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

[Kieran Bingham]

Hi Laurent,

On 13/02/2020 13:36, Laurent Pinchart wrote:
> 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.

This isn't used in any hot-path, so I'm not worried for now.

If it comes up in the future it can be investigated then.

Would you like to add a todo: ? or not worth it?


>>> +};
>>> +
>>> +} /* 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
--
Kieran