screen_savers/Nebula: Convert draw.S to C.

Hand-translated. I left the assembly in as comments for easy analysis,
I'll remove it in the next commit.

(I didn't do this on my own, I had help.)

src/add-ons/screen_savers/nebula/Draw.c

@@ -0,0 +1,148 @@
+// Hand-translated from x86 assembly.
+
+/* memshset (char *dst, int center_shade,int fixed_shade, int length_2) */
+/* dst is the *center* of the dst segment */
+/* center shade is the initial color (at center) (!! 8:8 also) */
+/* fixed_shade is the fixed point increment (8:8) */
+/* length_2 is the 1/2 length to set (to the left, and to the right) */
+
+/* a memaddshadedset function (or something like that ) */
+
+void memshset(char* dstParam, int center_shade, int fixed_shade, int half_length)
+{
+	unsigned char* dst;
+	unsigned char* source;
+	int offset;
+
+	if (half_length == 0)
+		return;
+
+//	movl	8(%ebp),%edi      /* dst */
+//	movl	12(%ebp),%eax	/* center_shade*/
+//	movl	16(%ebp),%ebx	  /* fixed_shade */
+//	movl	20(%ebp),%ecx	  /* half_length */
+//
+//@	orl		%ecx,%ecx
+//@	jz		2f
+//
+
+	dst = (unsigned char*)dstParam;
+	source = dst;
+//	movl	%edi,%esi
+	dst -= half_length; // Left segment
+//	subl	%ecx,%edi		/* %edi  left segment */
+	source += half_length; // Right segment
+//	addl	%ecx,%esi		/* %esi  right segment */
+	source++; // Don't overlap at middle
+//	incl	%esi			/* dont overlap at middle */
+//
+	offset = half_length;
+//	movl	%ecx,%edx
+	offset = -offset;
+//	negl	%edx
+	offset--; // For in-advance incl in loop
+//	decl	%edx			/* for in-advance incl in loop */
+
+	do {
+		int tmp;
+//1:
+		center_shade += fixed_shade; // Increment color.
+		center_shade &= 0xFFFF; // Mask so we can do overflow tests.
+//	addl	%ebx,%eax		/* increment color */
+		offset++;
+//	incl	%edx
+
+		tmp = dst[half_length] + (center_shade >> 8); // Increment left pixel.
+		//	addb	%ah,(%edi,%ecx)	/* increment  left pixel */
+		// Did it overflow?
+		if (tmp & 0xFF00) {
+		//	jc		3f				/* did overflow ? */
+			dst[half_length] = 255;
+//3:
+//	movb	$255,(%edi,%ecx)
+		} else {
+			dst[half_length] = tmp;
+		}
+
+
+		tmp = source[offset] + (center_shade >> 8); // Increment right pixel.
+		// Did it overflow?
+		if (tmp & 0xFF00) {
+			source[offset] = 255;
+//4:
+//	movb	$255,(%esi,%edx)
+//	decl	%ecx
+//	jnz		1b
+//
+//	popl	%ebx
+//	popl	%esi
+//	popl	%edi
+//
+//	leave
+//	ret
+		} else {
+			source[offset] = tmp;
+		}
+//	addb	%ah,(%esi,%edx) /* increment right pixel */
+//	jc		4f
+//
+	} while (--half_length != 0);
+//	decl	%ecx
+//	jnz		1b
+//
+//2:
+//	popl	%ebx
+//	popl	%esi
+//	popl	%edi
+//
+//	leave
+//	ret
+}
+
+
+/* do the "motion blur" (actually the pixel fading) */
+void mblur(char* srcParam, int nbpixels)
+{
+//	movl	8(%ebp),%edi      /* dst */
+//	movl	12(%ebp),%ecx     /* number */
+	unsigned int clear1UpperBit = 0x7f7f7f7f;
+	unsigned int clear3UpperBits = 0x1f1f1f1f;
+	unsigned long* src = (unsigned long*)srcParam;
+//	movl	$0x7f7f7f7f,%edx  /* clear 1 upper bits */
+//	movl	$0x1f1f1f1f,%esi  /* clear 3 upper bits */
+
+	if ((nbpixels >>= 2) == 0)
+	//	shrl	$2,%ecx
+		return;
+		//	jz	2f
+//
+	do {
+//1:
+		long eax, ebx;
+		eax = *src;
+	//	movl	(%edi),%eax
+		src++;
+	//	addl	$4,%edi
+	//
+		ebx = eax;
+	//	movl	%eax,%ebx
+		eax >>= 1;
+	//	shrl	$1,%eax
+	//
+	//
+		ebx >>= 3;
+	//	shrl	$3,%ebx
+		eax &= clear1UpperBit;
+	//	andl	%edx,%eax
+	//
+		ebx &= clear3UpperBits;
+	//	andl	%esi,%ebx
+		eax += ebx;
+	//	addl	%ebx,%eax
+	//
+		src[-1] = eax;
+	//	movl	%eax,-4(%edi)
+	} while (--nbpixels != 0);
+	//	decl	%ecx
+	//	jnz	1b
+}

