seekg

cobraun85 (5)
I am trying to read data from a file one line at a time. The file was originally written by this same program using \n to separate data. It seems I should use seekg to move to the next piece of data, but I'm not sure how to implement it.

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#include <iostream>
#include <fstream>
#include <iomanip>
#include <string>

using namespace std;

struct Item
{
	string ItemName;
	string BrandName;
	string UnitLabel;
	int Department;
	int Location;
	float UnitCost;
	Item* NextItem;
	Item* PreviousItem;
};

class ItemList
{
private:
	Item* FirstItem;
	int ListLength;

public:
	ItemList()
	{
		FirstItem = NULL;
		ListLength = 0;
	}
	void AddItem(string IN, string BN, string UL, int D, int L, float UC)
	{
		Item* NewItem = new Item;
		NewItem->ItemName = IN;
		NewItem->BrandName = BN;
		NewItem->UnitLabel = UL;
		NewItem->Department = D;
		NewItem->Location = L;
		NewItem->UnitCost = UC;
		NewItem->NextItem = FirstItem;
		FirstItem = NewItem;
		ListLength++;
	}
	bool ListOccupied()
	{
		return (FirstItem != NULL);
	}
	int Length()
	{
		return ListLength;
	}
	Item* FirstItemLoc()
	{
		return FirstItem;
	}
	void DisplayAllItemList(int i)
	{
		Item* CurrentItem = FirstItem;
		int ItemCount = 0;
		while(CurrentItem!=NULL)
		{
			if(ItemCount == i)
			{
				cout << CurrentItem->ItemName << "\t"
					 << CurrentItem->BrandName << "\t"
					 << CurrentItem->UnitCost << "\t"
					 << CurrentItem->UnitLabel << "\t"
					 << CurrentItem->Department << "\t"
					 << CurrentItem->Location << endl;
				CurrentItem = CurrentItem->NextItem;
				break;
			}
			ItemCount++;
			CurrentItem = CurrentItem->NextItem;
		}
	}
};

void AddItem(string&,string&,string&,int&,int&,float&);
bool MoreItems();
bool Menu(int&);
bool MoreLocations();
void SaveAllItemList(int,Item*);
void LoadAllItemList(string&,string&,string&,int&,int&,float&,ItemList);

int main()
{
	ItemList AllItems;
	string ItemName;
	string BrandName;
	string UnitLabel;
	int Department;
	int Location;
	float UnitCost;
	int CurrentTask=0;

	while(Menu(CurrentTask))
	{
		switch(CurrentTask)
		{
		case 0: 
		case 1: do
				{
					AddItem(ItemName,BrandName,UnitLabel,Department,Location,UnitCost);
					AllItems.AddItem(ItemName,BrandName,UnitLabel,Department,Location,UnitCost);
				}while(MoreItems());
				break;
		case 2: do
				{

				}while(MoreLocations());
				break;
		case 3: SaveAllItemList(AllItems.Length(),AllItems.FirstItemLoc());
				break;
		case 4: {  // Here's where I need help.
					int ListLength;
					ifstream inData;
					inData.open("list.out");
					inData >> ListLength;
					for(int i=0;i<ListLength;i++)
					{
						
						inData.seekg(2,ios_base::cur);
						getline(inData,ItemName);
						inData.seekg(1,ios_base::cur);
						getline(inData,BrandName);
						inData.seekg(1,ios_base::cur);
						inData >> UnitCost;
						inData.seekg(1,ios_base::cur);
						getline(inData,UnitLabel);
						inData.seekg(1,ios_base::cur);
						inData >> Department;
						inData.seekg(1,ios_base::cur);
						inData >> Location;
						AllItems.AddItem(ItemName,BrandName,UnitLabel,Department,Location,UnitCost);
					}
					inData.close();
					break;
				}
		case 5: for(int i=0;i<AllItems.Length();i++) AllItems.DisplayAllItemList(i);
				system("PAUSE");
		}
	}

