH_STRING, EMBEDDED_STRING, VOCABULARY
 };
 
 class Processor;
+class Quetzal;
 typedef void (Processor::*Opcode)();
 
 /**
  * Zcode processor
  */
 class Processor : public Errors, public GlkInterface, public virtual Mem {
+	friend class Quetzal;
 private:
 	int _finished;
 	zword zargs[8];
@@ -1510,11 +1512,6 @@ protected:
 	void z_store();
 
 	/**@}*/
-protected:
-	/**
-	 * Get the PC. Is implemented by the Processor class, which derives from Errors
-	 */
-	virtual zword getPC() const { return pcp - zmp; }
 public:
 	/**
 	 * Constructor
@@ -1530,6 +1527,50 @@ public:
 	 * Z-code interpreter main loop
 	 */
 	void interpret();
+
+	/**
+	 * \defgroup Memory access methods
+	 * @{
+	 */
+
+	/**
+	 * Square brackets operator
+	 */
+	zbyte &operator[](uint addr) { return zmp[addr]; }
+
+	/**
+	 * Read a code byte
+	 */
+	zbyte codeByte() { return *pcp++; }
+
+	/**
+	 * Read a code word
+	 */
+	zword codeWord() {
+		zword v = READ_BE_UINT16(pcp);
+		pcp += 2;
+		return v;
+	}
+
+	/**
+	 * Return a code word at a given address
+	 */
+	zword codeWordIdx(uint addr) const {
+		return READ_BE_UINT16(pcp + addr);
+	}
+
+	/**
+	 * Return the current program execution offset
+	 * @remarks		This virtual as a convenient way for the ancestor Err class to access
+	 */
+	virtual uint getPC() const override { return pcp - zmp; }
+
+	/**
+	 * Set the program execution offset
+	 */
+	void setPC(uint addr) { pcp = zmp + addr; }
+
+	 /**@}*/
 };
 
 } // End of namespace Frotz
diff --git a/engines/gargoyle/frotz/processor_streams.cpp b/engines/gargoyle/frotz/processor_streams.cpp
index d75819e661..50d642585d 100644
--- a/engines/gargoyle/frotz/processor_streams.cpp
+++ b/engines/gargoyle/frotz/processor_streams.cpp
@@ -21,6 +21,7 @@
  */
 
 #include "gargoyle/frotz/processor.h"
+#include "gargoyle/frotz/quetzal.h"
 
 namespace Gargoyle {
 namespace Frotz {
@@ -574,7 +575,7 @@ void Processor::z_save() {
 		if ((gfp = frotzopenprompt (FILE_SAVE)) == nullptr)
 			goto finished;
 
-		if (option_save_quetzal) {
+		if (_save_quetzal) {
 			success = save_quetzal (gfp, story_fp, blorb_ofs);
 		} else {
 			/* Write game file */
@@ -670,7 +671,7 @@ void Processor::z_restore() {
 		if ((gfp = frotzopenprompt(FILE_RESTORE)) == nullptr)
 			goto finished;
 
-		if (option_save_quetzal) {
+		if (_save_quetzal) {
 			success = restore_quetzal (gfp, story_fp, blorb_ofs);
 
