MemoryMappedFile.OpenExisting Method
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Opens an existing named memory-mapped file in system memory.
| OpenExisting(String) |
Opens an existing memory-mapped file that has the specified name in system memory. |
| OpenExisting(String, MemoryMappedFileRights) |
Opens an existing memory-mapped file that has the specified name and access rights in system memory. |
| OpenExisting(String, MemoryMappedFileRights, HandleInheritability) |
Opens an existing memory-mapped file that has the specified name, access rights, and inheritability in system memory. |
- Source:
- MemoryMappedFile.cs
- Source:
- MemoryMappedFile.cs
- Source:
- MemoryMappedFile.cs
Opens an existing memory-mapped file that has the specified name in system memory.
public:
static System::IO::MemoryMappedFiles::MemoryMappedFile ^ OpenExisting(System::String ^ mapName);[System.Runtime.Versioning.SupportedOSPlatform("windows")]
public static System.IO.MemoryMappedFiles.MemoryMappedFile OpenExisting(string mapName);public static System.IO.MemoryMappedFiles.MemoryMappedFile OpenExisting(string mapName);[<System.Runtime.Versioning.SupportedOSPlatform("windows")>]
static member OpenExisting : string -> System.IO.MemoryMappedFiles.MemoryMappedFilestatic member OpenExisting : string -> System.IO.MemoryMappedFiles.MemoryMappedFilePublic Shared Function OpenExisting (mapName As String) As MemoryMappedFileParameters
- mapName
- String
The name of the memory-mapped file.
Returns
A memory-mapped file that has the specified name.
- Attributes
Exceptions
mapName is null.
mapName is an empty string.
The file specified for mapName does not exist.
Examples
Opening a Persisted Memory-Mapped File
The following example opens a memory-mapped file named ImgA that has already been created from a file on disk (as shown in the example for the CreateFromFile(String) method).
using System;
using System.IO.MemoryMappedFiles;
using System.Runtime.InteropServices;
class Program
{
static void Main(string[] args)
{
// Assumes another process has created the memory-mapped file.
using (var mmf = MemoryMappedFile.OpenExisting("ImgA"))
{
using (var accessor = mmf.CreateViewAccessor(4000000, 2000000))
{
int colorSize = Marshal.SizeOf(typeof(MyColor));
MyColor color;
// Make changes to the view.
for (long i = 0; i < 1500000; i += colorSize)
{
accessor.Read(i, out color);
color.Brighten(20);
accessor.Write(i, ref color);
}
}
}
}
}
public struct MyColor
{
public short Red;
public short Green;
public short Blue;
public short Alpha;
// Make the view brigher.
public void Brighten(short value)
{
Red = (short)Math.Min(short.MaxValue, (int)Red + value);
Green = (short)Math.Min(short.MaxValue, (int)Green + value);
Blue = (short)Math.Min(short.MaxValue, (int)Blue + value);
Alpha = (short)Math.Min(short.MaxValue, (int)Alpha + value);
}
}
Imports System.IO.MemoryMappedFiles
Imports System.Runtime.InteropServices
Class Program
Public Shared Sub Main(ByVal args As String())
' Assumes another process has created the memory-mapped file.
Using mmf = MemoryMappedFile.OpenExisting("ImgA")
Using accessor = mmf.CreateViewAccessor(4000000, 2000000)
Dim colorSize As Integer = Marshal.SizeOf(GetType(MyColor))
Dim color As MyColor
' Make changes to the view.
Dim i As Long = 0
While i < 1500000
accessor.Read(i, color)
color.Brighten(30)
accessor.Write(i, color)
i += colorSize
End While
End Using
End Using
End Sub
End Class
Public Structure MyColor
Public Red As Short
Public Green As Short
Public Blue As Short
Public Alpha As Short
' Make the view brigher.
Public Sub Brighten(ByVal value As Short)
Red = CShort(Math.Min(Short.MaxValue, CInt(Red) + value))
Green = CShort(Math.Min(Short.MaxValue, CInt(Green) + value))
Blue = CShort(Math.Min(Short.MaxValue, CInt(Blue) + value))
Alpha = CShort(Math.Min(Short.MaxValue, CInt(Alpha) + value))
End Sub
End Structure
Opening a Non-Persisted Memory-Mapped File
The following example opens a memory-mapped file used for inter-process communication. This code example is part of a larger example provided for the CreateNew(String, Int64) method.
Remarks
The memory-mapped file can be either a persisted memory-mapped file (associated with a file on disk) or non-persisted.
