Is there any reasons to not use "mmap" to read files?

[sarn]

On Sunday, 6 February 2022 at 09:40:48 UTC, rempas wrote:
> This should have probably been posted in the "Learn" section 
> but I thought that it is an advanced topic so maybe people 
> other than me may learn something too. So here we go!
>
> I'm planning to make a change to my program to use "mmap" to 
> the contents of a file rather than "fgetc". This is because I 
> learned that "mmap" can do it faster. The thing is, are there 
> any problems that can occur when using "mmap"? I need to know 
> now because changing this means changing the design of the 
> program and this is not something pleasant to do so I want to 
> be sure that I won't have to change back in the future (where 
> the project will be even bigger).

One reason to use read/write based I/O by default is that it's 
more versatile.  It's kind of like an input range versus a random 
access in Phobos.

```
// Could not map file /dev/stdin (Invalid argument)
auto f = new MmFile("/dev/stdin");
```