从结尾截断长度未知的x字节流?(.NET)
我需要读取长度未知的流,不包括最后20个字节(散列数据)。设置大致如下: 源流(SHA1哈希最后20个字节)->SHA1哈希流(动态计算并在流结束时与嵌入式流哈希进行比较)->AES解密流->对数据进行填充 我不能在处理之前缓冲整个源流,因为它可能有很多GB,这一切都需要在运行中进行。源流不可查找。目前,SHA1流正在将最后20个字节读入它的缓冲区,这会破坏一切,我不知道有什么方法可以控制这种行为 我在考虑在源和SHA1流之间插入一个包装流,实现一个滚动缓冲区(?),将源流以4096字节的块形式呈现给AES包装器,然后在上次读取之前20字节“伪造”流的结尾。然后,20字节的散列将通过属性公开 这是最好的解决方案吗?我将如何实施它 粗略的代码流程如下(从内存中,可能无法编译): 编辑:流格式如下:从结尾截断长度未知的x字节流?(.NET),.net,stream,buffer,cryptostream,.net,Stream,Buffer,Cryptostream,我需要读取长度未知的流,不包括最后20个字节(散列数据)。设置大致如下: 源流(SHA1哈希最后20个字节)->SHA1哈希流(动态计算并在流结束时与嵌入式流哈希进行比较)->AES解密流->对数据进行填充 我不能在处理之前缓冲整个源流,因为它可能有很多GB,这一切都需要在运行中进行。源流不可查找。目前,SHA1流正在将最后20个字节读入它的缓冲区,这会破坏一切,我不知道有什么方法可以控制这种行为 我在考虑在源和SHA1流之间插入一个包装流,实现一个滚动缓冲区(?),将源流以4096字节的块形式
[ StreamFormat | String | Required ]
[ WrapperFlags | 8 Bit BitArray | Required ]
[ Sha1 Hashed Data Wrapper | Optional ]
[ AesIV | 16 Bytes | Required if Aes Encrypted ]
[ Aes Encrypted Data Wrapper | Optional ]
[ Gzip Compressed Data Wrapper | Optional ]
[ Payload Data | Binary | Required ]
[ End Gzip Compressed Data ]
[ End Aes Encrypted Data ]
[ End Sha1 Hashed Data ]
[ Sha1HashValue | 20 Bytes | Required if Sha1 Hashed ]
我已经给你写了一个快速的小数据流,可以提前缓冲20个字节。我唯一正确覆盖的真正实现是
Read()
成员,您可能需要根据您的情况检查其他Stream
成员。还有一个免费的测试类!奖金!我对它进行了更彻底的测试,但您可以根据自己的意愿调整这些测试用例。哦,顺便说一下,我没有测试长度小于20字节的流
测试用例
流类
公共类流,其在最终20字节之前:流
{
私有只读流sourceStream;
专用静态int tailbytescont=20;
最终20字节之前的公共流(流源流)
{
this.sourceStream=sourceStream;
}
公共字节[]TailBytes{get{return previousTailBuffer;}}
公共覆盖无效刷新()
{
sourceStream.Flush();
}
公共覆盖长寻道(长偏移,参见原始坐标系)
{
返回sourceStream.Seek(偏移量、原点);
}
公共覆盖无效设置长度(长值)
{
sourceStream.SetLength(值);
}
专用字节[]previousTailBuffer;
公共重写整型读取(字节[]缓冲区、整型偏移量、整型计数)
{
字节[]tailBuffer=新字节[tailbytescont];
int预期字节读取;
如果(previousTailBuffer==null)
expectedBytesRead=count+TailBytesCount;
其他的
expectedBytesRead=计数;
尝试
{
字节[]读取缓冲区=新字节[expectedBytesRead];
int actualBytesRead=sourceStream.Read(readBuffer、offset、expectedBytesRead);
如果(actualBytesRead==0)返回0;
如果(实际字节数<尾字节数)
{
int pickPreviousByteCount=尾字节计数-实际字节数;
如果(previousTailBuffer!=null)
{
int pickFromIndex=previousTailBuffer.Length-pickPreviousByteCount;
数组.Copy(previousTailBuffer,0,buffer,offset,count);
复制(previousTailBuffer、pickFromIndex、tailBuffer、0、pickPreviousByteCount);
}
复制(readBuffer,0,tailBuffer,pickPreviousByteCount,actualBytesRead);
返回实际字节数;
}
Copy(readBuffer,actualBytesRead-TailBytesCount,tailBuffer,0,TailBytesCount);
Copy(readBuffer,0,buffer,offset,actualBytesRead-TailBytesCount);
如果(实际字节读取<预期字节读取)
{
返回实际字节读取-尾字节计数;
}
返回计数;
}
最后
{
previousTailBuffer=tailBuffer;
}
}
公共重写无效写入(字节[]缓冲区、整数偏移量、整数计数)
{
写入(缓冲区、偏移量、计数);
}
公共覆盖布尔可读取
{
获取{return sourceStream.CanRead;}
}
公共覆盖布尔搜索
{
获取{return sourceStream.CanSeek;}
}
公共覆盖布尔可写
{
获取{return sourceStream.CanWrite;}
}
公共覆盖长长度
{
得到
{
if(sourceStream.Length
我已经为您编写了一个快速的小数据流,可以提前缓冲20个字节。我唯一正确覆盖的真正实现是Read()
成员,您可能需要根据您的情况检查其他Stream
成员。还有一个免费的测试类!奖金!我对它进行了更彻底的测试,但您可以根据自己的意愿调整这些测试用例。哦,顺便说一下,我没有测试长度小于20字节的流
测试用例
流类
公共类流,其在最终20字节之前:流
{
私有只读流sourceStream;
专用静态int tailbytescont=20;
最终20字节之前的公共流(流源流)
{
this.sourceStream=sourceStream;
}
公共字节[]TailBytes{get{return previousTailBuffer;}}
公共组织
[ StreamFormat | String | Required ]
[ WrapperFlags | 8 Bit BitArray | Required ]
[ Sha1 Hashed Data Wrapper | Optional ]
[ AesIV | 16 Bytes | Required if Aes Encrypted ]
[ Aes Encrypted Data Wrapper | Optional ]
[ Gzip Compressed Data Wrapper | Optional ]
[ Payload Data | Binary | Required ]
[ End Gzip Compressed Data ]
[ End Aes Encrypted Data ]
[ End Sha1 Hashed Data ]
[ Sha1HashValue | 20 Bytes | Required if Sha1 Hashed ]
[TestClass]
public class TruncateStreamTests
{
[TestMethod]
public void TestTruncateLast20Bytes()
