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robster

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Posted: 30th Dec 2010 23:32

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I'm new to this and I want to be able to save and load. Some example code would be good thanks.

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Hassan

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Posted: 31st Dec 2010 11:43

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the whole idea is to open a file and write the information you need so that when you read them, you can figure out where you was before the save, so simply, to save, open a file and save some values there, these are up to you, but usually you would save global variables, classes info, etc, and on loading, just read the saved file and assign each value you read to its global variable or create class instances or whatever you want to do

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robster

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Posted: 31st Dec 2010 13:44

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ok, but my problems comes when i don't know how to code it to save/load. thanks

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Hassan

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Posted: 31st Dec 2010 14:12

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very simple: (this is C-style file read/write, i don't like the std way, but if you do so, it is very easy to switch if you want)

bool SaveGame ( void )
{
//"w" stands for "write", so we will open a handle for writing to a file
FILE* fp = fopen ( "ENTER SAVE FILENAME HERE", "w" );
if ( !fp ) //error, failed to open the file
return false;

//TODO: any variable saving goes here, it varies from a program to a program depending on your variables..for example..

// the \n means a newline, you can read more about fprintf in the link below code
fprintf ( fp, "CharacterPosition = (%d,%d,%d);\n", characterX, characterY, characterZ );
fprintf ( fp, "MissionID = (%d);\n", missionID );
//etc etc, also you can make use of loops

fclose ( fp ); //the file handle must be closed

return true;
}
bool LoadGame ( void )
{
//same as saving, but instead of fopen ( .., "w" ), we make it "r" for "read"
FILE* fp = fopen ( "ENTER SAVE FILENAME HERE", "r" );
if ( !fp ) //error, failed to open the file
return false;

//TODO: we read the values here, this will need some parsing, which is up to you and your format, you simply read line by line and assign variables, im not going to insert and example here as it will take some time, but it's very easy

fclose ( fp ); //the file handle must be closed

return true;
}

+ Code Snippet

bool SaveGame ( void )
{
//"w" stands for "write", so we will open a handle for writing to a file
FILE* fp = fopen ( "ENTER SAVE FILENAME HERE", "w" );
if ( !fp ) //error, failed to open the file
return false;

//TODO: any variable saving goes here, it varies from a program to a program depending on your variables..for example..

// the \n means a newline, you can read more about fprintf in the link below code
fprintf ( fp, "CharacterPosition = (%d,%d,%d);\n", characterX, characterY, characterZ );
fprintf ( fp, "MissionID = (%d);\n", missionID );
//etc etc, also you can make use of loops

fclose ( fp ); //the file handle must be closed

return true;
}
bool LoadGame ( void )
{
//same as saving, but instead of fopen ( .., "w" ), we make it "r" for "read"
FILE* fp = fopen ( "ENTER SAVE FILENAME HERE", "r" );
if ( !fp ) //error, failed to open the file
return false;

//TODO: we read the values here, this will need some parsing, which is up to you and your format, you simply read line by line and assign variables, im not going to insert and example here as it will take some time, but it's very easy

fclose ( fp ); //the file handle must be closed

return true;
}

fprintf reference: http://www.cplusplus.com/reference/clibrary/cstdio/fprintf/

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robster

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Posted: 31st Dec 2010 16:48

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thanks for that il give it a go

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robster

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Posted: 31st Dec 2010 18:03

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ok im not really sure how to but i looked at your link and tryed not to come back and ask you again, but im not sure how to read the txt file and do something like if MissionID = 1 then load mission1.

I tried fscanf and fread but im kind of shooting in the dark here. thanks

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Matty H

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Posted: 31st Dec 2010 20:36 Edited at: 31st Dec 2010 20:36

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You can create a string and read each line of the file into the string with the getline function:

+ Code Snippet

    string line;
    if(myfile.is_open()){
       while(myfile.good()){
         getline (myfile, line);
         //...do stuff with string
       }
    }

There is lots to learn, you will need to know how to manipulate strings.

fulcrum physics - free collision/physics plug-in for DarkGDK

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robster

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Posted: 1st Jan 2011 14:48

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no luck

I think I should try to learn a bit more about strings because I'm not sure about them.

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TechLord

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Posted: 1st Jan 2011 15:26

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Heres an example of how to use File and String Libraries that come with Visual C++. I don't know what your experience is with using C++ but if you're very new to the language, I highly recommend you read this.

Super 3D Game Engine (S3GE) - The Ultimate All-in-1 3D Game Engine in development with Dark GDK.

