Question

What is the best and most effective way to extract a string from a string? I will need this operation to be preforms thousands of times.

I have this string and I’d like to extract the URL. The URL is always after the “url=” substring until the end of the string. For example:

http://foo.com/fooimage.php?d=AQA4GxxxpcDPnw&w=130&h=130&url=http00253A00252F00252Fi1.img.com00252Fvi00252FpV4Taseyww00252Fhslt.jpg

and I need to extract the

http00253A00252F00252Fi1.img.com00252Fvi00252FpV4Taseyww00252Fhslt.jpg

I want to avoid using split and such.

Answer 1

std::string inStr;

//this step is necessary
size_t pos = inStr.find("url=")；

if(pos !=  std::string::npos){
  char const * url = &inStr[pos + 4];
  // it is fine to  do any read only operations with url
  // if you would apply some modifications to url, please make a copy string
}