Parsing

[sanushks]

Is there a function in C which can read dual delimiters,
there is strtok which works using a single delimiter.. Is

i need to decode a file as such

123#!45!2#!678#!666#!45!6#!

in the above case #! is the delimter, if i use strtok and use(#! as delimiter) 45!2 in the above data will get tokenized too, anybody has a solution?

[ArkM]

No such library function:
it's not well-defined specification. For example, how about this delimiters set:

{ "!", "#", "#!" }

?
Elaborate non-contradictory specifications. It's not so hard to write a proper tokenizer in C...

[sanushks]

My specification is to read a record with the delimiter "#!" which appears as a sequence, any other pattern should not be considered as delimiter. I will have to read in this record from a file and write to another file with ~ as delimiter

Input:
123#!45!2#!678#!666#!45!6#!

Output:
123~45!2~678~666~45!6~

[ArkM]

/** Undestructive tokenizer. 
    @todo Add tsz < toksz test 
 */
const char* getTok(const char* s, char* tok, int toksz, const char* delim)
{
    if (s && *s) {
        int dlen = strlen(delim);
        const char* p = strstr(s,delim);
        int tsz = (p? p - s: strlen(s));
        if (tsz)
            memcpy(tok,s,tsz);
        tok[tsz] = '\0';
        return s + (p? tsz + dlen: tsz);
    }
    return 0;
}

int main()
{
    char tok[80];
    char str[] = "123#!45!2#!678#!666#!45!6#!";
    const char* p = str;
    while ((p = getTok(p,tok,sizeof tok,"#!")) != 0)
        printf("%s\n",tok);
    return 0;
}

[kvprajapati]

I think the following code help you to solve your problem.

char s1[100]="1123#!3344#!948#!20";
   char *p;
   int i=0;

   do
   {
     p=strtok(s1+i,"#!");
     i=i+strlen(p)+2;
     printf("\n%s",p);
     }while(p!=NULL);

Note: strtok is prototyped in string.h header file.

[Dave Sinkula]

Consider also sscanf .

#include <stdio.h>

int main(void)
{
   const char line[] = "123#!45!2#!678#!666#!45!6#!";
   char text[10];
   int n;
   const char *ptr = line;
   while ( sscanf(ptr, "%9[^#]#!%n", text, &n) == 1 )
   {
      printf("%s~", text);
      ptr += n;
   }
   putchar('\n');
   return 0;
}

/* my output
123~45!2~678~666~45!6~
*/

Although as posted this will mishandle lone #'s within the text, such as "123#!45!2#!678#!6#66#!45!6#!" . It may give you some ideas, though.

[cool_zephyr]

This should help..

#include<stdio.h>

int main(void)
{
    char *str="123#!45!2#!678#!666#!45!6#!";
    char *temp1,*temp2;
    char *new_str;

    temp1=str;
    new_str=temp2;

    while(*temp1!='\0')
    {
        if(*temp1=='#' && *(temp1+1)=='!')
        {
            *temp2='~';
            temp2++;
            temp1+=2;
        }

        *temp2=*temp1;
        temp2++;
        temp1++;
    }

    *temp1='\0';

    while(*new_str!='\0')
    {
        printf("%c",*new_str);
        new_str++;
    }

    return 0;
}

[sanushks]

The above code looks good, But is it more efficient than using strstr or sscanf?

[ArkM]

The above code looks good, But is it more efficient than using strstr or sscanf?

What's your efficiency criteria?
Is your application critically dependent on this tokenizing phase?
;)

[sanushks]

yes it is.. performance matters as tokenizing is the crucial part of the application

[ArkM]

yes it is.. performance matters as tokenizing is the crucial part of the application

Impossible!

Can you prove it? How many bytes per second is OK? What's i/o channels capacity?

Even if it's true: serious applications are never discussed on the forums like DaniWeb. True crucial parts of such applications are never assigned to programmers who can't tokenize a line with two-char delimiters ;)..

[sanushks]

Buddy u seem to be in war mode.. I'm jus asking for suggestions..
I know you are an expert..

[Dave Sinkula]

This should help..

Writing to read-only memory is undefined behavior. Maybe take another swing at this one.

[Aia]

cool_zephyr>

while(*temp1!='\0')
{
if(*temp1=='#' && *(temp1+1)=='!')
{
*temp2='~';
temp2++;
temp1+=2;
}

Declaring a pointer doesn't magically set apart memory for you to manipulate, so you can not write or use what you don't have.

[kvprajapati]

AIa>..so you can not write or use what you don't have.

Everybody knows the fact about declaring a pointer doesnot set memory. I want to know what happen when the following code is used.

char *str="Hello";

[Dave Sinkula]

Everybody knows the fact about declaring a pointer doesnot set memory. I want to know what happen when the following code is used.

char *str="Hello";

An array containing the string literal "Hello" (including the null terminator) will exist somewhere; the contents of this array should be considered non-modifiable.

The pointer-to-char str will exist; it is initialized with the location of the first element of the array containing the string literal (that is, str will point to the beginning of the array).

See also http://c-faq.com/aryptr/aryptr2.html

[Aia]

adatapost> Everybody knows the fact about declaring a pointer doesnot set memory.

cool_zephyr didn't, and I don't want to think you haven't been paying much attention since you joined almost a year ago? This forum is full of instances of this recurring theme. Which nullifies your statement that "everybody knows"

adatapost> I want to know what happen when the following code is used. char *str="Hello";
Depends what you do to it. You are creating a read-only literal string, that can be accessed by the pointer str. You try to change it by overwriting it and you enter the undefined dimension.

[Aia]

I know you are an expert..

I missed this one. I am going to apply the "theory of relativity" to that sentence.

[cool_zephyr]

sorry..but i'm a little confused