Refactor for reuse of file parsing logic

firewall-rules/parser.c

@@ -138,4 +138,50 @@ char* parse_rule(char line[], struct Rule* result) {
 
     fail:
     return NULL;
-}
+}
+
+#define MAX_RULES 128
+
+// parse_file parses a set of rules from the file named fname. The memory used
+// by the return value should be freed by the caller. If the return value is 
+// NULL, an error was encoutered and echo'd.
+struct Rule** parse_file(char fname[], size_t* num_parsed_rules) {
+    FILE *fp = fopen(fname, "r");
+    if (fp == NULL) {
+        perror("Read input file");
+        return NULL;
+    }
+
+    struct Rule** parsed_rules = malloc(sizeof(struct Rule*) * MAX_RULES);
+    *num_parsed_rules = 0;
+
+    char *line = NULL;
+    size_t line_size = 0;
+    while (getline(&line, &line_size, fp) != -1) {
+        if (*num_parsed_rules == MAX_RULES) {
+            fprintf(stderr, "Too many rules\n");
+            return NULL;
+        }
+        struct Rule* rule = (struct Rule*) malloc(sizeof(struct Rule));
+        char* endptr = parse_rule(line, rule);
+        if (endptr == NULL || *endptr != '\n') {
+            fprintf(stderr, "Ill formed rule: %s\n", line);
+            return NULL;
+        }
+        parsed_rules[*num_parsed_rules] = rule;
+        (*num_parsed_rules) += 1;
+    }
+    if (!feof(fp)) { // When we get here, getline has always returned -1 but may or may not have reached EOF.
+        // If it hasn't reached EOF, an error was thrown.
+        perror("Read line");
+        return NULL;
+    }
+    free(line);
+
+    if (fclose(fp) != 0) {
+        perror("Close input file");
+        return NULL;
+    }
+
+    return parsed_rules;
+}

firewall-rules/readFirewall.c

@@ -2,7 +2,6 @@
 #include <stdio.h>
 #include "parser.c"
 
-#define MAX_RULES 128
 
 int main(int argc, char* argv[]) {
     if (argc < 2) {
@@ -10,42 +9,11 @@ int main(int argc, char* argv[]) {
         return 1;
     }
 
-    char *fname = argv[1];
 
-    FILE *fp = fopen(fname, "r");
-    if (fp == NULL) {
-        perror("Read input file");
-        return 1;
-    }
+    size_t num_parsed_rules;
+    struct Rule** parsed_rules = parse_file(argv[1], &num_parsed_rules);
 
-    struct Rule** parsed_rules = malloc(sizeof(struct Rule*) * MAX_RULES);
-    uint num_parsed_rules = 0;
-
-    char *line = NULL;
-    size_t line_size = 0;
-    while (getline(&line, &line_size, fp) != -1) {
-        if (num_parsed_rules == MAX_RULES) {
-            fprintf(stderr, "Too many rules\n");
-            return 1;
-        }
-        struct Rule* rule = (struct Rule*) malloc(sizeof(struct Rule));
-        char* endptr = parse_rule(line, rule);
-        if (endptr == NULL || *endptr != '\n') {
-            fprintf(stderr, "Ill formed rule: %s\n", line);
-            return 1;
-        }
-        parsed_rules[num_parsed_rules] = rule;
-        num_parsed_rules += 1;
-    }
-    if (!feof(fp)) { // When we get here, getline has always returned -1 but may or may not have reached EOF.
-        // If it hasn't reached EOF, an error was thrown.
-        perror("Read line");
-        return 1;
-    }
-    free(line);
-
-    if (fclose(fp) != 0) {
-        perror("Close input file");
+    if (parsed_rules == NULL) {
         return 1;
     }