1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
|
# Copyright (C) 2019-2020 Chris Lalancette <clalancette@gmail.com>
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation;
# version 2.1 of the License.
# This library 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 the GNU
# Lesser General Public License for more details.
# You should have received a copy of the GNU Lesser General Public
# License along with this library; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
'''
PyCdlibIO class.
'''
from __future__ import absolute_import
import array
import io
import sys
from pycdlib import inode
from pycdlib import pycdlibexception
# For mypy annotations
if False: # pylint: disable=using-constant-test
from typing import Optional # NOQA pylint: disable=unused-import
class PyCdlibIO(io.RawIOBase):
'''
The class that implements the user-facing python io-style context manager.
Since ISOs are generally only readable, this is only a readable context
manager.
'''
__slots__ = ('_ctxt', '_fp', '_length', '_offset', '_open', '_startpos')
def __init__(self, ino, logical_block_size):
# type: (inode.Inode, int) -> None
super(PyCdlibIO, self).__init__()
self._ctxt = inode.InodeOpenData(ino, logical_block_size)
self._open = True
def __enter__(self):
# _fp is the real file descriptor. _length is the logical length
# of the file. _offset is the logical offset of this context
# into the file. _startpos is the absolute offset of the start of
# this file into the backing file.
(self._fp, self._length) = self._ctxt.__enter__()
self._startpos = self._fp.tell()
self._offset = 0
return self
def read(self, size=None):
# type: (Optional[int]) -> bytes
'''
Read and return up to size bytes.
Parameters:
size - Optional parameter to read size number of bytes; if None or
negative, all remaining bytes in the file will be read
Returns:
The number of bytes requested or the rest of the data left in the file,
whichever is smaller. If the file is at or past EOF, returns an empty
bytestring.
'''
if not self._open:
raise pycdlibexception.PyCdlibInvalidInput('I/O operation on closed file.')
if self._offset >= self._length:
return b''
if size is None or size < 0:
data = self.readall()
else:
readsize = min(self._length - self._offset, size)
data = self._fp.read(readsize)
self._offset += readsize
return data
def readall(self):
# type: () -> bytes
'''
Read and return the remaining bytes in the file.
Parameters:
None.
Returns:
The rest of the data left in the file. If the file is at or past EOF,
returns an empty bytestring.
'''
if not self._open:
raise pycdlibexception.PyCdlibInvalidInput('I/O operation on closed file.')
readsize = self._length - self._offset
if readsize > 0:
data = self._fp.read(readsize)
self._offset += readsize
else:
data = b''
return data
def readinto(self, b):
# type: (bytes) -> int
if not self._open:
raise pycdlibexception.PyCdlibInvalidInput('I/O operation on closed file.')
readsize = self._length - self._offset
if readsize > 0:
if sys.version_info >= (3, 0):
# Python 3
mv = memoryview(b) # type: ignore
m = mv.cast('B') # type: ignore
readsize = min(readsize, len(m))
data = self._fp.read(readsize)
n = len(data)
m[:n] = data
else:
# Python 2
readsize = min(readsize, len(b))
data = self._fp.read(readsize)
n = len(data)
try:
b[:n] = data
except TypeError as err:
if not isinstance(b, array.array):
raise err
b[:n] = array.array(b'b', data)
else:
n = 0
return n
def seek(self, offset, whence=0):
# type: (int, int) -> int
'''
Change the stream position to byte offset offset. The offset is
interpreted relative to the position indicated by whence. Valid values
for whence are:
* 0 -- start of stream (the default); offset should be zero or positive
* 1 -- current stream position; offset may be negative
* 2 -- end of stream; offset is usually negative
Parameters:
offset - The byte offset to seek to.
whence - The position in the file to start from (0 for start, 1 for
current, 2 for end)
Returns:
The new absolute position.
'''
if not self._open:
raise pycdlibexception.PyCdlibInvalidInput('I/O operation on closed file.')
if isinstance(offset, float):
raise pycdlibexception.PyCdlibInvalidInput('an integer is required')
if whence == 0:
# From beginning of file
if offset < 0:
raise pycdlibexception.PyCdlibInvalidInput('Invalid offset value (must be positive)')
if offset < self._length:
self._fp.seek(self._startpos + offset, 0)
self._offset = offset
elif whence == 1:
# From current file position
if self._offset + offset < 0:
raise pycdlibexception.PyCdlibInvalidInput('Invalid offset value (cannot seek before start of file)')
if self._offset + offset < self._length:
self._fp.seek(self._startpos + self._offset + offset, 0)
self._offset += offset
elif whence == 2:
# From end of file
if offset < 0 and abs(offset) > self._length:
raise pycdlibexception.PyCdlibInvalidInput('Invalid offset value (cannot seek before start of file)')
if self._length + offset < self._length:
self._fp.seek(self._length + offset, 0)
self._offset = self._length + offset
else:
raise pycdlibexception.PyCdlibInvalidInput('Invalid value for whence (options are 0, 1, and 2)')
return self._offset
def tell(self):
# type: () -> int
'''
Return the current stream position.
Parameters:
None.
Returns:
The current stream position.
'''
if not self._open:
raise pycdlibexception.PyCdlibInvalidInput('I/O operation on closed file.')
return self._offset
def length(self):
# type: () -> int
'''
Return the length of the current file.
Parameters:
None.
Returns:
The length of the file.
'''
if not self._open:
raise pycdlibexception.PyCdlibInvalidInput('I/O operation on closed file.')
return self._length
def readable(self):
# type: () -> bool
'''
Determine whether this file is readable.
Parameters:
None.
Returns:
True in all cases.
'''
if not self._open:
raise pycdlibexception.PyCdlibInvalidInput('I/O operation on closed file.')
return True
def seekable(self):
# type: () -> bool
'''
Determine whether this file is seekable.
Parameters:
None.
Returns:
True in all cases.
'''
if not self._open:
raise pycdlibexception.PyCdlibInvalidInput('I/O operation on closed file.')
return True
def close(self):
# type: () -> None
'''
Close this file stream.
Parameters:
None.
Returns:
Nothing.
'''
self._open = False
self._ctxt.__exit__()
def __exit__(self, *args):
self._ctxt.__exit__()
|
