Files services library: Add an "output stream" file impl helper class.

Files services library: Add an "output stream" file impl helper class.

Notes:
* This is an "impl" library, not a client library. I.e., it's for those
  who are implementing |mojo::files::File|s, not using them. This is a
  bit unusual, so maybe it should live in a subdirectory of
  mojo/services/files/public/cpp or something.
* Maybe the name of the class should also have "impl" in its name, e.g.,
  "OutputStreamFileImpl"? But have "impl" in a "public" class in a
  library would be strange. Maybe it should live in a namespace?

Still to do (separately):
* Fill in parts of the implementation, like Dup and the data pipe write
  methods.
* Add "input stream" and "input/output stream" versions of this.
* Convert things, like moterm, to use this (or an input/output version
  of this). The benefit is that as the implementation of this class gets
  filled in, things using it will automatically get a more complete
  implementation as well.

R=vardhan@google.com

Committed: https://chromium.googlesource.com/external/mojo/+/b8fecbf5a2ffa456a6056c2478fe9477d35ce389

[vardhan, 2015-09-25 17:19:16]

lgtm w/ a suggestion

https://codereview.chromium.org/1363183004/diff/1/mojo/services/files/public/...
File mojo/services/files/public/cpp/output_stream_file.h (right):

https://codereview.chromium.org/1363183004/diff/1/mojo/services/files/public/...
mojo/services/files/public/cpp/output_stream_file.h:22: class OutputStreamFile :
public mojo::files::File {
should this be under a mojo namespace? (or like mojo::services::internal:: or
something?)
or if we don't denote that this is part of 'services' in the namespace, how does
putting 'ServiceImpl' in the class name sound?

[viettrungluu, 2015-09-25 17:32:46]

On 2015/09/25 17:19:16, vardhan wrote:
> lgtm w/ a suggestion
> 
>
https://codereview.chromium.org/1363183004/diff/1/mojo/services/files/public/...
> File mojo/services/files/public/cpp/output_stream_file.h (right):
> 
>
https://codereview.chromium.org/1363183004/diff/1/mojo/services/files/public/...
> mojo/services/files/public/cpp/output_stream_file.h:22: class OutputStreamFile
:
> public mojo::files::File {
> should this be under a mojo namespace? (or like mojo::services::internal:: or
> something?)
> or if we don't denote that this is part of 'services' in the namespace, how
does
> putting 'ServiceImpl' in the class name sound?

It's not necessarily part of a "service", except in the sense that every
application is a service. (E.g., it could be part of a "client" application that
provides a mojo::files::File to a "service" that it's talking to.)

I don't really want to dump everything in the mojo:: namespace. We really should
reserve that for things that are standardized/core to some degree.

This isn't internal, and "internal" denotes stuff that isn't to be used by
others, so that's out.

"impl" would make sense, but that's kind of weird too. I'd consider
OutputStreamFileImpl, except for the reservation noted in the CL description.
I'll think about that some more.

[viettrungluu, 2015-09-25 17:48:09]

On 2015/09/25 17:32:46, viettrungluu wrote:
> On 2015/09/25 17:19:16, vardhan wrote:
> > lgtm w/ a suggestion
> > 
> >
>
https://codereview.chromium.org/1363183004/diff/1/mojo/services/files/public/...
> > File mojo/services/files/public/cpp/output_stream_file.h (right):
> > 
> >
>
https://codereview.chromium.org/1363183004/diff/1/mojo/services/files/public/...
> > mojo/services/files/public/cpp/output_stream_file.h:22: class
OutputStreamFile
> :
> > public mojo::files::File {
> > should this be under a mojo namespace? (or like mojo::services::internal::
or
> > something?)
> > or if we don't denote that this is part of 'services' in the namespace, how
> does
> > putting 'ServiceImpl' in the class name sound?
> 
> It's not necessarily part of a "service", except in the sense that every
> application is a service. (E.g., it could be part of a "client" application
that
> provides a mojo::files::File to a "service" that it's talking to.)
> 
> I don't really want to dump everything in the mojo:: namespace. We really
should
> reserve that for things that are standardized/core to some degree.
> 
> This isn't internal, and "internal" denotes stuff that isn't to be used by
> others, so that's out.
> 
> "impl" would make sense, but that's kind of weird too. I'd consider
> OutputStreamFileImpl, except for the reservation noted in the CL description.
> I'll think about that some more.

