1 # Copyright 2016 Facebook, Inc.

     2 # All rights reserved.

     3 #

     4 # Redistribution and use in source and binary forms, with or without

     5 # modification, are permitted provided that the following conditions are met:

     6 #

     7 #  * Redistributions of source code must retain the above copyright notice,

     8 #    this list of conditions and the following disclaimer.

     9 #

    10 #  * Redistributions in binary form must reproduce the above copyright notice,

    11 #    this list of conditions and the following disclaimer in the documentation

    12 #    and/or other materials provided with the distribution.

    13 #

    14 #  * Neither the name Facebook nor the names of its contributors may be used to

    15 #    endorse or promote products derived from this software without specific

    16 #    prior written permission.

    17 #

    18 # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"

    19 # AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

    20 # IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE

    21 # DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE

    22 # FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL

    23 # DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR

    24 # SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER

    25 # CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,

    26 # OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE

    27 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

    28 

    29 from __future__ import absolute_import

    30 from __future__ import division

    31 from __future__ import print_function

    32 # no unicode literals

    33 

    34 try:

    35     from . import bser

    36 except ImportError:

    37     from . import pybser as bser

    38 

    39 import ctypes

    40 

    41 EMPTY_HEADER = b"\x00\x01\x05\x00\x00\x00\x00"

    42 

    43 

    44 def _read_bytes(fp, buf):

    45     """Read bytes from a file-like object

    46 

    47     @param fp: File-like object that implements read(int)

    48     @type fp: file

    49 

    50     @param buf: Buffer to read into

    51     @type buf: bytes

    52 

    53     @return: buf

    54     """

    55 

    56     # Do the first read without resizing the input buffer

    57     offset = 0

    58     remaining = len(buf)

    59     while remaining > 0:

    60         l = fp.readinto((ctypes.c_char * remaining).from_buffer(buf, offset))

    61         if l is None or l == 0:

    62             return offset

    63         offset += l

    64         remaining -= l

    65     return offset

    66 

    67 

    68 def load(fp, mutable=True, value_encoding=None, value_errors=None):

    69     """Deserialize a BSER-encoded blob.

    70 

    71     @param fp: The file-object to deserialize.

    72     @type file:

    73 

    74     @param mutable: Whether to return mutable results.

    75     @type mutable: bool

    76 

    77     @param value_encoding: Optional codec to use to decode values. If

    78                            unspecified or None, return values as bytestrings.

    79     @type value_encoding: str

    80 

    81     @param value_errors: Optional error handler for codec. 'strict' by default.

    82                          The other most common argument is 'surrogateescape' on

    83                          Python 3. If value_encoding is None, this is ignored.

    84     @type value_errors: str

    85     """

    86     buf = ctypes.create_string_buffer(8192)

    87     SNIFF_BUFFER_SIZE = len(EMPTY_HEADER)

    88     header = (ctypes.c_char * SNIFF_BUFFER_SIZE).from_buffer(buf)

    89     read_len = _read_bytes(fp, header)

    90     if read_len < len(header):

    91         return None

    92 

    93     total_len = bser.pdu_len(buf)

    94     if total_len > len(buf):

    95         ctypes.resize(buf, total_len)

    96 

    97     body = (ctypes.c_char * (total_len - len(header))).from_buffer(

    98         buf, len(header))

    99     read_len = _read_bytes(fp, body)

   100     if read_len < len(body):

   101         raise RuntimeError('bser data ended early')

   102 

   103     return bser.loads(

   104         (ctypes.c_char * total_len).from_buffer(buf, 0),

   105         mutable,

   106         value_encoding,

   107         value_errors)