[英]Appending to MemoryStream
我正在尝试将一些数据附加到流中。 这适用于FileStream
,但由于固定的缓冲区大小,因此不适用于MemoryStream
。
将数据写入流的方法与创建流的方法分开(我在下面的例子中大大简化了它)。 创建流的方法不知道要写入流的数据长度。
public void Foo(){
byte[] existingData = System.Text.Encoding.UTF8.GetBytes("foo");
Stream s1 = new FileStream("someFile.txt", FileMode.Append, FileAccess.Write, FileShare.Read);
s1.Write(existingData, 0, existingData.Length);
Stream s2 = new MemoryStream(existingData, 0, existingData.Length, true);
s2.Seek(0, SeekOrigin.End); //move to end of the stream for appending
WriteUnknownDataToStream(s1);
WriteUnknownDataToStream(s2); // NotSupportedException is thrown as the MemoryStream is not expandable
}
public static void WriteUnknownDataToStream(Stream s)
{
// this is some example data for this SO query - the real data is generated elsewhere and is of a variable, and often large, size.
byte[] newBytesToWrite = System.Text.Encoding.UTF8.GetBytes("bar"); // the length of this is not known before the stream is created.
s.Write(newBytesToWrite, 0, newBytesToWrite.Length);
}
我的想法是向函数发送可扩展的MemoryStream
,然后将返回的数据附加到现有数据。
public void ModifiedFoo()
{
byte[] existingData = System.Text.Encoding.UTF8.GetBytes("foo");
Stream s2 = new MemoryStream(); // expandable capacity memory stream
WriteUnknownDataToStream(s2);
// append the data which has been written into s2 to the existingData
byte[] buffer = new byte[existingData.Length + s2.Length];
Buffer.BlockCopy(existingData, 0, buffer, 0, existingData.Length);
Stream merger = new MemoryStream(buffer, true);
merger.Seek(existingData.Length, SeekOrigin.Begin);
s2.CopyTo(merger);
}
任何更好(更有效)的解决方案?
可能的解决方案不是首先限制MemoryStream
的容量。 如果您事先不知道需要写入的总字节数,请创建一个具有未指定容量的MemoryStream
,并将其用于两次写入。
byte[] existingData = System.Text.Encoding.UTF8.GetBytes("foo");
MemoryStream ms = new MemoryStream();
ms.Write(existingData, 0, existingData.Length);
WriteUnknownData(ms);
毫无疑问,这比从byte[]
初始化MemoryStream
要差一些,但如果你需要继续写入流,我相信这是你唯一的选择。
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