code review 6098047: net: consolidate common socket functions

net: consolidate common socket functions

In resolving 3507, the fix had to be applied individually to
the four *Conn types, tcp, udp, rawip and unix, due to the
duplicate code in each Conn type.

This CL consolidates the common net.Conn methods that all four
*Conn types implement into a base conn type.


Pros:
* The fix for 3507 would have only needed to be applied to one
method. Further improvements, such as possibly removing the
c.fd != nil check in c.ok(), would benefit from this CL.
* Nearly 300 lines removed from the net package.
* The public interface and documentation are not changed.
* I think this is an excellent example of the power of embedding.

Cons:
* The net package is already distributed over many files, this
CL adds another place to look.
* The fix for 3507 was a total of 16 lines changed, this follow
up CL could be considered to be an overreaction as new Conn types
are unlikely to be added in the near future.

[dave_cheney.net, 2012-04-24 13:16:43]

Hello golang-dev@googlegroups.com,

I'd like you to review this change to
https://go.googlecode.com/hg/

[dave_cheney.net, 2012-04-24 13:28:05]

Discussion continued from 

https://groups.google.com/d/topic/golang-dev/rqRnYze6gyQ/discussion

With reference to the godoc output, I have diffed the output of the html and
found only two differences.

1. the source hyperlinks have changed, as the location of the function has
changed.

2. for some implementations of net.Conn#Read and net.Conn#Write, the n and err
return value names have been removed. eg

-                                       <dd>&nbsp; &nbsp; <a
href="#IPConn.Write">func (c *IPConn) Write(b []byte) (int, error)</a></dd>
+                                       <dd>&nbsp; &nbsp; <a
href="#IPConn.Write">func (c *IPConn) Write(b []byte) (n int, err
error)</a></dd>

This is because the prototype for those methods on some types included the names
of the values, others did not. I can add them back to net_posix.go/conn#Read and
conn#Write if requested.

[rsc, 2012-04-25 01:40:11]

LGTM

[rsc, 2012-04-25 01:40:44]

This is fantastic.  I've wanted this to happen from basically
the day that code got checked in.  Thanks for working on it.

[dave_cheney.net, 2012-04-25 01:49:13]

My pleasure, hopefully it will make the remaining code easier to maintain. 

Regarding the comments about Read and Write, do you have a preference?

On 25/04/2012, at 11:40, Russ Cox <rsc@golang.org> wrote:

> This is fantastic.  I've wanted this to happen from basically
> the day that code got checked in.  Thanks for working on it.

[rsc, 2012-04-25 02:10:24]

On Tue, Apr 24, 2012 at 21:49, Dave Cheney <dave@cheney.net> wrote:
> Regarding the comments about Read and Write, do you have a preference?

what's there (no names) looks fine to me

[dave_cheney.net, 2012-04-26 10:02:38]

Thank you for your feedback. I plan to submit this change tomorrow (friday)
night.

[dave_cheney.net, 2012-04-27 12:17:33]

*** Submitted as http://code.google.com/p/go/source/detail?r=fc4a62e14aba ***

net: consolidate common socket functions

In resolving 3507, the fix had to be applied individually to
the four *Conn types, tcp, udp, rawip and unix, due to the
duplicate code in each Conn type.

This CL consolidates the common net.Conn methods that all four
*Conn types implement into a base conn type.


Pros:
* The fix for 3507 would have only needed to be applied to one
method. Further improvements, such as possibly removing the
c.fd != nil check in c.ok(), would benefit from this CL.
* Nearly 300 lines removed from the net package.
* The public interface and documentation are not changed.
* I think this is an excellent example of the power of embedding.

Cons:
* The net package is already distributed over many files, this
CL adds another place to look.
* The fix for 3507 was a total of 16 lines changed, this follow
up CL could be considered to be an overreaction as new Conn types
are unlikely to be added in the near future.

R=golang-dev, rsc
CC=golang-dev
http://codereview.appspot.com/6098047