Hi ,
I read email's Sam carefully, but i didn't test yet.Do you think if i
implement same Sam i can implement string obj in structure?
--mohsen
On Sun, 2011-12-25 at 21:04 -0200, Juan Ramírez wrote:
> 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
> >
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