功能是基于赫夫曼树的数据结构的文本压缩，根据生成的HuffmanTree来产生字符的编码.即从叶子到根逆向求每个字符的Huffman编码。 -Function is based on the Huffman tree data structure of the text compression, according to the generated HuffmanTree to generate the character codes. That is, from leaf to the root reverse order to each character Huffman coding.