static-buffer

StaticArrayBuffer and StaticBuffer

Hello World Example

Print "Hello World" to console, we do it by executing write system call to 1 file descriptor which is STDOUT:

var StaticBuffer = require('static-buffer/buffer').StaticBuffer;
 
var sbuf = StaticBuffer.from([
    0x48, 0xc7, 0xc0, 1, 0, 0, 0,       // mov    $0x1,%rax         # System call `1` -- SYS_write
    0x48, 0xc7, 0xc7, 1, 0, 0, 0,       // mov    $0x1,%rdi         # File descriptor `1` -- STDOUT
    0x48, 0x8d, 0x35, 10, 0, 0, 0,      // lea    0x1(%rip),%rsi    # Data address
    0x48, 0xc7, 0xc2, 13, 0, 0, 0,      // mov    $13,%rdx          # Number of bytes to write -- 13
    0x0f, 0x05,                         // syscall                  # Execute the system call.
    0xc3,                               // retq                     # Return
    0x48, 0x65, 0x6C, 0x6C, 0x6F, 0x20, // Hello_
    0x57, 0x6F, 0x72, 0x6C, 0x64, 0x21, // World!
    0x0A, 0                             // \n\0
], 'rwe'); // r - readable, w - writable, e - executable
 
sbuf.call([], 0); // Hello World!

How it works

StaticArrayBuffer and StaticBuffer extend ArrayBuffer and Buffer classes and provide such extra functionality:

1. Allocate executable memory.
2. Execute the machine code in StaticBuffer using .call() method.
3. Change protection to backing memory.
4. Promise that actual data in memory will never be moved by runtime.

Memory protection flags:

• 'r' - readable
• 'w' - writable
• 'e' - executable

Usage

var StaticArrayBuffer = require('static-buffer/arraybuffer').StaticArrayBuffer;
var StaticBuffer = require('static-buffer/buffer').StaticArrayBuffer;

StaticArrayBuffer inherits from ArrayBuffer and provides the following extra functionality:

var sab = new StaticArrayBuffer(1024, 'rwe');
StaticArrayBuffer.isStaticArrayBuffer(sab); // true
 
// Call mathine code stored in `StaticArrayBuffer` at offset `offset`,
// providing `number[]` arguments to that machine code using standard
// calling conventions supported by your system, currently supports 
// up to 10 arguments.
var offset = 0;
var args = [1, 2, 3];
sab.call(args, offset);
 
// Change protection of the memory block.
sab.setProtection('rw');
 
// Get the actual address pointer of the memory that backs the `StaticArrayBuffer`.
offset = 0;
var addr = sab.getAddress(offset); // [number, number]
 
// Free the memory of the `StaticArrayBuffer`, after that your `StaticArrayBuffer`
// should not be used.
sab.free();
sab = null;

StaticBuffer inherits from Buffer and is backed by StaticArrayBuffer instead of ArrayBuffer that Buffer uses. It provides the following extra functionality:

var sbuf = new StaticBuffer(1024, 'rwe');
// or
var offset = 10, len = 10;
sbuf = new StaticBuffer(sab, offset, len);
// or use StaticBuffer.from() syntax
 
StaticBuffer.isStaticBuffer(sbuf); // true
 
sbuf.call([], 0);
sbuf.getAddress(0);
 
sbuf.buffer.free();
sbuf = null;