On 2016-06-10 06:14, Mark Wieder wrote:
Here's a working cross-platform replacement for the flaky built-in
hasMemory function.
The builtin 'hasMemory' function is not flaky - the question it asks
just has no meaning on modern operating systems (and should probably
actually be removed!).
For example, change your mouseUp to this:
on mouseUp
put freeMemory() into tBytesAvailable
repeat with i = 1 to tBytesAvailable * 4
put "a" after tString
end repeat
put "apparently there were" && tBytesAvailable && \
"bytes of memory available" & return after field 1
put "but I managed to allocate a string which requires" && \
the length of tString && "bytes" & return after field 1
end mouseUp
And try running it on a modern Mac (although I have no reason to suspect
it would be different on any other platform we support). In my case I
got:
apparently there were 8894284 bytes of memory available
but I managed to allocate a string which requires 35577136 bytes
The concept of 'free memory' on multi-user, pre-emptive, user/kernel
space split operating systems doesn't exist as the kernel allocates any
physical resources it has (including disk space to provide virtual
memory) to where it is needed at any point it wishes.
For example, a large amount of physical memory pages at any one time is
likely to be used to cache blocks on disks for files which are currently
in use. As the majority of these pages (those which have not been
modified in memory) can be dumped at any time, that measure does not
reflect how much memory any one process could allocate. Similarly,
processes which are inactive and consuming physical memory are likely to
have most of their memory usage paged to disk (i.e. into virtual memory)
when another active process needs more memory.
Warmest Regards,
Mark.
P.S. The 'hasMemory' function in LiveCode actually does the best it can
do - it sees if it can allocate a contiguous block of memory of the size
that has been requested (using malloc) and if that succeeds, it frees
the block and returns true. This should mean that (assuming nothing on
the system suddenly consumes all physical and virtual ram) you should be
able to do an action which requires that amount of memory immediately
after:
void MCLegacyEvalHasMemory(MCExecContext& ctxt, uinteger_t p_bytes,
bool& r_bool)
{
char *t_buffer = nil;
r_bool = nil != (t_buffer = (char*)malloc(p_bytes));
free(t_buffer);
}
--
Mark Waddingham ~ m...@livecode.com ~ http://www.livecode.com/
LiveCode: Everyone can create apps
_______________________________________________
use-livecode mailing list
use-livecode@lists.runrev.com
Please visit this url to subscribe, unsubscribe and manage your subscription
preferences:
http://lists.runrev.com/mailman/listinfo/use-livecode