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Hassan

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Posted: 2nd Jan 2011 16:56 Edited at: 2nd Jan 2011 17:03

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well for parsing, you simply do this: (might be a bit slow, but this is easiest)

//some variables to be used later on
char c = 0;
int pos = 0;
int stage = 0;
char variable[200];
char value[200];
while ( 1 )
{
   c = fgetc ( fp );//get the next char from the file
   if ( c == EOF ) //end of file, break loop
      break;
   if ( c == ';') //end of command
   {
      value[pos] = '\0';//null terminator
      pos = 0; //reset string position
      stage = 0; //reset reading stage
      //now variable and value strings contains the info you need for loading, for example, if you have this in the saved file :"ThisVar = 10;", now variable will have the string "ThisVar" and value will have "10", you can convert the "10" to an integer or float using atof and atoi
      //TODO: add what you want to do with the info here
      continue; //continue loop and search for other commands in the file
   }
   if ( c == '=' ) //if it's a '=', change stage
   {
      variable[pos] = '\0'; //add a null terminator (you need this at the end of a string to identify the "end of string")
      stage = 1; //next stage (get the value of the variable)
      pos = 0; //reset pos to start writing from element 0
   }
   if ( stage == 0 && c != ' ' /*ignore spaces*/ )
      variable[pos++] = c;
   else if ( stage == 1 && c != ' ' /*ignore spaces*/ )
      value[pos++] = c;
}

+ Code Snippet

//some variables to be used later on
char c = 0;
int pos = 0;
int stage = 0;
char variable[200];
char value[200];
while ( 1 )
{
   c = fgetc ( fp );//get the next char from the file
   if ( c == EOF ) //end of file, break loop
      break;
   if ( c == ';') //end of command
   {
      value[pos] = '\0';//null terminator
      pos = 0; //reset string position
      stage = 0; //reset reading stage
      //now variable and value strings contains the info you need for loading, for example, if you have this in the saved file :"ThisVar = 10;", now variable will have the string "ThisVar" and value will have "10", you can convert the "10" to an integer or float using atof and atoi
      //TODO: add what you want to do with the info here
      continue; //continue loop and search for other commands in the file
   }
   if ( c == '=' ) //if it's a '=', change stage
   {
      variable[pos] = '\0'; //add a null terminator (you need this at the end of a string to identify the "end of string")
      stage = 1; //next stage (get the value of the variable)
      pos = 0; //reset pos to start writing from element 0
   }
   if ( stage == 0 && c != ' ' /*ignore spaces*/ )
      variable[pos++] = c;
   else if ( stage == 1 && c != ' ' /*ignore spaces*/ )
      value[pos++] = c;
}

what happens there is:
you loop forever untill EOF character is read, store everything you read in the variable "variable", once a '=' is reached, terminate "variable" (by adding a '\0' at its ending) and go to stage 1 which is reading to "value" variable, now, once ';' is reached, terminate "value" and then use the info you have, repeat this untill EOF is reached

notice that we won't read the spaces (" "), why? because it will cause problems on your side, for example, in the file you have "ThisVar = 10", it will be read like "ThisVar " and " 10", no problem with the 10 but your string comparison won't succeed assuming you will compare "ThisVar" to "ThisVar "

also, for comparing, use:

+ Code Snippet

if ( strcmp ( variable, "ThisVar" ) == 0 )
{
   //variable is contains "ThisVar"
}

simplest method i believe, can be optimized in many ways to suit what you want, hope this helps

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robster

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Posted: 2nd Jan 2011 22:00

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@hassan ok so now if I want the "10" for example I do

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int i 

i = atoi (value);

then use the i however I want

I tried this but can't seem to get it to work sorry if I'm being stupid

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Hassan

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Posted: 3rd Jan 2011 14:48

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how come it doesn't work? maybe the value variable holds wrong data?

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robster

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Posted: 3rd Jan 2011 15:59 Edited at: 3rd Jan 2011 16:01

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I don't think so I have been doing allot of trail ans error with it.

my save file has only the one line: level = (3);

and for the moment I only want it to read of the 3 then put the 3 into levelID so I can use it (thats when I tried using atoi)

heres the code (not much changed from yours)

bool SaveGame ( void )
{
//"w" stands for "write", so we will open a handle for writing to a file
FILE* fp = fopen ( "savetest.txt", "w" );
if ( !fp ) //error, failed to open the file
return false;

//TODO: any variable saving goes here, it varies from a program to a program depending on your variables..for example..

