Add subdir for SRAM saves

src/file.c

@@ -14,19 +14,45 @@ const char* basename(const char* filename) {
     return &slash[1];
 }
 
-int replace_extension(char* filename, int max_len,
-                      const char* orig_name, const char* ext) {
+int make_filename(char* filename, int max_len,
+                  const char* orig_name,
+                  const char* subdir, const char* ext) {
     int status = 0;
     int remain = max_len;
 
     const char* orig_base = basename(orig_name);
     const char* orig_dot = strrchr(orig_base, '.');
 
+    int orig_path_len = orig_base - orig_name;
+
     int orig_base_len = (NULL == orig_dot) ?
-                        strlen(orig_name) :
-                        (orig_dot - orig_name);
+                        strlen(orig_base) :
+                        (orig_dot - orig_base);
+
+    // Part 1/4: Leading path
+    if (0 == status && orig_path_len <= remain) {
+        strncpy(filename, orig_name, orig_path_len);
+        remain -= orig_path_len;
+        filename += orig_path_len;
+    } else {
+        status = -1;
+    }
+
+    // Part 2/4: Subdirectory
+    if (0 == status && NULL != subdir) {
+        int subdir_len = strlen(subdir);
+        if ((subdir_len + 1) <= remain) {
+            strncpy(filename, subdir, subdir_len);
+            filename += subdir_len;
+            *filename++ = '/';
+            remain -= (subdir_len + 1);
+        } else {
+            status = -1;
+        }
+    }
 
-    if (orig_base_len <= remain) {
+    // Part 3/4: Basename
+    if (0 == status && orig_base_len <= remain) {
         strncpy(filename, orig_name, orig_base_len);
         remain -= orig_base_len;
         filename += orig_base_len;
@@ -34,12 +60,14 @@ int replace_extension(char* filename, int max_len,
         status = -1;
     }
 
+    // Part 4/4: Extension
     if (0 == status && NULL != ext) {
         int ext_len = strlen(ext);
         if ((ext_len + 1) <= remain) {
             *filename++ = '.';
             strncpy(filename, ext, ext_len);
             remain -= (ext_len + 1);
+            filename += ext_len;
         } else {
             status = -1;
         }

src/file.h

@@ -5,10 +5,12 @@
 // Return pointer to filename omitting path
 const char* basename(const char* filename);
 
-int replace_extension(char* filename, int max_len,
-                      const char* orig_name, const char* ext);
+int make_filename(char* filename, int max_len,
+                  const char* orig_name,
+                  const char* subdir, const char* ext);
 
 int write_file(const char* filename, const void* data, int len);
 int read_file(const char* filename, void* data, int len);
 
+
 #endif // NESE_FILE_H_

src/save.c

@@ -5,8 +5,9 @@
 
 static int make_sram_filename(char* sram_filename, int max_len,
                               const char* cart_filename) {
-    return replace_extension(  sram_filename, max_len,
-                               basename(cart_filename), "sram");
+    return make_filename(  sram_filename, max_len,
+                           basename(cart_filename),
+                           "sram", "sram");
 }
 
 int load_sram(nes_cart* cart, const char* cart_filename) {