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# -*- test-case-name: txweb2.test.test_stream -*-
import os
import time
from txweb2 import http, http_headers, responsecode, stream
# Some starts at writing a response filter to handle request ranges.
class UnsatisfiableRangeRequest(Exception):
pass
def canonicalizeRange((start, end), size):
"""Return canonicalized (start, end) or raises UnsatisfiableRangeRequest
exception.
NOTE: end is the last byte *inclusive*, which is not the usual convention
in python! Be very careful! A range of 0,1 should return 2 bytes."""
# handle "-500" ranges
if start is None:
start = max(0, size - end)
end = None
if end is None or end >= size:
end = size - 1
if start >= size:
raise UnsatisfiableRangeRequest
return start, end
def makeUnsatisfiable(request, oldresponse):
if request.headers.hasHeader('if-range'):
return oldresponse # Return resource instead of error
response = http.Response(responsecode.REQUESTED_RANGE_NOT_SATISFIABLE)
response.headers.setHeader("content-range", ('bytes', None, None, oldresponse.stream.length))
return response
def makeSegment(inputStream, lastOffset, start, end):
offset = start - lastOffset
length = end + 1 - start
if offset != 0:
before, inputStream = inputStream.split(offset)
before.close()
return inputStream.split(length)
def rangefilter(request, oldresponse):
if oldresponse.stream is None:
return oldresponse
size = oldresponse.stream.length
if size is None:
# Does not deal with indeterminate length outputs
return oldresponse
oldresponse.headers.setHeader('accept-ranges', ('bytes',))
rangespec = request.headers.getHeader('range')
# If we've got a range header and the If-Range header check passes, and
# the range type is bytes, do a partial response.
if (
rangespec is not None and http.checkIfRange(request, oldresponse) and
rangespec[0] == 'bytes'
):
# If it's a single range, return a simple response
if len(rangespec[1]) == 1:
try:
start, end = canonicalizeRange(rangespec[1][0], size)
except UnsatisfiableRangeRequest:
return makeUnsatisfiable(request, oldresponse)
response = http.Response(responsecode.PARTIAL_CONTENT, oldresponse.headers)
response.headers.setHeader('content-range', ('bytes', start, end, size))
content, after = makeSegment(oldresponse.stream, 0, start, end)
after.close()
response.stream = content
return response
else:
# Return a multipart/byteranges response
lastOffset = -1
offsetList = []
for arange in rangespec[1]:
try:
start, end = canonicalizeRange(arange, size)
except UnsatisfiableRangeRequest:
continue
if start <= lastOffset:
# Stupid client asking for out-of-order or overlapping ranges, PUNT!
return oldresponse
offsetList.append((start, end))
lastOffset = end
if not offsetList:
return makeUnsatisfiable(request, oldresponse)
content_type = oldresponse.headers.getRawHeaders('content-type')
boundary = "%x%x" % (int(time.time() * 1000000), os.getpid())
response = http.Response(responsecode.PARTIAL_CONTENT, oldresponse.headers)
response.headers.setHeader(
'content-type',
http_headers.MimeType('multipart', 'byteranges',
[('boundary', boundary)])
)
response.stream = out = stream.CompoundStream()
lastOffset = 0
origStream = oldresponse.stream
headerString = "\r\n--%s" % boundary
if len(content_type) == 1:
headerString += '\r\nContent-Type: %s' % content_type[0]
headerString += "\r\nContent-Range: %s\r\n\r\n"
for start, end in offsetList:
out.addStream(
headerString %
http_headers.generateContentRange(('bytes', start, end, size))
)
content, origStream = makeSegment(origStream, lastOffset, start, end)
lastOffset = end + 1
out.addStream(content)
origStream.close()
out.addStream("\r\n--%s--\r\n" % boundary)
return response
else:
return oldresponse
__all__ = ['rangefilter']
|
