Instrument editor undo (minus FixedQueue change) (#2094)

* add undo to instrument editor (check for diffs on the current DivInstrument in insEdit, record them in a stack)

* style fixes

* accidentally left some logs in

* typo in style fix

* cheat to avoid warning -Werror=class-memaccess on linux

* warn instead of assert on case where MemPatch application would exceed size of target buffer (which should never happen, if you're applying the patch to the same type it was generated from)

* instrument editor undo: don't check delta if no user input has come in that could potentially have dirtied the editor

* don't run a delta against cached instrument if not insEditOpen

* revert fixedQueue to before my 'fix' (if i touch it again i'll add unit tests)

* explicitly cast to (DivInstrumentPOD*) when memsetting DivInstrumentPOD in DivInstrument constructor, rather than relying on implicit memory layout

* use delete[] instead of free (whoops)

* MemPatch/DivInstrumentUndoStep -- remove clear() function (ambiguous whether it should free data, it only existed to set data to null after the swap, so just do that directly now). Also set data to null after delete.

* DivInstrument -- fix dangling undo-step pointers being created on duplicate (potentially leading to use-after-free), fix undo-step objects being shamelessly leaked

---------

Co-authored-by: Adam Lederer <adam@adamlederer.com>

src/engine/instrument.h

@@ -23,8 +23,10 @@
 #include "dataErrors.h"
 #include "../ta-utils.h"
 #include "../pch.h"
+#include "../fixedQueue.h"
 
 struct DivSong;
+struct DivInstrument;
 
 // NOTICE!
 // before adding new instrument types to this struct, please ask me first.
@@ -860,8 +862,7 @@ struct DivInstrumentSID2 {
     noiseMode(0) {}
 };
 
-struct DivInstrument {
-  String name;
+struct DivInstrumentPOD {
   DivInstrumentType type;
   DivInstrumentFM fm;
   DivInstrumentSTD std;
@@ -880,6 +881,77 @@ struct DivInstrument {
   DivInstrumentPowerNoise powernoise;
   DivInstrumentSID2 sid2;
 
+  DivInstrumentPOD() :
+    type(DIV_INS_FM) {
+  }
+};
+
+struct MemPatch {
+  MemPatch() :
+    data(NULL)
+    , offset(0)
+    , size(0) {
+  }
+
+  ~MemPatch() {
+    if (data) {
+      delete[] data;
+      data=NULL;
+    }
+  }
+
+  bool calcDiff(const void* pre, const void* post, size_t size);
+  void applyAndReverse(void* target, size_t inputSize);
+  bool isValid() const { return size>0; }
+
+  unsigned char* data;
+  size_t offset;
+  size_t size;
+};
+
+struct DivInstrumentUndoStep {
+  DivInstrumentUndoStep() :
+    name(""),
+    nameValid(false),
+    processTime(0) {
+  }
+
+  MemPatch podPatch;
+  String name;
+  bool nameValid;
+  size_t processTime;
+
+  void applyAndReverse(DivInstrument* target);
+  bool makeUndoPatch(size_t processTime_, const DivInstrument* pre, const DivInstrument* post);
+};
+
+struct DivInstrument : DivInstrumentPOD {
+  String name;
+
+  DivInstrument() :
+    name("") {
+      // clear and construct DivInstrumentPOD so it doesn't have any garbage in the padding
+      memset((unsigned char*)(DivInstrumentPOD*)this, 0, sizeof(DivInstrumentPOD));
+      new ((DivInstrumentPOD*)this) DivInstrumentPOD;
+  }
+
+  ~DivInstrument();
+
+  /**
+   * copy/assignment to specifically avoid leaking or dangling pointers to undo step
+   */
+  DivInstrument( const DivInstrument& ins );
+  DivInstrument& operator=( const DivInstrument& ins );
+
+  /**
+   * undo stuff
+   */
+  FixedQueue<DivInstrumentUndoStep*, 128> undoHist;
+  FixedQueue<DivInstrumentUndoStep*, 128> redoHist;
+  bool recordUndoStepIfChanged(size_t processTime, const DivInstrument* old);
+  int undo();
+  int redo();
+
   /**
    * these are internal functions.
    */
@@ -964,9 +1036,5 @@ struct DivInstrument {
    * @return whether it was successful.
    */
   bool saveDMP(const char* path);
-  DivInstrument():
-    name(""),
-    type(DIV_INS_FM) {
-  }
 };
 #endif