[Zope-Checkins] CVS: Zope/lib/python/ZPublisher - HTTPRangeSupport.py:1.6.70.1
Martijn Pieters
mj@zope.com
Sat, 13 Jul 2002 17:14:25 -0400
Update of /cvs-repository/Zope/lib/python/ZPublisher
In directory cvs.zope.org:/tmp/cvs-serv9855/lib/python/ZPublisher
Added Files:
Tag: zope-2_3-branch
HTTPRangeSupport.py
Log Message:
Backported HTTP Range support to Zope 2.3, for the benefit of Zope.org.
=== Added File Zope/lib/python/ZPublisher/HTTPRangeSupport.py ===
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##############################################################################
"""HTTP Range support utilities.
The RFC 2616 specification defines the 'Range' and 'If-Range' headers for
enabeling partial download of published resources. This module provides a
flag-interface and some support functions for implementing this functionality.
For an implementation example, see the File class in OFS/Image.py.
"""
__version__='$Revision: 1.6.70.1 $'[11:-2]
import re, string, sys
import Interface
WHITESPACE = re.compile('\s*', re.MULTILINE)
def parseRange(header):
"""RFC 2616 (HTTP 1.1) Range header parsing.
Convert a range header to a list of slice indexes, returned as (start, end)
tuples. If no end was given, end is None. Note that the RFC specifies the
end offset to be inclusive, we return python convention indexes, where the
end is exclusive. Syntactically incorrect headers are to be ignored, so if
we encounter one we return None.
"""
ranges = []
add = ranges.append
# First, clean out *all* whitespace. This is slightly more tolerant
# than the spec asks for, but hey, it makes this function much easier.
header = WHITESPACE.sub('', header)
# A range header only can specify a byte range
try: spec, sets = string.split(header, '=')
except ValueError: return None
if spec != 'bytes':
return None
# The sets are delimited by commas.
sets = string.split(sets, ',')
# Filter out empty values, things like ',,' are allowed in the spec
sets = filter(None, sets)
# We need at least one set
if not sets:
return None
for set in sets:
try: start, end = string.split(set, '-')
except ValueError: return None
# Catch empty sets
if not start and not end:
return None
# Convert to integers or None (which will raise errors if
# non-integers were used (which is what we want)).
try:
if start == '': start = None
else: start = int(start)
if end == '': end = None
else: end = int(end)
except ValueError:
return None
# Special case: No start means the suffix format was used, which
# means the end value is actually a negative start value.
# Convert this by making it absolute.
# A -0 range is converted to sys.maxint, which will result in a
# Unsatisfiable response if no other ranges can by satisfied either.
if start is None:
start, end = -end, None
if not start:
start = sys.maxint
elif end is not None:
end = end + 1 # Make the end of the range exclusive
if end is not None and end <= start:
return None
# And store
add((start, end))
return ranges
def optimizeRanges(ranges, size):
"""Optimize Range sets, given those sets and the length of the resource.
Optimisation is done by first expanding relative start values and open
ends, then sorting and combining overlapping ranges. We also remove
unsatisfiable ranges (where the start lies beyond the size of the resource).
"""
expanded = []
add = expanded.append
for start, end in ranges:
if start < 0:
start = size + start
end = end or size
if end > size: end = size
# Only use satisfiable ranges
if start < size:
add((start, end))
ranges = expanded
ranges.sort()
ranges.reverse()
optimized = []
add = optimized.append
start, end = ranges.pop()
while ranges:
nextstart, nextend = ranges.pop()
# If the next range overlaps
if nextstart < end:
# If it falls within the current range, discard
if nextend <= end:
continue
# Overlap, adjust end
end = nextend
else:
add((start, end))
start, end = nextstart, nextend
# Add the remaining optimized range
add((start, end))
return optimized
class HTTPRangeInterface(Interface.Base):
"""Objects implementing this Interface support the HTTP Range header.
Objects implementing support for the HTTP Range header will return partial
content as specified in RFC 2616. Note that the'If-Range' header must
either be implemented correctly or result in a normal '200 OK' response at
all times.
This interface specifies no methods, as this functionality can either be
implemented in the index_html or __call__ methods of a published object.
"""