Parsing S-expression

lisp.c

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

#define DATA_FILE "data.lisp"

struct Node {
  char *data;
  struct Node *next;
  struct Node *children;
};

void read_children(FILE *fp, struct Node **head);

int main(int argc, char *argv[]) {
  FILE *fp;
  fp = fopen(DATA_FILE, "r");
  
  struct Node *root;
  read_children(fp, &root);
  
  fclose(fp);

  return 0;
}

void read_children(FILE *fp, struct Node **head) {
  struct Node *node;
  
  int c;
  char buffer[32];
  
  while ((c = fgetc(fp)) != EOF) {
    if (c == '(') {
      node = calloc(1, sizeof(struct Node));
      read_children(fp, &node->children);
      node->next = *head;
      *head = node;
    }
    else if (c == ')') {
      break;
    }
    else if (!isspace(c)) {
      ungetc(c, fp);
      
      if (c == '"') {
        fscanf(fp, "\"%31[^\"]\"", buffer);
      } else {
        fscanf(fp, "%31[^() ]", buffer);
      }
      
      node = calloc(1, sizeof(struct Node));
      node->data = calloc(strlen(buffer), sizeof(char));
      strcpy(node->data, buffer);
      
      node->next = *head;
      *head = node;
    }
  }
}