• mw (37/37) Oct 13 2022 I'm checking file:
• mw (6/18) Oct 13 2022 and in ensureMapped(ulong i, ulong j),

mw <mingwu gmail.com> writes:

I'm checking file:

https://github.com/dlang/phobos/blob/master/std/mmfile.d

and found two  questions (issues?) I don't understand, can 
someone explain?

1) This ctor:

https://github.com/dlang/phobos/blob/master/std/mmfile.d#L79

version (linux) this(File file, Mode mode = Mode.read, ulong size 
= 0,
             void* address = null, size_t window = 0) scope

is not doc-ed: https://dlang.org/phobos/std_mmfile.html

and there is a version (Posix) implementation inside the doc-ed 
ctor:

https://github.com/dlang/phobos/blob/master/std/mmfile.d#L275

There is some code duplication of these two implementation, so is 
the version (linux) needed at all? or it's some dead legacy code 
that should be deleted together with this:

https://github.com/dlang/phobos/blob/master/std/mmfile.d#L87


2) in ensureMapped() why the requested mmap length are 3x window 
(2x is enough, since the start offset of the mmap must be 
multiples of pagesize):

https://github.com/dlang/phobos/blob/master/std/mmfile.d#L556
```
                     map(window*(block-1),3*window);
// should this be?:
                     map(window*(block),  2*window);
```

and
https://github.com/dlang/phobos/blob/master/std/mmfile.d#L582

```
                     
map(window*(iblock-1),cast(size_t)(window*(jblock-iblock+3)));
// should this be?:
                     map(window*(iblock),  
cast(size_t)(window*(jblock-iblock+2)));

```

So the mapped buffer size is consistent of 2x window?


Thanks.

mw <mingwu gmail.com> writes:

On Friday, 14 October 2022 at 00:30:55 UTC, mw wrote:
 2) in ensureMapped() why the requested mmap length are 3x 
 window (2x is enough, since the start offset of the mmap must 
 be multiples of pagesize):

...
 https://github.com/dlang/phobos/blob/master/std/mmfile.d#L582

 ```
                     
 map(window*(iblock-1),cast(size_t)(window*(jblock-iblock+3)));
 // should this be?:
                     map(window*(iblock),  
 cast(size_t)(window*(jblock-iblock+2)));

 ```

 So the mapped buffer size is consistent of 2x window?

and in ensureMapped(ulong i, ulong j),

enforce(j - i <= window)?

otherwise, what's the point of allowing user pass in `window` in 
the ctor, if it's not honored?