Guard against reading directories as ROM files.

crater.c

@@ -150,7 +150,7 @@ int main(int argc, char *argv[])
     if (rom_path[0] == '\0')
         FATAL("no image given")
 
-    if (!(rom = open_rom(rom_path))) {
+    if (!(rom = rom_open(rom_path))) {
         if (errno == ENOMEM)
             OUT_OF_MEMORY()
         else
@@ -162,6 +162,6 @@ int main(int argc, char *argv[])
 
     // TODO: start from here
 
-    close_rom(rom);
+    rom_close(rom);
     return 0;
 }

src/rom.c

@@ -1,34 +1,51 @@
 /* Copyright (C) 2014-2015 Ben Kurtovic <ben.kurtovic@gmail.com>
    Released under the terms of the MIT License. See LICENSE for details. */
 
+#include <errno.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <sys/stat.h>
 
 #include "rom.h"
 
 /* Create and return a ROM object located at the given path. Return NULL if
    there was an error; errno will be set appropriately. */
-rom_type* open_rom(const char *path)
+rom_type* rom_open(const char *path)
 {
     rom_type *rom;
     FILE* fp;
+    struct stat s;
 
     if (!(fp = fopen(path, "r")))
         return NULL;
-    if (!(rom = malloc(sizeof(rom_type))))
+
+    if (fstat(fileno(fp), &s)) {
+        fclose(fp);
+        return NULL;
+    }
+    if (!(s.st_mode & S_IFREG)) {
+        if (s.st_mode & S_IFDIR)
+            errno = EISDIR;
+        fclose(fp);
+        return NULL;
+    }
+
+    if (!(rom = malloc(sizeof(rom_type)))) {
+        fclose(fp);
         return NULL;
+    }
     rom->name = malloc(sizeof(char) * (strlen(path) + 1));
     strcpy(rom->name, path);
 
-    // load data from file into a buffer
+    // TODO: load data from file into a buffer
 
     fclose(fp);
     return rom;
 }
 
-/* Free a ROM object previously created with open_rom(). */
-void close_rom(rom_type *rom)
+/* Free a ROM object previously created with rom_open(). */
+void rom_close(rom_type *rom)
 {
     free(rom);
 }

src/rom.h

@@ -12,5 +12,5 @@ typedef struct {
 
 /* Functions */
 
-rom_type* open_rom(const char*);
-void close_rom(rom_type*);
+rom_type* rom_open(const char*);
+void rom_close(rom_type*);