[libcamera-devel] [PATCH 1/3] libcamera: utils: Add string splitter utility function

[Laurent Pinchart]

Hi Kieran,

On Thu, Feb 13, 2020 at 01:24:27PM +0000, Kieran Bingham wrote:
> On 13/02/2020 13:09, Kieran Bingham wrote:
> > From: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> > 
> > Add a utils::split() function that splits a string for the purpose of
> > iterating over substrings. It returns an object of unspecified type that
> > can be used in range-based for loops.
> > 
> > Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> 
> This is really helpful, thanks
> 
> Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
> 
> > ---
> >  Documentation/Doxyfile.in     |  1 +
> >  src/libcamera/include/utils.h | 34 +++++++++++++++++++
> >  src/libcamera/utils.cpp       | 62 +++++++++++++++++++++++++++++++++++
> >  3 files changed, 97 insertions(+)
> > 
> > diff --git a/Documentation/Doxyfile.in b/Documentation/Doxyfile.in
> > index 1c46b04b3f7e..beeaf6d3cf48 100644
> > --- a/Documentation/Doxyfile.in
> > +++ b/Documentation/Doxyfile.in
> > @@ -880,6 +880,7 @@ EXCLUDE_SYMBOLS        = libcamera::BoundMethodArgs \
> >                           libcamera::BoundMethodStatic \
> >                           libcamera::SignalBase \
> >                           libcamera::*::Private \
> > +                         libcamera::*::details::* \
> >                           std::*
> >  
> >  # The EXAMPLE_PATH tag can be used to specify one or more files or directories
> > diff --git a/src/libcamera/include/utils.h b/src/libcamera/include/utils.h
> > index e467eb21c518..080ea6614de0 100644
> > --- a/src/libcamera/include/utils.h
> > +++ b/src/libcamera/include/utils.h
> > @@ -108,6 +108,40 @@ inline _hex hex<uint64_t>(uint64_t value, unsigned int width)
> >  
> >  size_t strlcpy(char *dst, const char *src, size_t size);
> >  
> > +namespace details {
> > +
> > +class StringSplitter
> > +{
> > +public:
> > +	StringSplitter(const std::string &str, const std::string &delim);
> > +
> > +	class iterator
> > +	{
> > +	public:
> > +		iterator(const StringSplitter *ss, std::string::size_type pos);
> > +
> > +		iterator &operator++();
> > +		std::string operator*() const;
> > +		bool operator!=(const iterator &other) const;
> > +
> > +	private:
> > +		const StringSplitter *ss_;
> > +		std::string::size_type pos_;
> > +		std::string::size_type next_;
> > +	};
> > +
> > +	iterator begin() const;
> > +	iterator end() const;
> > +
> > +private:
> > +	std::string str_;
> > +	std::string delim_;

Note that I would really like if we could store references to str and
delim here, but my attempt to do so resulted in problems, I believe due
to the values passed to the StringSplitter constructor being
temporaries. I don't know if there's a good way to solve that.

> > +};
> > +
> > +} /* namespace details */
> > +
> > +details::StringSplitter split(const std::string &str, const std::string &delim);
> > +
> >  } /* namespace utils */
> >  
> >  } /* namespace libcamera */
> > diff --git a/src/libcamera/utils.cpp b/src/libcamera/utils.cpp
> > index 4beffdab5eb6..fe027c0b009c 100644
> > --- a/src/libcamera/utils.cpp
> > +++ b/src/libcamera/utils.cpp
> > @@ -199,6 +199,68 @@ size_t strlcpy(char *dst, const char *src, size_t size)
> >  	return strlen(src);
> >  }
> >  
> > +details::StringSplitter::StringSplitter(const std::string &str, const std::string &delim)
> > +	: str_(str), delim_(delim)
> > +{
> > +}
> > +
> > +details::StringSplitter::iterator::iterator(const details::StringSplitter *ss, std::string::size_type pos)
> > +	: ss_(ss), pos_(pos)
> > +{
> > +	next_ = ss_->str_.find(ss_->delim_, pos_);
> > +}
> > +
> > +details::StringSplitter::iterator &details::StringSplitter::iterator::operator++()
> > +{
> > +	pos_ = next_;
> > +	if (pos_ != std::string::npos) {
> > +		pos_ += ss_->delim_.length();
> > +		next_ = ss_->str_.find(ss_->delim_, pos_);
> > +	}
> > +
> > +	return *this;
> > +}
> > +
> > +std::string details::StringSplitter::iterator::operator*() const
> > +{
> > +	std::string::size_type count;
> > +	count = next_ != std::string::npos ? next_ - pos_ : next_;
> > +	return ss_->str_.substr(pos_, count);
> > +}
> > +
> > +bool details::StringSplitter::iterator::operator!=(const details::StringSplitter::iterator &other) const
> > +{
> > +	return pos_ != other.pos_;
> > +}
> > +
> > +details::StringSplitter::iterator details::StringSplitter::begin() const
> > +{
> > +	return iterator(this, 0);
> > +}
> > +
> > +details::StringSplitter::iterator details::StringSplitter::end() const
> > +{
> > +	return iterator(this, std::string::npos);
> > +}
> > +
> > +/**
> > + * \fn split(const std::string &str, const std::string &delim)
> > + * \brief Split a string based on a delimiter
> > + * \param[in] str The string to split
> > + * \param[in] delim The delimiter string
> > + *
> > + * This function splits the string \a str into substrings based on the
> > + * delimiter \a delim. It returns an object of unspecified type that can be
> > + * used in a range-based for loop and yields the substrings in sequence.
> > + *
> > + * \return An object that can be used in a range-based for loop to iterate over
> > + * the substrings
> > + */
> > +details::StringSplitter split(const std::string &str, const std::string &delim)
> > +{
> > +	return details::StringSplitter(str, delim);
> > +}
> > +
> >  } /* namespace utils */
> >  
> >  } /* namespace libcamera */

-- 
Regards,

Laurent Pinchart