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[英]What is the difference between calling Stream.Write and using a StreamWriter?
[英]Using StreamWriter to write in a Stream (for large Stream encryption)
我正在关注Rijndael加密的MSDN示例 ,只是我想加密并返回一个流。
以下不起作用。
它没有抛出任何异常,但在单步执行代码后,返回值没有数据。
public static Stream EncryptStream(Stream plainStream, byte[] Key, byte[] IV)
{
var encrypted = new MemoryStream()
// Create an RijndaelManaged object
// with the specified key and IV.
using (RijndaelManaged rijAlg = new RijndaelManaged())
{
rijAlg.Key = Key;
rijAlg.IV = IV;
// Create a decrytor to perform the stream transform.
ICryptoTransform encryptor = rijAlg.CreateEncryptor(rijAlg.Key, rijAlg.IV);
// Create the streams used for encryption.
using (MemoryStream msEncrypt = new MemoryStream())
{
using (CryptoStream csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))
{
using (StreamWriter swEncrypt = new StreamWriter(csEncrypt))
{
//Write all data to the stream.
swEncrypt.Write(plainStream);
}
msEncrypt.CopyTo(encrypted);
}
}
}
return encrypted;
}
我查看了Stream.Writer类的文档 ,认为它与它有关,不支持写入Stream。
我注意到有一个'对象'类型参数,所以我假设它会工作......这是正确的吗? 如果没有,我该怎么办?
顺便说一句,我将FileStream传递给它。 逐步执行代码,plainStream确实包含数据。
以下是一些加密和解密流的示例函数(用您喜欢的算法替换算法):
public static void Decrypt(Stream input, Stream output, byte[] key, byte[] iv)
{
using (SymmetricAlgorithm algo = SymmetricAlgorithm.Create()) // Creates the default implementation, which is RijndaelManaged.
{
using (CryptoStream stream = new CryptoStream(input, algo.CreateDecryptor(key, iv), CryptoStreamMode.Read))
{
byte[] bytes = new byte[16];
int read;
do
{
read = stream.Read(bytes, 0, bytes.Length);
output.Write(bytes, 0, read);
}
while (read > 0);
}
}
}
public static void Encrypt(Stream input, Stream output, byte[] key, byte[] iv)
{
using (SymmetricAlgorithm algo = SymmetricAlgorithm.Create()) //Creates the default implementation, which is RijndaelManaged.
{
using (CryptoStream stream = new CryptoStream(output, algo.CreateEncryptor(key, iv), CryptoStreamMode.Write))
{
byte[] bytes = new byte[16];
int read;
do
{
read = input.Read(bytes, 0, bytes.Length);
stream.Write(bytes, 0, read);
}
while (read > 0);
}
}
}
您可以将它们与任何输出流一起使用。 如果你想写一个大的输出流,你可以直接使用那个输出流(例如FileStream或ASP.NET Response.OutputStream等),你不应该使用一个中间的MemoryStream,它会消耗内存而不是真正的目的。
话虽这么说,如果你真的想使用MemoryStream,你会这样做:
MemoryStream output = new MemoryStream();
Encrypt(input, output, key, iv);
output.Position = 0; // rewind the stream, so you can use it from the beginning
使用流级别复制将一个流的内容复制到另一个流或使用相应的读/写器对(如TextReader
/ TextWriter
) - 如果混合比最有可能得到错误的结果。 即流级副本:
plainStream.CopyTo(csEncrypt);
除了实际将数据写入加密流(而不是由于StreamWrite.Write(Object)
调用而得到的plainStream
的类型名称)之外,您应该使用MemoryStream.ToArray
来复制结果内容 - 否则您将获得“对象处置异常” 。
复制代码应如下所示,而不是msEncrypt.CopyTo(encrypted);
var bytes = msEncrypt.ToArray();
encrypted.Write(bytes, 0, bytes.Length);
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