MemoryMappedFile.CreateViewAccessor Method

Definition

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()

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

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

A randomly accessible block of memory.

Exceptions

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.

CreateViewAccessor(Int64, Int64)

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);
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

A randomly accessible block of memory.

Exceptions

offset or size is a negative value.

-or-

size is greater than the logical address space.

Access to the memory-mapped file is unauthorized.

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 smaller or 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.

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.

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

A randomly accessible block of memory.

Exceptions

offset or size is a negative value.

-or-

size is greater than the logical address space.

access is invalid for the memory-mapped file.

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 smaller or 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.