Oh, that does sound tricky, including in some single threaded scenarios,
like the one below...
How would you modify the code below to avoid landing in invalid memory? I
can take a guess but ... still learning about the JS side of it
function decompress(data / * Uint8Array */) {
let dataPtr = Module._malloc(data.length);
let dataHeap = new Uint8Array(Module.HEAPU8.buffer, dataPtr,
data.length);
dataHeap.set(data);
let num_bytes_decomp= Module.C_getContentSize(dataHeap.byteOffset,
data.length);
let decompPtr = Module._malloc(num_bytes_decom);
let decompHeap = new Uint8Array(Module.HEAPU8.buffer, decompPtr,
num_bytes_decomp);
let len = Module.C_decompress(decompHeap.byteOffset, num_bytes_decomp,
dataHeap.byteOffset, data.length);
let result = new Uint8Array(decompHeap.subarray(0, len));
Module._free(dataHeap.byteOffset);
Module._free(decompHeap.byteOffset);
return result
}
Thank you in advance
On Thu, May 9, 2019 at 10:07 AM Alon Zakai <[email protected]> wrote:
> Memory growth does mean you need to be careful when accessing the heap
> from JavaScript. Emscripten will update the HEAPU8 etc. views, but if you
> held on to references to the old views, or subarrays of them etc., those
> would become invalid, and you'd silently miss updates to memory. Basically,
> growth has the effect of creating replacements for all the JS memory views.
>
> (This is even trickier with multithreaded code using memory growth.)
>
> On Wed, May 8, 2019 at 10:34 AM Marc Fawzi <[email protected]> wrote:
>
>> Hi,
>>
>> Somehow when writing a large amount of data (over the 16MB default) to
>> the Module heap (HEAPU8) I saw what could be a bug when ALLOW_MEMORY_GROWTH
>> was set. Basically, when I print out the content I saw Emscripten’s own
>> symbols, the C++ program symbols and a bunch of binary gibberish before the
>> start of the the data I had written, as if my read offset was somehow
>> smaller than my write offset. I’m working with someone else’ code and
>> trying to understand what’s going on but when setting the memory manually
>> at build time instead of allowing it to grow the code works just write and
>> I get the exact data I write back when I read it.
>>
>> Any guides or blog posts out there for working with the heap?
>>
>> Thanks,
>>
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