svn commit: r315773 - head/sbin/devd

[Cy Schubert]

In message <1490297671.58015.102.camel at freebsd.org>, Ian Lepore writes:
> On Thu, 2017-03-23 at 19:58 +0100, Roman Divacky wrote:
> > On Thu, Mar 23, 2017 at 02:36:51AM +0000, Warner Losh wrote:
> > > 
> > > Author: imp
> > > Date: Thu Mar 23 02:36:51 2017
> > > New Revision: 315773
> > > URL: https://svnweb.freebsd.org/changeset/base/315773
> > > 
> > > Log:
> > > Â  Implement quote escaping. String values may now contain " if you
> > > Â  it is preceded by \.
> > > Â Â 
> > > Â  foo="I \"like\" C++"
> > > Â Â 
> > > Â  gives the value 'I "like" C++' to the variable 'foo'. If a
> > > character
> > > Â  other than " follows the \, both the \ and that character are
> > > passed
> > > Â  through.
> > > Â Â 
> > > Â  Differential Revision: https://reviews.freebsd.org/D6286
> > > Â  Sponsored by: Netflix
> > > 
> > > Modified:
> > > Â  head/sbin/devd/devd.cc
> > > Â  head/sbin/devd/devd.hh
> > > 
> > > Modified: head/sbin/devd/devd.cc
> > > ===================================================================
> > > ===========
> > > --- head/sbin/devd/devd.cc	Thu Mar 23 02:33:27 2017	(
> > > r315772)
> > > +++ head/sbin/devd/devd.cc	Thu Mar 23 02:36:51 2017	(
> > > r315773)
> > > @@ -411,6 +411,32 @@ var_list::is_set(const string &var) cons
> > > Â 	return (_vars.find(var) != _vars.end());
> > > Â }
> > > Â 
> > > +/** fix_value
> > > + *
> > > + * Removes quoted characters that have made it this far. \" are
> > > + * converted to ". For all other characters, both \ and following
> > > + * character. So the string 'fre\:\"' is translated to 'fred\:"'.
> > > + */
> > > +const std::string &
> > > +var_list::fix_value(const std::string &val) const
> > > +{
> > > +	char *tmp, *dst;
> > > +	const char *src;
> > > +	std::string *rv;
> > > +
> > > +	dst = tmp = new char[val.length()];
> > > +	src = val.c_str();
> > > +	while (*src) {
> > > +		if (*src == '\\' && src[1] == '"')
> > > +			src++;
> > > +		else
> > > +			*dst++ = *src++;
> > > +	}
> > > +	rv = new string(tmp);
> > > +	delete tmp;
> > > +	return *rv;
> > > +}
> > Can the temporary char[] be stack allocated? Also, when returning a
> > reference to
> > a heap allocated string who is responsible for freeing it? Perhaps
> > you can just
> > return std::string and let the compiler optimize it?
> > 
> > Roman
> > 
> 
> Returning a reference to a new'd string is not good.
> 
> IMO, the implementation of the function should take into account the
> idea that embedded escaped quotes are rare. Â The function should be
> optimized for readability and the common case of simply copying the
> string unmodified, something like:
> 
> 
> std::string
> var_list::fix_value(const std::string &val) const
> {
> 	std::string rv(val);
> 	std::string::size_type pos(0);
> 
> 	while ((pos = rv.find("\\\"", pos)) != rv.npos) {
> 		rv.erase(pos, 1);
> 	}
> 	return (rv);
> }

This revision caused devd a little gas. It failed to start moused for usb 
attached mice (ums0 & ums1) to my latpop and nut failed to recognize my USB 
connected UPS on a server.  downstairs due to a permission issue which nut 
provides a devd.conf file with:

	chgrp uucp /dev/$cdev; chmod g+rw /dev/$cdev


-- 
Cheers,
Cy Schubert <Cy.Schubert at cschubert.com>
FreeBSD UNIX:  <cy at FreeBSD.org>   Web:  http://www.FreeBSD.org

	The need of the many outweighs the greed of the few.