Class: Buffer do not follow when the underlying ArrayBuffer is resized

Version

v21.7.1

Platform

Microsoft Windows NT 10.0.22631.0 x64

Subsystem

Class: Buffer

What steps will reproduce the bug?

const arraybuffer = new ArrayBuffer(4, { maxByteLength: 4096 });

const uint8array = new Uint8Array(arraybuffer);

uint8array.set([0,1,2,3]);

const buffer = Buffer.from(arraybuffer);

console.error(uint8array);
console.error(buffer);

arraybuffer.resize(8);
uint8array.set([4,5,6,7],4);

uint8array[0]=0xff;

console.error(uint8array);
console.error(buffer);

Output:

Uint8Array(4) [ 0, 1, 2, 3 ]
<Buffer 00 01 02 03>
Uint8Array(8) [
  255, 1, 2, 3,
    4, 5, 6, 7
]
<Buffer ff 01 02 03>

How often does it reproduce? Is there a required condition?

always

What is the expected behavior? Why is that the expected behavior?

Expecting buffer to be resized and output to be:

<Buffer ff 01 02 03 04 05 06 07>

What do you see instead?

<Buffer ff 01 02 03>

Additional information

If the resolution to this is that Buffer isn't going to support ArrayBuffer.resize() that should be reflected in the documentation.

Behavior comes from:

node/lib/buffer.js

Lines 476 to 505 in bae14b7

    
           function fromArrayBuffer(obj, byteOffset, length) { 
        
             // Convert byteOffset to integer 
        
             if (byteOffset === undefined) { 
        
               byteOffset = 0; 
        
             } else { 
        
               byteOffset = +byteOffset; 
        
               if (NumberIsNaN(byteOffset)) 
        
                 byteOffset = 0; 
        
             } 
        
             const maxLength = obj.byteLength - byteOffset; 
        
             if (maxLength < 0) 
        
               throw new ERR_BUFFER_OUT_OF_BOUNDS('offset'); 
        
             if (length === undefined) { 
        
               length = maxLength; 
        
             } else { 
        
               // Convert length to non-negative integer. 
        
               length = +length; 
        
               if (length > 0) { 
        
                 if (length > maxLength) 
        
                   throw new ERR_BUFFER_OUT_OF_BOUNDS('length'); 
        
               } else { 
        
                 length = 0; 
        
               } 
        
             } 
        
             return new FastBuffer(obj, byteOffset, length); 
        
           }

byteOffset and length are initially undefined, but the function ensures they are numbers, and if they are specified, the typed array's length stays fixed.

/cc @nodejs/buffer

Buffer has always been assumed to be non-resizable. I'm wondering if the right fix for now shouldn't be to forbid creating a Buffer from a resizable ArrayBuffer until we can make sure that all of Buffer's APIs handle it appropriately

I'm wondering if the right fix for now shouldn't be to forbid creating a Buffer from a resizable ArrayBuffer until we can make sure that all of Buffer's APIs handle it appropriately

This will break me. Please don't.

buffer: make Buffer work with resizable ArrayBuffer

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Class: Buffer do not follow when the underlying ArrayBuffer is resized #52195

Version

Platform

Subsystem

What steps will reproduce the bug?

How often does it reproduce? Is there a required condition?

What is the expected behavior? Why is that the expected behavior?

What do you see instead?

Additional information

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	function fromArrayBuffer(obj, byteOffset, length) {
	// Convert byteOffset to integer
	if (byteOffset === undefined) {
	byteOffset = 0;
	} else {
	byteOffset = +byteOffset;
	if (NumberIsNaN(byteOffset))
	byteOffset = 0;
	}

	const maxLength = obj.byteLength - byteOffset;

	if (maxLength < 0)
	throw new ERR_BUFFER_OUT_OF_BOUNDS('offset');

	if (length === undefined) {
	length = maxLength;
	} else {
	// Convert length to non-negative integer.
	length = +length;
	if (length > 0) {
	if (length > maxLength)
	throw new ERR_BUFFER_OUT_OF_BOUNDS('length');
	} else {
	length = 0;
	}
	}

	return new FastBuffer(obj, byteOffset, length);
	}

Class: Buffer do not follow when the underlying ArrayBuffer is resized #52195

Description

Version

Platform

Subsystem

What steps will reproduce the bug?

How often does it reproduce? Is there a required condition?

What is the expected behavior? Why is that the expected behavior?

What do you see instead?

Additional information

Activity

targos commented on Mar 24, 2024

jasnell commented on Mar 24, 2024

ronag commented on Aug 26, 2024

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