Circuit Simulator in C input - c

Question

I have to create a circuit based off the inputs of a text file i read.
The first text file I use has the circuit description and then the next has the actual binary values of the circuit you end up creating.
Example:
INPUTVAR 3 A B C
OUTPUTVAR 1 Q
AND A B w
AND A C x
OR w x Q
the format of this example means that there are 3 input variables called A, B , C. There is also 1 output variable called Q. The And creates an expression called w= A.B. along with x=A.C. and the or is Q = w.x. My problem is that I do not know how to read in this input since it isnt the same format every time. The amount of variables after the INPUTVAR depends on what that first number says. I am confused on how I can interpret this in code, I know how to read in data that is formatted. Any hints or help provided will be appreciated.
I believe I need to use fgets() to do it line by line.
with help I have came up with the following code
FILE *circuit;
circuit = fopen(argv[1],"r");
char line[50];
char *str;
while (fgets(line,sizeof(line),circuit) != NULL)
{
str = strtok(line," "); //space is DELIM
printf("str is: %s\n",str);
}
I am geting the following outputs from the text file that I included as an example:
str is: INPUTVAR
str is: OUTPUTVAR
str is: AND
str is: AND
str is: OR
How do I go about getting the characters after the first word of each line?

Answer 1

I adjusted your code [please pardon any gratuitous style cleanup]:
FILE *circuit;
circuit = fopen(argv[1], "r");
char line[50];
char *str;
char *cp;
while (1) {
cp = fgets(line, sizeof(line), circuit);
if (cp == NULL)
break;
cp = strchr(line,'\n');
if (cp != NULL)
*cp = 0;
cp = line;
while (1) {
str = strtok(cp, " ");
cp = NULL;
if (str == NULL)
break;
printf("str is: %s\n", str);
}
}
UPDATE: Per your request, here is a more generalized solution that gets you closer. This compiles but is untested. But, it should give you the idea.
// circuit -- circuit simulator
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
// command parsing control
// NOTE: this can be build up if desired
struct cmd {
const char *cmd_str; // command string
const char *(*cmd_parse)(struct cmd *); // command parse function
};
// forward declarations
const char *parse_inputvar(struct cmd *cmd);
const char *parse_outputvar(struct cmd *cmd);
const char *parse_and(struct cmd *cmd);
const char *parse_or(struct cmd *cmd);
// list of supported commands
struct cmd cmdlist[] = {
{ .cmd_str = "INPUTVAR", .cmd_parse = parse_inputvar },
{ .cmd_str = "OUTPUTVAR", .cmd_parse = parse_outputvar },
{ .cmd_str = "AND", .cmd_parse = parse_and },
{ .cmd_str = "OR", .cmd_parse = parse_or },
{ .cmd_str = NULL }
};
int
main(int argc,char **argv)
{
FILE *circuit;
char line[5000];
char *cp;
struct cmd *cmd;
const char *err;
--argc;
++argv;
circuit = fopen(*argv, "r");
while (1) {
cp = fgets(line, sizeof(line), circuit);
if (cp == NULL)
break;
cp = strchr(line,'\n');
if (cp != NULL)
*cp = 0;
cp = strtok(line," ");
err = NULL;
for (cmd = cmdlist; cmd->cmd_str != NULL; ++cmd) {
if (strcmp(cp,cmd->cmd_str) == 0) {
err = cmd->cmd_parse(cmd);
break;
}
}
if (cmd->cmd_str == NULL)
printf("unknown command -- '%s'\n",cp);
if (err != NULL)
printf("error in %s command -- %s\n",cmd->cmd_str,err);
}
fclose(circuit);
}
const char *
parse_inputvar(struct cmd *cmd)
{
char *cp;
char *sym;
int cnt;
int idx;
const char *err = NULL;
do {
// get the count string
cp = strtok(NULL," ");
if (cp == NULL) {
err = "missing count";
break;
}
// decode count string into number
cnt = atoi(cp);
if (cnt <= 0) {
err = "bad count";
break;
}
for (idx = 0; idx < cnt; ++idx) {
sym = strtok(NULL," ");
if (sym == NULL) {
err = "missing symbol";
break;
}
// NOTE: sym will be invalid after we return so we need to preserve
// it now
sym = strdup(sym);
// do whatever ...
}
} while (0);
return err;
}
const char *
parse_outputvar(struct cmd *cmd)
{
const char *err = NULL;
return err;
}
const char *
parse_and(struct cmd *cmd)
{
const char *err = NULL;
return err;
}
const char *
parse_or(struct cmd *cmd)
{
const char *err = NULL;
return err;
}

Answer 2

You can read the line of input, using fgets(), as a string and them do a split() function on it to parse it into numbers. The split creates an array of strings using spaces as delimiters. The first string will be INPUTVAR in string format, then you can do an atoi() on that to convert to a number.