From 413d14fb36add8747a83f2ab8520e20acd922bfc Mon Sep 17 00:00:00 2001
From: Augustin Cavalier <waddlesplash@gmail.com>
Date: Tue, 7 Jul 2015 15:37:06 -0400
Subject: [PATCH] screen_savers/Nebula: Convert draw_stars.S to C.

Hand-translated. I left the assembly in as comments for easy analysis,
I'll remove it in the next commit.
---
 src/add-ons/screen_savers/nebula/DrawStars.c  | 110 ++++++++++++++++++
 src/add-ons/screen_savers/nebula/Nebula.cpp   |  42 +++++--
 src/add-ons/screen_savers/nebula/draw_stars.S |  78 -------------
 src/add-ons/screen_savers/nebula/makefile     |   8 --
 4 files changed, 141 insertions(+), 97 deletions(-)
 create mode 100644 src/add-ons/screen_savers/nebula/DrawStars.c
 delete mode 100644 src/add-ons/screen_savers/nebula/draw_stars.S

diff --git a/src/add-ons/screen_savers/nebula/DrawStars.c b/src/add-ons/screen_savers/nebula/DrawStars.c
new file mode 100644
index 0000000000..f3542e28cb
--- /dev/null
+++ b/src/add-ons/screen_savers/nebula/DrawStars.c
@@ -0,0 +1,110 @@
+// Hand-translated from x86 assembly.
+
+/* this function needs a definition from outside (the width of the bitmap) */
+
+// #define STAR_WIDTH 320
+// #define STAR_FUNCTION draw_stars320
+
+/* draw a star (5 pixels) */
+void STAR_FUNCTION(char* dstParam, char incParam)
+{
+//	movl	8(%ebp),%edi      /* dst */
+//	movl	12(%ebp),%edx     /* inc */
+//
+	unsigned char* dst;
+	unsigned char inc;
+	dst = (unsigned char*)dstParam;
+	inc = (unsigned char)incParam;
+
+	dst[STAR_WIDTH] += inc;
+	if (dst[STAR_WIDTH] < inc) {
+	//	addb	%dl,(STAR_WIDTH)(%edi)
+		// Overflowed.
+		dst[STAR_WIDTH] = 255;
+		//	movb	$255,(STAR_WIDTH)(%edi)
+	}
+//	jnc		3f
+//
+//3:
+	inc >>= 1;
+//	shrb	$1,%dl
+	unsigned char al;
+	al = *dst;
+//	movb	(%edi),%al
+	unsigned char cl;
+	cl = dst[STAR_WIDTH - 1];
+//	movb	(STAR_WIDTH-1)(%edi),%cl
+	al += inc;
+//	addb	%dl,%al
+	if (al >= inc) {
+		cl += inc;
+		//	addb	%dl,%cl
+		if (cl < inc) {
+		//	jc		2f
+		// 2:
+			*dst = 255;
+			// movb	$255,(%edi)
+			dst[STAR_WIDTH - 1] = 255;
+			// movb	$255,(STAR_WIDTH-1)(%edi)
+		} else {
+			*dst = al;
+			// movb	%al,(%edi)
+			dst[STAR_WIDTH - 1] = cl;
+			// movb	%cl,(STAR_WIDTH-1)(%edi)
+		}
+	} else {
+	// 1:
+		cl += inc;
+		//	addb	%dl,%cl
+		if (cl < inc) {
+		//	jc		2f
+			*dst = 255;
+			// movb	$255,(%edi)
+			dst[STAR_WIDTH - 1] = 255;
+			// movb	$255,(STAR_WIDTH-1)(%edi)
+		} else {
+			*dst = 255;
+			// movb	$255,(%edi)
+			dst[STAR_WIDTH - 1] = cl;
+			// movb	%cl,(STAR_WIDTH-1)(%edi)
+		}
+	}
+	al = dst[STAR_WIDTH * 2];
+//	movb	2*STAR_WIDTH(%edi),%al
+	cl = dst[STAR_WIDTH + 1];
+//	movb	(STAR_WIDTH+1)(%edi),%cl
+	al += inc;
+//	addb	%dl,%al
+	if (al < inc) {
+	//	jc		11f
+		cl += inc;
+		//	addb	%dl,%cl
+		if (cl >= inc) {
+			dst[STAR_WIDTH * 2] = 255;
+			//	movb	$255,(2*STAR_WIDTH)(%edi)
+			dst[STAR_WIDTH + 1] = cl;
+			//	movb	%cl,(STAR_WIDTH+1)(%edi)
+			return;
+		}
+	} else {
+		cl += inc;
+		//	addb	%dl,%cl
+		if (cl >= inc) {
+		//	jc		21f
+			dst[STAR_WIDTH * 2] = al;
+			//	movb	%al,2*STAR_WIDTH(%edi)
+			dst[STAR_WIDTH + 1] = cl;
+			//	movb	%cl,(STAR_WIDTH+1)(%edi)
+			return;
+		}
+	}
+//
+//21:
+	dst[STAR_WIDTH * 2] = 255;
+//	movb	$255,2*STAR_WIDTH(%edi)
+	dst[STAR_WIDTH + 1] = 255;
+//	movb	$255,(STAR_WIDTH+1)(%edi)
+//	popl	%edi
+//	leave
+//	ret
+}
diff --git a/src/add-ons/screen_savers/nebula/Nebula.cpp b/src/add-ons/screen_savers/nebula/Nebula.cpp
index 6f6402bc5a..4f1e180d57 100644
--- a/src/add-ons/screen_savers/nebula/Nebula.cpp
+++ b/src/add-ons/screen_savers/nebula/Nebula.cpp
@@ -33,18 +33,38 @@ float presin[512];
 typedef unsigned short word;
 
