#include "readlines.h"

// C includes
#include<fcntl.h>
#include<unistd.h>
#include<stdlib.h>
#include<sys/stat.h>
#include<sys/mman.h>

std::vector<std::string> readlines(const char *filename){
	int fd = open(filename, O_RDONLY);
	if(fd < 0){
		perror(filename);
		return std::vector<std::string>();
	}
	struct stat sb;
	fstat(fd, &sb);
	char *mem = (char*)mmap(0, sb.st_size, PROT_READ, MAP_SHARED, fd, 0);
	std::vector<std::string> lines;
	size_t line_beginning = 0;
	for(size_t i = 0; i < sb.st_size; i++){
		if(mem[i] == '\n'){
			// add a line that begins at line_beginning and ends at i
			lines.push_back(std::string(mem + line_beginning, i - line_beginning));
			line_beginning = i + 1;		
		}
	}	
	munmap(mem, sb.st_size);	
	close(fd);
	return lines;
}