static int hdc_pe4[256][4] = {
{0,0,0,0},{0,0,0,1},{0,0,0,2},{0,0,0,3},
{0,0,1,0},{0,0,1,1},{0,0,1,2},{0,0,1,3},
{0,0,2,0},{0,0,2,1},{0,0,2,2},{0,0,2,3},
{0,0,3,0},{0,0,3,1},{0,0,3,2},{0,0,3,3},
{0,1,0,0},{0,1,0,1},{0,1,0,2},{0,1,0,3},
{0,1,1,0},{0,1,1,1},{0,1,1,2},{0,1,1,3},
{0,1,2,0},{0,1,2,1},{0,1,2,2},{0,1,2,3},
{0,1,3,0},{0,1,3,1},{0,1,3,2},{0,1,3,3},
{0,2,0,0},{0,2,0,1},{0,2,0,2},{0,2,0,3},
{0,2,1,0},{0,2,1,1},{0,2,1,2},{0,2,1,3},
{0,2,2,0},{0,2,2,1},{0,2,2,2},{0,2,2,3},
{0,2,3,0},{0,2,3,1},{0,2,3,2},{0,2,3,3},
{0,3,0,0},{0,3,0,1},{0,3,0,2},{0,3,0,3},
{0,3,1,0},{0,3,1,1},{0,3,1,2},{0,3,1,3},
{0,3,2,0},{0,3,2,1},{0,3,2,2},{0,3,2,3},
{0,3,3,0},{0,3,3,1},{0,3,3,2},{0,3,3,3},
{1,0,0,0},{1,0,0,1},{1,0,0,2},{1,0,0,3},
{1,0,1,0},{1,0,1,1},{1,0,1,2},{1,0,1,3},
{1,0,2,0},{1,0,2,1},{1,0,2,2},{1,0,2,3},
{1,0,3,0},{1,0,3,1},{1,0,3,2},{1,0,3,3},
{1,1,0,0},{1,1,0,1},{1,1,0,2},{1,1,0,3},
{1,1,1,0},{1,1,1,1},{1,1,1,2},{1,1,1,3},
{1,1,2,0},{1,1,2,1},{1,1,2,2},{1,1,2,3},
{1,1,3,0},{1,1,3,1},{1,1,3,2},{1,1,3,3},
{1,2,0,0},{1,2,0,1},{1,2,0,2},{1,2,0,3},
{1,2,1,0},{1,2,1,1},{1,2,1,2},{1,2,1,3},
{1,2,2,0},{1,2,2,1},{1,2,2,2},{1,2,2,3},
{1,2,3,0},{1,2,3,1},{1,2,3,2},{1,2,3,3},
{1,3,0,0},{1,3,0,1},{1,3,0,2},{1,3,0,3},
{1,3,1,0},{1,3,1,1},{1,3,1,2},{1,3,1,3},
{1,3,2,0},{1,3,2,1},{1,3,2,2},{1,3,2,3},
{1,3,3,0},{1,3,3,1},{1,3,3,2},{1,3,3,3},
{2,0,0,0},{2,0,0,1},{2,0,0,2},{2,0,0,3},
{2,0,1,0},{2,0,1,1},{2,0,1,2},{2,0,1,3},
{2,0,2,0},{2,0,2,1},{2,0,2,2},{2,0,2,3},
{2,0,3,0},{2,0,3,1},{2,0,3,2},{2,0,3,3},
{2,1,0,0},{2,1,0,1},{2,1,0,2},{2,1,0,3},
{2,1,1,0},{2,1,1,1},{2,1,1,2},{2,1,1,3},
{2,1,2,0},{2,1,2,1},{2,1,2,2},{2,1,2,3},
{2,1,3,0},{2,1,3,1},{2,1,3,2},{2,1,3,3},
{2,2,0,0},{2,2,0,1},{2,2,0,2},{2,2,0,3},
{2,2,1,0},{2,2,1,1},{2,2,1,2},{2,2,1,3},
{2,2,2,0},{2,2,2,1},{2,2,2,2},{2,2,2,3},
{2,2,3,0},{2,2,3,1},{2,2,3,2},{2,2,3,3},
{2,3,0,0},{2,3,0,1},{2,3,0,2},{2,3,0,3},
{2,3,1,0},{2,3,1,1},{2,3,1,2},{2,3,1,3},
{2,3,2,0},{2,3,2,1},{2,3,2,2},{2,3,2,3},
{2,3,3,0},{2,3,3,1},{2,3,3,2},{2,3,3,3},
{3,0,0,0},{3,0,0,1},{3,0,0,2},{3,0,0,3},
{3,0,1,0},{3,0,1,1},{3,0,1,2},{3,0,1,3},
{3,0,2,0},{3,0,2,1},{3,0,2,2},{3,0,2,3},
{3,0,3,0},{3,0,3,1},{3,0,3,2},{3,0,3,3},
{3,1,0,0},{3,1,0,1},{3,1,0,2},{3,1,0,3},
{3,1,1,0},{3,1,1,1},{3,1,1,2},{3,1,1,3},
{3,1,2,0},{3,1,2,1},{3,1,2,2},{3,1,2,3},
{3,1,3,0},{3,1,3,1},{3,1,3,2},{3,1,3,3},
{3,2,0,0},{3,2,0,1},{3,2,0,2},{3,2,0,3},
{3,2,1,0},{3,2,1,1},{3,2,1,2},{3,2,1,3},
{3,2,2,0},{3,2,2,1},{3,2,2,2},{3,2,2,3},
{3,2,3,0},{3,2,3,1},{3,2,3,2},{3,2,3,3},
{3,3,0,0},{3,3,0,1},{3,3,0,2},{3,3,0,3},
{3,3,1,0},{3,3,1,1},{3,3,1,2},{3,3,1,3},
{3,3,2,0},{3,3,2,1},{3,3,2,2},{3,3,2,3},
{3,3,3,0},{3,3,3,1},{3,3,3,2},{3,3,3,3}
};
这是每个字节固定的查找或者建树的规则。