Add string functions

parser.c

@@ -9,11 +9,21 @@
 _Noreturn void
 unreachable(char *file, size_t line)
 {
-	fprintf(stderr, "ERROR: unreachable code reached at %s:%zu\n", file,
-			line);
+	fprintf(stderr, "ERROR: unreachable code reached at %s:%zu\n", file, line);
 	exit(EXIT_FAILURE);
 }
+bool str_eq(Str a, Str b)
+{
+	return a.len == b.len && memcmp(a.str, b.str, a.len) == 0;
+}
+
+int str_cmp(Str a, Str b)
+{
+	int cmp = memcmp(a.str, b.str, a.len < b.len ? a.len : b.len);
+	return cmp == 0 ? (a.len > b.len) - (b.len > a.len) : cmp;
+}
+
 typedef struct {
 	const u8 *pos;
 	const u8 *end;

parser.h

@@ -36,6 +36,16 @@ typedef struct {
 } Str;
 #define STR(lit) (Str) { .str = (const u8 *) lit, .len = sizeof(lit) - 1 }
+// Compare equality of strings, returns true if equal, false otherwise.
+bool str_eq(Str a, Str b);
+
+// Lexicographically compare two strings. Returns:
+//  - 0 if the strings are equal,
+//  - a negative number if the first string is less than the second
+//  - a positive number if the first string is greater than the second
+int str_cmp(Str a, Str b);
+
+
 // See https://courses.fit.cvut.cz/NI-RUN/specs/ast.html for details about the
 // AST.