GLK: FROTZ: Added remaining memory methods

5 files changed, 217 insertions, 1 deletions

diff --git a/engines/gargoyle/frotz/mem.cpp b/engines/gargoyle/frotz/mem.cpp
index 57b282531d..ad60b89bbb 100644
--- a/engines/gargoyle/frotz/mem.cpp
+++ b/engines/gargoyle/frotz/mem.cpp
@@ -320,6 +320,103 @@ void Mem::storew(zword addr, zword value) {
 	storeb((zword)(addr + 1), lo(value));
 }
 
+void Mem::free_undo(int count) {
+	undo_t *p;
+
+	if (count > undo_count)
+		count = undo_count;
+	while (count--) {
+		p = first_undo;
+		if (curr_undo == first_undo)
+			curr_undo = curr_undo->next;
+		first_undo = first_undo->next;
+		free(p);
+		undo_count--;
+	}
+	if (first_undo)
+		first_undo->prev = NULL;
+	else
+		last_undo = NULL;
+}
+
+void Mem::reset_memory() {
+	story_fp = nullptr;
+	blorb_ofs = 0;
+	blorb_len = 0;
+
+	if (undo_mem) {
+		free_undo(undo_count);
+		delete undo_mem;
+	}
+
+	undo_mem = nullptr;
+	undo_count = 0;
+	delete[] zmp;
+	zmp = nullptr;
+}
+
+long Mem::mem_diff(zbyte *a, zbyte *b, zword mem_size, zbyte *diff) {
+	unsigned size = mem_size;
+	zbyte *p = diff;
+	unsigned j;
+	zbyte c = 0;
+
+	for (;;) {
+		for (j = 0; size > 0 && (c = *a++ ^ *b++) == 0; j++)
+			size--;
+		if (size == 0) break;
+		size--;
+		if (j > 0x8000) {
+			*p++ = 0;
+			*p++ = 0xff;
+			*p++ = 0xff;
+			j -= 0x8000;
+		}
+		if (j > 0) {
+			*p++ = 0;
+			j--;
+			if (j <= 0x7f) {
+				*p++ = j;
+			} else {
+				*p++ = (j & 0x7f) | 0x80;
+				*p++ = (j & 0x7f80) >> 7;
+			}
+		}
+
+		*p++ = c;
+		*(b - 1) ^= c;
+	}
+
+	return p - diff;
+}
+
+void Mem::mem_undiff(zbyte *diff, long diff_length, zbyte *dest) {
+	zbyte c;
+
+	while (diff_length) {
+		c = *diff++;
+		diff_length--;
+		if (c == 0) {
+			unsigned runlen;
+
+			if (!diff_length)
+				return;  // Incomplete run
+			runlen = *diff++;
+			diff_length--;
+			if (runlen & 0x80) {
+				if (!diff_length)
+					return; // Incomplete extended run
+				c = *diff++;
+				diff_length--;
+				runlen = (runlen & 0x7f) | (((unsigned)c) << 7);
+			}
+
+			dest += runlen + 1;
+		} else {
+			*dest++ ^= c;
+		}
+	}
+}
 
 } // End of namespace Scott
 } // End of namespace Gargoyle
diff --git a/engines/gargoyle/frotz/mem.h b/engines/gargoyle/frotz/mem.h
index c128994df1..a45eec5e7f 100644
--- a/engines/gargoyle/frotz/mem.h
+++ b/engines/gargoyle/frotz/mem.h
@@ -230,6 +230,11 @@ protected:
 	void storew(zword addr, zword value);
 
 	/**
+	 * Free count undo blocks from the beginning of the undo list
+	 */
+	void free_undo(int count);
+
+	/**
 	 * Generates a runtime error
 	 */
 	virtual void runtimeError(ErrorCode errNum) = 0;
@@ -238,6 +243,26 @@ protected:
 	 * Called when the flags are changed
 	 */
 	virtual void flagsChanged(zbyte value) = 0;
+
+	/**
+	 * Close the story file and deallocate memory.
+	 */
+	void reset_memory();
+
+	/**
+	 * Set diff to a Quetzal-like difference between a and b,
+	 * copying a to b as we go.  It is assumed that diff points to a
+	 * buffer which is large enough to hold the diff.
+	 * mem_size is the number of bytes to compare.
+	 * Returns the number of bytes copied to diff.
+	 *
+	 */
+	long mem_diff(zbyte *a, zbyte *b, zword mem_size, zbyte *diff);
+
+	/**
+	 * Applies a quetzal-like diff to dest
+	 */
+	void mem_undiff(zbyte *diff, long diff_length, zbyte *dest);
 public:
 	/**
 	 * Constructor
diff --git a/engines/gargoyle/frotz/processor.h b/engines/gargoyle/frotz/processor.h
index b70bf440a2..f9352ec19c 100644
--- a/engines/gargoyle/frotz/processor.h
+++ b/engines/gargoyle/frotz/processor.h
@@ -220,6 +220,18 @@ private:
 	virtual void flagsChanged(zbyte value) override;
 
