/// <summary>计算数据流校验码</summary>
/// <param name="stream"></param>
/// <param name="count"></param>
/// <returns></returns>
public static UInt32 Compute(Stream stream, Int32 count = -1)
{
var crc = new Crc32Util();
crc.Update(stream, count);
return(crc.Value);
}
/// <summary>计算校验码</summary>
/// <param name="buf"></param>
/// <param name="offset"></param>
/// <param name="count"></param>
/// <returns></returns>
public static UInt32 Compute(Byte[] buf, Int32 offset = 0, Int32 count = -1)
{
var crc = new Crc32Util();
crc.Update(buf, offset, count);
return(crc.Value);
}
/// <summary>计算数据流校验码，指定起始位置和字节数偏移量</summary>
/// <remarks>
/// 一般用于计算数据包校验码，需要回过头去开始校验，并且可能需要跳过最后的校验码长度。
/// position小于0时，数据流从当前位置开始计算校验；
/// position大于等于0时，数据流移到该位置开始计算校验，最后由count决定可能差几个字节不参与计算；
/// </remarks>
/// <param name="stream"></param>
/// <param name="position">如果大于等于0，则表示从该位置开始计算</param>
/// <param name="count">字节数偏移量，一般用负数表示</param>
/// <returns></returns>
public static UInt32 ComputeRange(Stream stream, Int64 position = -1, Int32 count = -1)
{
if (position >= 0)
{
if (count > 0)
{
count = -count;
}
count += (Int32)(stream.Position - position);
if (count == 0)
{
return(0);
}
stream.Position = position;
}
var crc = new Crc32Util();
crc.Update(stream, count);
return(crc.Value);
}