最好使用Stream：
public static Byte[] ReadMMFAllBytes(string fileName)
{
using (var mmf = MemoryMappedFile.OpenExisting(fileName))
{
using (var stream = mmf.CreateViewStream())
{
using (BinaryReader binReader = new BinaryReader(stream))
{
return binReader.ReadBytes((int)stream.Length);
}
}
}
}
如果以上所有内容都适用于您的应用程序，则以下代码应该有效：
static byte[] ReadMemoryMappedFile(string fileName)
{
long length = new FileInfo(fileName).Length;
using (var stream = File.Open(fileName, FileMode.OpenOrCreate, FileAccess.Read, FileShare.ReadWrite))
{
using (var mmf = MemoryMappedFile.CreateFromFile(stream, null, length, MemoryMappedFileAccess.Read, null, HandleInheritability.Inheritable, false))
{
using (var viewStream = mmf.CreateViewStream(0, length, MemoryMappedFileAccess.Read))
{
using (BinaryReader binReader = new BinaryReader(viewStream))
{
var result = binReader.ReadBytes((int)length);
return result;
}
}
}
}
}
你可以使用以下内容来写入数据:
private static void WriteData(string fileName, byte[] data)
{
using (var stream = File.Open(fileName, FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.ReadWrite))
{
using (var mmf = MemoryMappedFile.CreateFromFile(stream, null, data.Length, MemoryMappedFileAccess.ReadWrite, null, HandleInheritability.Inheritable, true))
{
using (var view = mmf.CreateViewAccessor())
{
view.WriteArray(0, data, 0, data.Length);
}
}
stream.SetLength(data.Length); // Make sure the file is the correct length, in case the data got smaller.
}
}
但是，如果您按照上述步骤进行操作，您可能会直接使用文件并避免内存映射。 如果将其映射到文件系统不可接受，则Guffa的答案是在数据本身中编码长度（或结束标记）。
你不能这样做。
视图访问器创建时会设置一个系统页面的最小大小，这意味着它可能比实际文件要大。视图流只是访问器的流形式，因此它也会产生相同的行为。
"视图以系统页面为单位提供，并且视图的大小将向上舍入到下一个系统页面大小"
http://msdn.microsoft.com/en-us/library/dd267577.aspx
访问器会在不抛出异常的情况下愉快地读取和写入实际文件之外的内容。在读取时，文件之外的任何字节都将被视为零。在写入时，写入文件之外的字节将被忽略。
要从具有与原始文件完全相同大小的内存映射文件中读取文件，您必须已经知道该大小。
使用MemoryMappedFile创建的流长度与文件系统页面大小对齐（通常为4096），您需要从其他地方获取文件大小。如果是内存映射文件，则可以使用以下代码：
byte[] ReadAllMemoryMappedFileBytes(string filePath)
{
var fileInfo = new FileInfo(filePath);
using (var file = MemoryMappedFile.CreateFromFile(filePath, FileMode.Open))
using (var stream = file.CreateViewAccessor())
{
byte[] bytes = new byte[fileInfo.Length];
stream.ReadArray(0, bytes, 0, bytes.Length);
return bytes;
}
}
using System.Data;
using System.IO;
using System.IO.Compression;
using System.IO.MemoryMappedFiles;
// ...
public void WriteToMemoryMap(DataSet ds, string key, string fileName)
{
var bytes = CompressData(ds);
using (MemoryMappedFile objMf = MemoryMappedFile.CreateFromFile(fileName, FileMode.OpenOrCreate, key, bytes.Length))
{
using (MemoryMappedViewAccessor accessor = objMf.CreateViewAccessor())
{
accessor.WriteArray(0, bytes, 0, bytes.Length);
}
}
}
public DataSet ReadFromMemoryMap(string fileName)
{
var fi = new FileInfo(fileName);
var length = (int)fi.Length;
var newBytes = new byte[length];
using (MemoryMappedFile objMf = MemoryMappedFile.CreateFromFile(fileName, FileMode.Open))
{
using (MemoryMappedViewAccessor accessor = objMf.CreateViewAccessor())
{
accessor.ReadArray(0, newBytes, 0, length);
}
}
return DecompressData(newBytes);
}
public byte[] CompressData(DataSet ds)
{
try
{
byte[] data = null;
var memStream = new MemoryStream();
var zipStream = new GZipStream(memStream, CompressionMode.Compress);
ds.WriteXml(zipStream, XmlWriteMode.WriteSchema);
zipStream.Close();
data = memStream.ToArray();
memStream.Close();
return data;
}
catch (Exception)
{
return null;
}
}
public DataSet DecompressData(byte[] data)
{
try
{
var memStream = new MemoryStream(data);
var unzipStream = new GZipStream(memStream, CompressionMode.Decompress);
var objDataSet = new DataSet();
objDataSet.ReadXml(unzipStream, XmlReadMode.ReadSchema);
unzipStream.Close();
memStream.Close();
return objDataSet;
}
catch (Exception)
{
return null;
}
}
using (MemoryMappedFile mmf = MemoryMappedFile.OpenExisting(MemoryMappedName))
{
using (MemoryMappedViewStream stream = mmf.CreateViewStream())
{
using (MemoryStream memStream = new MemoryStream())
{
stream.CopyTo(memStream);
return memStream.ToArray();
}
}
}
干杯！
' Usage Example:
' Dim ReadBytes As Byte() = ReadMemoryMappedFile(Name:="My MemoryMappedFile Name") ' Read the byte-sequence from memory.
' Dim Message As String = System.Text.Encoding.ASCII.GetString(ReadBytes.ToArray) ' Convert the bytes to String.
' Message = Message.Trim({ControlChars.NullChar}) ' Remove null chars (leading zero-bytes)
' MessageBox.Show(Message, "", MessageBoxButtons.OK) ' Show the message. '
'
''' <summary>
''' Reads a byte-sequence from a <see cref="IO.MemoryMappedFiles.MemoryMappedFile"/> without knowing the exact size.
''' Note that the returned byte-length is rounded up to 4kb,
''' this means if the mapped memory-file was written with 1 byte-length, this method will return 4096 byte-length.
''' </summary>
''' <param name="Name">Indicates an existing <see cref="IO.MemoryMappedFiles.MemoryMappedFile"/> assigned name.</param>
''' <returns>System.Byte().</returns>
Private Function ReadMemoryMappedFile(ByVal Name As String) As Byte()
Try
Using MemoryFile As IO.MemoryMappedFiles.MemoryMappedFile =
IO.MemoryMappedFiles.MemoryMappedFile.OpenExisting(Name, IO.MemoryMappedFiles.MemoryMappedFileRights.ReadWrite)
Using Stream = MemoryFile.CreateViewStream()
Using Reader As New BinaryReader(Stream)
Return Reader.ReadBytes(CInt(Stream.Length))
End Using ' Reader
End Using ' Stream
End Using ' MemoryFile
Catch exNoFile As IO.FileNotFoundException
Throw
Return Nothing
Catch ex As Exception
Throw
End Try
End Function