Document.cpp

#include <algorithm>
#include <iostream>
#include <vector>
#include <list>
#include "Document.h"

std::istream &operator>>(std::istream &is, Document &d)
{
	char ch = ' ';
	for ( ; is.get(ch);)
	{
		d.line.back().push_back(ch);	// add the character
	}
	if (ch == '\n')
	{
		d.line.push_back(Line{});		// add another line
	}
	if (d.line.back().size())
	{
		d.line.push_back(Line{});		// add final empty line
	}
	return is;
}

Document::Text_iterator &Document::Text_iterator::operator++()
{
	++pos;		// proceed to the next character
	if (pos == (*ln).end())
	{
		++ln;	// proceed to the next line
		pos = (*ln).begin();	// bad if ln == line.end(); so make sure it isn't
	}
	return *this;
}

Document::Text_iterator Document::Text_iterator::operator++(int n)
{
	auto ret = *this;
	pos += n;
	if (pos == (*ln).end())
	{
		++ln;
		pos = (*ln).begin();
	}
	ret = *this;
	return ret;
}

Document::Text_iterator Document::Text_iterator::find_txt(Document::Text_iterator first, Document::Text_iterator last, const std::string &s)
{
	if (s.size() == 0)
	{
		return last;
	}

	char first_char = s[0];
	while (true)
	{
		auto p = std::find(first, last, first_char);
		if (p == last || match(p, last, s))
		{
			return p;
		}
		first = ++p;
	}
}

bool Document::Text_iterator::match(Document::Text_iterator first, Document::Text_iterator last, const std::string &str)
{
	if (str.empty())
	{
		return false;
	}
	
	for (char i = 0, j = *first; i < str.length(), j != *last; ++i, ++j)
	{
		if (i != j)
		{
			return false;
		}
	}
	return true;
}

Document.h

#ifndef DOCUMENT_H
#define DOCUMENT_H

#include <list>
#include <iostream>
#include <vector>
#include <iterator>

using Line = std::vector<char>;

struct Document
{
	std::list<Line> line;
	class Text_iterator : public std::iterator<std::bidirectional_iterator_tag, Line, Line, Line*, Line&>
		// keep track of line and character position within a line
	{
		std::list<Line>::iterator ln;
		Line::iterator pos;
	public:
		// start iterator at line ll's character position pp
		Text_iterator(std::list<Line>::iterator ll, Line::iterator pp)
			: ln{ ll }, pos{ pp } {}
		char &operator*() { return *pos; }
		Text_iterator &operator++();
		Text_iterator operator++(int n);
		bool operator==(const Text_iterator &other) { return ln == other.ln && pos == other.pos; }
		bool operator!=(const Text_iterator &other) { return !(*this == other); }
		Text_iterator find_txt(Text_iterator first, Text_iterator last, const std::string &s);
		bool match(Text_iterator first, Text_iterator last, const std::string &str);
	};
	Document() { line.push_back(Line{}); }
	Text_iterator begin() { return Text_iterator(line.begin(), (*line.begin()).begin()); }
	Text_iterator end()
	{
		auto last = line.end();
		--last;		// we know know that the document is not empty
		return Text_iterator(last, (*last).end());
	}
};

std::istream &operator>>(std::istream &is, Document &d);

#endif

main.cpp

#include <iostream>
#include <fstream>
#include <list>
#include <vector>
#include "Document.h"

void print(Document &d);
void erase_line(Document &d, int n);
template<typename Iter>
void advance(Iter &p, int n);

int main()
{
	std::string str{ "hello world" };
	Document doc;
	for (int i = 0; i < str.length(); ++i)
	{
		doc.line.back().push_back(str[i]);
	}
	Document::Text_iterator it = doc.begin();
	auto matched = it.find_txt(it, doc.end(), "hello");
	if (matched != doc.end())
	{
		std::cout << "Found\n";
	}
}

void print(Document &d)
{
	for (auto p : d)
	{
		std::cout << p;
	}
}

void erase_line(Document &d, int n)
{
	if (n < 0 || n >= d.line.size() - 1)
	{
		return;
	}
	auto p = d.line.begin();
	advance(p, n);
	d.line.erase(p);
}

template<typename Iter>
void advance(Iter &p, int n)
{
	while (n > 0)
	{
		++p;
		--n;
	}
	if (n < 0)
	{
		while (n < 0)
		{
			--p;
			++n;
		}
	}
}