Load file data into memory and saving it back out - c++

Question

I'm working on a rough storage system for a small personal project. I have a struct that holds data for each stored file:
struct AssetTableRow {
std::string id = "Unnamed"; // a unique name given by the user
std::string guid = ""; // a guid generated based on the file data, used to detect duplicate files
std::string data; // binary data of the file
};
I load a file into it like this:
std::streampos size;
char* memblock;
std::ifstream file(filePath, std::ios::in | std::ios::binary | std::ios::ate);
if (file.is_open()) {
size = file.tellg();
memblock = new char[size];
file.seekg(0, std::ios::beg);
file.read(memblock, size);
file.close();
AssetTableRow row = AssetTableRow();
row.id = "myid";
row.guid = "myguid";
row.data = std::string(memblock);
AssetTable.push_back(row);
}
And then to try to write it back out to a file I used this:
std::ofstream file(destPath, std::ios::out | std::ios::binary);
if (file.is_open()) {
printf("Writing...\n", id.c_str());
// I think this is where it might be messing up
file.write((row.data.c_str(), row.data.c_str().size());
file.close();
printf("Done!\n", id.c_str());
}
Now when I try to open the file that got written out (.png sprite sheet) the photo viewer tells me it can't open a file of that type (but opening the original is fine).
If I open up the 2 files in Notepad++ (original on the left) I can see that they are indeed very different, there is almost no data in the output file!
I'm guessing this has something to do with the length on the write or read, but I've tried every different possible value I can think of for them and it doesn't seem to change anything.
If I print the data out to the console after it's read from the original file it appears as it does in the written file, so that leads me to believe the problem is with how I'm reading the file, but I fail to see any problems with that part of the code.
What is wrong with how I'm reading the file that it doesn't appear to be reading the whole file?
Also please forgive any awful mistakes I've made in my code, I'm still learning c++ and don't fully understand some parts of it so my code may not be the best.
EDIT:
As per Superman's advice about strings, I changed my my code to use char* for holding the data instead.
struct AssetTableRow {
std::string id = "Unnamed"; // a unique name given by the user
std::string guid = ""; // a guid generated based on the file data, used to detect duplicate files
char* data; // binary data of the file
};
And changed the read function so it's reading into the struct's data member:
std::ifstream file(actualPath, std::ios::in | std::ios::binary | std::ios::ate);
if (file.is_open()) {
AssetTableRow row = AssetTableRow();
size = file.tellg();
row.data = new char[size];
file.seekg(0, std::ios::beg);
file.read(row.data, size);
file.close();
row.id = "myid";
row.guid = "myguid";
printf("%s\n", row.data);
}
However I still see the same output from when I was using a string, so now I'm even more confused as to why this is happening.
EDIT2:
Upon further investigation I found that the size variable for reading the file reports the correct size in bytes. So now my guess is that for whatever reason it's not reading in the whole file