 	/**
+	 * This function does the dirty work for z_save_undo.
+	 */
+	int save_undo();
+
+	/**
+	 * This function does the dirty work for z_restore_undo.
+	 */
+	int restore_undo();
+
+	/**@}*/
+
+	/**
 	 * \defgroup Object support methods
 	 * @{
 	 */
diff --git a/engines/gargoyle/frotz/processor_input.cpp b/engines/gargoyle/frotz/processor_input.cpp
index b9c9604183..48951d2402 100644
--- a/engines/gargoyle/frotz/processor_input.cpp
+++ b/engines/gargoyle/frotz/processor_input.cpp
@@ -26,7 +26,6 @@ namespace Gargoyle {
 namespace Frotz {
 
 // TODO: Implement method stubs
-static void save_undo() {}
 static zword os_read_mouse() { return 0; }
 
 
diff --git a/engines/gargoyle/frotz/processor_mem.cpp b/engines/gargoyle/frotz/processor_mem.cpp
index 1f3944ea17..71abe77c1f 100644
--- a/engines/gargoyle/frotz/processor_mem.cpp
+++ b/engines/gargoyle/frotz/processor_mem.cpp
@@ -35,5 +35,88 @@ void Processor::flagsChanged(zbyte value) {
 	}
 }
 
+int Processor::save_undo() {
+	long diff_size;
+	zword stack_size;
+	undo_t *p;
+
+	if (_undo_slots == 0)
+		// undo feature unavailable
+		return -1;
+
+	// save undo possible
+	while (last_undo != curr_undo) {
+		p = last_undo;
+		last_undo = last_undo->prev;
+		delete p;
+		undo_count--;
+	}
+	if (last_undo)
+		last_undo->next = nullptr;
+	else
+		first_undo = nullptr;
+
+	if (undo_count == _undo_slots)
+		free_undo(1);
+
+	diff_size = mem_diff(zmp, prev_zmp, h_dynamic_size, undo_diff);
+	stack_size = _stack + STACK_SIZE - _sp;
+	do {
+		p = (undo_t *) malloc(sizeof(undo_t) + diff_size + stack_size * sizeof(*_sp));
+		if (p == nullptr)
+			free_undo(1);
+	} while (!p && undo_count);
+	if (p == nullptr)
+		return -1;
+
+	GET_PC(p->pc);
+	p->frame_count = _frameCount;
+	p->diff_size = diff_size;
+	p->stack_size = stack_size;
+	p->frame_offset = _fp - _stack;
+	memcpy(p + 1, undo_diff, diff_size);
+	memcpy((zbyte *)(p + 1) + diff_size, _sp, stack_size * sizeof(*_sp));
+
+	if (!first_undo) {
+		p->prev = nullptr;
+		first_undo = p;
+	} else {
+		last_undo->next = p;
+		p->prev = last_undo;
+	}
+
+	p->next = nullptr;
+	curr_undo = last_undo = p;
+	undo_count++;
+
+	return 1;
+}
+
+int Processor::restore_undo(void) {
+	if (_undo_slots == 0)
+		// undo feature unavailable
+		return -1;
+
+	if (curr_undo == nullptr)
+		// no saved game state
+		return 0;
+
+	// undo possible
+	memcpy(zmp, prev_zmp, h_dynamic_size);
+	SET_PC(curr_undo->pc);
+	_sp = _stack + STACK_SIZE - curr_undo->stack_size;
+	_fp = _stack + curr_undo->frame_offset;
+	_frameCount = curr_undo->frame_count;
+	mem_undiff((zbyte *)(curr_undo + 1), curr_undo->diff_size, prev_zmp);
+	memcpy(_sp, (zbyte *)(curr_undo + 1) + curr_undo->diff_size,
+		curr_undo->stack_size * sizeof(*_sp));
+
+	curr_undo = curr_undo->prev;
+
+	restart_header();
+
+	return 2;
+}
+
 } // End of namespace Scott
 } // End of namespace Gargoyle