C# 将char[]缓冲区传递给XmlSerializer
我有一个存储在char数组中的XML-C# 将char[]缓冲区传递给XmlSerializer,c#,xmlserializer,C#,Xmlserializer,我有一个存储在char数组中的XML-char[],我有一个int变量中的数据内容长度。我需要用XmlSerializer反序列化数据 出于性能方面的原因,我需要避免分配字符串对象,因为数据通常大于85kb,并且会导致Gen2对象 有没有办法将char[]传递给XmlSerializer,而不将其转换为字符串?它接受流或文本阅读器,但我找不到从char[]构造一个的方法 我在想象这样的事情(除了C#没有Chararray流或Chararray Reader): 正如更多信息一样,我们在分析现有代
char[]
,我有一个int变量中的数据内容长度。我需要用XmlSerializer反序列化数据
出于性能方面的原因,我需要避免分配字符串对象,因为数据通常大于85kb,并且会导致Gen2对象
有没有办法将char[]传递给XmlSerializer
,而不将其转换为字符串?它接受流
或文本阅读器
,但我找不到从char[]
构造一个的方法
我在想象这样的事情(除了C#没有Chararray流或Chararray Reader):
正如更多信息一样,我们在分析现有代码时发现了一个难点,因此这不是“过早优化”或“XY问题”。我重新编写了@György Kőszeg链接到类ChararyStream的代码。到目前为止,这在我的测试中有效:
public class CharArrayStream : Stream
{
private readonly char[] str;
private readonly int n;
public override bool CanRead => true;
public override bool CanSeek => true;
public override bool CanWrite => false;
public override long Length => n;
public override long Position { get; set; } // TODO: bounds check
public CharArrayStream(char[] str, int n)
{
this.str = str;
this.n = n;
}
public override long Seek(long offset, SeekOrigin origin)
{
switch (origin)
{
case SeekOrigin.Begin:
Position = offset;
break;
case SeekOrigin.Current:
Position += offset;
break;
case SeekOrigin.End:
Position = Length - offset;
break;
}
return Position;
}
private byte this[int i] => (byte)str[i];
public override int Read(byte[] buffer, int offset, int count)
{
// TODO: bounds check
var len = Math.Min(count, Length - Position);
for (int i = 0; i < len; i++)
{
buffer[offset++] = this[(int)(Position++)];
}
return (int)len;
}
public override int ReadByte() => Position >= Length ? -1 : this[(int)Position++];
public override void Flush() { }
public override void SetLength(long value) => throw new NotSupportedException();
public override void Write(byte[] buffer, int offset, int count) => throw new NotSupportedException();
public override string ToString() => throw new NotSupportedException();
}
谢谢,@György Kőszeg 将
TextReader
子类化以读取字符数组或等效字符非常简单。这是一个采用a的版本,它可以表示字符串
或char[]
字符数组的一部分:
public sealed class CharMemoryReader : TextReader
{
private ReadOnlyMemory<char> chars;
private int position;
public CharMemoryReader(ReadOnlyMemory<char> chars)
{
this.chars = chars;
this.position = 0;
}
void CheckClosed()
{
if (position < 0)
throw new ObjectDisposedException(null, string.Format("{0} is closed.", ToString()));
}
public override void Close() => Dispose(true);
protected override void Dispose(bool disposing)
{
chars = ReadOnlyMemory<char>.Empty;
position = -1;
base.Dispose(disposing);
}
public override int Peek()
{
CheckClosed();
return position >= chars.Length ? -1 : chars.Span[position];
}
public override int Read()
{
CheckClosed();
return position >= chars.Length ? -1 : chars.Span[position++];
}
public override int Read(char[] buffer, int index, int count)
{
CheckClosed();
if (buffer == null)
throw new ArgumentNullException(nameof(buffer));
if (index < 0)
throw new ArgumentOutOfRangeException(nameof(index));
if (count < 0)
throw new ArgumentOutOfRangeException(nameof(count));
if (buffer.Length - index < count)
throw new ArgumentException("buffer.Length - index < count");
return Read(buffer.AsSpan().Slice(index, count));
}
public override int Read(Span<char> buffer)
{
CheckClosed();
var nRead = chars.Length - position;
if (nRead > 0)
{
if (nRead > buffer.Length)
nRead = buffer.Length;
chars.Span.Slice(position, nRead).CopyTo(buffer);
position += nRead;
}
return nRead;
}
public override string ReadToEnd()
{
CheckClosed();
var s = position == 0 ? chars.ToString() : chars.Slice(position, chars.Length - position).ToString();
position = chars.Length;
return s;
}
public override string ReadLine()
{
CheckClosed();
var span = chars.Span;
var i = position;
for( ; i < span.Length; i++)
{
var ch = span[i];
if (ch == '\r' || ch == '\n')
{
var result = span.Slice(position, i - position).ToString();
position = i + 1;
