two test - mmap vs single read

from ctypes import *
import mmap
import struct
import timeit

class SgnHeader(Structure):
    _pack_ = 1
    _fields_ = [ ("ID", c_char * 64),
                 ("headLen", c_ulong),
                 ("RemarkLen", c_ulong),
                 ("usPackingType", c_ushort),
                 ("Squared", c_ushort),
                 ("SampleSize", c_ushort),
                 ("FreqDiskr", c_double),
                 ("dBand", c_double),
                 ("dCF", c_double),
                 ("tSamplesOrigin", c_ulonglong) ]

class Ipp16sc(Structure):
    _pack_ = 1
    _fields_ = [ ("re", c_short), ("im", c_short) ]

headerLen = sizeof( SgnHeader )
sampleLen = sizeof( Ipp16sc )

def doit():
    global headerLen
    global sampleLen

    f = open( "d:/InComing/Analiz/file/0_tone.sgn", "r+b" )
    m = mmap.mmap( f.fileno(), 0 )
    header = SgnHeader.from_buffer_copy( m[:headerLen] )
    samplesCount = ( len( m ) - headerLen ) / sampleLen
    s = Ipp16sc * samplesCount
    samples = s.from_buffer_copy( m[headerLen:] )
    for i in samples:
        i.re * i.re + i.im * i.im
    m.close()
    f.close()

def doit2():
    global headerLen
    global sampleLen

    f = open( "d:/InComing/Analiz/file/0_tone.sgn", "r+b" )
    f.seek(0, 2)
    fileSize = f.tell()
    f.seek(0)
    #print fileSize

    headerBytes = f.read( headerLen )
    header = SgnHeader.from_buffer_copy( headerBytes )

    structFmt = "=2h"
    s = struct.Struct( structFmt )
    samples = []
    samplesCount = ( fileSize - headerLen ) / sampleLen
    for i in range(samplesCount):
        sampleBytes = f.read( sampleLen )
        samples.append( s.unpack( sampleBytes ) )

    for i in samples:
        i[0] * i[0] + i[1] * i[1]
    f.close()

from timeit import Timer
t = Timer( "doit()", "from __main__ import doit" )
print t.timeit( number = 10 )
t = Timer( "doit2()", "from __main__ import doit2" )
print t.timeit( number = 10 )