On a related note: ObjectElements::VALUES_PER_HEADER is 2. Is this because 2 * sizeof(HeapSlot) is 16 bytes, which is equal to sizeof(ObjectElements)?
Nick On Wed, Jul 16, 2014 at 11:34 PM, Nicholas Nethercote <[email protected]> wrote: > On Wed, Jul 16, 2014 at 11:08 PM, Nicholas Nethercote > <[email protected]> wrote: >> Hi, >> >> Here's some code from pdf.js: >> >> function stringToArray(str) { >> var length = str.length; >> var array = []; >> for (var i = 0; i < length; ++i) { >> array[i] = str.charCodeAt(i); >> } >> return array; >> } >> >> This kind of code shows up in a number of places in pdf.js. Pretty >> simple -- filling in an array one element at a time. >> >> Underneath the covers, this causes the array to repeatedly double in >> size, which is annoying. And I thought I could avoid it because we >> know how big the array will be in advance. So I changed the 3rd line >> to this: >> >> var array = new Array(length); >> >> but I still get the same sort of doubling behaviour under the covers. > > Oh wait. It depends on the value of |length|. If it's 2050 or less, > then the right-sized array is allocated immediately. Otherwise, it > allocates 10 elements and then does the doubling thing. I guess > there's a limit to how much we'll pre-allocate. > > So using |new Array(length)| seems like the best thing, then. > > Nick _______________________________________________ dev-tech-js-engine-internals mailing list [email protected] https://lists.mozilla.org/listinfo/dev-tech-js-engine-internals
