From 8fcbb5c8e28b217233944a6d4001ea996ec6fa8a Mon Sep 17 00:00:00 2001
From: Matt Aliabadi <mattmaliabadi@gmail.com>
Date: Thu, 22 Aug 2013 00:26:13 -0700
Subject: [PATCH] started midi_to_json parser

---
 midi_to_json.py | 65 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 65 insertions(+)
 create mode 100644 midi_to_json.py

diff --git a/midi_to_json.py b/midi_to_json.py
new file mode 100644
index 0000000..eea66f3
--- /dev/null
+++ b/midi_to_json.py
@@ -0,0 +1,65 @@
+"""
+The idea is to provide an interface for translate
+a MIDI stream into JSON, and then to do it the other way.
+
+"""
+
+from struct import unpack, pack
+
+
+def read_varlen(data):
+    NEXTBYTE = 1
+    value = 0
+    while NEXTBYTE:
+        chr = ord(data.next())
+        if not (chr & 0x80):
+            NEXTBYTE = 0
+        chr = chr & 0x7f
+        value = value << 7
+        value += chr
+    return value
+
+
+def parse_midi_header(binfile):
+    header = binfile.read(4)
+    assert header == 'MThd'
+    length, format, tracks, res = unpack(">LHHH", binfile.read(10))
+    if length > 14:
+        binfile.read(length - 14)
+    return length, format, tracks, res
+
+
+def parse_track_header(binfile):
+    header = binfile.read(4)
+    assert header == 'MTrk'
+    return unpack(">L", binfile.read(4))[0]
+
+
+def parse_track(binfile, length):
+    data = iter(binfile.read(length))
+    while True:
+        try:
+            tick = read_varlen(data)
+            stsmsg = ord(data.next())
+            print tick
+            print stsmsg
+        except StopIteration:
+            break
+
+
+def midi_to_json(path):
+    if isinstance(path, basestring):
+        binfile = open(path, 'rb')
+    elif isinstance(path, file):
+        if not path.mode == 'rb':
+            raise ValueError('File must be opened in Read-Binary mode')
+        binfile = path
+    else:
+        raise ValueError
+    length, format, tracks, res = parse_midi_header(binfile)
+    tracklength = parse_track_header(binfile)
+    parse_track(binfile, tracklength)
+
+
+if __name__ == "__main__":
+    midi_to_json('arp.mid')