Dynamically allocating 3D array

Hi, Am I doing this right? the following code is suppose to allocate memory of type GLubyte which used to hold all the values which are read from ppm file. But for some reason the image donst get displayed i suspect that I am not allocating the memory properly. Just to clarify is there any problem with the way I am allocating 3D array. Any comments on this code would be appreciated as well

Code:

---

int AllocateMemory( void )
{
    unsigned int Count, Count1;
   
    if( ( IndiaMapPPM = malloc( sizeof(GLubyte **) * Width ) ) != NULL )
    {
        for( Count = 0; Count < Width; Count++ )
        {
            if( ( IndiaMapPPM[Count] = malloc( sizeof( GLubyte *) * Height ) ) != NULL )
            {
                for( Count1 = 0; Count1 < Height; Count1++ )
                {
                      if( ( IndiaMapPPM[Count][Count1] = malloc( sizeof(GLubyte) * RGB ) ) == NULL)
                      {
                          printf("Error: Malloc failed\n");
                          return 1;
                      }
                }
            }
            else
            {
                printf("Error: Malloc failed\n");
                return 1;
            }
        }
    }
    else
    {
        printf("Error: Malloc failed\n");
        return 1;
    }
    return 0;
}

---

Thank you

ssharish

There's a global GLubyte ***IndiaMapPPM and success is when AllocateMemory() returns 0?

Hi Dave, yes there is a globla variable GLubyte ***IndiaMapPPM and yes it return 0 when it is success.

Is it something to do with the GLubyte datatype. I suppose there is no difference between a char and GLubyte. And the following is a snap fo code where it show the way i am readin value from ppm file.

Code:

---

for( RowIndex = 0; RowIndex < Row; RowIndex++ )
          for( ColumnIndex = 0; ColumnIndex < Column; ColumnIndex++ )
              fscanf( ppmFile, "&#37;d%d%d", &IndiaMapPPM[RowIndex][ColumnIndex][0],
                                          &IndiaMapPPM[RowIndex][ColumnIndex][1],
                                          &IndiaMapPPM[RowIndex][ColumnIndex][2] );

---

Assuming that i have read the width and height of the ppm file. And

Code:

---

glDrawPixels( Width, Height, GL_RGB, GL_UNSIGNED_BYTE, IndiaMapPPM );

---

ssharish

There doesn't appear (to me, late at night) anything wrong here; although we're just allocating memory here ... there's many more chances to get it wrong elsewhere.

As noted, make sure you're not hiding this global variable with a local one elsewhere, that you fill it in at some point, etc.

I hope you're consistently using IndiaMapPPM[h][w][r] as a GLubyte. You shouldn't try to guess unless you have a good reason.

fscanf( ppmFile, "%d%d%d",

hmmm - what is the format of the file?

Hi Vart, here is a snap of my ppm file.

Code:

---

P3
# LEAD Tech.
628 658
255
255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255
255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255
255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255
255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255
255 255 255 255 255 255 255 255 255 255 255 255 255 255....

---

Blue - States, what type of file
DarkOrange - Information which is been commented out
Magenta - Row Column
Lime - max color

The interesting part here is, when I delcare the array straight away like

Code:

---

GLubyte IndiaMapPPM[628][658][3];

---

It just works fine. But when I allocate memory dynamically it gives me problem. If there was some problem with memory allocation or not allocated enough memory, i should have got sef fault when reading value into array. I font even get that. When I draw the pixel values, it just drawa call black, which i pretty wired. But this donst happen when I array is statically declared.

Here is some more bit of code of my PPMread function.

Code:

---

void ReadPPMFile( void )
{
    FILE *ppmFile;
    unsigned char Buffer[BUFSIZ];
    unsigned int Row, Column, MaxColor;
    int RowIndex, ColumnIndex, Flag = 0;
   
    if( ( ppmFile = fopen( PPMFILENAME, "r") ) == NULL )
    {
        printf("Error: PPM file cannot be opened\n");
        getchar();
        exit( 1 );
    }
   
    if( fgets( Buffer, sizeof(Buffer), ppmFile ) != NULL )
    {
        if( strncmp( Buffer, "P3", 3 ) == 0)
        {
            printf("Error: File is not an ppm format\n");
            getchar();
            exit( 1 );
        }
    }
    else
    {
        printf("Error: File is empty\n");
        getchar();
        exit ( 1 );
    }
   
    while( fgets( Buffer, sizeof( Buffer ), ppmFile) != NULL )
    {
        if( Buffer[0] == '#' )
            continue;
       
        if( sscanf( Buffer, "%d %d %d", &Row, &Column, &MaxColor ) != 3 )
        {
            if( sscanf( Buffer, "%d %d", &Row, &Column ) != 2 )
            {
                printf("Error: Reading row and column failed\n");
                getchar();
                exit( 1 );
            }
            else
            {
                if( fgets( Buffer, sizeof( Buffer ), ppmFile) != NULL )
                {
                    if( sscanf( Buffer, "%d", &MaxColor) != 1)
                    {
                        printf("Error: reading max color failed\n");
                        getchar();
                        exit( 1 );
                    }
                    break;
                }
            }
        }
        else
            break;
    }
   
    Width = Row;
    Height = Column;
   
    /* I have just commented this part since it wasn't working. */
    /* if( AllocateMemory() )
        exit(1);          */

    for( RowIndex = 0; RowIndex < Row; RowIndex++ )
          for( ColumnIndex = 0; ColumnIndex < Column; ColumnIndex++ )
              fscanf( ppmFile, "%d%d%d", &IndiaMapPPM[RowIndex][ColumnIndex][0],
                                          &IndiaMapPPM[RowIndex][ColumnIndex][1],
                                          &IndiaMapPPM[RowIndex][ColumnIndex][2] );
   
    fclose( ppmFile );
}

---

Thank you

ssharish

it seems - you are messing to much with globals
you allocation function insted of to receive dimentions as parameters uses some Width and Height values

wile your function reading from file initializes Row and Column values.

Stop messing with globals where you can just pass parameters to function

May be, I will try with sending parameter and see if that one works .

Thank you

ssharish

Note -- you don't always get segmentation faults when you read or write memory you shouldn't be meddling with. It could be your memory; or it could be within the page (is that the right term?) that your program's memory lives in -- most operating systems cannot check the bounds of your accessing exactly. I think I saw 4MB as a value for Windows. In other words, depending on where your memory started, you might have to overwrite as much as 4MB beyond the end of an array before Windows will notice.

For perfect bounds checking, I recommend Valgrind -- it's really good. Unfortunately, it only runs on Linux, so if you're using Windows, you'll have to find something else. There are lots of these sorts of tools around, however. http://en.wikipedia.org/wiki/Memory_debugger

I think it's possible that you have some sort of buffer overrun elsewhere . . . .

Code:

---

        if( Buffer[0] == '#' )
            continue;

---

Suggestion:

Code:

---

for(p = Buffer; isspace(*p); p ++);
if(*p == '#') continue;

---