 		} else {
diff --git a/engines/gargoyle/frotz/quetzal.cpp b/engines/gargoyle/frotz/quetzal.cpp
new file mode 100644
index 0000000000..183217a390
--- /dev/null
+++ b/engines/gargoyle/frotz/quetzal.cpp
@@ -0,0 +1,485 @@
+/* ScummVM - Graphic Adventure Engine
+ *
+ * ScummVM is the legal property of its developers, whose names
+ * are too numerous to list here. Please refer to the COPYRIGHT
+ * file distributed with this source distribution.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ */
+
+#include "gargoyle/frotz/quetzal.h"
+#include "gargoyle/frotz/processor.h"
+#include "common/memstream.h"
+
+namespace Gargoyle {
+namespace Frotz {
+
+/**
+ * Various parsing states within restoration.
+ */
+enum ParseState {
+	GOT_HEADER = 0x01,
+	GOT_STACK  = 0x02,
+	GOT_MEMORY = 0x04,
+	GOT_NONE   = 0x00,
+	GOT_ALL    = 0x07,
+	GOT_ERROR  = 0x80
+};
+
+
+bool Quetzal::read_word(Common::ReadStream *f, zword *result) {
+	*result = f->readUint16BE();
+	return true;
+}
+
+bool Quetzal::read_long(Common::ReadStream *f, uint *result) {
+	*result = f->readUint32BE();
+	return true;
+}
+
+bool Quetzal::save(Common::WriteStream *svf, Processor *proc) {
+	Processor &p = *proc;
+	uint ifzslen = 0, cmemlen = 0, stkslen = 0;
+	uint pc;
+	zword i, j, n;
+	zword nvars, nargs, nstk;
+	zbyte var;
+	long cmempos, stkspos;
+	int c;
+
+	// Set a temporary memory stream for writing out the data. This is needed, since we need to
+	// do some seeking within it at the end to fill out totals before properly writing it all out
+	Common::MemoryWriteStreamDynamic saveData(DisposeAfterUse::YES);
+	_out = &saveData;
+
+	// Write `IFZS' header.
+	write_chnk(ID_FORM, 0);
+	write_long(ID_IFZS);
+
+	// Write `IFhd' chunk
+	pc = p.getPC();
+	write_chnk(ID_IFhd, 13);
+	write_word(p.h_release);
+	for (i = H_SERIAL; i<H_SERIAL + 6; ++i)
+		write_byte(p[i]);
+
+	write_word(p.h_checksum);
+	write_long(pc << 8);		// Includes pad
+
+	// Write `CMem' chunk.
+	cmempos = svf->pos();
+	write_chnk(ID_CMem, 0);
+	_storyFile->seek(_blorbOffset);
+
+	// j holds current run length.
+	for (i = 0, j = 0, cmemlen = 0; i < p.h_dynamic_size; ++i) {
+		c = _storyFile->readByte();
+		c ^= p[i];
+
+		if (c == 0) {
+			// It's a run of equal bytes
+			++j;
+		} else {
+			// Write out any run there may be.
+			if (j > 0) {
+				for (; j > 0x100; j -= 0x100) {
+					write_run(0xFF);
+					cmemlen += 2;
+				}
+				write_run(j - 1);
+				cmemlen += 2;
+				j = 0;
+			}
+
+			// Any runs are now written. Write this (nonzero) byte
+			write_byte((zbyte)c);
+			++cmemlen;
+		}
+	}
+
+	// Reached end of dynamic memory. We ignore any unwritten run there may be at this point.
+	if (cmemlen & 1)
+		// Chunk length must be even.
+		write_byte(0);
+
+	// Write `Stks' chunk. You are not expected to understand this. ;)
+	stkspos = _storyFile->pos();
+	write_chnk(ID_Stks, 0);
+
+	// We construct a list of frame indices, most recent first, in `frames'.
+	// These indices are the offsets into the `stack' array of the word before
+	// the first word pushed in each frame.
+	frames[0] = p._sp - p._stack;	// The frame we'd get by doing a call now.
+	for (i = p._fp - p._stack + 4, n = 0; i < STACK_SIZE + 4; i = p._stack[i - 3] + 5)
+		frames[++n] = i;
+
+	// All versions other than V6 can use evaluation stack outside a function
+	// context. We write a faked stack frame (most fields zero) to cater for this.
+	if (p.h_version != V6) {
+		for (i = 0; i < 6; ++i)
+			write_byte(0);
+		nstk = STACK_SIZE - frames[n];
+		write_word(nstk);
+		for (j = STACK_SIZE - 1; j >= frames[n]; --j)
+			write_word(p._stack[j]);
+		stkslen = 8 + 2 * nstk;
+	}
+
+	// Write out the rest of the stack frames.
+	for (i = n; i > 0; --i) {
+		zword *pf = p._stack + frames[i] - 4;	// Points to call frame
+		nvars = (pf[0] & 0x0F00) >> 8;
+		nargs = pf[0] & 0x00FF;
+		nstk = frames[i] - frames[i - 1] - nvars - 4;
