feat: Initial commit

Laboratorio 1/Esercizio 1/main.c

@@ -0,0 +1,94 @@
+// Laboratorio 1 - Esercizio 1
+// Matteo Schiff - s295565
+
+#include <stdbool.h>
+#include <ctype.h>
+#include <stdio.h>
+
+char *cercaRegexp(char *src, char *regexp);
+
+// NOTE: regexp has to be incremented after calling this function
+bool checkChar(char src, char **regexp)
+{
+    switch (**regexp)
+    {
+    case '.':
+        return true;
+    case '[':
+        (*regexp)++;
+        int negate = **regexp == '^';
+
+        if (negate)
+            (*regexp)++;
+
+        do
+        {
+            if (src == **regexp) {
+            	while (**regexp != ']')
+		    (*regexp)++;
+		return !negate;
+	    }
+            (*regexp)++;
+        } while (**regexp != ']');
+
+        return negate;
+    case '\\':
+        (*regexp)++;
+        if (**regexp == 'a') {
+            return islower(src);
+        } else if (**regexp == 'A') {
+            return isupper(src);
+        }
+        return false; // NOTE: regex is not valid
+    default:
+        return src == **regexp;
+    }
+}
+
+bool matchSubstring(char *src, char *regexp)
+{
+    char *cur_s = src;
+    char *cur_meta = regexp;
+
+    while (*cur_meta != 0)
+    {
+        // match failed if regex check is false or if we reached the end
+        // of the string without reaching the end of the regex
+        if (*cur_s == 0 || !checkChar(*cur_s, &cur_meta)) 
+            return false;
+
+        cur_s++;
+        cur_meta++;
+    }
+
+    return true;
+}
+
+char *searchRegexp(char *src, char *regexp)
+{
+    char *cur_s = src;
+
+    while (*cur_s != 0)
+    {
+        if (matchSubstring(cur_s, regexp))
+            return cur_s;
+        cur_s++;
+    }
+    return 0;
+}
+
+int main(int argc, char ** argv) {
+    if (argc != 3) {
+        puts("USAGE: ./esercizio1 string regexp");
+        return 1;
+    }
+
+    char * substr = searchRegexp(argv[1], argv[2]);
+
+    if (!substr) {
+        puts("No matches");
+    } else {
+        puts(substr);
+    }
+    return 0;
+}