From 9397107e214184c41a264f21edc5d419da69d069 Mon Sep 17 00:00:00 2001
From: Ben Kurtovic <ben.kurtovic@gmail.com>
Date: Fri, 24 Apr 2015 13:17:16 -0500
Subject: [PATCH] Fix MMU mirroring algo, support reading 48 KB ROMs.

---
 src/assembler.c |  6 +++---
 src/mmu.c       | 21 +++++++++++++++++----
 src/rom.c       | 28 ++++++++--------------------
 src/util.c      |  2 +-
 4 files changed, 29 insertions(+), 28 deletions(-)

diff --git a/src/assembler.c b/src/assembler.c
index bae4d35..ffc88a2 100644
--- a/src/assembler.c
+++ b/src/assembler.c
@@ -91,7 +91,7 @@ static ErrorInfo* check_layout(
 {
     const ASMLine *clash = NULL;
 
-    if (loc->offset + loc->length >= size) {
+    if (loc->offset + loc->length > size) {
         clash = &bounds_sentinel;
     } else {
         for (size_t i = 0; i < loc->length; i++) {
@@ -226,7 +226,7 @@ static ErrorInfo* resolve_defaults(AssemblerState *state)
         const ASMInstruction *inst = state->instructions;
         while (inst) {
             size_t bound = inst->loc.offset + inst->loc.length;
-            if (bound >= state->rom_size)
+            if (bound > state->rom_size)
                 state->rom_size = bounding_rom_size(bound);
             inst = inst->next;
         }
@@ -234,7 +234,7 @@ static ErrorInfo* resolve_defaults(AssemblerState *state)
         const ASMData *data = state->data;
         while (data) {
             size_t bound = data->loc.offset + data->loc.length;
-            if (bound >= state->rom_size)
+            if (bound > state->rom_size)
                 state->rom_size = bounding_rom_size(bound);
             data = data->next;
         }
diff --git a/src/mmu.c b/src/mmu.c
index b79cdd6..64f83a5 100644
--- a/src/mmu.c
+++ b/src/mmu.c
@@ -52,15 +52,28 @@ void mmu_load_rom(MMU *mmu, const uint8_t *data, size_t size)
     if (size % MMU_ROM_BANK_SIZE)
         return;
 
-    size_t banks = size / MMU_ROM_BANK_SIZE;
+    size_t banks = size / MMU_ROM_BANK_SIZE, bank, mirror;
     if (banks > MMU_NUM_ROM_BANKS)
         banks = MMU_NUM_ROM_BANKS;
 
-    for (size_t bank = 0; bank < banks; bank++) {
-        for (size_t mirror = bank; mirror < banks; mirror += bank + 1) {
+    for (bank = 0; bank < banks; bank++) {
+        for (mirror = bank; mirror < MMU_NUM_ROM_BANKS; mirror += banks)
             mmu->rom_banks[mirror] = data + (bank * MMU_ROM_BANK_SIZE);
+    }
+
+#ifdef DEBUG_MODE
+    char temp_str[64];
+    DEBUG("Dumping MMU bank table:")
+    for (size_t group = 0; group < MMU_NUM_ROM_BANKS / 8; group++) {
+        for (size_t elem = 0; elem < 8; elem++) {
+            bank = 8 * group + elem;
+            snprintf(temp_str + 6 * elem, 7, "%02zX=%02zX ", bank,
+                     (mmu->rom_banks[bank] - data) >> 14);
         }
+        temp_str[47] = '\0';
+        DEBUG("- %s", temp_str)
     }
+#endif
 }
 
 /*
@@ -68,7 +81,7 @@ void mmu_load_rom(MMU *mmu, const uint8_t *data, size_t size)
 */
 static inline void map_slot(MMU *mmu, size_t slot, size_t bank)
 {
-    DEBUG("MMU mapping memory slot %zu to bank %zu", slot, bank)
+    DEBUG("MMU mapping memory slot %zu to bank 0x%02zX", slot, bank)
     mmu->map_slots[slot] = mmu->rom_banks[bank];
 }
 
diff --git a/src/rom.c b/src/rom.c
index de3e07f..4a65c88 100644
--- a/src/rom.c
+++ b/src/rom.c
@@ -20,18 +20,6 @@
 static size_t header_locations[NUM_LOCATIONS] = {0x7FF0, 0x3FF0, 0x1FF0};
 static const char header_magic[MAGIC_LEN + 1] = "TMR SEGA";
 
-/*
-    Return whether or not the given ROM image size is valid.
-*/
-static bool validate_size(off_t size)
-{
-    if (size & (size - 1))
-        return false;  // Ensure size is a power of two
-
-    off_t kbytes = size >> 10;
-    return kbytes >= 8 && kbytes <= 1024;
-}
-
 #ifdef DEBUG_MODE
 /*
     DEBUG FUNCTION: Print out the header to stdout.
@@ -96,15 +84,14 @@ static uint16_t compute_checksum(const uint8_t *data, size_t size, uint8_t range
 
 #ifdef DEBUG_MODE
 /*
-    DEBUG FUNCTION: Return the ROM's size as a string, according to its header.
+    DEBUG FUNCTION: Given a ROM size, return a pretty string.
 */
-static const char* parse_reported_size(uint8_t value)
+static const char* size_to_string(size_t size)
 {
     static char buffer[SIZE_CODE_BUF];
-    size_t size = size_code_to_bytes(value);
 
     if (!size)
-        strncpy(buffer, "Unknown", SIZE_CODE_BUF);
+        strncpy(buffer, "unknown", SIZE_CODE_BUF);
     else if (size >= (1 << 20))
         snprintf(buffer, SIZE_CODE_BUF, "%zu MB", size >> 20);
     else
@@ -162,7 +149,8 @@ static bool parse_header(ROM *rom, const uint8_t *header)
     DEBUG("  - version:       %u", rom->version)
     DEBUG("  - region code:   %u (%s)", rom->region_code,
           rom_region(rom) ? rom_region(rom) : "unknown")
-    DEBUG("  - reported size: %s", parse_reported_size(header[0xF] & 0xF))
+    DEBUG("  - reported size: %s",
+          size_to_string(size_code_to_bytes(header[0xF] & 0xF)))
     return true;
 }
 
@@ -191,7 +179,7 @@ static bool find_and_read_header(ROM *rom)
             return parse_header(rom, header);
         }
     }
-    DEBUG("  - could not find header")
+    DEBUG("  - couldn't find header")
     return false;
 }
 
@@ -240,8 +228,8 @@ const char* rom_open(ROM **rom_ptr, const char *path)
     DEBUG("Loading ROM %s:", rom->name)
 
     // Set rom->size:
-    DEBUG("- size: %lld", st.st_size)
-    if (!validate_size(st.st_size)) {
+    DEBUG("- size: %lld bytes (%s)", st.st_size, size_to_string(st.st_size))
+    if (size_bytes_to_code(st.st_size) == INVALID_SIZE_CODE) {
         rom_close(rom);
         fclose(fp);
         return rom_err_badsize;
diff --git a/src/util.c b/src/util.c
index 050c7a9..1be96bc 100644
--- a/src/util.c
+++ b/src/util.c
@@ -126,7 +126,7 @@ size_t size_code_to_bytes(uint8_t code)
 uint8_t size_bytes_to_code(size_t bytes)
 {
     if (bytes & ((1 << 10) - 1))
-        return 0;  // Not an even number of KB
+        return INVALID_SIZE_CODE;  // Not an even number of KB
 
     switch (bytes >> 10) {
         case    8: return 0xA;