+		pc = ((uint)pf[3] << 9) | pf[2];
+
+		// Check type of call
+		switch (pf[0] & 0xF000)	{
+		case 0x0000:
+			// Function
+			var = p[pc];
+			pc = ((pc + 1) << 8) | nvars;
+			break;
+
+		case 0x1000:
+			// Procedure
+			var = 0;
+			pc = (pc << 8) | 0x10 | nvars;	// Set procedure flag
+			break;
+
+		default:
+			p.runtimeError(ERR_SAVE_IN_INTER);
+			return 0;
+		}
+		if (nargs != 0)
+			nargs = (1 << nargs) - 1;	// Make args into bitmap
+
+		// Write the main part of the frame...
+		write_long(pc);
+		write_byte(var);
+		write_byte(nargs);
+		write_word(nstk);
+
+		// Write the variables and eval stack
+		for (j = 0, --pf; j<nvars + nstk; ++j, --pf)
+			write_word(*pf);
+
+		// Calculate length written thus far
+		stkslen += 8 + 2 * (nvars + nstk);
+	}
+
+	// Fill in variable chunk lengths
+	ifzslen = 3 * 8 + 4 + 14 + cmemlen + stkslen;
+	if (cmemlen & 1)
+		++ifzslen;
+
+	saveData.seek(4);
+	saveData.writeUint32BE(ifzslen);
+	saveData.seek(cmempos + 4);
+	saveData.writeUint32BE(cmemlen);
+	saveData.seek(stkspos + 4);
+	saveData.writeUint32BE(stkslen);
+
+	// Write the save data out
+	svf->write(saveData.getData(), saveData.size());
+
+	// After all that, still nothing went wrong!
+	return true;
+}
+
+
+int Quetzal::restore(Common::SeekableReadStream *svf, Processor *proc) {
+	Processor &p = *proc;
+	uint ifzslen, currlen, tmpl;
+	uint pc;
+	zword i, tmpw;
+	int fatal = 0;	// Set to -1 when errors must be fatal.
+	zbyte skip, progress = GOT_NONE;
+	int x, y;
+
+	// Check it's really an `IFZS' file.
+	tmpl = svf->readUint32BE();
+	ifzslen = svf->readUint32BE();
+	currlen = svf->readUint32BE();
+	if (tmpl != ID_FORM || currlen != ID_IFZS) {
+		p.print_string("This is not a saved game file!\n");
+		return 0;
+	}
+	if ((ifzslen & 1) || ifzslen<4)
+		// Sanity checks
+		return 0;
+	ifzslen -= 4;
+
+	// Read each chunk and process it
+	while (ifzslen > 0) {
+		// Read chunk header
+		if (ifzslen < 8)
+			// Couldn't contain a chunk
+			return 0;
+
+		tmpl = svf->readUint32BE();
+		currlen = svf->readUint32BE();
+		ifzslen -= 8;	// Reduce remaining by size of header
+
+		// Handle chunk body
+		if (ifzslen < currlen)
+			// Chunk goes past EOF?!
+			return 0;
+		skip = currlen & 1;
+		ifzslen -= currlen + (uint)skip;
+
+		switch (tmpl) {
+		// `IFhd' header chunk; must be first in file
+		case ID_IFhd:
+			if (progress & GOT_HEADER) {
+				p.print_string("Save file has two IFZS chunks!\n");
+				return fatal;
+			}
+			progress |= GOT_HEADER;
+			if (currlen < 13)
+				return fatal;
+
+			tmpw = svf->readUint16BE();
+			if (tmpw != p.h_release)
+				progress = GOT_ERROR;
+
+			for (i = H_SERIAL; i < H_SERIAL + 6; ++i) {
+				x = svf->readByte();
+				if (x != p[i])
+					progress = GOT_ERROR;
+			}
+
+			tmpw = svf->readUint16BE();
+			if (tmpw != p.h_checksum)
+				progress = GOT_ERROR;
+
+			if (progress & GOT_ERROR) {
+				p.print_string("File was not saved from this story!\n");
+				return fatal;
+			}
+
+			x = svf->readByte();
+			pc = (uint)x << 16;
+			x = svf->readByte();
+			pc |= (uint)x << 8;
+			x = svf->readByte();
+			pc |= (uint)x;
+
+			fatal = -1;		// Setting PC means errors must be fatal
+			p.setPC(pc);
+
+			svf->skip(13);	// Skip rest of chunk
+			break;
+
+		// `Stks' stacks chunk; restoring this is quite complex. ;)
+		case ID_Stks:
+			if (progress & GOT_STACK) {
+				p.print_string("File contains two stack chunks!\n");
+				break;
+			}
+			progress |= GOT_STACK;
+
+			fatal = -1;		// Setting SP means errors must be fatal
+			p._sp = p._stack + STACK_SIZE;
+
+			// All versions other than V6 may use evaluation stack outside any function context.
+			// As a result a faked function context will be present in the file here. We skip
+			// this context, but load the associated stack onto the stack proper...
+			if (p.h_version != V6) {
+				if (currlen < 8)
+					return fatal;
+
+				svf->skip(6);
