netlog.py

"""Simple utility to generate code to communicate between C and Python.

This utility generates C definitions and Python definitions in order to
send integers, strings, lists, and other custom types over a socket.

"""
import logtbl
import sys
from struct import unpack


def read_int32(buf, offset):
    """Reads a 32bit integer from the buffer."""
    return 4, unpack('I', buf[offset:offset+4])[0]


def read_ptr(buf, offset):
    """Read a pointer from the buffer."""
    length, value = read_int32(buf, offset)
    return length, '0x%08x' % value


def read_string(buf, offset):
    """Reads an utf8 string from the buffer."""
    length, maxlength = unpack('HH', buf[offset:offset+8])
    return length+4, (length, maxlength, buf[offset+4:offset+4+length])


def read_buffer(buf, offset):
    """Reads a memory buffer from the buffer."""
    length, maxlength = unpack('HH', buf[offset:offset+8])
    # only return the maxlength, as we don't log the actual buffer right now
    return 4, maxlength


def read_registry(buf, offset):
    """Read logged registry data from the buffer."""
    typ = unpack('H', buf[offset:offset+2])[0]
    # do something depending on type
    return


def read_list(buf, offset, fn):
    """Reads a list of _fn_ from the buffer."""
    count = unpack('H', buf[offset:offset+2])[0]
    ret, length = [], 0
    for x in xrange(count):
        item_length, item = fn(buf, offset+length)
        length += item_length
        ret.append(item)
    return item_length+2, ret


def parse_fmt(funcname, fmt, *args):
    typ = {
        's': read_string,
        'S': read_string,
        'u': read_string,
        'U': read_string,
        'b': read_buffer,
        'B': read_buffer,
        'i': read_int32,
        'l': read_int32,
        'L': read_int32,
        'p': read_ptr,
        'P': read_ptr,
        'o': read_string,
        'O': read_string,
        'a': None,
        'A': None,
        'r': read_registry,
        'R': read_registry,
    }


def generate_c_code(fname):
    lines = ['#include <stdio.h>', '', 'const char *logtbl[][2] = {']
    for index, (funcname, module, args) in enumerate(logtbl.table):
        lines.append('    {"%s", "%s"},' % (funcname, module))
    lines.append('    {NULL, NULL},')
    lines.append('};')
    lines.append('char logtbl_explained[sizeof(logtbl)/sizeof(char *)] = {0};')
    file(fname, 'w').write('\n'.join(lines) + '\n')

if __name__ == '__main__':
    if sys.argv[1] == 'c-header':
        generate_c_code(sys.argv[2])