	return 0;
}
void AddItem(string& IN, string& BN, string& UL, int& D, int& L, float& UC)
{
	system("cls");
	cout << "Enter data for new item below.\n\n"
		 << "\tItem Name:     ";
	cin.ignore();
	getline(cin,IN);
	cout << "\tBrand Name:    ";
	getline(cin,BN);
	cout << "\tUnit Cost:     ";
	cin >> UC;
	cout << "\tUnit Label:    ";
	cin.ignore();
	getline(cin,UL);
	cout << "\tDepartment:    ";
	cin >> D;
	cout << "\tLocation:      ";
	cin >> L;
}
bool MoreItems()
{
	char UserReply;
	do{
		cout << "Are there more items to enter? (Y/N) -->  ";
		cin >> UserReply;
		UserReply=toupper(UserReply);
		if(UserReply!='Y'&&UserReply!='N') cout << "*** Invalid response *** \n";
	}while(UserReply!='Y'&&UserReply!='N');
	return (UserReply=='Y');
}
bool Menu(int& CurrentTask)
{
	int UserReply;
	do
	{
		system("cls");
		cout << "What would you like to do?\n"
			 << "\t0)  Quit.\n"
			 << "\t1)  Add new item.\n"
			 << "\t2)  Add new location.\n"
			 << "\t3)  Save All Item list.\n"
			 << "\t4)  Load All Item list.\n"
			 << "\t5)  Display All Item list.\n\n"
			 << "Enter response here:  ";
		cin >> UserReply;
		if(UserReply<0&&UserReply>5)
		{
			cout << "*** Invalid Response ***";
			system("PAUSE");
		}
	}while(UserReply<0&&UserReply<5);
	if(UserReply==0) return false;
	else
	{
		CurrentTask = UserReply;
		return true;
	}
}
bool MoreLocations()
{
	char UserReply;
	do{
		cout << "Are there more locations to enter? (Y/N) -->  ";
		cin >> UserReply;
		UserReply=toupper(UserReply);
		if(UserReply!='Y'&&UserReply!='N') cout << "*** Invalid response *** \n";
	}while(UserReply!='Y'&&UserReply!='N');
	return (UserReply=='Y');
}
void SaveAllItemList(int ListLength, Item* FirstItem)
{
	ofstream outData;
	outData.open("list.out");
	outData << ListLength << "\n\n";
	for(int i=0;i<ListLength;i++)
	{
		Item* CurrentItem = FirstItem;
		int ItemCount = 0;
		while(CurrentItem!=NULL)
			{
				if(ItemCount == i)
				{
					outData << CurrentItem->ItemName << "\n"
							<< CurrentItem->BrandName << "\n"
							<< CurrentItem->UnitCost << "\n"
							<< CurrentItem->UnitLabel << "\n"
							<< CurrentItem->Department << "\n"
							<< CurrentItem->Location << "\n\n";
					break;
				}
				ItemCount++;
				CurrentItem = CurrentItem->NextItem;
			}
	}
	outData.close();

}


Here is the file:
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2

Bread
Sunbeam
1.99
unit
3
2

Milk
asdf
2.99
unit
3
1
Last edited on
Duthomhas (13206)
Either get each line with
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  std::string line;

  // read the line
  getline( inData, line );

  // convert it to what I want
  std::stringstream ss( line );
  ss >> CurrentItem->UnitCost;


Or ignore everything else on the line after reading your datum:
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  inData >> CurrentItem->UnitCost;
  inData.ignore( numeric_limits<streamsize>::max(), '\n' );


Hope this helps.
cobraun85 (5)
Won't your suggestion read each line as a string? Although several of the lines are meant to be handled as strings, I also need a float and two integers to remain their respective data types.
Duthomhas (13206)
In the file, _all_ your data is a string. The only difference between the two methods I posted is which stream you use to convert your data back into a float (as per the examples) or integer.
cobraun85 (5)
I see your point about each line being a string. I'm embarrased I didn't realize that on my own. I couldn't figure out how to use the code you provided but you did lead me in the right direction. I used atof() and atoi() and it works perfectly. Thank you for the help.

p.s. - If you have any suggestions on how to clean this code up any I would appreciate it. Thanks again.

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#include <iostream>
#include <fstream>
#include <iomanip>
#include <string>

using namespace std;

struct Item
{
	string ItemName;
	string BrandName;
	string UnitLabel;
	int Department;
	int Location;
	float UnitCost;
	Item* NextItem;
};

class ItemList
{
private:
	Item* FirstItem;
	int ListLength;

public:
	ItemList()
	{
		FirstItem = NULL;
		ListLength = 0;
	}
	void AddItem(string IN, string BN, string UL, int D, int L, float UC)
	{
		Item* NewItem = new Item;
		NewItem->ItemName = IN;
		NewItem->BrandName = BN;
		NewItem->UnitLabel = UL;
		NewItem->Department = D;
		NewItem->Location = L;
		NewItem->UnitCost = UC;
		NewItem->NextItem = FirstItem;
		FirstItem = NewItem;
		ListLength++;
	}
	bool ListOccupied()
	{
		return (FirstItem != NULL);
	}
	int Length()
	{
		return ListLength;
	}
	Item* FirstItemLoc()
	{
		return FirstItem;
	}
	void DisplayAllItemList(int i)
	{
		Item* CurrentItem = FirstItem;
		int ItemCount = 0;
		while(CurrentItem!=NULL)
		{
			if(ItemCount == i)
			{
				cout << CurrentItem->ItemName << "\t"
					 << CurrentItem->BrandName << "\t"
					 << CurrentItem->UnitCost << "\t"
					 << CurrentItem->UnitLabel << "\t"
					 << CurrentItem->Department << "\t"
					 << CurrentItem->Location << endl;
				CurrentItem = CurrentItem->NextItem;
				break;
			}
			ItemCount++;
			CurrentItem = CurrentItem->NextItem;
		}
	}
	void SaveItemList()
	{
		ofstream outData;
		outData.open("list.out");
		for(int i=0;i<ListLength;i++)
		{
			Item* CurrentItem = FirstItem;
			int ItemCount = 0;
			while(CurrentItem!=NULL)
				{
					if(ItemCount == i)
					{
						outData << CurrentItem->ItemName << "\n"
								<< CurrentItem->BrandName << "\n"
								<< CurrentItem->UnitCost << "\n"
								<< CurrentItem->UnitLabel << "\n"
								<< CurrentItem->Department << "\n"
								<< CurrentItem->Location;
						if(CurrentItem!=NULL) cout << "\n\n";
						break;
					}
					ItemCount++;
					CurrentItem = CurrentItem->NextItem;
				}
		}
		outData.close();
	}
	void LoadItemList()
	{
			ifstream inData;
			inData.open("list.out");
			while(!inData.eof())
			{
				string line;
				Item* NewItem = new Item;
				
