Hi,
If you want to write and read a raw structure to a file, using c++
objects is NOT recommended at all! At least not using fread/fwrite
Given that fields have fixed length, a good solution could be using a
raw char array, something like this:
#define FIELD_LENGTH 101
struct book {
char name[FIELD_LENGTH];
char author[FIELD_LENGTH];
char publisher[FIELD_LENGTH];
char translator[FIELD_LENGTH];
bool translation;
bool stock;
};
// Write
book mybook;
fwrite(&mybook, sizeof(book), 1, filePtr);
// Read
book mybook;
fread(&mybook, sizeof(book), 1, filePtr);
It will work awesomely, i promise!
Saludos!
Juan
On Sun, Dec 25, 2011 at 11:01 PM, Mohsen Pahlevanzadeh
<mohsen@xxxxxxxxxxxxxxxxx> wrote:
>
> Dear all,
> I have a program that it should write a struct in binary file.My struct
> is here:
> ///////////////////
> struct book{
> string name;
> string author;
> string publisher;
> string translator;
> bool translation;
> bool stock;
> };
> ////////////////////////
> Then i wrote the following function that write to file:
> ////////////////////////////
> void WriteFile::addNode(string name, string publisher, string author,
> bool stock,string translator , bool translation ){
> book * tmp = new book;
> int line = 1;
> short unsigned i;
> string memory;
>
> short unsigned size = 100 - strlen((const char *)name.data());
> memory = '`';
> for (i =0 ;i<size;i++)
> memory += '`';
> tmp->name = name + memory;
>
> size = 100 - strlen((const char *)publisher.data());
> memory = '`';
> for (i =0 ;i<size;i++)
> memory += '`';
> tmp->publisher = publisher + memory;
>
> size = 100 - strlen((const char *)author.data());
> memory = '`';
> for (i =0 ;i<size;i++)
> memory += '`';
> tmp->author = author + memory;
>
>
> size = 100 - strlen((const char *)translator.data());
> memory = '`';
> for (i =0 ;i<size;i++)
> memory += '`';
> tmp->translator = translator + memory;
>
> tmp->stock = stock;
> tmp->translation = translation;
>
> fseek(bookFilePtr,0L,SEEK_END);
> fwrite(ptr,408,1,bookFilePtr);
>
>
> ///////////////////////////
> Note that i wanted to use fixed length of each field, So, for example
> if a field has 30 character, i fill 71 character "`" at end of field. 30
> +71= 101
> So 4*string*101+2*bool*4=408 = length of struct.
>
> Then i wrote the following function to read all of records:
>
> ///////////////////////////////////////////////
> void ReadFile::printList(){
> fseek(bookFilePtr,0L,SEEK_SET); // set to begin of file
>
>
> int counter = 1;
> long int line = 1;
> int pageCounter = 1;
>
>
> while ( fread(bookPtrObj,408,1,bookFilePtr) == 1 ){
> string output;
> mvprintw(++line, 27,"***Title*****************Value*********" );
> output = "Name: " + bookPtrObj->name;
> mvprintw(++line, 27, output.data());
>
> output = "Publisher: " + bookPtrObj->publisher;
> mvprintw(++line, 27,output.data());
>
> output = "Author: " + bookPtrObj->author;
> mvprintw(++line, 27,output.data());
>
> output = "Translator: " + bookPtrObj->translator;
> if (bookPtrObj->translation == true )
> mvprintw(++line, 27,output.data());
>
> if (bookPtrObj->stock != true )
> mvprintw(++line, 27,"Stock: The given book doesn't
> exist.");
> else
> mvprintw(++line, 27,"Stock: The given book exist.");
>
> if ( pageCounter % 3 == 0){
> mvprintw(++line, 27,"Press any key to see next page...");
> getch();
> clear();
> line = 1;
>
> }
> pageCounter++;
> refresh();
>
> fseek(bookFilePtr, counter * sizeof(struct book) ,SEEK_SET); // seek
> to next data
> counter ++;
> }
> }
>
> ///////////////////////////////////////////////
>
> But i get the segmentation fault on read each field.
> Because i didn't specify length of each field in read.How i specify
> length of each field in reading?
>
> --mohsen
>