See also
Applies to
.NET 10 и други версии
| Продукт | Версии |
|---|---|
| .NET | Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9, 10 |
| .NET Framework | 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1 |
| .NET Standard | 2.0, 2.1 |
- Source:
- MemoryMappedFile.cs
- Source:
- MemoryMappedFile.cs
- Source:
- MemoryMappedFile.cs
Opens an existing memory-mapped file that has the specified name and access rights in system memory.
public:
static System::IO::MemoryMappedFiles::MemoryMappedFile ^ OpenExisting(System::String ^ mapName, System::IO::MemoryMappedFiles::MemoryMappedFileRights desiredAccessRights);[System.Runtime.Versioning.SupportedOSPlatform("windows")]
public static System.IO.MemoryMappedFiles.MemoryMappedFile OpenExisting(string mapName, System.IO.MemoryMappedFiles.MemoryMappedFileRights desiredAccessRights);public static System.IO.MemoryMappedFiles.MemoryMappedFile OpenExisting(string mapName, System.IO.MemoryMappedFiles.MemoryMappedFileRights desiredAccessRights);[<System.Runtime.Versioning.SupportedOSPlatform("windows")>]
static member OpenExisting : string * System.IO.MemoryMappedFiles.MemoryMappedFileRights -> System.IO.MemoryMappedFiles.MemoryMappedFilestatic member OpenExisting : string * System.IO.MemoryMappedFiles.MemoryMappedFileRights -> System.IO.MemoryMappedFiles.MemoryMappedFilePublic Shared Function OpenExisting (mapName As String, desiredAccessRights As MemoryMappedFileRights) As MemoryMappedFileParameters
- mapName
- String
The name of the memory-mapped file to open.
- desiredAccessRights
- MemoryMappedFileRights
One of the enumeration values that specifies the access rights to apply to the memory-mapped file.
Returns
A memory-mapped file that has the specified characteristics.
- Attributes
Exceptions
mapName is null.
mapName is an empty string.
desiredAccessRights is not a valid MemoryMappedFileRights enumeration value.
The file specified for mapName does not exist.
See also
Applies to
.NET 10 и други версии
| Продукт | Версии |
|---|---|
| .NET | Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9, 10 |
| .NET Framework | 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1 |
| .NET Standard | 2.0, 2.1 |
- Source:
- MemoryMappedFile.cs
- Source:
- MemoryMappedFile.cs
- Source:
- MemoryMappedFile.cs
Opens an existing memory-mapped file that has the specified name, access rights, and inheritability in system memory.
public:
static System::IO::MemoryMappedFiles::MemoryMappedFile ^ OpenExisting(System::String ^ mapName, System::IO::MemoryMappedFiles::MemoryMappedFileRights desiredAccessRights, System::IO::HandleInheritability inheritability);[System.Runtime.Versioning.SupportedOSPlatform("windows")]
public static System.IO.MemoryMappedFiles.MemoryMappedFile OpenExisting(string mapName, System.IO.MemoryMappedFiles.MemoryMappedFileRights desiredAccessRights, System.IO.HandleInheritability inheritability);public static System.IO.MemoryMappedFiles.MemoryMappedFile OpenExisting(string mapName, System.IO.MemoryMappedFiles.MemoryMappedFileRights desiredAccessRights, System.IO.HandleInheritability inheritability);[System.Security.SecurityCritical]
public static System.IO.MemoryMappedFiles.MemoryMappedFile OpenExisting(string mapName, System.IO.MemoryMappedFiles.MemoryMappedFileRights desiredAccessRights, System.IO.HandleInheritability inheritability);[<System.Runtime.Versioning.SupportedOSPlatform("windows")>]
static member OpenExisting : string * System.IO.MemoryMappedFiles.MemoryMappedFileRights * System.IO.HandleInheritability -> System.IO.MemoryMappedFiles.MemoryMappedFilestatic member OpenExisting : string * System.IO.MemoryMappedFiles.MemoryMappedFileRights * System.IO.HandleInheritability -> System.IO.MemoryMappedFiles.MemoryMappedFile[<System.Security.SecurityCritical>]
static member OpenExisting : string * System.IO.MemoryMappedFiles.MemoryMappedFileRights * System.IO.HandleInheritability -> System.IO.MemoryMappedFiles.MemoryMappedFilePublic Shared Function OpenExisting (mapName As String, desiredAccessRights As MemoryMappedFileRights, inheritability As HandleInheritability) As MemoryMappedFileParameters
- mapName
- String
The name of the memory-mapped file to open.
- desiredAccessRights
- MemoryMappedFileRights
One of the enumeration values that specifies the access rights to apply to the memory-mapped file.
- inheritability
- HandleInheritability
One of the enumeration values that specifies whether a handle to the memory-mapped file can be inherited by a child process. The default is None.
Returns
A memory-mapped file that has the specified characteristics.
- Attributes
Exceptions
mapName is null.
mapName is an empty string.
desiredAccessRights is not a valid MemoryMappedFileRights enumeration value.
-or-
inheritability is not a valid HandleInheritability enumeration value.
The requested access is invalid for the memory-mapped file.
The file specified for mapName does not exist.
See also
Applies to
.NET 10 и други версии
| Продукт | Версии |
|---|---|
| .NET | Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9, 10 |
| .NET Framework | 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1 |
| .NET Standard | 2.0, 2.1 |
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