Initial support for the dodo platform (#49)

* First attempt at dodo support

Successfully compiles 0xDEADBEEF (see https://play.dodolabs.io/#), but
doesn't compile any of the other sample games due to missing itoa,
srand, and rand implementations.

* Add version check

* Fix CLEAR_SPRITE comment formatting

* Fix missing newline at end of file

* Remove redundant #pragma once

mos-platform/CMakeLists.txt

@@ -46,3 +46,4 @@ add_subdirectory(nes-nrom-128)
 add_subdirectory(nes-nrom-256)
 add_subdirectory(nes-slrom)
 add_subdirectory(osi-c1p)
+add_subdirectory(dodo)

mos-platform/dodo/CMakeLists.txt

@@ -0,0 +1,24 @@
+platform(dodo COMPLETE PARENT common)
+
+if(NOT CMAKE_CROSSCOMPILING)
+  return()
+endif()
+
+install(FILES api.h TYPE INCLUDE)
+
+add_platform_object_file(dodo-crt0-o crt0.o crt0.s)
+
+add_platform_library(dodo-crt0) 
+merge_libraries(dodo-crt0
+  common-zero-bss
+  common-init-stack
+  common-exit-loop
+)
+
+add_platform_library(dodo-c api.s)
+merge_libraries(dodo-c
+  common-c
+)
+
+target_include_directories(dodo-c SYSTEM BEFORE PUBLIC .)
+target_compile_options(dodo-c PUBLIC -mcpu=mos65c02)

mos-platform/dodo/api.h

@@ -0,0 +1,143 @@
+#ifndef _API_H
+#define _API_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+// Specify version compiled against. Semantic versioning enforcement takes place
+// in CHECK_VERSION
+#define MAJOR 1
+#define MINOR 1
+#define REVISION 0
+
+#define byte unsigned char
+
+/*
+ * Parameter	Type	Description
+ * sprite	*byte	pointer to the sprite image data
+ * x	byte	x coordinate
+ * y	byte	y coordinate
+ * w	byte	width of sprite
+ * h	byte	height of sprite, must be multiple of 8
+ * f	byte	boolean that specifies whether or not to flip horizontally
+ * m	mode	drawing mode, see below
+ */
+void DRAW_SPRITE(byte *sprite, byte x, byte y, byte w, byte h, byte f, byte m);
+/* normal, replaces everything underneath the sprite */
+#define DRAW_NOP 0x0
+/* logical OR, fastest mode */
+#define DRAW_OR 0x1
+/* logical AND */
+#define DRAW_AND 0x2
+/* logical XOR */
+#define DRAW_XOR 0x4
+
+/* Push video memory to the OLED (expensive) */
+void DISPLAY();
+
+/*
+Erases the rectangular portiion of the screen defined by the parameters. Note
+that background graphics will be erased as well.
+
+Parameter	Type	Description
+x	byte	x coordinate
+y	byte	y coordinate
+w	byte	width
+h	byte	height, must be multiple of 8
+*/
+void CLEAR_SPRITE(byte x, byte y, byte w, byte h);
+
+/*
+Sets a pixel to a specific color
+Parameter	Type	Description
+x	byte	x coordinate
+y	byte	y coordinate
+c	byte	color, 0 for black, 1 for white
+*/
+void SET_PIXEL(byte x, byte y, byte c);
+
+/*
+Bresenham line algorithm
+
+Parameter	Type	Description
+x0	byte	x coordinate of first point
+y0	byte	y coordinate of first point
+x1	byte	x coordinate of second point
+y1	byte	y coordinate of second point
+c	byte	color, 0 for black, 1 for white
+Note: Computationally expensive, it is recommended to draw lines sparingly.
+*/
+void DRAW_LINE(byte x0, byte y0, byte x1, byte y1, byte c);
+
+void DELAY_MS(byte delay);
+void LED_ON();
+void LED_OFF();
+
+/* Waits for an interrupt to fire. WAIT() should be called at the end of the
+ * game loop in order to synchronize the frame rate to a consistent 20 FPS.  */
+void WAIT();
+
+void LOAD_MUSIC(byte *music);
+void PLAY_EFFECT(byte *effect);
+void PLAY_EFFECT_ONCE(byte *effect);
+void SPI_ENABLE();
+void SPI_DISABLE();
+void SPI_WRITE(byte v);
+
+/* Clear the graphics in video memory */
+void CLEAR();
+
+/*
+Copying the background back and forth between video memory and a buffer is
+useful for games with background graphics.  This technique would be used
+instead of calling CLEAR_SPRITE().  Typically a game should copy the
+background where a sprite will be drawn, draw the sprite, call DISPLAY() to
+show the graphics, and then erase the sprite by copying the buffer back into
+video memory.
+
+The buffer needs to be a page taller than the sprite.  For instance, if the
+sprite is 24x16 pixels (2 pages tall, 48 total bytes).  The buffer needs to
+be 24*24 pixels (3 pages tall, 72 total bytes)
+
+Parameter	Type	Description
+data	*byte	pointer to byte array
+x	byte	x coordinate
+y	byte	y coordinate
+w	byte	width
+h	byte	height
+dir	byte	direction, 0 = vmem -> buffer, 1 = buffer -> vmem
+*/
+void COPY_BACKGROUND(byte *data, byte x, byte y, byte w, byte h, byte dir);
+
+void DRAW_STRING(const char *text);
+void SET_CURSOR(byte row, byte col);
+
+/* Returns a byte that is packed with the button state. For each bit that is
+ * unset the corresponding button is pushed.
+ * Bit Position	Mask	Button
+ * 1	1	up
+ * 2	2	down
+ * 3	4	left
+ * 4	8	right
+ * 5	16	a
+ * 6	32	b
+ */
+byte READ_BUTTONS();
+
+void GET_PIXEL(byte x, byte y);
+
+void GET_VERSION(byte *p);
+void CHECK_VERSION(byte major, byte minor, byte revision);
+
+void LOAD_PERSISTENT(byte *buffer);
+void SAVE_PERSISTENT(byte *buffer);
+
+// This will spin forever if there is a version mismatch
+#define api_init() CHECK_VERSION(MAJOR, MINOR, REVISION)
+
+#ifdef __cplusplus
+} // extern "C"
+#endif
+
+#endif