This is typically how I read in an asset in a game. MMAP is your friend.

mapfile.cpp

#include "Platform.h"

bool Platform::mapFile(const char* filename, uint8_t** bytes, long* length) {
    FILE* fin = fopen(Platform::pathForFile(filename).c_str(), "rb");
    
    if (!fin) {
        dbgLog("error opening file '%s'", filename);
        return false;
    }
    
	// seek to end, get size
	fseek(fin, 0L, SEEK_END);
	*length = ftell(fin);
    
	// rewind to beginning
	fseek(fin, 0L, SEEK_SET);
    
    // map the entire file to memory
    *bytes = (uint8_t*)mmap(NULL, *length, PROT_READ, MAP_SHARED, fileno(fin), 0);
    
    // no need for file anymore
    fclose(fin);
    
    return true;
}

void Platform::unmapFile(uint8_t** bytes, long* length) {
    munmap(*bytes, *length);
}

mapfile.h

#pragma once

namespace Platform
{

bool mapFile(const char* filename, uint8_t** bytes, long* length);
void unmapFile(uint8_t** bytes, long* length);

};