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109 lines
3.0 KiB
Python
109 lines
3.0 KiB
Python
# -*- coding: ISO-8859-1 -*-
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# standard library imports
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from types import StringType
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from struct import unpack
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# custom import
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from DataTypeConverters import readBew, readVar, varLen
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class RawInstreamFile:
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"""
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It parses and reads data from an input file. It takes care of big
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endianess, and keeps track of the cursor position. The midi parser
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only reads from this object. Never directly from the file.
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"""
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def __init__(self, infile=''):
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"""
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If 'file' is a string we assume it is a path and read from
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that file.
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If it is a file descriptor we read from the file, but we don't
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close it.
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Midi files are usually pretty small, so it should be safe to
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copy them into memory.
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"""
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if infile:
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if isinstance(infile, StringType):
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infile = open(infile, 'rb')
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self.data = infile.read()
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infile.close()
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else:
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# don't close the f
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self.data = infile.read()
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else:
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self.data = ''
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# start at beginning ;-)
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self.cursor = 0
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# setting up data manually
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def setData(self, data=''):
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"Sets the data from a string."
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self.data = data
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# cursor operations
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def setCursor(self, position=0):
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"Sets the absolute position if the cursor"
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self.cursor = position
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def getCursor(self):
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"Returns the value of the cursor"
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return self.cursor
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def moveCursor(self, relative_position=0):
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"Moves the cursor to a new relative position"
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self.cursor += relative_position
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# native data reading functions
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def nextSlice(self, length, move_cursor=1):
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"Reads the next text slice from the raw data, with length"
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c = self.cursor
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slc = self.data[c:c+length]
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if move_cursor:
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self.moveCursor(length)
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return slc
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def readBew(self, n_bytes=1, move_cursor=1):
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"""
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Reads n bytes of date from the current cursor position.
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Moves cursor if move_cursor is true
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"""
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return readBew(self.nextSlice(n_bytes, move_cursor))
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def readVarLen(self):
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"""
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Reads a variable length value from the current cursor position.
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Moves cursor if move_cursor is true
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"""
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MAX_VARLEN = 4 # Max value varlen can be
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var = readVar(self.nextSlice(MAX_VARLEN, 0))
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# only move cursor the actual bytes in varlen
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self.moveCursor(varLen(var))
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return var
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if __name__ == '__main__':
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test_file = 'test/midifiles/minimal.mid'
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fis = RawInstreamFile(test_file)
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print fis.nextSlice(len(fis.data))
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test_file = 'test/midifiles/cubase-minimal.mid'
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cubase_minimal = open(test_file, 'rb')
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fis2 = RawInstreamFile(cubase_minimal)
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print fis2.nextSlice(len(fis2.data))
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cubase_minimal.close()
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