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

[Basile B.]

On Saturday, 12 February 2022 at 16:48:26 UTC, user1234 wrote:
> On Saturday, 12 February 2022 at 13:17:19 UTC, rempas wrote:
>> On Wednesday, 9 February 2022 at 02:07:05 UTC, user1234 wrote:
>>>
>>> `std.file.readText()` is just fine... your really want to do 
>>> an os with call `fgetc` for every single byte that has to be 
>>> read ?
>>
>> Good point! I was really wondering if "fgetc" does a system 
>> call every single time that it is called or if the text is 
>> buffered just like with "printf". I will use "read" in any 
>> case just to be sure tho. I don't want to use Phobos tho so I 
>> cannot use "file.readText". Thank you for your time!
>
> I think that nowadays fgetc does not make sense anymore, maybe 
> in the past when the amount of memory available was very 
> reduced... source files are 100 kb top. You can load 100 of 
> them, the fingerprint is still small. What will likely consume 
> the more is the AST.
>
> Otherwise readText is easy to translate, it's just fopen then 
> fread then fclose, + a few checks for the errors, not a big 
> deal to translate.

The problem with phobos and if used to program a compiler is 
_dynamic arrays_, because of how they are managed.

With Styx I had used phobos because I knew the memory management 
was designed to work similarly with arrays, i.e functions can 
return arrays, but using the "sink" style would have not caused 
any problem (by "sink" style I mean when the buffer is owned by 
the calling frame, and passed as parameter, e.g like in many 
C-style APIs)

Then the amount of phobos code to translate in order to bootstrap 
[was 
minimal](https://gitlab.com/styx-lang/styx/-/raw/master/src/system.sx):

std.paths:

- isAbsolute
- isDir
- isFile
- dirName
- baseName
- exists
- cwd
- dirEntries
- setExtension

std.files:

- read (or readText)
- write (not even used I realize now)

std.process

- pipeProcess (actually just used to optionally --run after 
compile)

std.getopt

- getopt (tho libc functions for that could have been used... dmd 
itself doesnt have any special functions for the arg processing 
in the driver IIRC)

Add to this a few things from libc and unistd and you're good. 
You dont need more.