Add display buffer read/write mappers

include/apple2.dbuf.h

@@ -0,0 +1,11 @@
+#ifndef _APPLE2_DBUF_H_
+#define _APPLE2_DBUF_H_
+
+#include "apple2.h"
+#include "vm_segment.h"
+
+extern SEGMENT_READER(apple2_dbuf_read);
+extern SEGMENT_WRITER(apple2_dbuf_write);
+extern void apple2_dbuf_map(vm_segment *);
+
+#endif

sources.cmake

@@ -1,6 +1,7 @@
 set(erc_sources
 	apple2.c
 	apple2.bank.c
+	apple2.dbuf.c
 	apple2.dd.c
 	apple2.draw.c
 	apple2.mem.c

src/apple2.dbuf.c

@@ -0,0 +1,84 @@
+/*
+ * apple2.dbuf.c
+ */
+
+#include "apple2.dbuf.h"
+
+/*
+ * Handle reads from text page 1 and hires graphics page 1 (the display
+ * buffers).
+ */
+SEGMENT_READER(apple2_dbuf_read)
+{
+    apple2 *mach = (apple2 *)_mach;
+
+    // When 80STORE is high, we are allowed to look into two other flags
+    // to see if they are set and modify our behavior accordingly.
+    if (mach->memory_mode & MEMORY_80STORE) {
+        // If the address is contained within text page 1, then we need
+        // to look up memory in aux. (Uh, don't ask why we switch page 1
+        // with the PAGE2 flag.) Otherwise, if the address is contained
+        // in hires graphics page 1, then that must also use aux memory
+        // if _both_ the PAGE2 and HIRES bits are set.
+        if (addr >= 0x400 && addr < 0x800 && 
+            mach->memory_mode & MEMORY_PAGE2
+           ) {
+            segment = mach->aux;
+        } else if (addr >= 0x2000 && addr < 0x4000 &&
+                   mach->memory_mode & MEMORY_PAGE2 & MEMORY_HIRES
+                  ) {
+            segment = mach->aux;
+        }
+    }
+
+    // In all other cases, we _must_ use the segment that was passed in.
+    // That segment may be aux memory if MEMORY_READ_AUX is set, and if
+    // so, that would be the desired behavior.
+    return segment->memory[addr];
+}
+
+/*
+ * Many of the cautions and notes in the apple2_dbuf_read function
+ * apply here as well.
+ */
+SEGMENT_WRITER(apple2_dbuf_write)
+{
+    apple2 *mach = (apple2 *)_mach;
+
+    if (mach->memory_mode & MEMORY_80STORE) {
+        if (addr >= 0x400 && addr < 0x800 && 
+            mach->memory_mode & MEMORY_PAGE2
+           ) {
+            segment = mach->aux;
+        } else if (addr >= 0x2000 && addr < 0x4000 &&
+                   mach->memory_mode & MEMORY_PAGE2 &&
+                   mach->memory_mode & MEMORY_HIRES
+                  ) {
+            segment = mach->aux;
+        }
+    }
+
+    // Again, segment is allowed to be that which was passed in if
+    // 80STORE is low. 
+    segment->memory[addr] = value;
+}
+
+/*
+ * Map the text page 1 and hires graphics page 1 addresses to the dbuf
+ * read and write functions.
+ */
+void 
+apple2_dbuf_map(vm_segment *segment)
+{
+    size_t addr;
+
+    for (addr = 0x400; addr < 0x800; addr++) {
+        vm_segment_read_map(segment, addr, apple2_dbuf_read);
+        vm_segment_write_map(segment, addr, apple2_dbuf_write);
+    }
+
+    for (addr = 0x2000; addr < 0x4000; addr++) {
+        vm_segment_read_map(segment, addr, apple2_dbuf_read);
+        vm_segment_write_map(segment, addr, apple2_dbuf_write);
+    }
+}

src/apple2.mem.c

@@ -2,9 +2,10 @@
  * apple2.mem.c
  */
 
+#include "apple2.bank.h"
+#include "apple2.dbuf.h"
 #include "apple2.h"
 #include "apple2.mem.h"
-#include "apple2.bank.h"
 #include "objstore.h"
 
 /*
@@ -21,6 +22,9 @@ apple2_mem_map(apple2 *mach, vm_segment *segment)
     // of it.
     apple2_bank_map(segment);
 
+    // Here we handle the 80STORE bit for our display buffers.
+    apple2_dbuf_map(segment);
+
     // We will do the mapping for the zero page and stack addresses.
     // Accessing those addresses can be affected by bank-switching, but
     // those addresses do not actually exist in the capital

tests/apple2.dbuf.c

@@ -0,0 +1,69 @@
+#include <criterion/criterion.h>
+
+#include "apple2.h"
+#include "apple2.dbuf.h"
+#include "vm_segment.h"
+
+static apple2 *mach = NULL;
+
+static void
+setup()
+{
+    mach = apple2_create(100, 100);
+    vm_segment_set_map_machine(mach);
+}
+
+static void
+teardown()
+{
+    apple2_free(mach);
+    vm_segment_set_map_machine(NULL);
+}
+
+TestSuite(apple2_dbuf, .init = setup, .fini = teardown);
+
+Test(apple2_dbuf, map)
+{
+    size_t addr;
+    int i;
+    vm_segment *segments[2];
+
+    segments[0] = mach->main;
+    segments[1] = mach->aux;
+    for (i = 0; i < 2; i++) {
+        for (addr = 0x400; addr < 0x800; addr++) {
+            cr_assert_eq(segments[i]->read_table[addr], apple2_dbuf_read);
+            cr_assert_eq(segments[i]->write_table[addr], apple2_dbuf_write);
+        }
+
+        for (addr = 0x2000; addr < 0x4000; addr++) {
+            cr_assert_eq(segments[i]->read_table[addr], apple2_dbuf_read);
+            cr_assert_eq(segments[i]->write_table[addr], apple2_dbuf_write);
+        }
+    }
+}
+
+/*
+ * This test also works on apple2_dbuf_write.
+ *
+ * Test(apple2_dbuf, write)
+ */
+Test(apple2_dbuf, read)
+{
+    apple2_set_memory_mode(mach, MEMORY_80STORE | MEMORY_PAGE2);
+    vm_segment_set(mach->main, 0x400, 123);
+    vm_segment_set(mach->main, 0x2000, 234);
+    cr_assert_neq(mach->main->memory[0x400], 123);
+    cr_assert_eq(mach->aux->memory[0x400], 123);
+    cr_assert_eq(mach->main->memory[0x2000], 234);
+    cr_assert_neq(mach->aux->memory[0x2000], 234);
+
+    apple2_set_memory_mode(mach, MEMORY_80STORE | MEMORY_PAGE2 | MEMORY_HIRES);
+    vm_segment_set(mach->main, 0x2000, 234);
+    cr_assert_eq(mach->main->memory[0x2000], 234);
+    cr_assert_eq(mach->aux->memory[0x2000], 234);
+}
+
+Test(apple2_dbuf, write)
+{
+}