+				tmpw = svf->readUint16BE();
+
+				if (tmpw > STACK_SIZE) {
+					p.print_string("Save-file has too much stack (and I can't cope).\n");
+					return fatal;
+				}
+
+				currlen -= 8;
+				if (currlen < (uint)tmpw * 2)
+					return fatal;
+				for (i = 0; i < tmpw; ++i)
+					*--p._sp = svf->readUint16BE();
+				currlen -= tmpw * 2;
+			}
+
+			// We now proceed to load the main block of stack frames
+			for (p._fp = p._stack + STACK_SIZE, p._frameCount = 0;
+					currlen > 0; currlen -= 8, ++p._frameCount) {
+				if (currlen < 8)				return fatal;
+				if (p._sp - p._stack < 4) {
+					// No space for frame
+					p.print_string("Save-file has too much stack (and I can't cope).\n");
+					return fatal;
+				}
+
+				// Read PC, procedure flag and formal param count
+				tmpl = svf->readUint32BE();
+				y = (int)(tmpl & 0x0F);		// Number of formals
+				tmpw = y << 8;
+
+				// Read result variable
+				x = svf->readByte();
+
+				// Check the procedure flag...
+				if (tmpl & 0x10) {
+					tmpw |= 0x1000;		// It's a procedure
+					tmpl >>= 8;			// Shift to get PC value
+				} else {
+					// Functions have type 0, so no need to or anything
+					tmpl >>= 8;			// Shift to get PC value
+					--tmpl;				// Point at result byte. */
+
+					// Sanity check on result variable...
+					if (p[tmpl] != (zbyte)x) {
+						p.print_string("Save-file has wrong variable number on stack (possibly wrong game version?)\n");
+						return fatal;
+					}
+				}
+
+				*--p._sp = (zword)(tmpl >> 9);		// High part of PC
+				*--p._sp = (zword)(tmpl & 0x1FF);	// Low part of PC
+				*--p._sp = (zword)(p._fp - p._stack - 1);	// FP
+
+				// Read and process argument mask
+				x = svf->readByte();
+				++x;		// Should now be a power of 2
+				for (i = 0; i<8; ++i)
+					if (x & (1 << i))
+						break;
+				if (x ^ (1 << i)) {
+					// Not a power of 2
+					p.print_string("Save-file uses incomplete argument lists (which I can't handle)\n");
+					return fatal;
+				}
+
+				*--p._sp = tmpw | i;
+				p._fp = p._sp;	// FP for next frame
+
+				// Read amount of eval stack used
+				tmpw = svf->readUint16BE();
+
+				tmpw += y;	// Amount of stack + number of locals
+				if (p._sp - p._stack <= tmpw) {
+					p.print_string("Save-file has too much stack (and I can't cope).\n");
+					return fatal;
+				}
+				if (currlen < (uint)tmpw * 2)
+					return fatal;
+				
+				for (i = 0; i < tmpw; ++i)
+					--*p._sp = svf->readUint16BE();
+				currlen -= tmpw * 2;
+			}
+
+			// End of `Stks' processing...
+			break;
+
+		// Any more special chunk types must go in HERE or ABOVE
+		// `CMem' compressed memory chunk; uncompress it
+		case ID_CMem:
+			if (!(progress & GOT_MEMORY)) {
+				// Don't complain if two
+				_storyFile->seek(_blorbOffset);
+				
+				i = 0;	// Bytes written to data area
+				for (; currlen > 0; --currlen) {
+					x = svf->readByte();
+					if (x == 0) {
+						// Start of run
+						// Check for bogus run
+						if (currlen < 2) {
+							p.print_string("File contains bogus `CMem' chunk.\n");
+							svf->skip(currlen);
+
+							currlen = 1;
+							i = 0xFFFF;
+							break; // Keep going; may be a `UMem' too
+						}
+
+						// Copy story file to memory during the run
+						--currlen;
+						x = svf->readByte();
+						for (; x >= 0 && i < p.h_dynamic_size; --x, ++i)
+							p[i] = svf->readByte();
+					} else {
+						// Not a run
+						y = svf->readByte();
+						p[i] = (zbyte)(x ^ y);
+						++i;
+					}
+
+					// Make sure we don't load too much
+					if (i > p.h_dynamic_size) {
+						p.print_string("warning: `CMem' chunk too long!\n");
+						svf->skip(currlen);
+						break;	// Keep going; there may be a `UMem' too
+					}
+				}
+
+				// If chunk is short, assume a run
+				for (; i < p.h_dynamic_size; ++i)
+					p[i] = svf->readByte();
+
+				if (currlen == 0)
+					progress |= GOT_MEMORY;		// Only if succeeded
