Hello I'm writing this method. I want it to extract from a given buffer a portion that is in a given place. I have a string like this something=one;something=two and I want to get "one"
This is my idea :
static std::string Utils::getHeader( unsigned char * buffer)
{
std::string *str = new std::string(buffer);
std::size_t b_pos = str->find("=");
std::size_t a_pos = str->find(";");
return str->substr((a_pos + 1) ,(b_pos + 1));
}
but on eclipse I get this error in reference to the std::string substr method
Invalid arguments ...
Candidates are:
std::basic_string<char,std::char_traits<char>,std::allocator<char>> substr(?, ?)
Can someone explain me why I get this error and how I can fix it?
The code should probably look like:
static std::string Utils::getHeader(unsigned char * buffer, size_t size)
{
if(!buffer || !size)
return "";
const std::string str(reinterpret_cast<char*>(buffer), size);
std::size_t b_pos = str.find("=");
if(b_pos == std::string::npos)
throw ...;
std::size_t a_pos = str.find(";");
if(a_pos == std::string::npos)
throw ...;
if(b_pos > a_pos)
throw ...'
return str.substr((a_pos + 1), (b_pos + 1));
}
substr takes a starting position and a length. Maybe something like:
const size_t start = b_pos + 1;
const size_t length = (a_pos + 1) - (b_pos + 1) + 1;
And then, return str.substr(start, length);.
I'm not certain of the a_pos + 1 and b_pos + 1 is correct, though. Be certain that's what you want.
Ok, assuming you know that the input string is formatted as you mentioned you probably want something like this:
static std::string Utils::getHeader(const std::string & params) {
size_t start = params.find('=') +1; // Don't include =
size_t length = params.find(';') - start; // Already not including ';'
return str.substr(start, length);
}
