asp.net - How to read and write a file using Memory Mapped File C#? -


i have image in d drive "d:\image\1.tiff". want read file , write in location, example in path "d:\project\". how using memory mapped file?

the createfromfile methods create memory-mapped file existing file on disk. following example creates memory-mapped view of part of extremely large file , manipulates portion of it.

using system; using system.io; using system.io.memorymappedfiles; using system.runtime.interopservices;  class program {     static void main(string[] args)     {         long offset = 0x10000000; // 256 megabytes          long length = 0x20000000; // 512 megabytes           // create memory-mapped file.          using (var mmf = memorymappedfile.createfromfile(@"c:\extremelylargeimage.data", filemode.open,"imga"))         {             // create random access view, 256th megabyte (the offset)              // 768th megabyte (the offset plus length).              using (var accessor = mmf.createviewaccessor(offset, length))             {                 int colorsize = marshal.sizeof(typeof(mycolor));                 mycolor color;                  // make changes view.                  (long = 0; < length; += colorsize)                 {                     accessor.read(i, out color);                     color.brighten(10);                     accessor.write(i, ref color);                 }             }         }     } }  public struct mycolor {     public short red;     public short green;     public short blue;     public short alpha;      // make view brighter.      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);     } }

the following example opens same memory-mapped file process.

using system; using system.io.memorymappedfiles; using system.runtime.interopservices;   class program {     static void main(string[] args)     {         // assumes process has created 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 view.                  (long = 0; < 1500000; += 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 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);     } }

you can read more @ :http://www.codeproject.com/articles/138290/programming-memory-mapped-files-with-the-net-frame


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