Modern Fs MemoryMappedFile Data

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MemoryMappedFile.Data

Returns a pointer to the mapped bytes, valid until Close.

Syntax

MemoryMappedFile.Data( )

Notes

• ubyte ptr

Examples

#import "std/fs"
using fs

dim td as FsResultUStr = CreateTempDir( "fbdoc" )
dim as ustring dir_ = td.Value( )
dim as ustring p = PathJoin( dir_, "f.txt" )
WriteAllText( p, "hello" )

dim mm as MemoryMappedFile
mm.Open( p )

'' A raw pointer to the mapped bytes -- reading it touches the file
'' through the page cache, with no read call at all
dim as uint8 ptr b = mm.Data( )
print b[ 0 ]                 '' 104 -- "h"
print chr( b[ 0 ] ) & chr( b[ 1 ] )       '' he

'' VALID ONLY WHILE THE MAPPING IS OPEN. After Close( ) the pointer
'' dangles, and using it is a page fault rather than an error code.
mm.Close( )

RemoveDirAll( dir_ )

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Library: Filesystem Library
Category: Filesystem
Documented under: Locking, Mapping And Watching