More than 8 strings

**lockpatrick** · 07-06-2002

Code:

#include <stdio.h>
#include <stdlib.h>
#define MAXLINES 8

int main()
{
	char *lines[MAXLINES];
	int n=0; 
	char buffer[80];

	puts("Enter one line at time enter a blank when done.");

	while((n<MAXLINES) && (gets(buffer) !=0) && (buffer[0] !='\0'))
	{
		if((lines[n]=(char*)malloc(strlen(buffer)+1)) ==NULL)
			return -1;

		strcpy(lines[n++],buffer);
	}

 return 0;
}

Question:
Over here, there are 8 arrays to store 8 independent strings. The length of each strings is unlimited as long as the memory is available, so, there is flexibility i.e. no wastage of space.
But that’s only for the length of the string. I found out that by declaring 8 arrays, the program is no longer flexible. The user cannot enter more than 8 independent strings and if the user enter less than 8, memory is wasted. How do I implement the flexibility as in the length of those strings?

**zahid** · 07-06-2002

How about link list?

**Sebastiani** · 07-07-2002

Memory is cheap. Even an array of 1000 char*'s is a mere 4K. So don't be so bashful. Also, you should really switch to fgets(), because if the user enters more than 80 characters in your program, it will certainly crash!

A linked list is the only way to go if you want a real dynamic structure, though. Just a suggestion.

Code:

//.............................



int IsEmpty(char buff[] )
 {
   int x, len = strlen(buff);

   for( x = 0; x < len; x++)
    {
      if( !isspace(buff[x]) )  return 1;  
    }

 return 0;
 }


//.............................




#define MAXLINES 1000

int main()
{
 char *lines[MAXLINES];
 int n=0; 
 char buffer[80];

 puts("Enter one line at time enter a blank when done.");

 while( n < MAXLINES ) 
  {
    fgets(buffer, 80, stdin); //...This function prevents overflow!!

    if( IsEmpty( buffer ) ) break;

    if( (lines[n]=(char*)malloc(strlen(buffer)+1) ) ==NULL)  return -1;

    strcpy(lines[n++],buffer);  
  }

 return 0;
}

**pinko_liberal** · 07-07-2002

or use realloc
a quick and dirty solution

Code:

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#define MAXBUF 1024

int
add_str(char ***ppstr,int strpos)
{
	char buf[MAXBUF];
	char **tmppstr;
	int l;
	tmppstr=realloc(*ppstr,(strpos+1)*sizeof(**ppstr));
    if(tmppstr==NULL)
	{
		perror(NULL);
		return 1;
	}
	fgets(buf,MAXBUF,stdin);
	/*
	remove '\n' from buf if you wish here
	*/
	if(ferror(stdin))
	{
		perror(NULL);
		return 1;
	}
	if( (tmppstr[strpos]=malloc(strlen(buf)+1))==NULL )
	{
		perror(NULL);
		return 1;
	}
	strcpy(tmppstr[strpos],buf);
	*ppstr=tmppstr;
	return 0;
}



int
main(void)
{
	char **pstr=NULL;
	int strpos=0,i;
	for(i=0;i<5;i++)
	{
		add_str(&pstr,i);
    }
	for(i=0;i<5;++i)
		printf("%s",pstr[i]);
	/*
	    to write a function to free memory
		free_str(&pstr,5);
	 */

	return 0;
}

**shaik786** · 07-07-2002

>The length of each strings is unlimited as long as the memory is available, so, there is flexibility i.e. no wastage of space.
False. With char buffer[80];, you have a maximum of 80 characters that you can read in each line, and if the user entered more, there are always possibilities that your program would crash. And if the user entered less, what about the extra space in each line?
Try to avoid, gets(), implement fgest() instead, a reliable counterpart.

>How do I implement the flexibility as in the length of those strings?
Data Structures is your solution (Linked List, Binary Tree, ...)

**The Dog** · 07-07-2002

Well, compliments of myself and quazah's valuable insight,
here's a solution:

Code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define MAXLINES 5

int AddString(char*** a_string, const char* text, int* size);

int main()
{
	char **lines=NULL;
	int n=0, i; 
	char buffer[100];

	puts("Enter one line at time enter a blank when done.");

	while((n!=MAXLINES) && (fgets(buffer,99,stdin) != NULL) && (buffer[0] !='\0') )
		AddString(&lines,buffer,&n);
		
	for(i=0;i<n;i++)
	{
		printf("%s",lines[i]);
		free(lines[i]);
	}
    
                
    free(lines);
    return 0;
}



int AddString(char*** a_string, const char* text, int* size)
{
	int i=0,j=0;
	char** newlist;	
	
	if( (newlist = malloc(sizeof(char*)*(*size+1)))==NULL);
	
	for(i=0; i < *size;i++)
    	newlist[i] = (*a_string)[i];
	
	free(*a_string);
	
	if( (newlist[i] = malloc(strlen(text)+1)) == NULL )return 1;
	memcpy(newlist[i],text,strlen(text)+1);
    *a_string = newlist;
	*size += 1;
    return 0;
}

**The Dog** · 07-07-2002

One thing that i hadn't bothered to check was that you should
change this,

Code:

while((n!=MAXLINES) && (fgets(buffer,99,stdin) != NULL) && (buffer[0] !='\0') )

//with this

while( (fgets(buffer,99,stdin) != NULL) && (buffer[0] !='\n') )

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