test/py/u_boot_utils.py

# Copyright (c) 2016, NVIDIA CORPORATION. All rights reserved.
#
# SPDX-License-Identifier: GPL-2.0

# Utility code shared across multiple tests.

import hashlib
import os
import os.path
import sys
import time

def md5sum_data(data):
    '''Calculate the MD5 hash of some data.

    Args:
        data: The data to hash.

    Returns:
        The hash of the data, as a binary string.
    '''

    h = hashlib.md5()
    h.update(data)
    return h.digest()

def md5sum_file(fn, max_length=None):
    '''Calculate the MD5 hash of the contents of a file.

    Args:
        fn: The filename of the file to hash.
        max_length: The number of bytes to hash. If the file has more
            bytes than this, they will be ignored. If None or omitted, the
            entire file will be hashed.

    Returns:
        The hash of the file content, as a binary string.
    '''

    with open(fn, 'rb') as fh:
        if max_length:
            params = [max_length]
        else:
            params = []
        data = fh.read(*params)
    return md5sum_data(data)

class PersistentRandomFile(object):
    '''Generate and store information about a persistent file containing
    random data.'''

    def __init__(self, u_boot_console, fn, size):
        '''Create or process the persistent file.

        If the file does not exist, it is generated.

        If the file does exist, its content is hashed for later comparison.

        These files are always located in the "persistent data directory" of
        the current test run.

        Args:
            u_boot_console: A console connection to U-Boot.
            fn: The filename (without path) to create.
            size: The desired size of the file in bytes.

        Returns:
            Nothing.
        '''

        self.fn = fn

        self.abs_fn = u_boot_console.config.persistent_data_dir + '/' + fn

        if os.path.exists(self.abs_fn):
            u_boot_console.log.action('Persistent data file ' + self.abs_fn +
                ' already exists')
            self.content_hash = md5sum_file(self.abs_fn)
        else:
            u_boot_console.log.action('Generating ' + self.abs_fn +
                ' (random, persistent, %d bytes)' % size)
            data = os.urandom(size)
            with open(self.abs_fn, 'wb') as fh:
                fh.write(data)
            self.content_hash = md5sum_data(data)

def attempt_to_open_file(fn):
    '''Attempt to open a file, without throwing exceptions.

    Any errors (exceptions) that occur during the attempt to open the file
    are ignored. This is useful in order to test whether a file (in
    particular, a device node) exists and can be successfully opened, in order
    to poll for e.g. USB enumeration completion.

    Args:
        fn: The filename to attempt to open.

    Returns:
        An open file handle to the file, or None if the file could not be
            opened.
    '''

    try:
        return open(fn, 'rb')
    except:
        return None

def wait_until_open_succeeds(fn):
    '''Poll until a file can be opened, or a timeout occurs.

    Continually attempt to open a file, and return when this succeeds, or
    raise an exception after a timeout.

    Args:
        fn: The filename to attempt to open.

    Returns:
        An open file handle to the file.
    '''

    for i in xrange(100):
        fh = attempt_to_open_file(fn)
        if fh:
            return fh
        time.sleep(0.1)
    raise Exception('File could not be opened')

def wait_until_file_open_fails(fn, ignore_errors):
    '''Poll until a file cannot be opened, or a timeout occurs.

    Continually attempt to open a file, and return when this fails, or
    raise an exception after a timeout.

    Args:
        fn: The filename to attempt to open.
        ignore_errors: Indicate whether to ignore timeout errors. If True, the
            function will simply return if a timeout occurs, otherwise an
            exception will be raised.

    Returns:
        Nothing.
    '''

    for i in xrange(100):
        fh = attempt_to_open_file(fn)
        if not fh:
            return
        fh.close()
        time.sleep(0.1)
    if ignore_errors:
        return
    raise Exception('File can still be opened')

def run_and_log(u_boot_console, cmd, ignore_errors=False):
    '''Run a command and log its output.

    Args:
        u_boot_console: A console connection to U-Boot.
        cmd: The command to run, as an array of argv[].
        ignore_errors: Indicate whether to ignore errors. If True, the function
            will simply return if the command cannot be executed or exits with
            an error code, otherwise an exception will be raised if such
            problems occur.

    Returns:
        Nothing.
    '''

    runner = u_boot_console.log.get_runner(cmd[0], sys.stdout)
    runner.run(cmd, ignore_errors=ignore_errors)
    runner.close()