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Fast Base32 Implementation in Pure Ruby
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| module Base32 | |
| TABLE = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ234567' | |
| TABLE_REVERSE = Array.new(256) | |
| TABLE.each_byte.with_index{|c, i| TABLE_REVERSE[c.ord] = i} | |
| TABLE_REVERSE.freeze | |
| PADDING = [0, 0, 0, 0, 0].pack('C*').freeze | |
| def self.encode32(str, padding: false) | |
| bytes = String.new(str, encoding: Encoding::ASCII_8BIT) | |
| bytesize = bytes.bytesize | |
| bytes << PADDING | |
| chunksize = (bytesize + 4) / 5 | |
| ret = String.new(capacity: chunksize * 8) | |
| chunksize.times do |i| | |
| s = i * 5 | |
| b1 = bytes[s].ord | |
| b2 = bytes[s + 1].ord | |
| b3 = bytes[s + 2].ord | |
| b4 = bytes[s + 3].ord | |
| b5 = bytes[s + 4].ord | |
| ret << TABLE[b1 >> 3] | |
| ret << TABLE[b1 << 2 & 0x1c | b2 >> 6] | |
| ret << TABLE[b2 >> 1 & 0x1f] | |
| ret << TABLE[b2 << 4 & 0x10 | b3 >> 4] | |
| ret << TABLE[b3 << 1 & 0x1e | b4 >> 7] | |
| ret << TABLE[b4 >> 2 & 0x1f] | |
| ret << TABLE[b4 << 3 & 0x18 | b5 >> 5] | |
| ret << TABLE[b5 & 0x1f] | |
| end | |
| if padding | |
| (((bytesize * 8 + 4) / 5)...(ret.size)).each do |i| | |
| ret[i] = '=' | |
| end | |
| ret | |
| else | |
| ret[0, (bytesize * 8 + 4) / 5] | |
| end | |
| end | |
| def self.decode32(str) | |
| ret = String.new(capacity: (str.bytesize * 5 + 3) / 8) | |
| current = 0 | |
| pos = 0 | |
| str.each_byte do |b| | |
| c = TABLE_REVERSE[b] | |
| break unless c | |
| case pos | |
| when 0 | |
| current = c << 3 | |
| pos = 5 | |
| when 1, 2 | |
| current |= c << (3 - pos) | |
| pos += 5 | |
| when 3 | |
| current |= c | |
| ret << current.ord | |
| pos = 0 | |
| else | |
| current |= c >> (pos - 3) | |
| ret << current.ord | |
| current = (c << (11 - pos)) & 0xff | |
| pos -= 3 | |
| end | |
| end | |
| ret | |
| end | |
| end |
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