resize

    fn resize(ctx: *anyopaque, memory: []u8, alignment: Alignment, new_len: usize, _: usize) bool {
        @disableInstrumentation();

        const f: *FuzzSingleThreadedAllocator = @ptrCast(@alignCast(ctx));
        const i = f.allocIndex(memory, alignment);

        const start = memory.ptr - f.buf.ptr;
        const old_end = start + memory.len;
        const new_end = start +| new_len;
        if (new_end > f.buf.len or f.smith.value(bool)) {
            return false;
        }

        if (new_len <= memory.len) {
            // The fill is not decreased so memory is not reused.
        } else if (f.fill == old_end) {
            f.fill = new_end;
        } else {
            return false;
        }
        f.allocs.items(.len)[i] = new_len;
        return true;
    }