From afe764d0346ef341e8a8897d5ef2259fb305794f Mon Sep 17 00:00:00 2001
From: Ben Kurtovic <ben.kurtovic@gmail.com>
Date: Mon, 23 Mar 2015 19:17:29 -0400
Subject: [PATCH] Improve ROM loading.

---
 crater.c  | 19 ++++++++--------
 makefile  |  5 ++++-
 src/rom.c | 77 +++++++++++++++++++++++++++++++++++++++++++++++----------------
 src/rom.h | 10 ++++++++-
 4 files changed, 80 insertions(+), 31 deletions(-)

diff --git a/crater.c b/crater.c
index fb3333f..6177669 100644
--- a/crater.c
+++ b/crater.c
@@ -37,19 +37,18 @@ int main(int argc, char *argv[])
         retval = retval ? EXIT_SUCCESS : EXIT_FAILURE;
     } else {
         ROM *rom;
+        const char* errmsg;
 
-        printf("crater: a Sega Game Gear emulator\n\n");
-        if (!(rom = rom_open(config->rom_path))) {
-            if (errno == ENOMEM)
-                OUT_OF_MEMORY()
-            else
-                FATAL_ERRNO("couldn't load ROM image '%s'", config->rom_path)
-        }
-        printf("Loaded ROM image: %s\n", rom->name);
+        if ((errmsg = rom_open(&rom, config->rom_path))) {
+            ERROR("couldn't load ROM image '%s': %s", config->rom_path, errmsg)
+            retval = EXIT_FAILURE;
+        } else {
+            printf("crater: emulating: %s\n", rom->name);
 
-        // TODO: emulate game here...
+            // TODO: emulate game here...
 
-        rom_close(rom);
+            rom_close(rom);
+        }
     }
 
     config_destroy(config);
diff --git a/makefile b/makefile
index 1db52d4..d4330b6 100644
--- a/makefile
+++ b/makefile
@@ -26,13 +26,16 @@ ifdef DEBUG
 	MODE   = debug
 endif
 
-.PHONY: all clean
+.PHONY: all clean test
 
 all: $(BNRY)
 
 clean:
 	$(RM) $(BUILD) $(PROGRAM) $(PROGRAM)$(DEVEXT)
 
+test:
+	@echo "not implemented yet"
+
 $(DIRS):
 	$(MKDIR) $@
 
diff --git a/src/rom.c b/src/rom.c
index e684be6..2113200 100644
--- a/src/rom.c
+++ b/src/rom.c
@@ -2,51 +2,86 @@
    Released under the terms of the MIT License. See LICENSE for details. */
 
 #include <errno.h>
+#include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/stat.h>
 
 #include "rom.h"
+#include "logging.h"
 
 /*
-    Create and return a ROM object located at the given path. Return NULL if
-    there was an error; errno will be set appropriately.
+    Return whether or not the given ROM image size is valid.
 */
-ROM* rom_open(const char *path)
+static bool validate_size(off_t size)
+{
+    off_t kbytes = size >> 10;
+    if (kbytes << 10 != size)
+        return false;
+    if (kbytes < 8 || kbytes > 1024)
+        return false;
+    return !(kbytes & (kbytes - 1));
+}
+
+/*
+    Create and load a ROM image located at the given path.
+
+    rom_ptr will point to the new object if created successfully, and NULL will
+    be returned. Otherwise, rom_ptr will not be modified and an error string
+    will be returned. The error string should not be freed.
+*/
+const char* rom_open(ROM **rom_ptr, const char *path)
 {
     ROM *rom;
     FILE* fp;
-    struct stat s;
+    struct stat st;
 
     if (!(fp = fopen(path, "r")))
-        return NULL;
+        return strerror(errno);
 
-    if (fstat(fileno(fp), &s)) {
+    if (fstat(fileno(fp), &st)) {
         fclose(fp);
-        return NULL;
+        return strerror(errno);
     }
-    if (!(s.st_mode & S_IFREG)) {
-        errno = (s.st_mode & S_IFDIR) ? EISDIR : ENOENT;
+    if (!(st.st_mode & S_IFREG)) {
         fclose(fp);
-        return NULL;
+        return (st.st_mode & S_IFDIR) ? rom_err_isdir : rom_err_notfile;
     }
 
-    if (!(rom = malloc(sizeof(ROM)))) {
+    if (!(rom = malloc(sizeof(ROM))))
+        OUT_OF_MEMORY()
+
+    // Set defaults:
+    rom->name = NULL;
+    rom->data = NULL;
+    rom->size = 0;
+
+    // Set rom->name:
+    if (!(rom->name = malloc(sizeof(char) * (strlen(path) + 1))))
+        OUT_OF_MEMORY()
+    strcpy(rom->name, path);
+
+    // Set rom->size:
+    if (!validate_size(st.st_size)) {
+        rom_close(rom);
         fclose(fp);
-        return NULL;
+        return rom_err_badsize;
     }
-    rom->name = malloc(sizeof(char) * (strlen(path) + 1));
-    if (!rom->name) {
+    rom->size = st.st_size;
+
+    // Set rom->data:
+    if (!(rom->data = malloc(sizeof(char) * st.st_size)))
+        OUT_OF_MEMORY()
+    if (!(fread(rom->data, st.st_size, 1, fp))) {
+        rom_close(rom);
         fclose(fp);
-        return NULL;
+        return rom_err_badread;
     }
-    strcpy(rom->name, path);
-
-    // TODO: load data from file into a buffer
 
     fclose(fp);
-    return rom;
+    *rom_ptr = rom;
+    return NULL;
 }
 
 /*
@@ -54,5 +89,9 @@ ROM* rom_open(const char *path)
 */
 void rom_close(ROM *rom)
 {
+    if (rom->name)
+        free(rom->name);
+    if (rom->data)
+        free(rom->data);
     free(rom);
 }
diff --git a/src/rom.h b/src/rom.h
index 5d493cc..3b3333f 100644
--- a/src/rom.h
+++ b/src/rom.h
@@ -3,14 +3,22 @@
 
 #pragma once
 
+/* Error strings */
+
+static const char* rom_err_isdir   = "Is a directory";
+static const char* rom_err_notfile = "Is not a regular file";
+static const char* rom_err_badsize = "Invalid size";
+static const char* rom_err_badread = "Couldn't read the entire file";
+
 /* Structs */
 
 typedef struct {
     char* name;
     char* data;
+    unsigned size;
 } ROM;
 
 /* Functions */
 
-ROM* rom_open(const char*);
+const char* rom_open(ROM**, const char*);
 void rom_close(ROM*);