From b27be3c1592c26609a26b6d0f82dcaf88aad5763 Mon Sep 17 00:00:00 2001
From: Brooke Vibber <bvibber@pobox.com>
Date: Sun, 28 Dec 2025 09:23:38 -0800
Subject: [PATCH] Add a C shell, which currently just passes through

This is a first step toward moving the UI to C and
adding file and network I/O in C. The fractal core
will remain in assembler as well as the multiplier.
---
 Makefile                  | 10 ++++---
 atari-xex.cfg             | 62 +++++++++++++++++++++++++++++++++++++++
 mandel.s => mandel-core.s |  4 +--
 mandel.c                  | 15 ++++++++++
 mandel.h                  |  4 +++
 5 files changed, 89 insertions(+), 6 deletions(-)
 create mode 100644 atari-xex.cfg
 rename mandel.s => mandel-core.s (99%)
 create mode 100644 mandel.c
 create mode 100644 mandel.h

diff --git a/Makefile b/Makefile
index 711adcd..c94074b 100644
--- a/Makefile
+++ b/Makefile
@@ -2,8 +2,11 @@
 
 all : mandel.xex
 
-mandel.xex : mandel.o tables.o atari-asm-xex.cfg
-	ld65 -C ./atari-asm-xex.cfg --mapfile mandel.map -o $@ mandel.o tables.o
+mandel.xex : mandel.o mandel-core.o tables.o atari-xex.cfg
+	ld65 -C ./atari-xex.cfg --mapfile mandel.map -o $@ mandel.o mandel-core.o tables.o atari.lib
+
+mandel.s : mandel.c mandel.h
+	cc65 -o $@ mandel.c
 
 %.o : %.s
 	ca65 -o $@ $<
@@ -13,8 +16,7 @@ tables.s : tables.js
 
 clean :
 	rm -f tables.s
+	rm -f mandel.s
 	rm -f *.o
 	rm -f *.xex
 	rm -f mandel.map
-
-
diff --git a/atari-xex.cfg b/atari-xex.cfg
new file mode 100644
index 0000000..ee41c4c
--- /dev/null
+++ b/atari-xex.cfg
@@ -0,0 +1,62 @@
+# Sample linker configuration for C programs using the Atari binary file support.
+# Use with: cl65 -tatari -Catari-xex.cfg prog.c -o prog.xex
+FEATURES {
+    STARTADDRESS: default = $2000;
+}
+SYMBOLS {
+    __SYSTEM_CHECK__:    type = import;  # force inclusion of "system check" load chunk
+    __STACKSIZE__:       type = weak, value = $0800; # 2k stack
+    __STARTADDRESS__:    type = export, value = %S;
+    __RESERVED_MEMORY__: type = weak, value = $0000;
+    __SYSCHKHDR__:       type = export, value = 0; # Disable system check header
+    __SYSCHKTRL__:       type = export, value = 0; # Disable system check trailer
+}
+MEMORY {
+    ZP:         file = "", define = yes, start = $0082, size = $007E;
+# "system check" load chunk
+    SYSCHKCHNK: file = %O,               start = $2E00, size = $0300;
+# "main program" load chunk
+# Note we reserve $4000-7fff for the bank-switch window.
+    #MAIN:       file = %O, define = yes, start = %S,    size = $BC20 - __STACKSIZE__ - __RESERVED_MEMORY__ - %S;
+    MAIN:       file = %O, define = yes, start = %S,    size = $4000 - __STACKSIZE__ - __RESERVED_MEMORY__ - %S;
+
+# Note $a000-$bfff is against the BASIC cartridge, may require booting with OPTION.
+    TABLES:  file = %O, define = yes, start = $8000, size = $a000 - $8000;
+}
+FILES {
+    %O: format = atari;
+}
+FORMATS {
+    atari: runad = start,
+           initad = SYSCHKCHNK: __SYSTEM_CHECK__;
+}
+SEGMENTS {
+    ZEROPAGE:  load = ZP,         type = zp;
+    EXTZP:     load = ZP,         type = zp,                optional = yes;
+    SYSCHK:    load = SYSCHKCHNK, type = rw,  define = yes, optional = yes;
+    STARTUP:   load = MAIN,       type = ro,  define = yes;
+    LOWBSS:    load = MAIN,       type = rw,                optional = yes;  # not zero initialized
+    LOWCODE:   load = MAIN,       type = ro,  define = yes, optional = yes;
+    ONCE:      load = MAIN,       type = ro,                optional = yes;
+    CODE:      load = MAIN,       type = ro,  define = yes;
+    RODATA:    load = MAIN,       type = ro;
+    DATA:      load = MAIN,       type = rw;
+    INIT:      load = MAIN,       type = rw,                optional = yes;
+    BSS:       load = MAIN,       type = bss, define = yes;
+    TABLES:    load = TABLES,     type = ro,  optional = yes, align = 256;
+}
+FEATURES {
+    CONDES: type    = constructor,
+            label   = __CONSTRUCTOR_TABLE__,
+            count   = __CONSTRUCTOR_COUNT__,
+            segment = ONCE;
+    CONDES: type    = destructor,
+            label   = __DESTRUCTOR_TABLE__,
+            count   = __DESTRUCTOR_COUNT__,
+            segment = RODATA;
+    CONDES: type    = interruptor,
+            label   = __INTERRUPTOR_TABLE__,
+            count   = __INTERRUPTOR_COUNT__,
+            segment = RODATA,
+            import  = __CALLIRQ__;
+}
diff --git a/mandel.s b/mandel-core.s
similarity index 99%
rename from mandel.s
rename to mandel-core.s
index b52f24a..6ebb089 100644
--- a/mandel.s
+++ b/mandel-core.s
@@ -361,7 +361,7 @@ z_buffer:
         .word 0
     .endrepeat
 
-.export start
+.export _mandel_start
 
 ;max_fill_level = 6
 max_fill_level = 3
@@ -1745,7 +1745,7 @@ zero_byte_loop:
     rts
 .endproc
 
-.proc start
+.proc _mandel_start
 
     jsr imul8xe_init
 
diff --git a/mandel.c b/mandel.c
new file mode 100644
index 0000000..f287fa3
--- /dev/null
+++ b/mandel.c
@@ -0,0 +1,15 @@
+/**
+ * The UI and I/O wrapper for the Mandelbrot runner, in C.
+ *
+ * For the moment *all* logic is in mandel-core.s, I'm just
+ * trying to get this to run within a cc65 environment.
+ * Eventually just the inner loop fun will live in there.
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+#include "mandel.h"
+
+void main(void) {
+    mandel_start();
+}
\ No newline at end of file
diff --git a/mandel.h b/mandel.h
new file mode 100644
index 0000000..e43fad7
--- /dev/null
+++ b/mandel.h
@@ -0,0 +1,4 @@
+#include <inttypes.h>
+
+// From mandel-core.s:
+extern void mandel_start(void);