 extern "C" {
-	#include "Draw.c"
+#include "Draw.c"
 
-	void draw_stars320(char *, char);
-	void draw_stars512(char *, char);
-	void draw_stars576(char *, char);
-	void draw_stars640(char *, char);
-	void draw_stars800(char *, char);
-	void draw_stars1024(char *, char);
-	void draw_stars1152(char *, char);
-	void draw_stars1280(char *, char);
-	void draw_stars1400(char *, char);
-	void draw_stars1600(char *, char);
+#define STAR_WIDTH 320
+#define STAR_FUNCTION draw_stars320
+#include "DrawStars.c"
+#define STAR_WIDTH 512
+#define STAR_FUNCTION draw_stars512
+#include "DrawStars.c"
+#define STAR_WIDTH 576
+#define STAR_FUNCTION draw_stars576
+#include "DrawStars.c"
+#define STAR_WIDTH 640
+#define STAR_FUNCTION draw_stars640
+#include "DrawStars.c"
+#define STAR_WIDTH 800
+#define STAR_FUNCTION draw_stars800
+#include "DrawStars.c"
+#define STAR_WIDTH 1024
+#define STAR_FUNCTION draw_stars1024
+#include "DrawStars.c"
+#define STAR_WIDTH 1152
+#define STAR_FUNCTION draw_stars1152
+#include "DrawStars.c"
+#define STAR_WIDTH 1280
+#define STAR_FUNCTION draw_stars1280
+#include "DrawStars.c"
+#define STAR_WIDTH 1400
+#define STAR_FUNCTION draw_stars1400
+#include "DrawStars.c"
+#define STAR_WIDTH 1600
+#define STAR_FUNCTION draw_stars1600
+#include "DrawStars.c"
 }
 
