avocado.utils: Add astring library

Add string manipulation APIs to the avocado.utils namespace.
Signed-off-by: NLucas Meneghel Rodrigues <lmr@redhat.com>

avocado/utils/astring.py

+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+#
+# See LICENSE for more details.
+#
+# Copyright: Red Hat Inc. 2013-2014
+# Authors: Lucas Meneghel Rodrigues <lmr@redhat.com>
+
+"""
+Operations with strings (conversion and sanitization).
+
+The unusual name aims to avoid causing name clashes with the stdlib module
+string. Even with the dot notation, people may try to do things like
+
+import string
+...
+from avocado.utils import string
+
+And not notice until their code starts failing.
+"""
+
+import re
+
+
+def bitlist_to_string(data):
+    """
+    Transform from bit list to ASCII string.
+
+    :param data: Bit list to be transformed
+    """
+    result = []
+    pos = 0
+    c = 0
+    while pos < len(data):
+        c += data[pos] << (7 - (pos % 8))
+        if (pos % 8) == 7:
+            result.append(c)
+            c = 0
+        pos += 1
+    return ''.join([chr(c) for c in result])
+
+
+def string_to_bitlist(data):
+    """
+    Transform from ASCII string to bit list.
+
+    :param data: String to be transformed
+    """
+    data = [ord(c) for c in data]
+    result = []
+    for ch in data:
+        i = 7
+        while i >= 0:
+            if ch & (1 << i) != 0:
+                result.append(1)
+            else:
+                result.append(0)
+            i -= 1
+    return result
+
+
+def strip_console_codes(output, custom_codes=None):
+    """
+    Remove the Linux console escape and control sequences from the console
+    output. Make the output readable and can be used for result check. Now
+    only remove some basic console codes using during boot up.
+
+    :param output: The output from Linux console
+    :type output: string
+    :param custom_codes: The codes added to the console codes which is not
+                         covered in the default codes
+    :type output: string
+    :return: the string wihout any special codes
+    :rtype: string
+    """
+    if "\x1b" not in output:
+        return output
+
+    old_word = ""
+    return_str = ""
+    index = 0
+    output = "\x1b[m%s" % output
+    console_codes = "%[G@8]|\[[@A-HJ-MPXa-hl-nqrsu\`]"
+    console_codes += "|\[[\d;]+[HJKgqnrm]|#8|\([B0UK]|\)"
+    if custom_codes is not None and custom_codes not in console_codes:
+        console_codes += "|%s" % custom_codes
+    while index < len(output):
+        tmp_index = 0
+        tmp_word = ""
+        while (len(re.findall("\x1b", tmp_word)) < 2
+               and index + tmp_index < len(output)):
+            tmp_word += output[index + tmp_index]
+            tmp_index += 1
+
+        tmp_word = re.sub("\x1b", "", tmp_word)
+        index += len(tmp_word) + 1
+        if tmp_word == old_word:
+            continue
+        try:
+            special_code = re.findall(console_codes, tmp_word)[0]
+        except IndexError:
+            if index + tmp_index < len(output):
+                raise ValueError("%s is not included in the known console "
+                                 "codes list %s" % (tmp_word, console_codes))
+            continue
+        if special_code == tmp_word:
+            continue
+        old_word = tmp_word
+        return_str += tmp_word[len(special_code):]
+    return return_str