Dealing With Multi Dim Char Arrays

I'm trying to write a prog that reads a dictionary and writes the contents to a 2D character array. I'm having a bit of trouble though mainly with passing the array into a function. This compiles, but crashes. I think its because I need to allocate memory in the function or something.

Code:

---

#include <stdio.h>
#define MAXLEN 30

static FILE *OpenFile(char *file, char *mode);
void LoadDictionary(char *dict[0][0]);

int main()
{
    char dictionary[MAXLEN][250000];
    LoadDictionary(&dictionary[0][0]);
   
    getchar();
   
}   

void LoadDictionary(char *dict[0][0])
{
    char c;
    int x=0, y=0;
    FILE *in;   
   
    in=OpenFile("Dictionary,txt", "r");
    while((c=fgetc(in)) != EOF)
    { 
        if(c == '\n')
        {   
            c='\0'; 
            dict[x][y]=c; 
            y++;     
        }
        else
            dict[x][y]=c; 
        x++;
        if(x > MAXLEN-1)x=0; 
    }
    fclose(in);       
}

static FILE *OpenFile(char *file, char *mode)
{
    FILE *fp = fopen (file, mode);
    if (fp == NULL)
    {
        perror ("Unable to open file");
        return NULL;
    }
    return fp;
}

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Also. If, say I wanted to print the first hundred lines from my character array, how would I do that? This is an example of a guess I made, but I doubt it would work:

Code:

---

    for(i=0; i<100; i++)
        printf("%s", dictionary[0][i]);

---

You're trying to allocate a 7.5 million byte static array, which is probably too big. Try allocating the memory dynamically instead. (And to test whether this is the problem, try reducing the size by say a factor of 10 or 100, and see what happens.)

Ok, I'll do that. Wouldent have thought that 7.5MB should be a problem though. Big arrays like screen buffers dont use much less.

> char dictionary[MAXLEN][250000];
Maybe it doesn't like 7.5MB of stuff on the stack, when many systems have a default limit of 1MB.

Though quite why you only have 30 words with up to 250000 chars in their definition is strange.

> void LoadDictionary(char *dict[0][0]);
Given your array, the prototype should be
void LoadDictionary( char dict[ ][250000] );

And you call it with
LoadDictionary( dictionary );

Ok thanks Salem, it compiles now.

Quote:

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Though quite why you only have 30 words with up to 250000 chars in their definition is strange.

---

I was imagining the contents of the array as if drawn out where words would be stored in rows.

Anyway, now I am trying to print out the array entries. What I got is a bit of a mess:

Code:

---

    int y, x;
    for(y=0; y<100; y++)
        for(x=0; x<30; x++)
            if(dictionary[x][y]=='\0')
            {
              printf("\n");
              break;
            }
            else
                printf("%c", dictionary[x][y]);

---

Is there any way to use "%s" in a printf to print out the nth row/column in a multi dim array?

Given
char arr[X][Y];

If each row has a \0, then
for ( i = 0 ; i < X ; i++ ) printf("%s\n", arr[ i ] );
prints a whole row in one step.

Ok, now this makes sense why my x/y are in the wrong order. Cheers.

I have been trying to change my program to use a dynamic array, instead of a static one. I'm getting MAVs at the moment and I'm not sure if its possible to do this the way I am trying to do it.

Basically my struct that holds a word is 20 Bytes. I allocated memory for 250000 of them (first line in bold). Then when I load up the dictionary I send the struct pointer in, and the struct size. When a word is loaded the pointer gets incremented by 20 to jump to the next word, but this wont seem to work.

The only reason that I can think of for this not to work would be that the memory allocated might not be contiguous, but maybe its something else. Any ideas?

Code:

---

#include <stdio.h>
#include <stdlib.h>
#define MAXLEN 20
#define MAXIT 250000

struct dir
{
    char word[MAXLEN];
}; 

static FILE *OpenFile(char *file, char *mode);
void LoadDictionary(dir *ptr, int size);

int main()
{
    struct dir *p;
  p = (struct dir *) malloc(MAXIT * MAXLEN);
    LoadDictionary(p, MAXLEN);
    getchar(); 
}   

void LoadDictionary(dir *ptr, int size)
{
    char c;
    int x=0, y;
    FILE *in;   
   
    in=OpenFile("Dictionary.txt", "r");
    while((c=fgetc(in)) != EOF)
    { 
        if(c == '\n' || x==19)
        {   
            ptr->word[x]='\0';
            x=0;
            ptr+=size; //Jump to next entry. Wont work
        }
        else
        {
            ptr->word[x]=c; 
            x++;
        }
    }
    fclose(in);       
}

static FILE *OpenFile(char *file, char *mode)
{
    FILE *fp = fopen (file, mode);
    if (fp == NULL)
    {
        perror ("Unable to open file");
        return NULL;
    }
    return fp;
}

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I worked out what was wrong. Just had to increment the pointer by 1 instead of the struct size. This always seems to happen to me just after I post.