				getline(inData,NewItem->ItemName);
				getline(inData,NewItem->BrandName);
				getline(inData,line);
				NewItem->UnitCost = atof(line.c_str());
				getline(inData,NewItem->UnitLabel);
				getline(inData,line);
				NewItem->Department = atoi(line.c_str());
				getline(inData,line);
				NewItem->Location = atoi(line.c_str());
				getline(inData,line);

				NewItem->NextItem = FirstItem;
				FirstItem = NewItem;
				ListLength++;

			}
			inData.close();
	}
};

void AddItem(string&,string&,string&,int&,int&,float&);
bool MoreItems();
bool Menu(int&);
bool MoreLocations();
void SaveAllItemList(int,Item*);
void LoadAllItemList(string&,string&,string&,int&,int&,float&,ItemList);

int main()
{
	ItemList AllItems;
	string ItemName;
	string BrandName;
	string UnitLabel;
	int Department;
	int Location;
	float UnitCost;
	int CurrentTask=0;

	while(Menu(CurrentTask))
	{
		switch(CurrentTask)
		{
		case 0: 
		case 1: do
				{
					AddItem(ItemName,BrandName,UnitLabel,Department,Location,UnitCost);
					AllItems.AddItem(ItemName,BrandName,UnitLabel,Department,Location,UnitCost);
				}while(MoreItems());
				break;
		case 2: do
				{

				}while(MoreLocations());
				break;
		case 3: AllItems.SaveItemList();
				break;
		case 4: AllItems.LoadItemList();
				break;
		case 5: for(int i=0;i<AllItems.Length();i++) AllItems.DisplayAllItemList(i);
				cout << "\nListLength = " << AllItems.Length() << "\n\n";
				system("PAUSE");
		}
	}

	return 0;
}
void AddItem(string& IN, string& BN, string& UL, int& D, int& L, float& UC)
{
	system("cls");
	cout << "Enter data for new item below.\n\n"
		 << "\tItem Name:     ";
	cin.ignore();
	getline(cin,IN);
	cout << "\tBrand Name:    ";
	getline(cin,BN);
	cout << "\tUnit Cost:     ";
	cin >> UC;
	cout << "\tUnit Label:    ";
	cin.ignore();
	getline(cin,UL);
	cout << "\tDepartment:    ";
	cin >> D;
	cout << "\tLocation:      ";
	cin >> L;
}
bool MoreItems()
{
	char UserReply;
	do{
		cout << "Are there more items to enter? (Y/N) -->  ";
		cin >> UserReply;
		UserReply=toupper(UserReply);
		if(UserReply!='Y'&&UserReply!='N') cout << "*** Invalid response *** \n";
	}while(UserReply!='Y'&&UserReply!='N');
	return (UserReply=='Y');
}
bool Menu(int& CurrentTask)
{
	int UserReply;
	do
	{
		system("cls");
		cout << "What would you like to do?\n"
			 << "\t0)  Quit.\n"
			 << "\t1)  Add new item.\n"
			 << "\t2)  Add new location.\n"
			 << "\t3)  Save All Item list.\n"
			 << "\t4)  Load All Item list.\n"
			 << "\t5)  Display All Item list.\n\n"
			 << "Enter response here:  ";
		cin >> UserReply;
		if(UserReply<0&&UserReply>5)
		{
			cout << "*** Invalid Response ***";
			system("PAUSE");
		}
	}while(UserReply<0&&UserReply<5);
	if(UserReply==0) return false;
	else
	{
		CurrentTask = UserReply;
		return true;
	}
}
bool MoreLocations()
{
	char UserReply;
	do{
		cout << "Are there more locations to enter? (Y/N) -->  ";
		cin >> UserReply;
		UserReply=toupper(UserReply);
		if(UserReply!='Y'&&UserReply!='N') cout << "*** Invalid response *** \n";
	}while(UserReply!='Y'&&UserReply!='N');
	return (UserReply=='Y');
}
Last edited on
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