C++ Convert char array to string array - c++

Question

I have next C++ code in VS2019 under Windows 10:
char const* const fileName = "random_StringArray_10000000";
FILE* infile;
long fileSize;
char* buffer;
size_t readBytes;
infile = fopen(fileName, "rb");
if (infile == NULL)
{
fputs("File error", stderr); exit(1);
}
fseek(infile, 0, SEEK_END);
fileSize = ftell(infile);
rewind(infile);
buffer = (char*)malloc(sizeof(char) * fileSize);
if (buffer == NULL)
{
fputs("Memory error", stderr); exit(2);
}
auto start = chrono::steady_clock::now();
readBytes = fread(buffer, 1, fileSize, infile);
auto end = chrono::steady_clock::now();
if (readBytes != fileSize)
{
fputs("Reading error", stderr); exit(3);
}
fclose(infile);
free(buffer);
auto elapsed_ms = chrono::duration_cast<chrono::milliseconds>(end - start);
cout << "Elapsed ms: " << elapsed_ms.count() << endl;
cout << "String count: " << stringCount << endl;
system("pause");
return 0;
This method used because it is fastest way to read file from disk under VS2019.
Now i need to convert char array to the string array.
random_StringArray_10000000 - UTF8 text file.
Strings lenght 8 - 120 symbols.
Hex view of this file:
0x0D 0x0A separate strings.
Which fastest way to convert char array (buffer) to the C++ string array?

Answer 1

There seems to be a regularity to your data, all strings are eight characters long and separated by the same two characters. With that in mind the following seems fairly fast.
size_t arraySize = readBytes/10;
std::string* array = new std::string[arraySize];
for (size_t i = 0; i < arraySize; ++i)
array[i].assign(buffer + 10*i, 8);
Of course timing is necessary to be sure what is fastest.

Answer 2

Reading lines of text from a file is much simpler if you use the classes from the c++ standard library.
This should be all of the code you need:
#include <fstream>
#include <vector>
#include <string>
#include <iostream>
int main()
{
char const* const fileName = "random_StringArray_10000000";
std::ifstream in(fileName);
if (!in)
{
std::cout << "File error\n";
return 1;
}
std::vector<std::string> lines;
std::string line;
while (std::getline(in, line))
{
lines.push_back(std::move(line));
}
return 0;
}

Answer 3

char as[ ] = "a char array"; : is a char array
char const* const fileName = "random_StringArray_10000000"; : is a c string
This is also a c string:
char* cs = const_cast<char*>( fileName );
If you want std::string use:
std::string s(as);
I wasn't sure which string conversion you wanted so I just added what I could off the top of my head. But here's a compilable example too.