bufferfromfile

BufferFromFile

Module in JavaScript providing convenient means for using files as buffer making mmap behind the scene. BufferFromFile uses mmap to map file from hard drive to memory returning ArrayBuffer or TypedBuffer which can be manipulated just like ordinary buffer. mmap() creates a new mapping in the virtual address space of the calling process. During mmap operation all performance issues addressed operation system, so it's nearly fastest way to get data from / store on hard drive in Java Script. This method of data access do zero copy, unlike others. Just like native version of the routine BufferFromFile can accept ( protection ), ( flags ), ( offset ), ( size ) and even ( advise ) parameters each of which has default value. BufferFromFIle works on Windows, OSX, Lynux other Unix-like systems. This module doesn't depend of NaN and deprecated versions of Nodejs.

Usage:

Sample simply mmap a file

var buffer = BufferFromFile( filePath ).Uint8Array();

// edit single byte

buffer[ 0 ] = 48 + Math.round( Math.random()*9 );

// print the buffer

console.log( 'buffer.length :',buffer.length );
console.log( 'buffer.toString :',buffer.toString() );

// unmap file

BufferFromFile.unmap( buffer );

Sample make read only buffer from a file

// mmap file

var filePath = __dirname + '/TestFile.txt';
var buffer = BufferFromFile({ filePath : filePath, protection : BufferFromFile.Protection.read }).Uint8Array();

// attempt to write data would give error

/* buffer[ 0 ] = 48 + Math.round( Math.random()*9 ); */

// read data and status

console.log( 'buffer.toString :',buffer.toString() );
console.log( 'status',BufferFromFile.status( buffer ) );

// unmap file

BufferFromFile.unmap( buffer );

Sample make read only buffer from a file

// mmap file

var buffer = BufferFromFile( filePath ).Uint8Array();

// write data

buffer[ 0 ] = 48 + Math.round( Math.random()*9 );

// flush written data to make sure data on will get on hard drive shortly

BufferFromFile.flush( buffer );

// rewrite data

buffer[ 0 ] = 48 + Math.round( Math.random()*9 );

// unmap file

BufferFromFile.unmap( buffer );