I have thought about this some more, and will put everything inside a
"files_impl" namespace, and in a "files_impl" subdirectory. I'll send out a need
CL shortly.

[viettrungluu, 2015-09-25 17:48:27]

On 2015/09/25 17:48:09, viettrungluu wrote:
> On 2015/09/25 17:32:46, viettrungluu wrote:
> > On 2015/09/25 17:19:16, vardhan wrote:
> > > lgtm w/ a suggestion
> > > 
> > >
> >
>
https://codereview.chromium.org/1363183004/diff/1/mojo/services/files/public/...
> > > File mojo/services/files/public/cpp/output_stream_file.h (right):
> > > 
> > >
> >
>
https://codereview.chromium.org/1363183004/diff/1/mojo/services/files/public/...
> > > mojo/services/files/public/cpp/output_stream_file.h:22: class
> OutputStreamFile
> > :
> > > public mojo::files::File {
> > > should this be under a mojo namespace? (or like mojo::services::internal::
> or
> > > something?)
> > > or if we don't denote that this is part of 'services' in the namespace,
how
> > does
> > > putting 'ServiceImpl' in the class name sound?
> > 
> > It's not necessarily part of a "service", except in the sense that every
> > application is a service. (E.g., it could be part of a "client" application
> that
> > provides a mojo::files::File to a "service" that it's talking to.)
> > 
> > I don't really want to dump everything in the mojo:: namespace. We really
> should
> > reserve that for things that are standardized/core to some degree.
> > 
> > This isn't internal, and "internal" denotes stuff that isn't to be used by
> > others, so that's out.
> > 
> > "impl" would make sense, but that's kind of weird too. I'd consider
> > OutputStreamFileImpl, except for the reservation noted in the CL
description.
> > I'll think about that some more.
> 
> I have thought about this some more, and will put everything inside a
> "files_impl" namespace, and in a "files_impl" subdirectory. I'll send out a
need
> CL shortly.

"need" = "new", by which I really meant "updated"

[viettrungluu, 2015-09-25 17:49:50]

On 2015/09/25 17:48:27, viettrungluu wrote:
> On 2015/09/25 17:48:09, viettrungluu wrote:
> > On 2015/09/25 17:32:46, viettrungluu wrote:
> > > On 2015/09/25 17:19:16, vardhan wrote:
> > > > lgtm w/ a suggestion
> > > > 
> > > >
> > >
> >
>
https://codereview.chromium.org/1363183004/diff/1/mojo/services/files/public/...
> > > > File mojo/services/files/public/cpp/output_stream_file.h (right):
> > > > 
> > > >
> > >
> >
>
https://codereview.chromium.org/1363183004/diff/1/mojo/services/files/public/...
> > > > mojo/services/files/public/cpp/output_stream_file.h:22: class
> > OutputStreamFile
> > > :
> > > > public mojo::files::File {
> > > > should this be under a mojo namespace? (or like
mojo::services::internal::
> > or
> > > > something?)
> > > > or if we don't denote that this is part of 'services' in the namespace,
> how
> > > does
> > > > putting 'ServiceImpl' in the class name sound?
> > > 
> > > It's not necessarily part of a "service", except in the sense that every
> > > application is a service. (E.g., it could be part of a "client"
application
> > that
> > > provides a mojo::files::File to a "service" that it's talking to.)
> > > 
> > > I don't really want to dump everything in the mojo:: namespace. We really
> > should
> > > reserve that for things that are standardized/core to some degree.
> > > 
> > > This isn't internal, and "internal" denotes stuff that isn't to be used by
> > > others, so that's out.
> > > 
> > > "impl" would make sense, but that's kind of weird too. I'd consider
> > > OutputStreamFileImpl, except for the reservation noted in the CL
> description.
> > > I'll think about that some more.
> > 
> > I have thought about this some more, and will put everything inside a
> > "files_impl" namespace, and in a "files_impl" subdirectory. I'll send out a
> need
> > CL shortly.
> 
> "need" = "new", by which I really meant "updated"

On second thought, a further subdirectory is just crazy, so I'll skip that.

[viettrungluu, 2015-09-25 17:57:00]

OK, PTAL.

[vardhan, 2015-09-25 18:08:39]

lgtm

[viettrungluu, 2015-09-25 18:11:31]

Committed patchset #2 (id:20001) manually as
b8fecbf5a2ffa456a6056c2478fe9477d35ce389 (presubmit successful).