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Top Forums Shell Programming and Scripting Extract sequences of bytes from binary for differents blocks Post 302845007 by wisecracker on Tuesday 20th of August 2013 02:36:12 PM
Old 08-20-2013
This is a starter Python 3.3.x code to extract the blocks using a user function...

This should be more than enough to get you going with your binary manipulation.

Once each block is placed into its respective _variable_ it is seriously easy to extract sub-blocks of data from each major block extracted from the binary file...
Code:
# BinarySearch.py
# DEMO to extract binary data...
# Written in such a way as to be easily understood.
# NOTE:- There are more Pythonic ways to do this...

import os
import sys

# The _variable_ used to test with...
block_one=b"?"
block_two=b"?"
subscript_begin=0

# Set to a _temporary_ directory. NOTE:- 4 different platforms shown...
# Change to suit your platform and path
if sys.platform=="linux2": os.chdir("/tmp/")
if sys.platform=="darwin": os.chdir("/Users/barrywalker/")
if sys.platform=="win32": os.chdir("C:\\Windows\\Temp\\")
if sys.platform=="amiga": os.chdir("T:")

# A basic "bin_extract()" function to extract binary data from a binary file...
def bin_extract(subscript_start=0, subscript_end=0, filename="?", char_start=b"\x00\xFF", char_end=b"\xFF\x00"):
	bin_var=b""
	toggle=0
	binfile=open(filename, "rb")
	for position in range(subscript_start, subscript_end, 1):
		binfile.seek(position)
		if binfile.read(2)==char_start:
			bin_var=bin_var+char_start[1:2]
			toggle=1
		if toggle>=1: bin_var=bin_var+binfile.read(1)
		if binfile.read(2)==char_end:
			bin_var=bin_var+char_end[0:1]
			toggle=0
			break
	binfile.close()
	return(bin_var, position)

# Test...
# ******** Do the first iteration and find the first block... *******
block_one, subscript_begin=bin_extract(0, 816, "BinaryFile", b"\xFF\x32", b"\xFF\x34")
print(block_one)
print(subscript_begin)
# When successful..........
# Just extract the required data from the _variable_ "new_binary" using standard simple Python methods
# and when finished with set new values to the function for the next block run using "subscript_begin"
# + or - 2 as the next "subscript_start" in the function, something like below...
block_two, subscript_begin=bin_extract((subscript_begin+2), 816, "BinaryFile", b"\xFF\x32", b"\xFF\x34")
print(block_two)
print(subscript_begin)
# DEMO end...

Hope this helps.
CYA.
 

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textutil::split(n)				    Text and string utilities, macro processing 				textutil::split(n)

__________________________________________________________________________________________________________________________________________________

NAME
textutil::split - Procedures to split texts SYNOPSIS
package require Tcl 8.2 package require textutil::split ?0.7? ::textutil::split::splitn string ?len? ::textutil::split::splitx string ?regexp? _________________________________________________________________ DESCRIPTION
The package textutil::split provides commands that split strings by size and arbitrary regular expressions. The complete set of procedures is described below. ::textutil::split::splitn string ?len? This command splits the given string into chunks of len characters and returns a list containing these chunks. The argument len defaults to 1 if none is specified. A negative length is not allowed and will cause the command to throw an error. Providing an empty string as input is allowed, the command will then return an empty list. If the length of the string is not an entire multiple of the chunk length, then the last chunk in the generated list will be shorter than len. ::textutil::split::splitx string ?regexp? This command splits the string and return a list. The string is split according to the regular expression regexp instead of a simple list of chars. Note that if you parentheses are added into the regexp, the parentheses part of separator will be added into the result list as additional element. If the string is empty the result is the empty list, like for split. If regexp is empty the string is split at every character, like split does. The regular expression regexp defaults to "[\t \r\n]+". BUGS, IDEAS, FEEDBACK This document, and the package it describes, will undoubtedly contain bugs and other problems. Please report such in the category textutil of the Tcllib SF Trackers [http://sourceforge.net/tracker/?group_id=12883]. Please also report any ideas for enhancements you may have for either package and/or documentation. SEE ALSO
regexp(n), split(n), string(n) KEYWORDS
regular expression, split, string textutil 0.7 textutil::split(n)
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