init

Author: FMS-Cat

midi-parser.lua

@@ -0,0 +1,286 @@
+-- Usage:
+-- midi = midiParser( filePath )
+
+local midiParser = function( _path )
+
+  local ret = {}
+
+  ------------------
+  -- prepare file --
+  ------------------
+
+  if _path == nil then
+    error( 'path is not defined' )
+  end
+
+  local file = io.open( _path, 'rb' )
+  if file == nil then
+		error( 'not found: ' .. _path )
+	end
+
+  local midi = file:read( '*all' )
+  midi = string.gsub( midi, '\r\n', '\n' )
+
+  --------------------
+  -- some functions --
+  --------------------
+
+  local byteArray = function( _start, _length )
+    local retArray = {}
+    for i = 1, _length do
+      retArray[ i ] = string.byte( midi, i + _start - 1 )
+    end
+    return retArray
+  end
+
+  local bytesToNumber = function( _start, _length )
+    local retNumber = 0
+    for i = 1, _length do
+      retNumber = retNumber + string.byte( midi, i + _start - 1 ) * math.pow( 256, _length - i )
+    end
+    return retNumber
+  end
+
+  local vlq = function( _start ) -- Variable-length quantity
+    local retNumber = 0
+    local head = 0
+    local byte = 0
+    repeat
+      byte = string.byte( midi, _start + head )
+      retNumber = retNumber * 128 + ( byte - math.floor( byte / 128 ) * 128 )
+      head = head + 1
+    until math.floor( byte / 128 ) ~= 1
+    return retNumber, head
+  end
+
+  local isSameTable = function( _a, _b )
+    for i, v in ipairs( _a ) do
+      if _a[ i ] ~= _b[ i ] then
+        return false
+      end
+    end
+    return true
+  end
+
+  ------------------
+  -- check format --
+  ------------------
+
+  local head = 1
+
+  if not isSameTable( byteArray( head, 4 ), { 77, 84, 104, 100 } ) then
+    error( 'input file seems not to be a .mid file' )
+  end
+  head = head + 4 -- header chunk magic number
+  head = head + 4 -- header chunk length
+
+  ret.format = bytesToNumber( head, 2 )
+
+  if not ( ret.format == 0 or ret.format == 1 ) then
+    error( 'not supported such format of .mid' )
+  end
+  head = head + 2 -- format
+
+  head = head + 2 -- trackCount
+
+  ret.timebase = bytesToNumber( head, 2 )
+  head = head + 2 -- timeBase
+
+  ------------------------
+  -- fight against .mid --
+  ------------------------
+
+  ret.tracks = {}
+
+  while head < string.len( midi ) do
+
+    if not isSameTable( byteArray( head, 4 ), { 77, 84, 114, 107 } ) then -- if chunk is not track chunk
+
+      head = head + 4 -- unknown chunk magic number
+      head = head + 4 + bytesToNumber( head, 4 ) -- chunk length + chunk data
+
+    else
+
+      head = head + 4 -- track chunk magic number
+
+      local chunkLength = bytesToNumber( head, 4 )
+      head = head + 4 -- chunk length
+      local chunkStart = head
+
+      local track = {}
+      track.messages = {}
+      table.insert( ret.tracks, track )
+
+      local status = 0
+      while head < chunkStart + chunkLength do
+
+        local deltaTime, deltaHead = vlq( head ) -- timing
+        head = head + deltaHead
+
+        local tempStatus = byteArray( head, 1 )[ 1 ]
+
+        if math.floor( tempStatus / 128 ) == 1 then -- event, running status
+          head = head + 1
+          status = tempStatus
+        end
+
+        local type = math.floor( status / 16 )
+        local channel = status - type * 16
+
+        if type == 8 then -- note off
+          local data = byteArray( head, 2 )
+          head = head + 2
+
+          table.insert( track.messages, {
+            time = deltaTime,
+            type = 'off',
+            channel = channel,
+            number = data[ 1 ],
+            velocity = data[ 2 ]
+          } )
+
+        elseif type == 9 then -- note on
+          local data = byteArray( head, 2 )
+          head = head + 2
+
+          table.insert( track.messages, {
+            time = deltaTime,
+            type = 'on',
+            channel = channel,
+            number = data[ 1 ],
+            velocity = data[ 2 ]
+          } )
+
+        elseif type == 10 then -- polyphonic keypressure
+          head = head + 2
+
+        elseif type == 11 then -- control change
+          head = head + 2
+
+        elseif type == 12 then -- program change
+          head = head + 1
+
+        elseif type == 13 then -- channel pressure
+          head = head + 1
+
+        elseif type == 14 then -- pitch bend
+          head = head + 2
+
+        elseif status == 255 then -- meta event
+          local metaType = byteArray( head, 1 )[ 1 ]
+          head = head + 1
+          local metaLength, metaHead = vlq( head )
+
+          if metaType == 3 then -- track name
+            head = head + metaHead
+            track.name = string.sub( midi, head, head + metaLength - 1 )
+            head = head + metaLength
+
+            table.insert( track.messages, {
+              time = deltaTime,
+              type = 'meta',
+              meta = 'Track Name',
+              text = track.name
+            } )
+
+          elseif metaType == 4 then -- instrument name
+            head = head + metaHead
+            track.instrument = string.sub( midi, head, head + metaLength - 1 )
+            head = head + metaLength
+
+            table.insert( track.messages, {
+              time = deltaTime,
+              type = 'meta',
+              meta = 'Instrument Name',
+              text = track.instrument
+            } )
+
+          elseif metaType == 5 then -- lyric
+            head = head + metaHead
+            track.lyric = string.sub( midi, head, head + metaLength - 1 )
+            head = head + metaLength
+
+            table.insert( track.messages, {
+              time = deltaTime,
+              type = 'meta',
+              meta = 'Lyric',
+              text = track.lyric
+            } )
+
+          elseif metaType == 47 then -- end of track
+            head = head + 1
+
+            table.insert( track.messages, {
+              time = deltaTime,
+              type = 'meta',
+              meta = 'End of Track'
+            } )
+
+            break
+
+          elseif metaType == 81 then -- tempo
+            head = head + 1
+
+            local micros = bytesToNumber( head, 3 )
+            head = head + 3
+
+            table.insert( track.messages, {
+              time = deltaTime,
+              type = 'meta',
+              meta = 'Set Tempo',
+              tempo = micros
+            } )
+
+          elseif metaType == 88 then -- time signature
+            head = head + 1
+
+            local sig = byteArray( head, 4 )
+            head = head + 4
+
+            table.insert( track.messages, {
+              time = deltaTime,
+              type = 'meta',
+              meta = 'Time Signature',
+              signature = sig
+            } )
+
+          elseif metaType == 89 then -- key signature
+            head = head + 1
+
+            local sig = byteArray( head, 2 )
+            head = head + 2
+
+            table.insert( track.messages, {
+              time = deltaTime,
+              type = 'meta',
+              meta = 'Key Signature',
+              signature = sig
+            } )
+
+          else -- comment
+            head = head + metaHead
+            local text = string.sub( midi, head, head + metaLength - 1 )
+            head = head + metaLength
+
+            table.insert( track.messages, {
+              time = deltaTime,
+              type = 'meta',
+              meta = 'Unknown Text: ' .. event[ 2 ],
+              text = text
+            } )
+
+          end
+
+        end
+
+      end
+
+    end
+
+  end
+
+  return ret
+
+end
+
+return midiParser