From 3adefd733b854b0abc8ff4ad6989335bc9bff919 Mon Sep 17 00:00:00 2001
From: Dimitri Diakopoulos <ddiakopoulos@gmail.com>
Date: Tue, 29 Dec 2015 21:08:19 -0500
Subject: [PATCH] utility functions to convert between delta and absolute tick
 formats

---
 src/midi_file_writer.cpp |  5 ++---
 src/midi_file_writer.h   |  7 ++++++-
 src/midi_utils.h         | 42 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 50 insertions(+), 4 deletions(-)

diff --git a/src/midi_file_writer.cpp b/src/midi_file_writer.cpp
index 4c0acb9..09ea2dc 100644
--- a/src/midi_file_writer.cpp
+++ b/src/midi_file_writer.cpp
@@ -123,7 +123,6 @@ void MidiFileWriter::addEvent(int tick, int track, std::shared_ptr<MidiMessage>
     if (track > tracks.size()) 
         throw std::out_of_range("track idx exceeds availble tracks");
 
-    std::cout << tick << std::endl;
     tracks[track].push_back(std::make_shared<TrackEvent>(tick, track, m));
 }
 
@@ -155,9 +154,9 @@ void MidiFileWriter::write(std::ostream & out)
             // Suppress end-of-track meta messages (one will be added
             // automatically after all track data has been written).
             if (msg->getMetaEventSubtype() == uint8_t(MetaEventType::END_OF_TRACK)) continue;
-                    
+
             util::write_variable_length(event->tick, trackRawData);
-                    
+            
             if ((msg->getMessageType() == uint8_t(MessageType::SYSTEM_EXCLUSIVE)) || (event->m->getMessageType() == uint8_t(MessageType::EOX)))
             {
                 // 0xf0 == Complete sysex message (0xf0 is part of the raw MIDI).
diff --git a/src/midi_file_writer.h b/src/midi_file_writer.h
index 8dd9295..5658342 100644
--- a/src/midi_file_writer.h
+++ b/src/midi_file_writer.h
@@ -56,7 +56,12 @@ class MidiFileWriter
     
     void addTrack(); 
 
-    void write(std::ostream & out); 
+    void write(std::ostream & out);
+    
+    std::vector<MidiTrack> & getTracks() { return tracks; }
+    
+    bool useAbsoluteTicks = false;
+    
 };
     
 } // mm
diff --git a/src/midi_utils.h b/src/midi_utils.h
index 417cd74..7653925 100644
--- a/src/midi_utils.h
+++ b/src/midi_utils.h
@@ -29,6 +29,7 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #define MODERNMIDI_UTIL_H
 
 #include "modernmidi.h"
+#include "midi_event.h"
 
 namespace mm 
 {
@@ -46,6 +47,47 @@ namespace mm
     // can be provided.
     uint8_t frequencyToNote(float freq);
     uint8_t frequencyToNote(float freq, float A);
+    
+    // In-place conversion of tracks in absolute tick format
+    // to a delta tick format
+    inline void ConvertToDeltaTicks(std::vector<MidiTrack> & tracks)
+    {
+        for (int i = 0; i < tracks.size(); i++)
+        {
+            for (auto & event_list : tracks)
+            {
+                int lastTickValue = 0;
+                for (auto & event : event_list)
+                {
+                    const auto msg = event->m;
+                    int tmpTick = event->tick;
+                    event->tick -= lastTickValue;
+                    lastTickValue = tmpTick;
+                }
+            }
+        }
+    }
+    
+    // In-place conversion of tracks in delta tick format
+    // to an absolute tick format
+    inline void ConvertToAbsoluteTicks(std::vector<MidiTrack> & tracks)
+    {
+        for (int i = 0; i < tracks.size(); i++)
+        {
+            for (auto & event_list : tracks)
+            {
+                int runningTickCounter = 0;
+                for (auto & event : event_list)
+                {
+                    const auto msg = event->m;
+                    int tmpTick = event->tick;
+                    event->tick = runningTickCounter;
+                    runningTickCounter += tmpTick;
+                }
+            }
+        }
+    }
+    
 
 } // mm