private static void BuildCode(string[] st, HuffmanNode x, string s)
{
if (x.isLeaf())
{
st[x.Ch] = s;
return;
}
BuildCode(st, x.Left, s + '0');
BuildCode(st, x.Right, s + '1');
}
private static void WriteTrie(BitVirtualSteam bvStream, HuffmanNode x)
{
if (x.isLeaf())
{
bvStream.Write(true);
bvStream.Write(x.Ch);
return;
}
bvStream.Write(false);
WriteTrie(bvStream, x.Left);
WriteTrie(bvStream, x.Right);
}
public static string Expand(byte[] bytes)
{
int index = 0;
BitArray bits = new BitArray(bytes);
BitVirtualSteam bvStream = new BitVirtualSteam(bytes);
HuffmanNode root = ReadTrie(bvStream, ref index);
BitArray lenbs = new BitArray(32);
for (int i = 0; i < 32; i++)
{
lenbs[i] = bits[index++];
}
byte[] lenBytes = new byte[4];
lenbs.CopyTo(lenBytes, 0);
//int N = BitConverter.ToInt32(lenBytes);
int N = bvStream.ReadInt();
char[] chars = new char[N];
for (int i = 0; i < N; i++)
{
HuffmanNode x = root;
while (!x.isLeaf())
{
//一直往前读取
if (bvStream.ReadBoolean())
{
x = x.Right;
}
else
{
x = x.Left;
}
}
chars[i] = x.Ch;
}
return(string.Join("", chars));
}