if (ch == '\r' && position < span.Length && span[position] == '\n')
position++;
return result;
}
}
if (i > position)
{
var result = span.Slice(position, i - position).ToString();
position = i;
return result;
}
return null;
}
public override int ReadBlock(char[] buffer, int index, int count) => Read(buffer, index, count);
public override int ReadBlock(Span<char> buffer) => Read(buffer);
public override Task<String> ReadLineAsync() => Task.FromResult(ReadLine());
public override Task<String> ReadToEndAsync() => Task.FromResult(ReadToEnd());
public override Task<int> ReadBlockAsync(char[] buffer, int index, int count) => Task.FromResult(ReadBlock(buffer, index, count));
public override Task<int> ReadAsync(char[] buffer, int index, int count) => Task.FromResult(Read(buffer, index, count));
public override ValueTask<int> ReadBlockAsync(Memory<char> buffer, CancellationToken cancellationToken = default) =>
cancellationToken.IsCancellationRequested ? new ValueTask<int>(Task.FromCanceled<int>(cancellationToken)) : new ValueTask<int>(ReadBlock(buffer.Span));
public override ValueTask<int> ReadAsync(Memory<char> buffer, CancellationToken cancellationToken = default) =>
cancellationToken.IsCancellationRequested ? new ValueTask<int>(Task.FromCanceled<int>(cancellationToken)) : new ValueTask<int>(Read(buffer.Span));
}
公共密封类CharMemoryReader:TextReader
{
私人只读存储器;
私人职位;
公共角色MemoryReader(只读内存角色)
{
this.chars=chars;
这个位置=0;
}
void CheckClosed()
{
如果(位置<0)
抛出新的ObjectDisposedException(null,string.Format(“{0}已关闭。”,ToString());
}
public override void Close()=>Dispose(true);
受保护的覆盖无效处置(布尔处置)
{
chars=ReadOnlyMemory.Empty;
位置=-1;
基地。处置(处置);
}
公共覆盖int Peek()
{
CheckClosed();
返回位置>=字符长度?-1:字符跨度[位置];
}
公共覆盖int Read()
{
CheckClosed();
返回位置>=字符长度?-1:字符跨度[position++];
}
公共重写整型读取(字符[]缓冲区,整型索引,整型计数)
{
CheckClosed();
if(buffer==null)
抛出新ArgumentNullException(nameof(buffer));
如果(指数<0)
抛出新ArgumentOutOfRangeException(nameof(index));
如果(计数<0)
抛出新ArgumentOutOfRangeException(nameof(count));
if(buffer.Length-索引<计数)
抛出新的ArgumentException(“buffer.Length-index0)
{
如果(nRead>buffer.Length)
nRead=缓冲区长度;
字符跨度切片(位置,nRead).CopyTo(缓冲区);
位置+=nRead;
}
返回nRead;
}
公共重写字符串ReadToEnd()
{
CheckClosed();
var s=position==0?chars.ToString():chars.Slice(position,chars.Length-position).ToString();
位置=字符长度;
返回s;
}
公共重写字符串读取行()
{
CheckClosed();
var span=字符span;
var i=位置;
对于(;i位置)
{
var result=span.Slice(位置,i-position).ToString();
位置=i;
返回结果;
}
返回null;
}
公共重写int ReadBlock(char[]缓冲区,int索引,int计数)=>Read(缓冲区,索引,计数);
公共覆盖int ReadBlock(Span buffer)=>读取(buffer);
公共重写任务ReadLineSync()=>Task.FromResult(ReadLine());
公共重写任务ReadToEndAsync()=>Task.FromResult(ReadToEnd());
public override Task ReadBlockAsync(char[]buffer,int index,int count)=>Task.FromResult(ReadBlock(buffer,index,count));
public override Task ReadAsync(char[]buffer,int index,int count)=>Task.FromResult(Read(buffer,index,count));
public override ValueTask ReadBlockAsync(内存缓冲区,CancellationToken CancellationToken=default)=>
cancellationToken.IsCancellationRequested?新值任务(Task.FromCancelled(cancellationToken)):新值任务(ReadBlock(buffer.Span));
public override ValueTask ReadAsync(内存缓冲区,CancellationToken CancellationToken=default)=>
cancellationToken.IsCancellationRequested?新的ValueTask(Task.FromCancelled(cancellationToken)):新的ValueTask(Read(buffer.Span));
}
然后将其与以下扩展方法之一一起使用:
public static partial class XmlSerializationHelper
{
public static T LoadFromXml<T>(this char [] xml, int contentLength, XmlSerializer serial = null) =>
new ReadOnlyMemory<char>(xml, 0, contentLength).LoadFromXml<T>(serial);
public static T LoadFromXml<T>(this ReadOnlyMemory<char> xml, XmlSerializer serial = null)
{
serial = serial ?? new XmlSerializer(typeof(T));
using (var reader = new CharMemoryReader(xml))
return (T)serial.Deserialize(reader);
}
}
公共静态部分类XmlSerializationHelper
{
公共静态T LoadFromXml(此字符[]xml,int contentLength,XmlSerializer serial=null)=>
新的ReadOnlyMemory(xml,0,contentLength);
公共静态T LoadFromXml(此只读内存xml,XmlSerializer serial=null)
