Parse variable names from string

[Victor Lagerkvist]

Hello, I have the need to parse variable names from a string and save them
somewhere safe for future usage. Here's my first attempt (I don't have any
rules for valid names yet) - but I have a feeling that it's unnecessary
complex? Any input would be greatly appreciated.

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

int get_ops(char *sen, char ***atom, char limit);

int main(void)
{
char *test = "a, b, c, d"; /* The real input is stripped of spaces */
char **atom;
get_ops(test, &atom, ',');
return 0;
}

int get_ops(char *sen, char ***atom, char limit)
{
int i, j, k;
char **tmp1, *tmp2;
*atom = malloc(sizeof (char *));
**atom = malloc(1);
for (i = j = k = 0; sen != '\0'; ++i) {
if (sen != limit) {
tmp2 = realloc((*atom)[k], j+2);
if (tmp2 == NULL)
return -2;
(*atom)[k] = tmp2;
tmp2 = NULL;
(*atom)[k][j++] = sen;
}
else if (sen == limit) {
(*atom)[k++][j] = '\0';
tmp1 = realloc(*atom, (k +1)*sizeof(char *));

if (tmp1 == NULL)
return -2;
*atom = tmp1;
tmp1 = NULL;
(*atom)[k] = malloc(1);
j = 0;
}
}
return 0;
}

 

[user923005]

Hello, I have the need to parse variable names from a string and save them
somewhere safe for future usage. Here's my first attempt (I don't have any
rules for valid names yet) - but I have a feeling that it's unnecessary
complex? Any input would be greatly appreciated.

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

int get_ops(char *sen, char ***atom, char limit);

int main(void)
{
char *test = "a, b, c, d"; /* The real input is stripped of spaces */
char **atom;
get_ops(test, &atom, ',');
return 0;

}

int get_ops(char *sen, char ***atom, char limit)
{
int i, j, k;
char **tmp1, *tmp2;
*atom = malloc(sizeof (char *));
**atom = malloc(1);
for (i = j = k = 0; sen != '\0'; ++i) {
if (sen != limit) {
tmp2 = realloc((*atom)[k], j+2);
if (tmp2 == NULL)
return -2;
(*atom)[k] = tmp2;
tmp2 = NULL;
(*atom)[k][j++] = sen;
}
else if (sen == limit) {
(*atom)[k++][j] = '\0';
tmp1 = realloc(*atom, (k +1)*sizeof(char *));

if (tmp1 == NULL)
return -2;
*atom = tmp1;
tmp1 = NULL;
(*atom)[k] = malloc(1);
j = 0;
}
}
return 0;

}

I guess that it is not nearly complex enough.
If you are gathering variable names from {presumably} C source code,
it will have to be fully grammar aware.
Normally, parsers put variable names into a hash table.
I suggest that you get an existing C parser, and just read the
variable list it creates when it scans a source file.
Here is a place to find a C grammar:
http://www.devincook.com/goldparser/grammars/index.htm
It works with the Gold Parser.
There are C grammars all over the place, so I am sure you can find one
for YACC or Antlr or whatever.

 

[Victor Lagerkvist]

I guess that it is not nearly complex enough.
If you are gathering variable names from {presumably} C source code,
it will have to be fully grammar aware.
Normally, parsers put variable names into a hash table.
I suggest that you get an existing C parser, and just read the
variable list it creates when it scans a source file.
Here is a place to find a C grammar:
http://www.devincook.com/goldparser/grammars/index.htm
It works with the Gold Parser.
There are C grammars all over the place, so I am sure you can find one
for YACC or Antlr or whatever.

Actually, the only functionality I truly need is the names of the variables
(there's only one "type") and the number of them - everything else is a
bonus! They are given by the user from standard input, line by line, such
as:
<< build a, b, c

And that's all there is (more or less any types of names should be allowed),
and for some reason I usually become a sad panda when the code "runs away".

 

[user923005]

Actually, the only functionality I truly need is the names of the variables
(there's only one "type") and the number of them - everything else is a
bonus! They are given by the user from standard input, line by line, such
as:
<< build a, b, c

And that's all there is (more or less any types of names should be allowed),
and for some reason I usually become a sad panda when the code "runs away".- Hide quoted text -

In that case, why not just store them in a hash table to ensure you do
not have duplicates.

 

[Victor Lagerkvist]

In that case, why not just store them in a hash table to ensure you do
not have duplicates.

Ah, that would no doubt be sleek in this case. I thank thee for thine input.

 

[Malcolm McLean]

Hello, I have the need to parse variable names from a string and save them
somewhere safe for future usage. Here's my first attempt (I don't have any
rules for valid names yet) - but I have a feeling that it's unnecessary
complex? Any input would be greatly appreciated.

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

int get_ops(char *sen, char ***atom, char limit);

int main(void)
{
char *test = "a, b, c, d"; /* The real input is stripped of spaces */
char **atom;
get_ops(test, &atom, ',');
return 0;
}

int get_ops(char *sen, char ***atom, char limit)
{
int i, j, k;
char **tmp1, *tmp2;
*atom = malloc(sizeof (char *));
**atom = malloc(1);
for (i = j = k = 0; sen != '\0'; ++i) {
if (sen != limit) {
tmp2 = realloc((*atom)[k], j+2);
if (tmp2 == NULL)
return -2;
(*atom)[k] = tmp2;
tmp2 = NULL;
(*atom)[k][j++] = sen;
}
else if (sen == limit) {
(*atom)[k++][j] = '\0';
tmp1 = realloc(*atom, (k +1)*sizeof(char *));

if (tmp1 == NULL)
return -2;
*atom = tmp1;
tmp1 = NULL;
(*atom)[k] = malloc(1);
j = 0;
}
}
return 0;
}

If you impose an order on the variables in the string, sscanf() will read
them in one go.
If you allow variables in any order, it is a bit more complicated. You need
getword() and possibly getvalue() functions, which gobble up an input
string.

You might want to take a look at the option parser from my website. It
solves a very similar problem to yours, except that the varaibles are
contained in the program's arguments rather tha concatenated together into a
string.