很久以来一直都以为eD2k Hash就是MD4（罪魁祸首），这几天才发现错得很离谱。
花了点时间查资料，写了个用以生成eD2k链接的模块，包括AICH部分。代码有个偷懒的地方，读取文件的缓存大小必须为PART_SIZE，如果要拿去用的话请留意。Ruby 1.8.6和1.8.7的File.size在Windows平台下有bug，当文件尺寸比较大时会返回负数，这一点也请留意。
部分代码移植自pyaich和Python的Base64模块，GPL许可证。
require 'openssl'
module OtNtH
module Digest
# fit for eD2k Hash
PART_SIZE = 9_728_000
BLOCK_SIZE = 184_320
class ED2K
def initialize
@h = ''
@l = 0
end
def update(part)
@h += OpenSSL::Digest::MD4.new(part).digest
@l = part.size
end
def hexdigest
@h += OpenSSL::Digest::MD4.new('').digest if @l == PART_SIZE
OpenSSL::Digest::MD4.new(@h).hexdigest
end
def name
'ED2K'
end
end # class ED2K
class AICH
class HashTree
attr_accessor :dataSize, :isLeft, :baseSize, :hash, :leftTree, :rightTree
def initialize(dataSize, isLeftBranch, baseSize)
@dataSize = dataSize
@isLeft = isLeftBranch
@baseSize = baseSize
@hash = nil
@leftTree = nil
@rightTree = nil
end
def loadLowestLevelHashes(hashList)
if @dataSize <= @baseSize then
@hash = hashList.shift
return true
else
extra = @dataSize % @baseSize != 0 ? 1 : 0
numBlocks = @dataSize / @baseSize + extra
extra = isLeft ? 1 : 0
sizeLeft = ((numBlocks + extra)/2) * @baseSize
sizeRight = @dataSize - sizeLeft
leftBaseSize = sizeLeft <= PART_SIZE ? BLOCK_SIZE : PART_SIZE
@leftTree = HashTree.new(sizeLeft, true, leftBaseSize)
rightBaseSize = sizeRight <= PART_SIZE ? BLOCK_SIZE : PART_SIZE
@rightTree = HashTree.new(sizeRight, false, rightBaseSize)
return @leftTree.loadLowestLevelHashes(hashList) && @rightTree.loadLowestLevelHashes(hashList)
end
end
def reCalculateHash
if @leftTree and @rightTree then
return false if (not @leftTree.reCalculateHash) or (not @rightTree.reCalculateHash)
h = OpenSSL::Digest::SHA1.new
h.update(@leftTree.hash)
h.update(@rightTree.hash)
@hash = h.digest
return true
else
return true
end
end
end
def initialize
@hash_list = []
@data_size = 0
end
def update(part)
psize = part.size
@data_size += psize
pos = 0
while pos < psize
@hash_list.push OpenSSL::Digest::SHA1.new(part[pos, BLOCK_SIZE]).digest
pos += BLOCK_SIZE
end
end
def hexdigest
blockSize = @data_size <= PART_SIZE ? BLOCK_SIZE : PART_SIZE
tree = HashTree.new(@data_size, true, blockSize)
tree.loadLowestLevelHashes(@hash_list)
tree.reCalculateHash
return Base32.encode32(tree.hash)
end
def name
'ED2K'
end
end # class AICH
end # module Digest
module Base32
B32TAB = 'abcdefghijklmnopqrstuvwxyz23456789'
module_function
def encode32(str)
parts = []
quanta, leftover = str.size.divmod(5)
if leftover != 0 then
str += ("\0" * (5 - leftover))
quanta += 1
end
quanta.times do |i|
c1, c2, c3 = str[i*5..(i+1)*5].unpack('nnC')
c2 += (c1 & 1) << 16
c3 += (c2 & 3) << 8
parts.push(
B32TAB[c1 >> 11],
B32TAB[(c1 >> 6) & 0x1f],
B32TAB[(c1 >> 1) & 0x1f],
B32TAB[c2 >> 12],
B32TAB[(c2 >> 7) & 0x1f],
B32TAB[(c2 >> 2) & 0x1f],
B32TAB[c3 >> 5],
B32TAB[c3 & 0x1f]
)
end
encoded = parts.join('')
case leftover
when 1
encoded[0..-6] + '====='
when 2
encoded[0..-4] + '===='
when 3
encoded[0..-3] + '==='
when 4
encoded[0..-1] + '='
else
encoded
end
end
end # module Base32
end # module OtNtH
if __FILE__ == $0 then
exit if not File.exists?(ARGV[0])
a = OtNtH::Digest::AICH.new
e = OtNtH::Digest::ED2K.new
File.open(ARGV[0], 'rb') do |f|
buf = ''
while f.read(OtNtH::Digest::PART_SIZE, buf)
a.update(buf)
e.update(buf)
end
end
puts "ed2k://|file|#{File.basename(ARGV[0])}|#{File.size(ARGV[0])}|#{e.hexdigest}|h=#{a.hexdigest}|/"
end
