From e91843034b5030f31b7f0ebf3d1b4166e1cf63da Mon Sep 17 00:00:00 2001
From: Maxim Poliakovski <maximumspatium@googlemail.com>
Date: Tue, 15 Feb 2022 15:49:12 +0100
Subject: [PATCH] Superdrive: method for retrieving disk data.

---
 devices/floppy/superdrive.cpp | 25 +++++++++++++++++++++----
 devices/floppy/superdrive.h   |  3 ++-
 2 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/devices/floppy/superdrive.cpp b/devices/floppy/superdrive.cpp
index e926d56..a0d327f 100644
--- a/devices/floppy/superdrive.cpp
+++ b/devices/floppy/superdrive.cpp
@@ -187,8 +187,8 @@ void MacSuperDrive::switch_drive_mode(int mode)
             for (int trk = 0; trk < 16; trk++) {
                 this->sectors_per_track[grp * 16 + trk] = 12 - grp;
                 this->rpm_per_track[grp * 16 + trk] = gcr_rpm_per_group[grp];
-                this->track_start_block[grp * 16 + trk] = blk_num;
-                blk_num += 12 - grp;
+                this->track2lblk[grp * 16 + trk] = blk_num;
+                blk_num += (12 - grp) * this->num_sides;
             }
         }
 
@@ -201,7 +201,7 @@ void MacSuperDrive::switch_drive_mode(int mode)
         for (int trk = 0; trk < 80; trk++) {
             this->sectors_per_track[trk] = sectors_per_track;
             this->rpm_per_track[trk] = 300;
-            this->track_start_block[trk] = trk * sectors_per_track;
+            this->track2lblk[trk] = trk * sectors_per_track * 2;
         }
 
         this->drive_mode = RecMethod::MFM;
@@ -230,10 +230,27 @@ void MacSuperDrive::init_track_search(int pos)
 
 SectorHdr MacSuperDrive::next_sector_header()
 {
+    this->cur_sector++;
+    if (this->cur_sector >= this->sectors_per_track[this->cur_track]) {
+        this->cur_sector = 0;
+    }
+
+    // MFM sector numbering is 1-based so we need to bump sector number
+    int sector_num = this->cur_sector + ((this->rec_method == RecMethod::MFM) ? 1 : 0);
+
     return SectorHdr {
         this->cur_track,
         this->cur_head,
-        this->cur_sector++,
+        sector_num,
         this->format_byte
     };
 }
+
+char* MacSuperDrive::get_sector_data_ptr(int sector_num)
+{
+    return this->disk_data.get() +
+        ((this->track2lblk[this->cur_track] +
+         (this->cur_head * this->sectors_per_track[this->cur_track]) +
+          sector_num - 1) * 512
+    );
+}
diff --git a/devices/floppy/superdrive.h b/devices/floppy/superdrive.h
index 1015eb7..86871f0 100644
--- a/devices/floppy/superdrive.h
+++ b/devices/floppy/superdrive.h
@@ -91,6 +91,7 @@ public:
     double get_sector_delay();
     void init_track_search(int pos);
     SectorHdr next_sector_header();
+    char* get_sector_data_ptr(int sector_num);
 
 protected:
     void set_disk_phys_params();
@@ -117,7 +118,7 @@ private:
     int     num_sides;
     int     sectors_per_track[80];
     int     rpm_per_track[80];
-    int     track_start_block[80]; // logical block number of the first sector in a track
+    int     track2lblk[80]; // convert track number to first logical block number
 
     std::unique_ptr<FloppyImgConverter>  img_conv;