Python script for searching a large binary file for .NEF file headers.

count_nef_files.py

#!/usr/bin/env python
import sys

# .NEF (Nikon Electronic Format) headers 
SIGNATURE = '\x4d\x4d\x00\x2a\x00\x00\x00\x08\x00'

def read_chunks(stream, overlap = len(SIGNATURE), size = 100 * 2 ** 20):
    '''Read chunks from the stream with a small overlap.'''
    data = stream.read(size)
    while True:
        yield data
        new_data = stream.read(size)
        if new_data == '':
            break
        data = data[-overlap:] + new_data

f = open(sys.argv[1])
for chunk in read_chunks(f):
    n = chunk.count(SIGNATURE)
    if n > 0:
        print 'Found %d potential NEF file headers near chunk starting at %d' % (n, f.tell())