"""
A curses-based interactive Python console with a hexadecimal view of
a file.  Useful to hack around or try to guess the format of binary files.
"""
import curses, curses.textpad
import sys, traceback, atexit
from cStringIO import StringIO
from struct import pack, unpack


def init():
    global f, stdscr
    stdscr = None
    if len(sys.argv) != 2:
        print >> sys.stderr, "usage: hexamine.py <file>"
        sys.exit(2)
    f = open(sys.argv[1], 'rb')
    # Initialize curses
    stdscr=curses.initscr()
    atexit.register(done)
    # Turn off echoing of keys, and enter cbreak mode,
    # where no buffering is performed on keyboard input
    curses.noecho() ; curses.cbreak()

    # In keypad mode, escape sequences for special keys
    # (like the cursor keys) will be interpreted and
    # a special value like curses.KEY_LEFT will be returned
    stdscr.keypad(1)
    stdscr.clear()

def done():
    stdscr.keypad(0)
    curses.echo() ; curses.nocbreak()
    curses.endwin()
    if sys.exc_info() != (None, None, None):
        traceback.print_exc()		# Print the exception


init()

stdscr_y, stdscr_x = stdscr.getmaxyx()
headerwidth = 12
itemwidth = 9
columns = (stdscr_x - headerwidth) // itemwidth
if columns < 1: columns = 1
while columns & (columns-1): columns -= 1  # down to a power of two
lineskip = 4*columns
pageskip = lineskip * (stdscr_y-2)

p = 0
promptwin = stdscr.subwin(stdscr_y-1, 4)
promptpad = curses.textpad.Textbox(promptwin)
extralines = []

def go(position):
    global p
    p = position

def search(value, position=None):
    if position is None: position = p
    value = pack('l', value)
    f.seek(position+4)
    data = '?'
    while data:
        data = f.read(4)
        if data == value:
            go(f.tell()-4)
            return f.tell()-4
    f.seek(0)
    for i in xrange(position//4):
        data = f.read(4)
        if data == value:
            go(f.tell()-4)
            print 'search wrapped'
            return f.tell()-4
    print 'not found'
    return None
s=search

def display():
    global p, filesize
    if p < 0: p = 0
    f.seek(0,2)
    filesize = f.tell()
    if p >= filesize:
        p = filesize - lineskip*(stdscr_y//2)
    f.seek(((p//4) & -columns) * 4)
    for y in range(stdscr_y-1-len(extralines)):
        line = ['%08x: ' % f.tell()]
        for j in range(columns):
            data = f.read(4)
            if len(data) == 4:
                line.append('%08x' % unpack('l', data))
            else:
                while data:
                    line.append('%02x' % ord(data[0]))
                    data = data[1:]
        stdscr.move(y, 0)
        stdscr.clrtoeol()
        if len(line) > 1:
            stdscr.addstr(y, 0, ' '.join(line))
    for y in range(len(extralines)):
        stdscr.move(stdscr_y-1-len(extralines) + y, 0)
        stdscr.clrtoeol()
        stdscr.addstr(stdscr_y-1-len(extralines) + y, 0,
                      extralines[y], curses.A_BOLD)
    stdscr.move(stdscr_y-1, 0)     # Move the cursor
    stdscr.addstr(stdscr_y-1, 0, '>>>')
    stdscr.refresh()
    promptwin.refresh()

def dispatch(c):
    global p
    if   c==curses.KEY_DOWN:  p += lineskip
    elif c==curses.KEY_UP:    p -= lineskip
    elif c==curses.KEY_NPAGE: p += pageskip
    elif c==curses.KEY_PPAGE: p -= pageskip
    elif c==curses.KEY_HOME:  p = 0
    elif c==curses.KEY_END:   p = filesize-lineskip*(stdscr_y//2)
    elif c==4:                sys.exit(0)
    elif c==curses.KEY_ENTER or c==10:
        stdscr.move(stdscr_y-1, 0)     # Move the cursor
        stdscr.refresh()
        cmd = promptpad.gather()
        promptwin.clear()
        del extralines[:]
        run(cmd)
    else:
        promptpad.do_command(c)

def run(cmd):
    if cmd:
        old_stdout = sys.stdout
        old_stderr = sys.stderr
        try:
            sys.stdout = sys.stderr = fbuf = StringIO()
            try:
                co = compile(cmd, '<string>', 'single')
                exec co in globals()
            except:
                traceback.print_exc()
        finally:
            sys.stdout = old_stdout
            sys.stderr = old_stderr
        fbuf.seek(0)
        extralines[:] = [s.rstrip()[:stdscr_x] for s in fbuf.readlines()]
        if len(extralines) > stdscr_y//2:
            extralines[:] = extralines[:stdscr_y//2] + ['(...)']


while 1:
    display()
    c=stdscr.getch()	     # Get a keystroke
    dispatch(c)