On Tuesday, 11 April 2017 at 01:59:57 UTC, Jonathan M Davis wrote:
On Tuesday, April 11, 2017 01:42:32 Jethro via
Digitalmars-d-learn wrote:
arrays have the ability to reserve but when setting the length
to 0, it removes the reserve!! ;/
char[] buf;
buf.reserve = 1000;
buf.length = 0;
assert(buf.capacity == 0);
But I simply want to clear the buffer, not change it's
reserve/capacity.
I've tried to hack by setting the length to 0 through a
pointer, but that still clears the capacity!
I want to do this because I want to be able to reuse the array
without ever reallocating(I'll set the capacity to the max
that will ever be used, I don't have to worry about conflicts
since it will always be ran serially).
[snip]
You can't reuse the memory of a dynamic array by simply setting
its length to 0. If that were allowed, it would risk allow
dynamic arrays to stomp on each others memory (since there is
no guarantee that there are no other dynamic arrays referring
to the same memory). However, if you know that there are no
other dynamic arrays referrin to the same memory, then you can
call assumeSafeAppend on the dynamic array, and then the
runtime will assume that there are no other dynamic arrays
referring to the same memory.
[snip]
Another technique that works for many cases is to use an Appender
(std.array). Appender supports reserve and clear, the latter
setting the length to zero without reallocating. A typical use
case is an algorithm doing a series of appends, then setting the
length to zero and starts appending again.
--Jon
