Read and write names of midi tracks #99

Author: Datseris

src/miditrack.jl

@@ -1,4 +1,4 @@
-export getnotes, addnote!, addnotes!, addevent!
+export getnotes, addnote!, addnotes!, addevent!, trackname, addtrackname!
 export MIDITrack
 
 """
@@ -211,3 +211,66 @@ function programchange(track::MIDITrack, time::Integer, channel::UInt8, program:
     program -= 1
     addevent!(track, time, MIDIEvent(0, PROGRAMCHANGE | channel, UInt8[program]))
 end
+
+"""
+    trackname(track::MIDI.MIDITrack)
+
+Return the name of the given [`MIDITrack`](@ref) as a string,
+by finding the "track name" [`MetaEvent`](@ref).
+"""
+function trackname(track::MIDI.MIDITrack)
+
+    pos = findnameevent(track)
+    if pos == 0
+        return "No track name found"
+    # check if there really is a name
+    elseif length(track.events[pos].data) == 0
+        return "No track name found"
+    else
+        event = track.events[pos]
+        # extract the name (string(Char()) takes care of ASCII encoding)
+        trackname = string(Char(event.data[1]))
+        for c in event.data[2:end]
+            trackname *= string(Char(c))
+        end
+        return trackname
+    end
+end
+
+"""
+    addtrackname!(track::MIDI.MIDITrack, name::String)
+
+Add a name of the given [`MIDITrack`](@ref) by attaching the correct
+"track name" [`MetaEvent`](@ref) to the track.
+"""
+function addtrackname!(track::MIDI.MIDITrack, name::String)
+    # construct fitting name event
+    data = UInt8[]
+    for i = 1:length(name)
+        push!(data, UInt8(name[i]))
+    end
+    meta = MetaEvent(0,0x03,data)
+
+    # remove existing name
+    prev = findnameevent(track)
+    if prev != 0
+        deleteat!(track.events, prev)
+    end
+
+    # add event to track
+    addevent!(track, 0, meta)
+end
+
+function findnameevent(track::MIDI.MIDITrack)
+    # find track name MetaEvent
+    # (has dt zero and occurs before any other event with nonzero dt)
+    position = 0
+    for (i,event) in enumerate(track.events)
+        if event.dT != 0
+            break
+        elseif event.dT == 0 && isa(event, MIDI.MetaEvent) && event.metatype == 0x03
+            position = i
+        end
+    end
+    return position
+end

test/miditrack.jl

@@ -73,4 +73,31 @@ invalidtestvalues = [
             @test n1 == n2
         end
     end
+
+    @testset "Track names" begin
+
+        # correct tracks
+        midi = readMIDIfile("doxy.mid")
+        @test trackname(midi.tracks[2]) == "Drums"
+        @test trackname(midi.tracks[3]) == "Bass"
+        @test trackname(midi.tracks[4]) == "ORIGINAL"
+
+        # broken track
+        midi.tracks[2].events = midi.tracks[2].events[10:end]
+        @test trackname(midi.tracks[2]) == "No track name found"
+
+        # add track name
+        addtrackname!(midi.tracks[2],"Uagadugu")
+        @test trackname(midi.tracks[2]) == "Uagadugu"
+
+        # replace track name
+        addtrackname!(midi.tracks[2],"Overwrite")
+        @test trackname(midi.tracks[2]) == "Overwrite"
+
+        # save and reopen
+        writeMIDIfile("changedname.mid",midi)
+        midi = readMIDIfile("changedname.mid")
+        @test trackname(midi.tracks[2]) == "Overwrite"
+        rm("changedname.mid")
+    end
 end