Source Code for Module echonest.remix.support.midi.RawInstreamFile

  1  # -*- coding: ISO-8859-1 -*-
 
  2  
 
  3  # standard library imports
 
  4  from types import StringType 
  5  from struct import unpack 
  6  
 
  7  # custom import
 
  8  from DataTypeConverters import readBew, readVar, varLen 
  9  
 
 10  
 
 11 -class RawInstreamFile: 
 12      
 
 13      """
 
 14      
 
 15      It parses and reads data from an input file. It takes care of big 
 
 16      endianess, and keeps track of the cursor position. The midi parser 
 
 17      only reads from this object. Never directly from the file.
 
 18      
 
 19      """ 
 20      
 
 21 -    def __init__(self, infile=''): 
 22          """ 
 
 23          If 'file' is a string we assume it is a path and read from 
 
 24          that file.
 
 25          If it is a file descriptor we read from the file, but we don't 
 
 26          close it.
 
 27          Midi files are usually pretty small, so it should be safe to 
 
 28          copy them into memory.
 
 29          """ 
 30          if infile: 
 31              if isinstance(infile, StringType): 
 32                  infile = open(infile, 'rb') 
 33                  self.data = infile.read() 
 34                  infile.close() 
 35              else: 
 36                  # don't close the f
 
 37                  self.data = infile.read() 
 38          else: 
 39              self.data = '' 
 40          # start at beginning ;-)
 
 41          self.cursor = 0 
 42  
 
 43  
 
 44      # setting up data manually
 
 45      
 
 46 -    def setData(self, data=''): 
 47          "Sets the data from a string." 
 48          self.data = data 
 49      
 
 50      # cursor operations
 
 51  
 
 52 -    def setCursor(self, position=0): 
 53          "Sets the absolute position if the cursor" 
 54          self.cursor = position 
 55  
 
 56  
 
 57 -    def getCursor(self): 
 58          "Returns the value of the cursor" 
 59          return self.cursor 
 60          
 
 61          
 
 62 -    def moveCursor(self, relative_position=0): 
 63          "Moves the cursor to a new relative position" 
 64          self.cursor += relative_position 
 65  
 
 66      # native data reading functions
 
 67          
 
 68 -    def nextSlice(self, length, move_cursor=1): 
 69          "Reads the next text slice from the raw data, with length" 
 70          c = self.cursor 
 71          slc = self.data[c:c+length] 
 72          if move_cursor: 
 73              self.moveCursor(length) 
 74          return slc 
 75          
 
 76          
 
 77 -    def readBew(self, n_bytes=1, move_cursor=1): 
 78          """
 
 79          Reads n bytes of date from the current cursor position.
 
 80          Moves cursor if move_cursor is true
 
 81          """ 
 82          return readBew(self.nextSlice(n_bytes, move_cursor)) 
 83  
 
 84  
 
 85 -    def readVarLen(self): 
 86          """
 
 87          Reads a variable length value from the current cursor position.
 
 88          Moves cursor if move_cursor is true
 
 89          """ 
 90          MAX_VARLEN = 4 # Max value varlen can be 
 91          var = readVar(self.nextSlice(MAX_VARLEN, 0)) 
 92          # only move cursor the actual bytes in varlen
 
 93          self.moveCursor(varLen(var)) 
 94          return var 
 95  
 
 96  
 
 97  
 
 98  if __name__ == '__main__': 
 99  
 
100      test_file = 'test/midifiles/minimal.mid' 
101      fis = RawInstreamFile(test_file) 
102      print fis.nextSlice(len(fis.data)) 
103  
 
104      test_file = 'test/midifiles/cubase-minimal.mid' 
105      cubase_minimal = open(test_file, 'rb') 
106      fis2 = RawInstreamFile(cubase_minimal) 
107      print fis2.nextSlice(len(fis2.data)) 
108      cubase_minimal.close() 
109