Why do structs disappear in my file when i write to it - c++

Question

Whenever I write a struct to a binary file, any structs after it go away, although any structs written before it remain.
I'm opening the file stream in binary output mode and my structs contain only primitive datatypes.
I also made sure to make separate file streams for each operation.
Output:
create players
765
51
save 1
765
save 2
765
51
** struct definition**
struct player{
int UUID;
};
Function saving the structs
//updates player information in the player database
bool savePlayer(player playerData){
//count how manny playrs are in file
// Create our objects.
fstream countstream;
int count = 0;
countstream.open ("player.bin", ios::binary | ios::in);
if(countstream.is_open()){
countstream.seekg(0, ios::end); //set position to end
count = countstream.tellg()/sizeof(player);
//retuns number of players in file by getting
//the index of the position and dividing it by the size of each player
//no loops required :D
}
countstream.close();
bool found = false;
//if file is not empty,look through it
if(count > 0){
player playerTable[count];
fstream readstream;
readstream.open ("player.bin", ios::binary | ios::in);
//build table
for(int i = 0; i < count; i++){
readstream.seekg(i, ios::beg); //set position to end
readstream.read(reinterpret_cast <char *> (&playerTable[i]),
sizeof(player));
readstream.close();
}
//check table
for(int i = 0; i < count; i++){
if(playerTable[i].UUID == playerData.UUID){
found = true;
playerTable[i] = playerData;
}
}
//write table back to file
if(found){
fstream writestream; //create writestream
writestream.open ("player.bin", ios::binary | ios::out);
for(int i = 0; i < count; i++){
writestream.seekg(i, ios::beg); //set position to player
writestream.write(reinterpret_cast <char *> (&playerTable[i]),
sizeof(player));
if(!writestream.fail()){
writestream.close();
return true;
}
else{
writestream.close();
return false;
}
readstream.close();
}
}
}
//append if not found
if(!found){
fstream appendstream;
appendstream.open ("player.bin", ios::binary | ios::out |
ios::app);
appendstream.write(reinterpret_cast <char *> (&playerData),
sizeof(player));
appendstream.close();
if(!appendstream.fail()){
appendstream.close();
return true;
}
else{
appendstream.close();
return false;
}
}
return false;
}
Any suggestions will be appreciated.

Answer 1

You're making this much harder than necessary. You don't need to read all the data into an array. You can read each item into a variable, and check if it's the one you want to replace. And by opening the file in both read and write mode, you can simply overwrite that entry in the file while reading it.
bool savePlayer(player playerData){
player curPlayer;
fstream stream;
stream.open ("player.bin", ios::binary | ios::in | ios::out);
while(stream.read(reinterpret_cast<char*>(&curPlayer), sizeof(curPlayer))){
if (curPlayer.UUID == playerData.UUID) {
stream.seekg(-(sizeof curPlayer), ios::cur); // back up to location of current player
break;
}
}
stream.write(reinterpret_cast<char*>(&playerData), sizeof playerData);
stream.close();
return false;
}