+				break;
+			}
+
+			// Intentional fall-through
+
+		case ID_UMem:
+			if (!(progress & GOT_MEMORY)) {
+				// Must be exactly the right size
+				if (currlen == p.h_dynamic_size) {
+					if (svf->read(p.zmp, currlen) == currlen) {
+						progress |= GOT_MEMORY;	// Only on success
+						break;
+					}
+				} else {
+					p.print_string("`UMem' chunk wrong size!\n");
+				}
+				
+				// Fall into default action (skip chunk) on errors
+			}
+
+			// Intentional fall-through
+
+		default:
+			svf->seek(currlen, SEEK_CUR);		// Skip chunk
+			break;
+		}
+
+		if (skip)
+			svf->skip(1);						// Skip pad byte
+	}
+
+	// We've reached the end of the file. For the restoration to have been a
+	// success, we must have had one of each of the required chunks.
+	if (!(progress & GOT_HEADER))
+		p.print_string("error: no valid header (`IFhd') chunk in file.\n");
+	if (!(progress & GOT_STACK))
+		p.print_string("error: no valid stack (`Stks') chunk in file.\n");
+	if (!(progress & GOT_MEMORY))
+		p.print_string("error: no valid memory (`CMem' or `UMem') chunk in file.\n");
+
+	return (progress == GOT_ALL ? 2 : fatal);
+}
+
+} // End of namespace Scott
+} // End of namespace Gargoyle
diff --git a/engines/gargoyle/frotz/quetzal.h b/engines/gargoyle/frotz/quetzal.h
new file mode 100644
index 0000000000..69751553e2
--- /dev/null
+++ b/engines/gargoyle/frotz/quetzal.h
@@ -0,0 +1,97 @@
+/* ScummVM - Graphic Adventure Engine
+ *
+ * ScummVM is the legal property of its developers, whose names
+ * are too numerous to list here. Please refer to the COPYRIGHT
+ * file distributed with this source distribution.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ */
+
+#ifndef GARGOYLE_FROTZ_QUETZAL
+#define GARGOYLE_FROTZ_QUETZAL
+
+#include "gargoyle/glk_types.h"
+#include "gargoyle/frotz/frotz_types.h"
+
+namespace Gargoyle {
+namespace Frotz {
+
+enum QueztalTag {
+	ID_FORM = MKTAG('F', 'O', 'R', 'M'),
+	ID_IFZS = MKTAG('I', 'F', 'Z', 'S'),
+	ID_IFhd = MKTAG('I', 'F', 'h', 'd'),
+	ID_UMem = MKTAG('U', 'M', 'e', 'm'),
+	ID_CMem = MKTAG('C', 'M', 'e', 'm'),
+	ID_Stks = MKTAG('S', 't', 'k', 's'),
+	ID_ANNO = MKTAG('A', 'N', 'N', 'O')
+};
+
+class Processor;
+
+class Quetzal {
+private:
+	Common::SeekableReadStream *_storyFile;
+	Common::WriteStream *_out;
+	size_t _blorbOffset;
+	int _slot;
+	zword frames[STACK_SIZE / 4 + 1];
+private:
+	/**
+	 * Read a 16-bit value from the file
+	 */
+	bool read_word(Common::ReadStream *f, zword *result);
+
+	/**
+	 * Read  32-bit value from the file
+	 */
+	bool read_long(Common::ReadStream *f, uint *result);
+
+	void write_byte(zbyte b) { _out->writeByte(b); }
+	void write_bytx(zword b) { _out->writeByte(b & 0xFF); }
+	void write_word(zword w) { _out->writeUint16BE(w); }
+	void write_long(uint l) { _out->writeUint32BE(l); }
+	void write_run(zword run) { _out->writeUint16LE(run); }
+	void write_chnk(QueztalTag id, zword len) {
+		_out->writeUint32BE(id);
+		_out->writeUint32BE(len);
+	}
+public:
+	/**
+	 * Constructor
+	 */
+	Quetzal(Common::SeekableReadStream *storyFile, size_t blorbOffset, int slot) :
+		_storyFile(storyFile), _blorbOffset(blorbOffset), _slot(slot) {}
+
+	/*
+	 * Save a game using Quetzal format.
+	 * @param svf	Savegame file
+	 * @returns		Returns true if OK, false if failed
+	 */
+	bool save(Common::WriteStream *svf, Processor *proc);
+
+	/**
+	 * Restore a saved game using Quetzal format
+	 * @param svf	Savegame file
+	 * @returns		Return 2 if OK, 0 if an error occurred before any damage was done,
+	 *				-1 on a fatal error
+	 */
+	int restore(Common::SeekableReadStream *svf, Processor *proc);
+};
+
+} // End of namespace Frotz
+} // End of namespace Gargoyle
+
+#endif
diff --git a/engines/gargoyle/gargoyle.h b/engines/gargoyle/gargoyle.h
index aeaa0c0bad..676708ff41 100644
--- a/engines/gargoyle/gargoyle.h
+++ b/engines/gargoyle/gargoyle.h
@@ -174,6 +174,13 @@ public:
 	}
 
