问题描述
我在字符串中有一些数据.我有一个将流作为输入的函数.我想将数据提供给函数,而不必将完整的字符串复制到流中.本质上,我正在寻找可以包装字符串并从中读取的流类.
I have some data in a string. I have a function that takes a stream as input. I want to provide my data to my function without having to copy the complete string into a stream. Essentially I'm looking for a stream class that can wrap a string and read from it.
我在网上看到的唯一建议是不是一个流的StringReader,或者创建一个内存流并对其进行写入,这意味着复制数据.我可以编写自己的流对象,但棘手的部分是处理编码,因为流以字节为单位.有没有一种方法而无需编写新的流类?
The only suggestions I've seen online suggest the StringReader which is NOT a stream, or creating a memory stream and writing to it, which means copying the data. I could write my own stream object but the tricky part is handling encoding because a stream deals in bytes. Is there a way to do this without writing new stream classes?
我正在BizTalk中实现管道组件. BizTalk完全通过流处理所有内容,因此您总是将内容通过流传递给BizTalk. BizTalk将始终以小块的形式从该流中读取,因此,如果我可以从流中读取BizTalk的需求,则将整个字符串复制到流中(特别是如果字符串很大的话)是没有意义的.
I'm implementing pipeline components in BizTalk. BizTalk deals with everything entirely with streams, so you always pass things to BizTalk in a stream. BizTalk will always read from that stream in small chunks, so it doesn't make sense to copy the entire string to a stream (especially if the string is large), if I can read from the stream how BizTalk wants it.
推荐答案
这是一个适当的StringReaderStream
,具有以下缺点:
Here is a proper StringReaderStream
with following drawbacks:
-
Read
的缓冲区长度必须至少为maxBytesPerChar
.通过保留内部一个charbuff = new byte[maxBytesPerChar]
,可以为小型缓冲区实现Read
.但是对于大多数用法而言,并不是必须的. - 否
Seek
,可以进行搜索,但一般来说会非常棘手. (有些寻求案例,例如寻求开始,寻求结束,很容易实现.)
- The buffer for
Read
has to be at leastmaxBytesPerChar
long. It's possible to implementRead
for small buffers by keeping internal one charbuff = new byte[maxBytesPerChar]
. But's not necessary for most usages. - No
Seek
, it's possible to do seek, but would be very tricky generaly. (Some seek cases, like seek to beginning, seek to end, are simple to implement. )
/// <summary>
/// Convert string to byte stream.
/// <para>
/// Slower than <see cref="Encoding.GetBytes()"/>, but saves memory for a large string.
/// </para>
/// </summary>
public class StringReaderStream : Stream
{
private string input;
private readonly Encoding encoding;
private int maxBytesPerChar;
private int inputLength;
private int inputPosition;
private readonly long length;
private long position;
public StringReaderStream(string input)
: this(input, Encoding.UTF8)
{ }
public StringReaderStream(string input, Encoding encoding)
{
this.encoding = encoding ?? throw new ArgumentNullException(nameof(encoding));
this.input = input;
inputLength = input == null ? 0 : input.Length;
if (!string.IsNullOrEmpty(input))
length = encoding.GetByteCount(input);
maxBytesPerChar = encoding == Encoding.ASCII ? 1 : encoding.GetMaxByteCount(1);
}
public override bool CanRead => true;
public override bool CanSeek => false;
public override bool CanWrite => false;
public override long Length => length;
public override long Position
{
get => position;
set => throw new NotImplementedException();
}
public override void Flush()
{
}
public override int Read(byte[] buffer, int offset, int count)
{
if (inputPosition >= inputLength)
return 0;
if (count < maxBytesPerChar)
throw new ArgumentException("count has to be greater or equal to max encoding byte count per char");
int charCount = Math.Min(inputLength - inputPosition, count / maxBytesPerChar);
int byteCount = encoding.GetBytes(input, inputPosition, charCount, buffer, offset);
inputPosition += charCount;
position += byteCount;
return byteCount;
}
public override long Seek(long offset, SeekOrigin origin)
{
throw new NotImplementedException();
}
public override void SetLength(long value)
{
throw new NotImplementedException();
}
public override void Write(byte[] buffer, int offset, int count)
{
throw new NotImplementedException();
}
}
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