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Diffstat (limited to 'cxmanage_api/simg.py')
| -rw-r--r-- | cxmanage_api/simg.py | 239 |
1 files changed, 239 insertions, 0 deletions
diff --git a/cxmanage_api/simg.py b/cxmanage_api/simg.py new file mode 100644 index 0000000..6ae8bf8 --- /dev/null +++ b/cxmanage_api/simg.py @@ -0,0 +1,239 @@ +# Copyright (c) 2012, Calxeda Inc. +# +# All rights reserved. +# +# Redistribution and use in source and binary forms, with or without +# modification, are permitted provided that the following conditions are +# met: +# +# * Redistributions of source code must retain the above copyright +# notice, this list of conditions and the following disclaimer. +# * Redistributions in binary form must reproduce the above copyright +# notice, this list of conditions and the following disclaimer in the +# documentation and/or other materials provided with the distribution. +# * Neither the name of Calxeda Inc. nor the names of its contributors +# may be used to endorse or promote products derived from this software +# without specific prior written permission. +# +# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS +# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT +# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS +# FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE +# COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, +# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, +# BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS +# OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND +# ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR +# TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF +# THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH +# DAMAGE. + + +import struct + +from cxmanage_api.crc32 import get_crc32 + + +HEADER_LENGTH = 60 +MIN_HEADER_LENGTH = 28 + + +class SIMGHeader: + """Container for an SIMG header. + + >>> from cxmanage_api.simg import SIMGHeader + >>> simg = SIMGHeader() + + :param header_string: SIMG Header value. + :type header_string: string + + """ + + def __init__(self, header_string=None): + """Default constructor for the SIMGHeader class.""" + if (header_string == None): + self.magic_string = 'SIMG' + self.hdrfmt = 2 + self.priority = 0 + self.imgoff = HEADER_LENGTH + self.imglen = 0 + self.daddr = 0 + self.flags = 0 + self.crc32 = 0 + self.version = '' + else: + header_string = header_string.ljust(HEADER_LENGTH, chr(0)) + tup = struct.unpack('<4sHHIIIII32s', header_string) + self.magic_string = tup[0] + self.hdrfmt = tup[1] + self.priority = tup[2] + self.imgoff = tup[3] + self.imglen = tup[4] + self.daddr = tup[5] + self.flags = tup[6] + self.crc32 = tup[7] + if (self.hdrfmt >= 2): + self.version = tup[8] + else: + self.version = '' + + def __str__(self): + return struct.pack('<4sHHIIIII32s', self.magic_string, self.hdrfmt, + self.priority, self.imgoff, self.imglen, self.daddr, + self.flags, self.crc32, self.version) + +def create_simg(contents, priority=0, daddr=0, skip_crc32=False, align=False, + version=None): + """Create an SIMG version of a file. + + >>> from cxmanage_api.simg import create_simg + >>> simg = create_simg(contents='foobarbaz') + >>> simg + 'SIMG\\x02\\x00\\x00\\x00<\\x00\\x00\\x00\\t\\x00\\x00\\x00\\x00\\x00\\x00 + \\x00\\xff\\xff\\xff\\xffK\\xf3\\xea\\x0c\\x00\\x00\\x00\\x00\\x00\\x00 + \\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00 + \\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00foobarbaz' + + :param contents: Contents of the SIMG file. + :type contents: string + :param priority: SIMG Header priority value. + :type priority: integer + :param daddr: SIMG Header daddr value. + :type daddr: integer + :param skip_crc32: Flag to skip crc32 calculating. + :type skip_crc32: boolean + :param align: Flag used to turn on/off image offset of 4096. + :type align: boolean + :param version: Version string. + :type version: string + + :returns: String representation of the SIMG file. + :rtype: string + + """ + if (version == None): + version = '' + + header = SIMGHeader() + header.priority = priority + header.imglen = len(contents) + header.daddr = daddr + header.version = version + + if (align): + header.imgoff = 4096 + # Calculate crc value + if (skip_crc32): + crc32 = 0 + else: + crc32 = get_crc32(contents, get_crc32(str(header)[:MIN_HEADER_LENGTH])) + # Get SIMG header + header.flags = 0xFFFFFFFF + header.crc32 = crc32 + return str(header).ljust(header.imgoff, chr(0)) + contents + +def has_simg(simg): + """Returns true if this string has an SIMG header. + + >>> from cxmanage_api.simg import create_simg + >>> simg=create_simg(contents='foobarbaz') + >>> from cxmanage_api.simg import has_simg + >>> has_simg(simg=simg) + True + + :param simg: SIMG string (representation of a SIMG file). + :type simg: string + + :returns: Whether or not the string has a SIMG header. + :rtype: boolean + + """ + if (len(simg) < MIN_HEADER_LENGTH): + return False + header = SIMGHeader(simg[:HEADER_LENGTH]) + # Check for magic word + return (header.magic_string == 'SIMG') + +def valid_simg(simg): + """Return true if this is a valid SIMG. + + >>> from cxmanage_api.simg import create_simg + >>> simg=create_simg(contents='foobarbaz') + >>> from cxmanage_api.simg import valid_simg + >>> valid_simg(simg=simg) + True + + :param simg: SIMG string (representation of a SIMG file). + :type simg: string + + :returns: Whether or not the SIMG is valid. + :rtype: boolean + + """ + if (not has_simg(simg)): + return False + header = SIMGHeader(simg[:HEADER_LENGTH]) + + # Check offset + if (header.imgoff < MIN_HEADER_LENGTH): + return False + + # Check length + start = header.imgoff + end = start + header.imglen + contents = simg[start:end] + if (len(contents) < header.imglen): + return False + + # Check crc32 + crc32 = header.crc32 + if (crc32 != 0): + header.flags = 0 + header.crc32 = 0 + if (crc32 != get_crc32(contents, + get_crc32(str(header)[:MIN_HEADER_LENGTH]))): + return False + return True + +def get_simg_header(simg): + """Returns the header of this SIMG. + + >>> from cxmanage_api.simg import get_simg_header + >>> get_simg_header(x) + <cxmanage_api.simg.SIMGHeader instance at 0x7f4d1ce9aef0> + + :param simg: Path to SIMG file. + :type simg: string + + :returns: The SIMG header. + :rtype: string + + :raises ValueError: If the SIMG cannot be read. + + """ + if (not valid_simg(simg)): + raise ValueError("Failed to read invalid SIMG") + return SIMGHeader(simg[:HEADER_LENGTH]) + +def get_simg_contents(simg): + """Returns the contents of this SIMG. + + >>> from cxmanage_api.simg import get_simg_contents + >>> get_simg_contents(simg=simg) + 'foobarbaz' + + :param simg: Path to SIMG file. + :type simg: string + + :returns: Contents of this SIMG. + :rtype: string + + """ + header = get_simg_header(simg) + start = header.imgoff + end = start + header.imglen + return simg[start:end] + + +# End of file: ./simg.py + |