 	/**
+	 * Return the filename for a given save slot
+	 */
+	Common::String getSaveName(uint slot) const {
+		return Common::String::format("%s.%.3u", getTargetName().c_str(), slot);
+	}
+
+	/**
 	 * Display a message in a GUI dialog
 	 */
 	void GUIError(const char *msg, ...);
diff --git a/engines/gargoyle/module.mk b/engines/gargoyle/module.mk
index 14cc04801e..4694449349 100644
--- a/engines/gargoyle/module.mk
+++ b/engines/gargoyle/module.mk
@@ -38,6 +38,7 @@ MODULE_OBJS := \
 	frotz/processor_table.o \
 	frotz/processor_text.o \
 	frotz/processor_variables.o \
+	frotz/quetzal.o \
 	scott/detection.o \
 	scott/scott.o
 
diff --git a/engines/gargoyle/streams.cpp b/engines/gargoyle/streams.cpp
index d5671f136a..6a8708425a 100644
--- a/engines/gargoyle/streams.cpp
+++ b/engines/gargoyle/streams.cpp
@@ -1563,7 +1563,7 @@ frefid_t Streams::iterate(frefid_t fref, glui32 *rock) {
 
 const Common::String FileReference::getSaveName() const {
 	assert(_slotNumber != -1);
-	return Common::String::format("%s.%.3d", g_vm->getTargetName().c_str(), _slotNumber);
+	return g_vm->getSaveName(_slotNumber);
 }
 
 bool FileReference::exists() const {