From 2f815b312045ae740e88d4dc44dcc3cbf70a9d98 Mon Sep 17 00:00:00 2001
From: Nathaniel Walizer <robots.are.love@gmail.com>
Date: Sun, 16 Mar 2025 23:15:58 -0700
Subject: [PATCH] Refactor cart loading for early mapper failure

---
 src/linux/port.c | 89 ++++++++++++++++++++++++++++++++++++++++++++----
 src/nese.c       | 39 ++-------------------
 src/nese.h       |  2 +-
 src/port.h       |  3 --
 4 files changed, 86 insertions(+), 47 deletions(-)

diff --git a/src/linux/port.c b/src/linux/port.c
index cf758c1..1064d7d 100644
--- a/src/linux/port.c
+++ b/src/linux/port.c
@@ -7,6 +7,7 @@
 
 #include <SDL.h>
 
+#include "cart.h"
 #include "nese.h"
 #include "port.h"
 
@@ -14,7 +15,7 @@
 #include "log.h"
 
 
-void* nese_map_file(FILE* file, int size) {
+static void* nese_map_file(FILE* file, int size) {
     void* addr = mmap(NULL, size, PROT_READ, MAP_SHARED,
                       fileno(file), 0);
     if (MAP_FAILED == addr || NULL == addr) {
@@ -24,16 +25,30 @@ void* nese_map_file(FILE* file, int size) {
     return addr;
 }
 
-int nese_unmap_file(void* addr, int size) {
+static int nese_unmap_file(void* addr, int size) {
     return munmap(addr, size);
 }
 
+static int nese_file_size(FILE* file) {
+    int size = -1;
+    if (0 == fseek(file, 0, SEEK_END)) {
+        size = ftell(file);
+    }
+    return size;
+}
+
 
 typedef struct {
-    nes* sys;
+    const char* filename;
+    FILE* file;
+    int filesize;
+    void* cart_data;
+} cart_info;
 
+typedef struct {
+    nes* sys;
+    cart_info cart;
     int64_t t_target;
-
     SDL_Window* window;
     SDL_Renderer* renderer;
     SDL_Texture* texture;
@@ -321,22 +336,82 @@ static void plat_done(platform_data* plat) {
 }
 
 
+static int load_cart(const char* filename, platform_data* plat) {
+    int status = 0;
+    int filesize = 0;
+    void* cart_data = NULL;
+
+    FILE* file = fopen(filename, "rb");
+    if (NULL == file) {
+        status = -1;
+    } else {
+        filesize = nese_file_size(file);
+        cart_data = nese_map_file(file, filesize);
+        if (NULL == cart_data) {
+            fprintf(stderr, "Failed to map %s\n", filename);
+            status = -1;
+        } else {
+            status = nes_cart_load_mem(cart_data, filesize,
+                                       plat->sys);
+        }
+    }
+
+    if (0 == status) {
+        plat->cart.filename = filename;
+        plat->cart.filesize = filesize;
+        plat->cart.file = file;
+        plat->cart.cart_data = cart_data;
+    }
+
+    return status;
+}
+
+static void unload_cart(cart_info* cart) {
+    if (cart->cart_data) {
+        nese_unmap_file(cart->cart_data, cart->filesize);
+        cart->cart_data = NULL;
+        cart->filesize = 0;
+    }
+
+    if (cart->file) {
+        fclose(cart->file);
+        cart->file = NULL;
+    }
+}
+
+
 // This is too big for the stack.
 static nes sys = {0};
 
 
 int main(int argc, char* argv[]) {
+    int status = 0;
+
     // This should be tiny enough to keep on the stack.
     platform_data plat = {
         .sys = &sys,
     };
-    int status = plat_init(&plat);
+
     if (argc <= 1) {
         LOGE("No ROM file provided.");
         status = -1;
-    } else if (0 == status) {
-        status = nese_start(&sys, argv[1], &plat);
     }
+
+    if (0 == status) {
+        status = load_cart(argv[1], &plat);
+    }
+
+    if (0 == status) {
+        status = plat_init(&plat);
+    }
+
+    if (0 == status) {
+        status = nese_start(&sys, &plat);
+    }
+
+    unload_cart(&plat.cart);
+
     plat_done(&plat);
+
     return status;
 }
diff --git a/src/nese.c b/src/nese.c
index 64ee31c..ff4d2e3 100644
--- a/src/nese.c
+++ b/src/nese.c
@@ -5,47 +5,14 @@
 #include "port.h"
 
 
-static int nese_file_size(FILE* file) {
-    int size = -1;
-    if (0 == fseek(file, 0, SEEK_END)) {
-        size = ftell(file);
-    }
-    return size;
-}
-
-
-int nese_start(nes* sys, const char* filename, void* plat) {
-    int status = 0;
-    void* cart_data = NULL;
-    int filesize = -1;
-    FILE* file = NULL;
-
-    file = fopen(filename, "rb");
-
-    if (NULL == file) {
-        status = -1;
-    }
-
-    if (0 == status) {
-        filesize = nese_file_size(file);
-        cart_data = nese_map_file(file, filesize);
-        if (NULL == cart_data) {
-            fprintf(stderr, "Failed to map %s\n", filename);
-            status = -1;
-        } else {
-            status = nes_cart_load_mem(cart_data, filesize, sys);
-        }
-    }
-
+int nese_start(nes* sys, void* plat) {
     nes_init(sys);
 
     nes_reset(sys);
 
-    nes_loop(sys, plat);
-
-    if (cart_data) nese_unmap_file(cart_data, filesize);
+    int status = nes_loop(sys, plat);
 
     nes_done(sys);
 
-    return 0;
+    return status;
 }
diff --git a/src/nese.h b/src/nese.h
index a738f8b..59ad16a 100644
--- a/src/nese.h
+++ b/src/nese.h
@@ -4,7 +4,7 @@
 #include "nes.h"
 
 
-int nese_start(nes* sys, const char* filename, void*);
+int nese_start(nes* sys, void*);
 
 
 #endif // NESE_H_
diff --git a/src/port.h b/src/port.h
index 8389e69..a522a7c 100644
--- a/src/port.h
+++ b/src/port.h
@@ -6,9 +6,6 @@
 #include "input.h"
 
 
-void* nese_map_file(FILE* file, int size);
-int nese_unmap_file(void* addr, int size);
-
 int nese_frame_start(void*, uint8_t background);
 int nese_line_ready(void*, uint8_t* buffer, int line);
 int nese_frame_ready(void*);