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Allow configuration of ETag length in fileserver #371

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Allow configuration of ETag length in fileserver #371

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42 changes: 27 additions & 15 deletions aiocoap/cli/fileserver.py
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Original file line number Diff line number Diff line change
Expand Up @@ -79,11 +79,12 @@ class PreconditionFailed(error.ConstructionRenderableError):
class FileServer(Resource, aiocoap.interfaces.ObservableResource):
# Resource is only used to give the nice render_xxx methods

def __init__(self, root, log, *, write=False):
def __init__(self, root, log, *, write=False, etag_length=8):
super().__init__()
self.root = root
self.log = log
self.write = write
self.etag_length = etag_length

self._observations = {} # path -> [last_stat, [callbacks]]

Expand Down Expand Up @@ -138,11 +139,10 @@ async def needs_blockwise_assembly(self, request):
# Only GETs to non-directory access handle it explicitly
return False

@staticmethod
def hash_stat(stat):
def hash_stat(self, stat):
# The subset that the author expects to (possibly) change if the file changes
data = (stat.st_mtime_ns, stat.st_ctime_ns, stat.st_size)
return hashlib.sha256(repr(data).encode("ascii")).digest()[:8]
return hashlib.sha256(repr(data).encode("ascii")).digest()[:self.etag_length]

async def render_get(self, request):
if request.opt.uri_path == (".well-known", "core"):
Expand All @@ -157,17 +157,21 @@ async def render_get(self, request):
except FileNotFoundError:
raise NoSuchFile()

etag = self.hash_stat(st)
if self.etag_length:
etag = self.hash_stat(st)

if etag in request.opt.etags:
response = aiocoap.Message(code=codes.VALID)
else:
if S_ISDIR(st.st_mode):
response = await self.render_get_dir(request, path)
elif S_ISREG(st.st_mode):
response = await self.render_get_file(request, path)
if etag in request.opt.etags:
response = aiocoap.Message(code=codes.VALID)
response.opt.etag = etag
return response

response.opt.etag = etag
if S_ISDIR(st.st_mode):
response = await self.render_get_dir(request, path)
elif S_ISREG(st.st_mode):
response = await self.render_get_file(request, path)

if self.etag_length:
response.opt.etag = etag
return response

async def render_put(self, request):
Expand Down Expand Up @@ -353,6 +357,14 @@ def build_parser():
nargs="?",
default=False,
)
p.add_argument(
"--etag-length",
help="Control length of ETag, 0-32 (0 disables)",
metavar="LENGTH",
default=8,
type=int,
choices=range(0,33),
)
p.add_argument("--write", help="Allow writes by any user", action="store_true")
p.add_argument(
"path",
Expand All @@ -367,7 +379,7 @@ def build_parser():
return p

async def start_with_options(
self, path, verbosity=0, register=False, server_opts=None, write=False
self, path, verbosity=0, register=False, server_opts=None, write=False, etag_length=8
):
log = logging.getLogger("fileserver")
coaplog = logging.getLogger("coap-server")
Expand All @@ -381,7 +393,7 @@ async def start_with_options(
log.setLevel(logging.DEBUG)
coaplog.setLevel(logging.DEBUG)

server = FileServer(path, log, write=write)
server = FileServer(path, log, write=write, etag_length=etag_length)
if server_opts is None:
self.context = await aiocoap.Context.create_server_context(server)
else:
Expand Down