{
串行=串行??新的XmlSerializer(typeof(T));
使用(var reader=new CharMemoryReader(xml))
返回(T)串行。反序列化(读取器);
}
}
例如
var result=buffer.LoadFromXml(contentLength,\u xmlSerializer);
注:
字符数组的内容基本上与不带字符的UTF-16编码内存流相同,因此可以创建一个自定义char[]
实现流
public sealed class CharMemoryReader : TextReader { private ReadOnlyMemory<char> chars; private int position; public CharMemoryReader(ReadOnlyMemory<char> chars) { this.chars = chars; this.position = 0; } void CheckClosed() { if (position < 0) throw new ObjectDisposedException(null, string.Format("{0} is closed.", ToString())); } public override void Close() => Dispose(true); protected override void Dispose(bool disposing) { chars = ReadOnlyMemory<char>.Empty; position = -1; base.Dispose(disposing); } public override int Peek() { CheckClosed(); return position >= chars.Length ? -1 : chars.Span[position]; } public override int Read() { CheckClosed(); return position >= chars.Length ? -1 : chars.Span[position++]; } public override int Read(char[] buffer, int index, int count) { CheckClosed(); if (buffer == null) throw new ArgumentNullException(nameof(buffer)); if (index < 0) throw new ArgumentOutOfRangeException(nameof(index)); if (count < 0) throw new ArgumentOutOfRangeException(nameof(count)); if (buffer.Length - index < count) throw new ArgumentException("buffer.Length - index < count"); return Read(buffer.AsSpan().Slice(index, count)); } public override int Read(Span<char> buffer) { CheckClosed(); var nRead = chars.Length - position; if (nRead > 0) { if (nRead > buffer.Length) nRead = buffer.Length; chars.Span.Slice(position, nRead).CopyTo(buffer); position += nRead; } return nRead; } public override string ReadToEnd() { CheckClosed(); var s = position == 0 ? chars.ToString() : chars.Slice(position, chars.Length - position).ToString(); position = chars.Length; return s; } public override string ReadLine() { CheckClosed(); var span = chars.Span; var i = position; for( ; i < span.Length; i++) { var ch = span[i]; if (ch == '\r' || ch == '\n') { var result = span.Slice(position, i - position).ToString(); position = i + 1; if (ch == '\r' && position < span.Length && span[position] == '\n') position++; return result; } } if (i > position) { var result = span.Slice(position, i - position).ToString(); position = i; return result; } return null; } public override int ReadBlock(char[] buffer, int index, int count) => Read(buffer, index, count); public override int ReadBlock(Span<char> buffer) => Read(buffer); public override Task<String> ReadLineAsync() => Task.FromResult(ReadLine()); public override Task<String> ReadToEndAsync() => Task.FromResult(ReadToEnd()); public override Task<int> ReadBlockAsync(char[] buffer, int index, int count) => Task.FromResult(ReadBlock(buffer, index, count)); public override Task<int> ReadAsync(char[] buffer, int index, int count) => Task.FromResult(Read(buffer, index, count)); public override ValueTask<int> ReadBlockAsync(Memory<char> buffer, CancellationToken cancellationToken = default) => cancellationToken.IsCancellationRequested ? new ValueTask<int>(Task.FromCanceled<int>(cancellationToken)) : new ValueTask<int>(ReadBlock(buffer.Span)); public override ValueTask<int> ReadAsync(Memory<char> buffer, CancellationToken cancellationToken = default) => cancellationToken.IsCancellationRequested ? new ValueTask<int>(Task.FromCanceled<int>(cancellationToken)) : new ValueTask<int>(Read(buffer.Span)); }
public static partial class XmlSerializationHelper { public static T LoadFromXml<T>(this char [] xml, int contentLength, XmlSerializer serial = null) => new ReadOnlyMemory<char>(xml, 0, contentLength).LoadFromXml<T>(serial); public static T LoadFromXml<T>(this ReadOnlyMemory<char> xml, XmlSerializer serial = null) { serial = serial ?? new XmlSerializer(typeof(T)); using (var reader = new CharMemoryReader(xml)) return (T)serial.Deserialize(reader); } }
var result = buffer.LoadFromXml<MyEntity>(contentLength, _xmlSerializer);