{
string testInput = "This is a string.-- final 20 bytes --";
string expectedOutput = "This is a string.";
string testOutput;
using (var testStream = new StreamWhichEndsBeforeFinal20Bytes(new MemoryStream(Encoding.ASCII.GetBytes(testInput))))
using (var streamReader = new StreamReader(testStream, Encoding.ASCII))
{
testOutput = streamReader.ReadLine();
}
Assert.AreEqual(expectedOutput, testOutput);
}
[TestMethod]
public void TestTruncateLast20BytesRead3BytesAtATime()
{
string testInput = "This is a really really really really really long string, longer than all the others\n\rit even has some carriage returns in it, etc.-- final 20 bytes --";
string expectedOutput = "This is a really really really really really long string, longer than all the others\n\rit even has some carriage returns in it, etc.";
StringBuilder testOutputBuilder = new StringBuilder();
using (var testStream = new StreamWhichEndsBeforeFinal20Bytes(new MemoryStream(Encoding.ASCII.GetBytes(testInput))))
{
int bytesRead = 0;
do
{
byte[] buffer = new byte[3];
bytesRead = testStream.Read(buffer, 0, 3);
testOutputBuilder.Append(Encoding.ASCII.GetString(buffer, 0, bytesRead));
} while (bytesRead > 0);
}
Assert.AreEqual(expectedOutput, testOutputBuilder.ToString());
}
}
public class StreamWhichEndsBeforeFinal20Bytes : Stream
{
private readonly Stream sourceStream;
private static int TailBytesCount = 20;
public StreamWhichEndsBeforeFinal20Bytes(Stream sourceStream)
{
this.sourceStream = sourceStream;
}
public byte[] TailBytes { get { return previousTailBuffer; } }
public override void Flush()
{
sourceStream.Flush();
}
public override long Seek(long offset, SeekOrigin origin)
{
return sourceStream.Seek(offset, origin);
}
public override void SetLength(long value)
{
sourceStream.SetLength(value);
}
private byte[] previousTailBuffer;
public override int Read(byte[] buffer, int offset, int count)
{
byte[] tailBuffer = new byte[TailBytesCount];
int expectedBytesRead;
if (previousTailBuffer == null)
expectedBytesRead = count + TailBytesCount;
else
expectedBytesRead = count;
try
{
byte[] readBuffer = new byte[expectedBytesRead];
int actualBytesRead = sourceStream.Read(readBuffer, offset, expectedBytesRead);
if (actualBytesRead == 0) return 0;
if (actualBytesRead < TailBytesCount)
{
int pickPreviousByteCount = TailBytesCount - actualBytesRead;
if (previousTailBuffer != null)
{
int pickFromIndex = previousTailBuffer.Length - pickPreviousByteCount;
Array.Copy(previousTailBuffer, 0, buffer, offset, count);
Array.Copy(previousTailBuffer, pickFromIndex, tailBuffer, 0, pickPreviousByteCount);
}
Array.Copy(readBuffer, 0, tailBuffer, pickPreviousByteCount, actualBytesRead);
return actualBytesRead;
}
Array.Copy(readBuffer, actualBytesRead - TailBytesCount, tailBuffer, 0, TailBytesCount);
Array.Copy(readBuffer, 0, buffer, offset, actualBytesRead - TailBytesCount);
if (actualBytesRead < expectedBytesRead)
{
return actualBytesRead - TailBytesCount;
}
return count;
}
finally
{
previousTailBuffer = tailBuffer;
}
}
public override void Write(byte[] buffer, int offset, int count)
{
sourceStream.Write(buffer, offset, count);
}
public override bool CanRead
{
get { return sourceStream.CanRead; }
}
public override bool CanSeek
{
get { return sourceStream.CanSeek; }
}
public override bool CanWrite
{
get { return sourceStream.CanWrite; }
}
public override long Length
{
get
{
if (sourceStream.Length < TailBytesCount) return sourceStream.Length;
return sourceStream.Length - TailBytesCount;
}
}
public override long Position
{
get { return sourceStream.Position; }
set { sourceStream.Position = value; }
}
}