Added a more-disciplined version of #read_ber.

This commit is contained in:
blackhedd 2006-11-27 23:07:24 +00:00
parent 832334116a
commit 4db9f2c7cc

View file

@ -102,6 +102,10 @@ module Net
# packets coming from streams that don't block when # packets coming from streams that don't block when
# we ask for more data (like StringIOs). At it is, # we ask for more data (like StringIOs). At it is,
# this can throw TypeErrors and other nasties. # this can throw TypeErrors and other nasties.
#--
# BEWARE, this violates DRY and is largely equal in functionality to
# read_ber_from_string. Eventually that method may subsume the functionality
# of this one.
# #
def read_ber syntax=nil def read_ber syntax=nil
# don't bother with this line, since IO#getc by definition returns nil on eof. # don't bother with this line, since IO#getc by definition returns nil on eof.
@ -127,42 +131,8 @@ module Net
newobj = read contentlength newobj = read contentlength
# This exceptionally clever and clear bit of code is verrrry slow. # This exceptionally clever and clear bit of code is verrrry slow.
=begin
objtype = nil
[syntax, BuiltinSyntax].each {|syn|
if syn && (ot = syn[tagclass]) && (ot = ot[encoding]) && ot[tag]
objtype = ot[tag]
break
end
}
=end
objtype = (syntax && syntax[id]) || BuiltinSyntax[id] objtype = (syntax && syntax[id]) || BuiltinSyntax[id]
=begin
Replaced this case with if/else because Symbol#=== profiled surprisingly hot.
obj = case objtype
when :boolean
newobj != "\000"
when :string
(newobj || "").dup
when :integer
j = 0
newobj.each_byte {|b| j = (j << 8) + b}
j
when :array
seq = []
sio = StringIO.new( newobj || "" )
# Interpret the subobject, but note how the loop
# is built: nil ends the loop, but false (a valid
# BER value) does not!
while (e = sio.read_ber(syntax)) != nil
seq << e
end
seq
else
raise BerError.new( "unsupported object type: class=#{tagclass}, encoding=#{encoding}, tag=#{tag}" )
end
=end
# == is expensive so sort this if/else so the common cases are at the top. # == is expensive so sort this if/else so the common cases are at the top.
obj = if objtype == :string obj = if objtype == :string
@ -206,6 +176,75 @@ module Net
end end
#--
# Violates DRY! This replicates the functionality of #read_ber.
# Eventually this method may replace that one.
# This version of #read_ber behaves properly in the face of incomplete
# data packets. If a full BER object is detected, we return an array containing
# the detected object and the number of bytes consumed from the string.
# If we don't detect a complete packet, return nil.
#
# Observe that weirdly we recursively call the original #read_ber in here.
# That needs to be fixed if we ever obsolete the original method in favor of this one.
def read_ber_from_string str, syntax=nil
id = str[0] or return nil
n = str[1] or return nil
n_consumed = 2
lengthlength,contentlength = if n <= 127
[1,n]
else
n1 = n & 127
return nil unless str.length >= (n_consumed + n1)
j = 0
n1.times {
j = (j << 8) + str[n_consumed]
n_consumed += 1
}
[1 + (n1), j]
end
return nil unless str.length >= (n_consumed + contentlength)
newobj = str[n_consumed...(n_consumed + contentlength)]
n_consumed += contentlength
objtype = (syntax && syntax[id]) || BuiltinSyntax[id]
# == is expensive so sort this if/else so the common cases are at the top.
obj = if objtype == :array
seq = BerIdentifiedArray.new
seq.ber_identifier = id
sio = StringIO.new( newobj || "" )
# Interpret the subobject, but note how the loop
# is built: nil ends the loop, but false (a valid
# BER value) does not!
# Also, we can use the standard read_ber method because
# we know for sure we have enough data. (Although this
# might be faster than the standard method.)
while (e = sio.read_ber(syntax)) != nil
seq << e
end
seq
elsif objtype == :string
s = BerIdentifiedString.new( newobj || "" )
s.ber_identifier = id
s
elsif objtype == :integer
j = 0
newobj.each_byte {|b| j = (j << 8) + b}
j
elsif objtype == :boolean
newobj != "\000"
elsif objtype == :null
n = BerIdentifiedNull.new
n.ber_identifier = id
n
else
raise BerError.new( "unsupported object type: id=#{id}" )
end
[obj, n_consumed]
end
end # module BERParser end # module BERParser
end # module BER end # module BER