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
|
# Example Python plugin.
#
# This example can be freely used for any purpose.
# Run it from the build directory like this:
#
# ./nbdkit -f -v python ./plugins/python/examples/url.py \
# url=http://example.com/disk.img
#
# Or run it after installing nbdkit like this:
#
# nbdkit -f -v python ./plugins/python/examples/url.py \
# url=http://example.com/disk.img
#
# The -f -v arguments are optional. They cause the server to stay in
# the foreground and print debugging, which is useful when testing.
import urllib.request
import nbdkit
# There are several variants of the API. nbdkit will use this
# constant to determine which one you want to use. This is the latest
# version at the time this example was written.
API_VERSION = 2
url = None
# Parse the url parameter.
def config(key, value):
global url
if key == "url":
url = value
else:
raise RuntimeError("unknown parameter: " + key)
def config_complete():
if url is None:
raise RuntimeError("url parameter is required")
# Although Python code cannot be run in parallel, if your
# plugin callbacks sleep then you can improve parallelism
# by relaxing the thread model.
def thread_model():
return nbdkit.THREAD_MODEL_PARALLEL
# This is called when a client connects.
def open(readonly):
return 1
def get_size(h):
rq = urllib.request.Request(url, method='HEAD')
rp = urllib.request.urlopen(rq)
headers = rp.info()
# Check the server supports range requests.
if headers.get_all('accept-ranges') == []:
raise RuntimeError("server does not support range requests")
content_length = int(headers.get_all('content-length')[0])
return content_length
def pread(h, buf, offset, flags):
count = len(buf)
headers = {"range": "bytes=%d-%d" % (offset, offset+count-1)}
rq = urllib.request.Request(url, b"", headers)
rp = urllib.request.urlopen(rq)
b = rp.read()
if len(b) != count:
raise RuntimeError("incorrect length of data returned: perhaps the " +
"server does not really support range requests")
buf[:] = b
|
