protected static Dictionary <byte[], BitArray> GetCodeBook(IEnumerable <Stream> streams, byte compressLevel)
{
var weightDictionary = new Dictionary <byte[], ulong>(new ByteArrayEqualityComparer());
foreach (var stream in streams)
{
// 移动输入流的位置到开头
stream.Seek(0, SeekOrigin.Begin);
// 循环读取单位字节数到缓冲数组中，之后进行计数操作
while (stream.Position < stream.Length)
{
int readByte;
// 建立一个具有合适大小的字节缓存数组
var buffer = new byte[Math.Min(compressLevel, stream.Length - stream.Position)];
for (var i = 0; i < compressLevel && (readByte = stream.ReadByte()) >= 0; i++)
{
buffer[i] = (byte)readByte;
}
if (weightDictionary.ContainsKey(buffer))
{
weightDictionary[buffer]++;
}
else
{
weightDictionary[buffer] = 1;
}
}
}
// 创建哈夫曼树
var huffmanTree =
HuffmanTree <byte[]> .CreateFromWeightDictionary(weightDictionary, new ByteArrayEqualityComparer());
// 获取编码本
var codeBook = huffmanTree.CodeBook;
return(codeBook);
}