 const uint32 kMsgWidth  = 'widt';
diff --git a/src/add-ons/screen_savers/nebula/draw_stars.S b/src/add-ons/screen_savers/nebula/draw_stars.S
deleted file mode 100644
index df27e83889..0000000000
--- a/src/add-ons/screen_savers/nebula/draw_stars.S
+++ /dev/null
@@ -1,78 +0,0 @@
-
-.text
-
-/* this function needs a definition from outside (the width of the bitmap) */
-
-// #define STAR_WIDTH 320
-// #define STAR_FUNCTION draw_stars320
-
-/* draw a star (5 pixels) */
-.globl	STAR_FUNCTION
-.type   STAR_FUNCTION,@function
-
-STAR_FUNCTION:
-	pushl	%ebp
-	movl	%esp,%ebp
-
-	pushl	%edi
-
-	movl	8(%ebp),%edi      /* dst */
-	movl	12(%ebp),%edx     /* inc */
-
-	addb	%dl,(STAR_WIDTH)(%edi)
-	jnc		3f
-	movb	$255,(STAR_WIDTH)(%edi)
-
-3:
-	shrb	$1,%dl
-	movb	(%edi),%al
-	movb	(STAR_WIDTH-1)(%edi),%cl
-	addb	%dl,%al
-	jc		1f
-	addb	%dl,%cl
-	jc		2f
-	movb	%al,(%edi)
-	movb	%cl,(STAR_WIDTH-1)(%edi)
-	jmp		31f
-1:
-	addb	%dl,%cl
-	jc		2f
-	movb	$255,(%edi)
-	movb	%cl,(STAR_WIDTH-1)(%edi)
-
-	jmp 	31f
-
-2:	
-	movb	$255,(%edi)
-	movb	$255,(STAR_WIDTH-1)(%edi)
-
-
-31:		
-	movb	2*STAR_WIDTH(%edi),%al
-	movb	(STAR_WIDTH+1)(%edi),%cl
-	addb	%dl,%al
-	jc		11f
-	addb	%dl,%cl
-	jc		21f
-	movb	%al,2*STAR_WIDTH(%edi)
-	movb	%cl,(STAR_WIDTH+1)(%edi)
-	popl	%edi
-	leave
-	ret
-
-	
-11:	
-	addb	%dl,%cl
-	jc		21f
-	movb	$255,(2*STAR_WIDTH)(%edi)
-	movb	%cl,(STAR_WIDTH+1)(%edi)
-	popl	%edi
-	leave
-	ret
-	
-21:	
-	movb	$255,2*STAR_WIDTH(%edi)
-	movb	$255,(STAR_WIDTH+1)(%edi)
-	popl	%edi
-	leave
-	ret
diff --git a/src/add-ons/screen_savers/nebula/makefile b/src/add-ons/screen_savers/nebula/makefile
index c074f5808e..9e6d0ab932 100644
--- a/src/add-ons/screen_savers/nebula/makefile
+++ b/src/add-ons/screen_savers/nebula/makefile
@@ -7,8 +7,6 @@ LIBS	= -lbe -lscreensaver
 NAME	= Nebula
 FILES 	= Nebula
 ASMFILES =
-STARFILE = draw_stars
-STARWIDTHS = 320 512 576 640 800 1024 1152 1280 1400 1600
 OBJDIR	= obj.x86
 
 STARFILES	:= $(foreach f, $(STARWIDTHS), $(STARFILE)$(f))
@@ -38,11 +36,5 @@ Nebula: $(OBJS)
 $(OBJDIR)/%.o : %.cpp
 	$(CC) -c $*.cpp -o $(OBJDIR)/$*.o $(CFLAGS)
 
-$(OBJDIR)/$(STARFILE)%.o : $(STARFILE).S
-	$(CC) -c $(STARFILE).S -DSTAR_WIDTH=$* -DSTAR_FUNCTION=draw_stars$* -o $@
-
-$(OBJDIR)/%.o : %.S
-	$(CC) -c $*.S -o $(OBJDIR)/$*.o  $(CFLAGS)
-
 tar zip backup:
 	@zip `basename $(NAME)`-`date +%Y-%m-%d`.zip *.[chS]* *.rsrc makefile