Class: Resedit::Huffman

Inherits:
Object
  • Object
show all
Defined in:
lib/resedit/text/huffman.rb

Defined Under Namespace

Classes: Balancer, Node

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(zeroLeft, reverseBitsInByte = false) ⇒ Huffman

Returns a new instance of Huffman.



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# File 'lib/resedit/text/huffman.rb', line 66

def initialize(zeroLeft, reverseBitsInByte=false)
    @tree=Huffman::Node.new()
    @zeroLeft, @reverseBits = zeroLeft,reverseBitsInByte
end

Instance Attribute Details

#tree ⇒ Object (readonly)

Returns the value of attribute tree.



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# File 'lib/resedit/text/huffman.rb', line 64

def tree
  @tree
end

Instance Method Details

#balancer ⇒ Object 



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# File 'lib/resedit/text/huffman.rb', line 95

def balancer()
    return Huffman::Balancer.new(self)
end

#debug ⇒ Object 



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# File 'lib/resedit/text/huffman.rb', line 99

def debug()
    tbl=decodeTable()
    info="---huffman table---\n"
    bts={}
    tbl.keys.sort.each{|sz|
        tbl[sz].each{|k,v|
            fmt = "0x%02X\t%2d\t%0" + sz.to_s + "b\n"
            info += sprintf(fmt,v,sz,k)
            if not bts[v]
                bts[v] = 1
            else
                bts[v] += 1
            end
        }
    }
    info += sprintf("---%d bytes---\n",bts.length)
    for i in 0..255
        if !bts[i]
            info+=sprintf("0x%02X - ABSENT\n", i)
        else
            info+=sprintf("0x%02X - %d times\n", i, bts[i]) if bts[i]!=1
        end
    end
    App.get().logd(info)
end

#decode(bitstream, endl = 0) ⇒ Object 



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# File 'lib/resedit/text/huffman.rb', line 130

def decode(bitstream, endl=0)
    res = ''
    tbl = decodeTable()
    max = tbl.keys.max
    pos = 0
    byte = bitstream[pos].ord
    bytelen = 8
    buf = 0
    buflen = 0
    while true
        buf <<= 1
        buflen += 1
        raise "Huffman decode length overflow" if buflen>max
        buf |= byte & 1
        byte >>= 1
        bytelen -= 1
        if tbl[buflen] && tbl[buflen][buf]
            return res if tbl[buflen][buf] == endl
            res += tbl[buflen][buf].chr
            buf = 0
            buflen = 0
        end

        next if bytelen>0
        pos += 1
        break if pos >= bitstream.length
        bytelen = 8
        byte = revbyte(bitstream[pos].ord)
    end
    return res
end

#decodeTable(recalc = false) ⇒ Object 



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# File 'lib/resedit/text/huffman.rb', line 71

def decodeTable(recalc=false)
    if @recalc || !@decodeTbl
        tbl = @tree.getLeafs(@zeroLeft ? '0' : '1', @zeroLeft ? '1' : '0')
        @decodeTbl = {}
        tbl.each{|k,v|
            @decodeTbl[k.length] = {} if !@decodeTbl[k.length]
            @decodeTbl[k.length][k.to_i(2)] = v
        }
    end
    return @decodeTbl
end

#encode(bytes, endl = 0) ⇒ Object 



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# File 'lib/resedit/text/huffman.rb', line 162

def encode(bytes, endl=0)
    if endl != nil && bytes[-1] != endl
        bytes += endl.chr
    end
    res = ''
    tbl = encodeTable()
    byte = 0
    bytelen = 0
    bytes.each_byte{|b|
        raise sprintf("No byte in encode table: %02X", b)  if !tbl[b]
        val = tbl[b][0]
        for _ in 0..tbl[b][1]-1
            byte |= ((val & 1) << bytelen)
            val >>= 1
            bytelen += 1
            if bytelen == 8
                res += revbyte(byte).chr
                bytelen = 0
                byte = 0
            end
        end
    }
    res += revbyte(byte).chr if bytelen > 0
    return res
end

#encodeTable(recalc = false) ⇒ Object 



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# File 'lib/resedit/text/huffman.rb', line 83

def encodeTable(recalc=false)
    if @recalc || !@encodeTbl
        tbl = @tree.getLeafs(@zeroLeft ? '0' : '1', @zeroLeft ? '1' : '0')
        @encodeTbl = {}
        tbl.each{|k,v|
            @encodeTbl[v] = [k.reverse.to_i(2), k.length]
        }
    end
    return @encodeTbl
end

#revbyte(byte) ⇒ Object 



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# File 'lib/resedit/text/huffman.rb', line 125

def revbyte(byte)
    return byte if !@reverseBits
    return sprintf("%08b", byte).reverse.to_i(2)
end