CODEWITHSUNDEEP
c++algorithmvector
djsp
djsp

Reputation: 2293

c++ copy-until algorithm

I have a function that is expected to receive a list of individual characters through a const char *. If I had to copy each character to a vector<char>, what would be the best (i.e.: most efficient) way to perform the operation?

I have thought about copy in algorithm, not sure if it's the more "elegant" solution:

void
example
    (const char * const s)
{
    copy(s, s+strlen(s), myvector.begin())
}

(hope that, given my "personal" indenting style, the code is still readable for you)

But I'm sure the STL implements something that allows me to copy until a null character is found in the string.

(If you wonder why I'm receiving a const char *, well, that's the type the compiler creates when the user makes use of a temporal variable, and my function is expected to be called like example("fvh"). Alternative solutions are welcomed)

Thanks in advance. Best regards, Kalrish

EDIT:

After trying what @ipc and @juanchopanza said, I feel stupid: it works like a charm.

Not still sure if I will lose performance, but, in any case, the compiler makes the implicit conversion, and it's pure C++, so it is definitely the way to go.

Thanks a lot, and sorry. Good luck, Kalrish

Upvotes: 1

Views: 931

Answers (2)

Yakk - Adam Nevraumont
Yakk - Adam Nevraumont

Reputation: 275340

I am not aware of a copy until.

Here is a copy until '\0' however:

#include <cstddef>
#include <algorithm>
#include <iostream>
#include <iterator>

struct str_copy_iterator {
  bool at_end;
  char const* ptr;
  char operator*() const { return *ptr; }
  typedef char value_type;
  typedef std::ptrdiff_t difference_type;
  typedef char* pointer;
  typedef char& reference;
  typedef std::output_iterator_tag iterator_category;
  str_copy_iterator():at_end(true) {}
  str_copy_iterator(char const* p):at_end(!p||!*p), ptr(p) {}
  str_copy_iterator& operator++() {
    ++ptr;
    at_end = !*ptr;
    return *this;
  }
  str_copy_iterator operator++(int) {
    str_copy_iterator tmp = *this;
    ++(*this);
    return tmp;
  }
  bool operator!=( str_copy_iterator const& o ) const {
     return !(*this == o);
  }
  bool operator==( str_copy_iterator const& o ) const {
    if (at_end)
      return o.at_end;
    if (o.at_end)
      return false;
    return ptr == o.ptr;
  }
};
int main() {
   const char* bob = "hello world!";
   char buff[100] = {};
   std::copy(str_copy_iterator(bob), str_copy_iterator(), &buff[0] );
   std::cout << buff << "\n";
}

extending the str_copy_iterator into a generic iterator_until wrapper is left as an exercise to the reader.

Upvotes: 2

juanchopanza
juanchopanza

Reputation: 227390

You can use an std::string, and the std::vector::assign method.

void example(const std::string& s)
{
    myvector.assign(s.begin(), s.end()):
}

Upvotes: 0

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