searching binary file

[csstudent123]

Hello I am completely baffled by bin file read/write and positioning. Here I wish to search a chemical name info by symbol. Here is my struct

struct chemicalElement {

    int atomicNumber;
	char name[118];
	char symbol[3];
	float mass;
};

I successfully wrote to file.dat as binary but having problem in reading and searching...here is my func...

void searchSymbol(char sym, chemicalElement chemEl[]){

    ifstream binFile;
    unsigned short int i=0;

    binFile.open("chemicalEl.dat", ios::binary);

    if(binFile.good())
        cout<<"File read for search"<<endl;

    while(binFile.good()){/////Here I am lost what to do and how
        binFile.read((char*)&chemEl[i], sizeof(chemicalElement));
        if(strcmp(chemEl[i].symbol, sym)==0 )
            cout<<chemEl[i];///display all info about that element
        else
            i++;

    }
    binFile.close();


}

[Yay295]

I would recommend not opening the file as binary if you want to search for text within it.

[LbXjz8AR]

Try using the topic of classes and objects. I hope u get my point.

[csstudent123]

I managed to search the file but my output is like this

262 Dunium Db   105
272 Lawrencium  Lr     103
.......

using tab for every space

my binary file write function

struct chemicalElement {

    int atomicNumber;
	char name[17];
	char symbol[3];
	float mass;

};


void makeBin(chemicalElement chemEl){

    ifstream read;
    ofstream rite;

    read.open("chemicalElements.txt", ios::in);//open for read
    rite.open("chemicalEl.dat", ios::binary);//open binary file for write
    if (read.good())
        cout<<"Open success for read"<<endl;

    while(read.good()){
        read>>chemEl.mass;
        read>>chemEl.name;
        read>>chemEl.symbol;
        read>>chemEl.atomicNumber;
        rite.write((char*)&chemEl, sizeof(chemicalElement));//write to binary file

    }
    read.close();

    rite.close();
}

//Search binary file by mass 

void getInfo(float Mass, chemicalElement chemEl){

 ifstream binFile;


    binFile.open("chemicalEl.dat", ios::binary);

    if(binFile.good())
        cout<<"File read for search"<<endl<<endl;


    while(binFile.good()){
        binFile.read((char*)&chemEl, sizeof(chemicalElement));

        if(chemEl.mass>Mass){//search from minimum mass
            cout<<chemEl.mass<<"\t"<<chemEl.name<<"\t"<<chemEl.symbol<<"\t"<<chemEl.atomicNumber<<endl;
           }
        else{
            if(binFile.eof())
                cout<<"Element not found";
            }
    }
    binFile.close();

}

I want equal spacing for all outputs

[LbXjz8AR]

try to put "\n" in alterante in line 52. after chemE1.name<<\n<<..
try putting \n as i showed. It will give you the mass, namee, symbol and atomic number. See if it works.

[dhayden]

void searchSymbol(char sym, chemicalElement chemEl[]){
...
if(strcmp(chemEl[i].symbol, sym)==0 )

sym should be declared as char*, not char.

Also why are you passing and populating the whole array? Should you just return the one item that you find?
void searchSymbol(char &sym, chemicalElement& chemEl){
Similarly, getInfo() needs to pass chemEl by reference if you want the caller to have access to the result:
void getInfo(float Mass, chemicalElement& chemEl){

    while(read.good()){
        read>>chemEl.mass;
        read>>chemEl.name;
        read>>chemEl.symbol;
        read>>chemEl.atomicNumber;
        rite.write((char*)&chemEl, sizeof(chemicalElement));//write to binary file 

This will probably fail at the end of the file. It should be:

    while(true){
        read>>chemEl.mass;
        read>>chemEl.name;
        read>>chemEl.symbol;
        read>>chemEl.atomicNumber;
        if (!read.good()) break;
        rite.write((char*)&chemEl, sizeof(chemicalElement));//write to binary file
     }

Similarly your read loop should be:
while(binFile.read((char*)&chemEl, sizeof(chemicalElement))) {