Fix unstored pregap offset regression

The previous fix for mixed unstored and stored pregaps (CUE file PREGAP
and INDEX 00) broke standard unstored pregap handling.

Author: morio

src/CUEParser.cpp

@@ -75,7 +75,6 @@ const CUETrackInfo *CUEParser::next_track(uint64_t prev_file_size)
     bool got_track = false;
     bool got_data = false;
     bool got_pause = false; // true if a period of silence (INDEX 00) was encountered for a track
-    uint32_t stored_pregap = 0;
     while(!(got_track && got_data) && start_line())
     {
         if (strncasecmp(m_parse_pos, "FILE ", 5) == 0)
@@ -105,6 +104,7 @@ const CUETrackInfo *CUEParser::next_track(uint64_t prev_file_size)
             m_track_info.track_mode = parse_track_mode(skip_space(endptr));
             m_track_info.sector_length = get_sector_length(m_track_info.file_mode, m_track_info.track_mode);
             m_track_info.unstored_pregap_length = 0;
+            m_track_info.stored_pregap_length = 0;
             m_track_info.data_start = 0;
             m_track_info.track_start = 0;
             got_track = true;
@@ -131,14 +131,12 @@ const CUETrackInfo *CUEParser::next_track(uint64_t prev_file_size)
             {
                 // Stored pregap that is present both on CD and in data file
                 m_track_info.track_start = m_track_info.file_start + time + m_track_info.cumulative_offset;
-                stored_pregap = time;
                 got_pause = true;
             }
             else if (index == 1)
             {
                 // Data content of the track
                 m_track_info.data_start = m_track_info.file_start + time + m_track_info.cumulative_offset;
-                stored_pregap = time - stored_pregap;
                 got_data = true;
             }
         }
@@ -163,7 +161,15 @@ const CUETrackInfo *CUEParser::next_track(uint64_t prev_file_size)
         if (got_pause)
         {
             // Advance file position by any stored pregap
-            m_track_info.file_offset += stored_pregap * m_track_info.sector_length;
+            m_track_info.stored_pregap_length = m_track_info.data_start - m_track_info.track_start;
+            m_track_info.file_offset += (uint64_t)(m_track_info.stored_pregap_length) * m_track_info.sector_length;
+            m_track_info.track_start += m_track_info.unstored_pregap_length;
+            m_track_info.data_start += m_track_info.unstored_pregap_length;
+        }
+        else
+        {
+            uint32_t adjustment = m_track_info.data_start - (m_track_info.track_start + m_track_info.unstored_pregap_length);
+            m_track_info.file_offset += (uint64_t)adjustment * m_track_info.sector_length;
         }
 
         return &m_track_info;

src/CUEParser.h

@@ -73,6 +73,10 @@ struct CUETrackInfo
     // These frames of silence are not stored in the underlying data file.
     uint32_t unstored_pregap_length;
 
+    // The CD frames of PREGAP time at the start of this track,
+    // which are present both on CD and in data file.
+    uint32_t stored_pregap_length;
+    
     // The cumulative lba offset of unstored data
     uint32_t cumulative_offset;
 

test/CUEParser_test.cpp

@@ -409,12 +409,12 @@ FILE "mixed-cd.bin" BINARY
     if (track)
     {
         uint32_t pregap_offset = 2 * 75;
-        uint32_t start2_i0 = ((29 * 60) + 9) * 75 + 48;
-        uint32_t start2_i1 = ((29 * 60) + 10) * 75 + 48;
+        uint32_t start2_i0 = ((29 * 60) + 9) * 75 + 48 + pregap_offset;
+        uint32_t start2_i1 = ((29 * 60) + 10) * 75 + 48 + pregap_offset;
 
         TEST(strcmp(track->filename, "mixed-cd.bin") == 0);
         TEST(track->file_mode == CUEFile_BINARY);
-        TEST(track->file_offset == start2_i1 * 2352);
+        TEST(track->file_offset == (start2_i1 - pregap_offset) * 2352);
         TEST(track->file_index == 1);
         TEST(track->track_number == 2);
         TEST(track->track_mode == CUETrack_AUDIO);