MemoryMappedFile.CreateViewAccessor Method

Definition

Namespace:

System.IO.MemoryMappedFiles

Assembly:

System.IO.MemoryMappedFiles.dll

Creates a MemoryMappedViewAccessor that maps to a view of the memory-mapped file.

Overloads

CreateViewAccessor()	Creates a MemoryMappedViewAccessor that maps to a view of the memory-mapped file.
CreateViewAccessor(Int64, Int64)	Creates a MemoryMappedViewAccessor that maps to a view of the memory-mapped file, and that has the specified offset and size.
CreateViewAccessor(Int64, Int64, MemoryMappedFileAccess)	Creates a MemoryMappedViewAccessor that maps to a view of the memory-mapped file, and that has the specified offset, size, and access restrictions.

CreateViewAccessor()

Source:

MemoryMappedFile.cs

Creates a MemoryMappedViewAccessor that maps to a view of the memory-mapped file.

public:
 System::IO::MemoryMappedFiles::MemoryMappedViewAccessor ^ CreateViewAccessor();

public System.IO.MemoryMappedFiles.MemoryMappedViewAccessor CreateViewAccessor ();

member this.CreateViewAccessor : unit -> System.IO.MemoryMappedFiles.MemoryMappedViewAccessor

Public Function CreateViewAccessor () As MemoryMappedViewAccessor

Returns

MemoryMappedViewAccessor

A randomly accessible block of memory.

Exceptions

UnauthorizedAccessException

Access to the memory-mapped file is unauthorized.

Remarks

You can use the view returned by this method for random access to a memory-mapped file.

See also

• Memory-Mapped Files

CreateViewAccessor(Int64, Int64)

Source:

MemoryMappedFile.cs

Creates a MemoryMappedViewAccessor that maps to a view of the memory-mapped file, and that has the specified offset and size.

public:
 System::IO::MemoryMappedFiles::MemoryMappedViewAccessor ^ CreateViewAccessor(long offset, long size);

public System.IO.MemoryMappedFiles.MemoryMappedViewAccessor CreateViewAccessor (long offset, long size);

member this.CreateViewAccessor : int64 * int64 -> System.IO.MemoryMappedFiles.MemoryMappedViewAccessor

Public Function CreateViewAccessor (offset As Long, size As Long) As MemoryMappedViewAccessor

Parameters

offset

Int64

The byte at which to start the view.

size

Int64

The size of the view. Specify 0 (zero) to create a view that starts at offset and ends approximately at the end of the memory-mapped file.

Returns

MemoryMappedViewAccessor

A randomly accessible block of memory.

Exceptions

ArgumentOutOfRangeException

offset or size is a negative value.

-or-

size is greater than the logical address space.

UnauthorizedAccessException

Access to the memory-mapped file is unauthorized.

IOException

An I/O error occurred.

Examples

The following example creates a view of a memory-mapped file and edits it. This code example is part of a larger example provided for the MemoryMappedFile class.

// Create a random access view, from the 256th megabyte (the offset)
// to the 768th megabyte (the offset plus length).
using (var accessor = mmf.CreateViewAccessor(offset, length))
{
    int colorSize = Marshal.SizeOf(typeof(MyColor));
    MyColor color;

    // Make changes to the view.
    for (long i = 0; i < length; i += colorSize)
    {
        accessor.Read(i, out color);
        color.Brighten(10);
        accessor.Write(i, ref color);
    }
}

' Create a random access view, from the 256th megabyte (the offset)
' to the 768th megabyte (the offset plus length).
Using accessor = mmf.CreateViewAccessor(offset, length)
    Dim colorSize As Integer = Marshal.SizeOf(GetType(MyColor))
    Dim color As MyColor
    Dim i As Long = 0

    ' Make changes to the view.
    Do While (i < length)
        accessor.Read(i, color)
        color.Brighten(10)
        accessor.Write(i, color)
        i += colorSize
    Loop
End Using

Remarks

You can use the view returned by this method for random access to a memory-mapped file.

To create a complete view of the memory-mapped file, specify 0 (zero) for the size parameter. If you do this, the size of the view might be larger than the size of the source file on disk. This is because views are provided in units of system pages, and the size of the view is rounded up to the next system page size.

See also

• Memory-Mapped Files

CreateViewAccessor(Int64, Int64, MemoryMappedFileAccess)

Source:

MemoryMappedFile.cs

Creates a MemoryMappedViewAccessor that maps to a view of the memory-mapped file, and that has the specified offset, size, and access restrictions.

public:
 System::IO::MemoryMappedFiles::MemoryMappedViewAccessor ^ CreateViewAccessor(long offset, long size, System::IO::MemoryMappedFiles::MemoryMappedFileAccess access);

public System.IO.MemoryMappedFiles.MemoryMappedViewAccessor CreateViewAccessor (long offset, long size, System.IO.MemoryMappedFiles.MemoryMappedFileAccess access);

member this.CreateViewAccessor : int64 * int64 * System.IO.MemoryMappedFiles.MemoryMappedFileAccess -> System.IO.MemoryMappedFiles.MemoryMappedViewAccessor

Public Function CreateViewAccessor (offset As Long, size As Long, access As MemoryMappedFileAccess) As MemoryMappedViewAccessor

Parameters

offset

Int64

The byte at which to start the view.

size

Int64

The size of the view. Specify 0 (zero) to create a view that starts at offset and ends approximately at the end of the memory-mapped file.

access

MemoryMappedFileAccess

One of the enumeration values that specifies the type of access allowed to the memory-mapped file. The default is ReadWrite.

Returns

MemoryMappedViewAccessor

A randomly accessible block of memory.

Exceptions

ArgumentOutOfRangeException

offset or size is a negative value.

-or-

size is greater than the logical address space.

UnauthorizedAccessException

access is invalid for the memory-mapped file.

IOException

An I/O error occurred.

Remarks

You can use the view returned by this method for random access to a memory-mapped file.

To create a complete view of the memory-mapped file, specify 0 (zero) for the size parameter. If you do this, the size of the view might be larger than the size of the source file on disk. This is because views are provided in units of system pages, and the size of the view is rounded up to the next system page size.

See also

• Memory-Mapped Files