File relative

How to read the file

• std::ifstream input stream, for reading files

• file() file function, ( filepath ,bit flags(open mode))

• std::ios::ate at the end, this mean once the file open we seek the end immediately

• std::ios::binary open the file in binary mode, raw stream of bytes, avoid any unwanted text transformations

• std::ios::ate | std::ios::binary we want both gpointer o to end the file (so can use tellg()) , and read as binary

why {} instead of ():

1. uniform initialization. so we tell this is object definition, not function declaration.

2. strict type checking, prevent implicit type conversion

Open file error check

if (!file.is_open()){
  throw std::runtime_error("fail to open file: " + filepath)
  //filepath is incorrect or no permission to open the file
  }

File size

the last of file

file.tellg() return std::streamposdata, means the pointer’s location in the file

size_t filesize = static_cast<size_t>(file.tellg());

other example:

double value = 3.14;
int intValue = static_cast<int>(value); // transfer to >integer
std::cout << intValue; // output: 3

the first of the file

file.seekg(0); //move the pointer to the beginning

Create buffer

file.read(buffer.data(), fileSize);

file.close();

return buffer;