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buffers: handle bad length argument in constructor

Coerce fractional, negative and non-numeric length arguments to numbers.
Fractional numbers are rounded up, negative numbers and non-numeric values
are set to zero.
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bnoordhuis committed Sep 24, 2011
1 parent fcba145 commit d1571314390d9a0f8d697d8e70987f7a9e1ef98d
Showing with 25 additions and 3 deletions.
  1. +12 −3 lib/buffer.js
  2. +13 −0 test/simple/test-buffer.js
@@ -196,6 +196,15 @@ SlowBuffer.prototype.slice = function(start, end) {
};


function coerce(length) {
// Coerce length to a number (possibly NaN), round up
// in case it's fractional (e.g. 123.456) then do a
// double negate to coerce a NaN to 0. Easy, right?
length = ~~Math.ceil(+length);
return length < 0 ? 0 : length;
}


// Buffer

function Buffer(subject, encoding, offset) {
@@ -207,22 +216,22 @@ function Buffer(subject, encoding, offset) {

// Are we slicing?
if (typeof offset === 'number') {
this.length = encoding;
this.length = coerce(encoding);
this.parent = subject;
this.offset = offset;
} else {
// Find the length
switch (type = typeof subject) {
case 'number':
this.length = subject;
this.length = coerce(subject);
break;

case 'string':
this.length = Buffer.byteLength(subject, encoding);
break;

case 'object': // Assume object is an array
this.length = subject.length;
this.length = coerce(subject.length);
break;

default:
@@ -689,3 +689,16 @@ buf.write('123456', 'base64');
assert.equal(Buffer._charsWritten, 6);
buf.write('00010203040506070809', 'hex');
assert.equal(Buffer._charsWritten, 18);

// Check for fractional length args, junk length args, etc.
// https://github.com/joyent/node/issues/1758
Buffer(3.3).toString(); // throws bad argument error in commit 43cb4ec
assert.equal(Buffer(-1).length, 0);
assert.equal(Buffer(NaN).length, 0);
assert.equal(Buffer(3.3).length, 4);
assert.equal(Buffer({length:3.3}).length, 4);
assert.equal(Buffer({length:"BAM"}).length, 0);

// Make sure that strings are not coerced to numbers.
assert.equal(Buffer("99").length, 2);
assert.equal(Buffer("13.37").length, 5);

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