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@alanjrogers
Created October 16, 2010 02:38
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Can't remember where I found this, but it works a treat.
require 'iconv'
module AppleBinaryPropertyList
MIME_TYPE = 'application/octet-stream' # Don't know what to use, so use a very generic type for now
CFData = Struct.new(:data) # For marking strings as binary data which will be decoded as a CFData object
# Convert a Ruby data structure into an OS X binary property list file. (.plist)
# Works as you'd expect. Integers are limited to 4 bytes, even though the format implies longer values can be written.
# Strings are assumed to be in UTF-8 format. Symbols are written as strings.
def self.convert(data)
write("", data)
end
# Alternative interface which writes data to the out object using <<
def self.write(out, data)
# Find out how many objects there are, so we know how big the references are
count = count_objects(data)
ref_format, ref_size = int_format_and_size(count)
# Now serialize all the objects
values = Array.new
append_values(data, values, ref_format)
# Write header, then the values, calculating offsets as they're written
out << 'bplist00'
offset = 8
offsets = Array.new
values.each do |v|
offsets << offset
out << v
offset += v.length
end
# How big should the offset ints be?
# Decoder gets upset if the size can't fit the entire file, even if it's not strictly needed, so add the length of the last value.
offset_format, offset_size = int_format_and_size(offsets.last + values.last.length)
# Write the offsets
out << offsets.pack(offset_format)
# Write trailer
out << [0,0,offset_size,ref_size, 0,values.length, 0,0, 0,offset].pack("NnCCNNNNNN")
out
end
private
def self.count_objects(data)
case data
when Array
data.inject(1) { |sum,x| sum + count_objects(x) }
when Hash
# Note: Assumes that the keys aren't a Hash or Array
data.length + count_objects(data.values)
else
1
end
end
def self.append_values(data, values, ref_format)
case data
# Constant values
when nil
# values << "\x00"
raise "Can't store a nil in a binary plist. While the format supports it, decoders don't like it."
when false
values << "\x08"
when true
values << "\x09"
when Integer
raise "Integer out of range to write in binary plist" if data < -2147483648 || data > 0x7FFFFFFF
values << packed_int(data)
when Float
values << "\x23#{[data].pack("d").reverse}"
when Symbol
append_values(data.to_s, values, ref_format)
when String
if data =~ /[\x80-\xff]/
# Has high bits set, so is UTF-8 and must be reencoded for the plist file
c = Iconv.iconv(PLIST_TEXT_ENCODING, INPUT_TEXT_ENCODING, data).join
values << "#{objhdr_with_length(0x60, c.length / 2)}#{c}"
else
# Just ASCII
o = objhdr_with_length(0x50, data.length)
o << data
values << o
end
when AppleBinaryPropertyList::CFData
o = objhdr_with_length(0x40, data.data.length)
o << data.data
values << o
when Time
v = data.getutc.to_f - DATE_EPOCH_OFFSET_APPLE_UNIX
values << "\x33#{[v].pack("d").reverse}"
when Hash
o = objhdr_with_length(0xd0, data.length)
values << o # now, so we get the refs of other objects right
ks = Array.new
vs = Array.new
data.each do |k,v|
ks << values.length
append_values(k, values, ref_format)
vs << values.length
append_values(v, values, ref_format)
end
o << ks.pack(ref_format)
o << vs.pack(ref_format)
when Array
o = objhdr_with_length(0xa0, data.length)
values << o # now, so we get the refs of other objects right
refs = Array.new
data.each do |e|
refs << values.length # index in array of object we're about to write
append_values(e, values, ref_format)
end
o << refs.pack(ref_format)
else
raise "Couldn't serialise value of class #{data.class.name}"
end
end
def self.int_format_and_size(i)
if i > 0xffff
['N*',4]
elsif i > 0xff
['n*',2]
else
['C*',1]
end
end
def self.packed_int(data)
if data < 0
# Need to use 64 bits for negative numbers.
[0x13,0xffffffff,data].pack("CNN")
elsif data > 0xffff
[0x12,data].pack("CN")
elsif data > 0xff
[0x11,data].pack("Cn")
else
[0x10,data].pack("CC")
end
end
def self.objhdr_with_length(id, length)
if length < 0xf
(id + length).chr
else
(id + 0xf).chr + packed_int(length)
end
end
# Difference between Apple and UNIX timestamps
DATE_EPOCH_OFFSET_APPLE_UNIX = 978307200
# Text encoding
INPUT_TEXT_ENCODING = 'UTF-8'
PLIST_TEXT_ENCODING = 'UTF-16BE'
end
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