// the \n means a newline, you can read more about fprintf in the link below code
fprintf ( fp, "Level = (%d);\n", level );

//etc etc, also you can make use of loops

fclose ( fp ); //the file handle must be closed

return true;
}

bool LoadGame ( void )
{
//same as saving, but instead of fopen ( .., "w" ), we make it "r" for "read"
FILE* fp = fopen ( "savetest.txt", "r" );
if ( !fp ) //error, failed to open the file
return false;
 
//some variables to be used later on

while ( 1 )
{
   c = fgetc ( fp );//get the next char from the file
   if ( c == EOF ) //end of file, break loop
      break;

if ( c == ';') //end of command
   {
      value[pos] = '\0';//null terminator
      pos = 0; //reset string position
      stage = 0; //reset reading stage
      //now variable and value strings contains the info you need for loading, for example, if you have this in the saved file :"ThisVar = 10;", now variable will have the string "ThisVar" and value will have "10", you can convert the "10" to an integer or float using atof and atoi
      //TODO: add what you want to do with the info here
	  levelID = atoi (value);
      continue; //continue loop and search for other commands in the file
   }

if ( c == '=' ) //if it's a '=', change stage
   {
      variable[pos] = '\0'; //add a null terminator (you need this at the end of a string to identify the "end of string")
      stage = 1; //next stage (get the value of the variable)
      pos = 0; //reset pos to start writing from element 0
   }
   if ( stage == 0 && c != ' ' /*ignore spaces*/ )
      variable[pos++] = c;
   else if ( stage == 1 && c != ' ' /*ignore spaces*/ )
      value[pos++] = c;
}

fclose ( fp ); //the file handle must be closed

return true;
}

+ Code Snippet

bool SaveGame ( void )
{
//"w" stands for "write", so we will open a handle for writing to a file
FILE* fp = fopen ( "savetest.txt", "w" );
if ( !fp ) //error, failed to open the file
return false;

//TODO: any variable saving goes here, it varies from a program to a program depending on your variables..for example..

// the \n means a newline, you can read more about fprintf in the link below code
fprintf ( fp, "Level = (%d);\n", level );




//etc etc, also you can make use of loops

fclose ( fp ); //the file handle must be closed

return true;
}

bool LoadGame ( void )
{
//same as saving, but instead of fopen ( .., "w" ), we make it "r" for "read"
FILE* fp = fopen ( "savetest.txt", "r" );
if ( !fp ) //error, failed to open the file
return false;
 
//some variables to be used later on

while ( 1 )
{
   c = fgetc ( fp );//get the next char from the file
   if ( c == EOF ) //end of file, break loop
      break;

   if ( c == ';') //end of command
   {
      value[pos] = '\0';//null terminator
      pos = 0; //reset string position
      stage = 0; //reset reading stage
      //now variable and value strings contains the info you need for loading, for example, if you have this in the saved file :"ThisVar = 10;", now variable will have the string "ThisVar" and value will have "10", you can convert the "10" to an integer or float using atof and atoi
      //TODO: add what you want to do with the info here
	  levelID = atoi (value);
      continue; //continue loop and search for other commands in the file
   }

   if ( c == '=' ) //if it's a '=', change stage
   {
      variable[pos] = '\0'; //add a null terminator (you need this at the end of a string to identify the "end of string")
      stage = 1; //next stage (get the value of the variable)
      pos = 0; //reset pos to start writing from element 0
   }
   if ( stage == 0 && c != ' ' /*ignore spaces*/ )
      variable[pos++] = c;
   else if ( stage == 1 && c != ' ' /*ignore spaces*/ )
      value[pos++] = c;
}



fclose ( fp ); //the file handle must be closed

return true;
}

should I have changed it more ^ ?

btw I do call LoadGame (); and SaveGame (); later on in the code however I can't tell if LoadGame Works the only indicator I can think of using is dbPrint (levelID); and if it shows 3 I would be happy but it only shows 0

thanks
rob

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Hawkblood

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Posted: 4th Jan 2011 18:40

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When you open a file to read/write data other than text you should use the binary function:
FILE* f=fopen("file.ext","rb"); (the "rb" is "read binary")
You will have to do the same with the write. This takes care of any character parsing that the file system does when reading such as an EOF combination.

The fastest code is the code never written.

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Hassan

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Posted: 5th Jan 2011 15:34 Edited at: 5th Jan 2011 15:37

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oh sorry my fault, forgot a continue statement:

+ Code Snippet

   if ( c == '=' ) //if it's a '=', change stage
   {
      variable[pos] = '\0'; //add a null terminator (you need this at the end of a string to identify the "end of string")
      stage = 1; //next stage (get the value of the variable)
      pos = 0; //reset pos to start writing from element 0
      continue;
   }

i believe value variable had "=3", because it added the = to it

also, you got one little problem there, this function is supposed to read all file info, you did:
levelID = atoi (value);
instantly without any checking,
it should look more like

+ Code Snippet

if ( strcmp ( variable, "levelID" ) == 0 ) //if this is the variable levelID
   levelID = atoi ( value );
//etc etc

or you could write a function to this for you as it will look messy with too many variables

also, im not sure whether fgetc reads the \n character (end of line), but just in case, you can add this:

+ Code Snippet

   if ( stage == 0 && c != ' ' && c != '\n' /*ignore spaces and newline characters*/ )
      variable[pos++] = c;
   else if ( stage == 1 && c != ' ' && c != '\n' /*ignore spaces and newline characters*/ )
      value[pos++] = c;

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