src/add-ons/screen_savers/nebula/Nebula.cpp

@@ -33,8 +33,7 @@ float presin[512];
 typedef unsigned short word;
 
 extern "C" {
-	void memshset(char *dst, int center_shade,int fixed_shade, int length_2);
+	#include "Draw.c"
-	void mblur(char *src, int nbpixels);
 
 	void draw_stars320(char *, char);
 	void draw_stars512(char *, char);

src/add-ons/screen_savers/nebula/draw.S

@@ -1,136 +0,0 @@
-
-.text
-
-/* memshset (char *dst, int center_shade,int fixed_shade, int length_2) */
-/* dst is the *center* of the dst segment */
-/* center shade is the initial color (at center) (!! 8:8 also) */
-/* fixed_shade is the fixed point increment (8:8) */
-/* length_2 is the 1/2 length to set (to the left, and to the right) */
-
-/* a memaddshadedset function (or something like that ) */
-		
-.globl memshset
-.type  memshset,@function
-
-
-memshset:
-	pushl	%ebp
-	movl	%esp,%ebp
-	
-	pushl	%edi		/* registres a sauvegarder (convention gcc) */
-	pushl	%esi
-	pushl	%ebx
-
-	movl	8(%ebp),%edi      /* dst */
-	movl	12(%ebp),%eax
-	movl	16(%ebp),%ebx	  /* fixed point */
-	movl	20(%ebp),%ecx	  /* half length */
-
-	orl		%ecx,%ecx
-	jz		2f
-
-	movl	%edi,%esi
-	subl	%ecx,%edi		/* %edi  left segment */
-	addl	%ecx,%esi		/* %esi  right segment */
-	incl	%esi			/* dont overlap at middle */
-	
-	movl	%ecx,%edx
-	negl	%edx
-	decl	%edx			/* for in-advance incl in loop */
-1:
-	addl	%ebx,%eax		/* increment color */
-	incl	%edx
-	
-	addb	%ah,(%edi,%ecx)	/* increment  left pixel */
-	jc		3f				/* did overflow ? */
-	
-	addb	%ah,(%esi,%edx) /* increment right pixel */
-	jc		4f
-
-	decl	%ecx
-	jnz		1b
-
-2:	
-	popl	%ebx
-	popl	%esi
-	popl	%edi
-
-	leave
-	ret
-/* function goes on (several exit points): */
-3:
-	movb	$255,(%edi,%ecx)
-	addb	%ah,(%esi,%edx)        /* we recopy all the code.. to avoid jmps   (hmm some asm guru here :	 is it really efficient ?.. */
-	jc		4f
-	decl	%ecx
-	jnz		1b
-	
-	popl	%ebx
-	popl	%esi
-	popl	%edi
-
-	leave
-	ret
-
-4:
-	movb	$255,(%esi,%edx)
-	decl	%ecx
-	jnz		1b
-	
-	popl	%ebx
-	popl	%esi
-	popl	%edi
-
-	leave
-	ret
-/* function really stops here  */
-
-
-/*********************************** motion blur **********************************/
-
-/* do the "motion blur" (actually the pixel fading) */
-.globl  mblur
-.type   mblur,@function
-	
-mblur:	
-	pushl	%ebp
-	movl	%esp,%ebp
-	
-	pushl	%edi
-	pushl	%esi
-	pushl	%ebx
-	
-	movl	8(%ebp),%edi      /* dst */
-	movl	12(%ebp),%ecx     /* number */
-	movl	$0x7f7f7f7f,%edx  /* clear 1 upper bits */
-	movl	$0x1f1f1f1f,%esi  /* clear 3 upper bits */
-	shrl	$2,%ecx
-	jz	2f
-
-1:
-	movl	(%edi),%eax
-	addl	$4,%edi
-	
-	movl	%eax,%ebx
-	shrl	$1,%eax
-
-	
-	shrl	$3,%ebx
-	andl	%edx,%eax
-	
-	andl	%esi,%ebx
-	addl	%ebx,%eax
-
-	decl	%ecx
-	movl	%eax,-4(%edi)
-	
-
-	jnz	1b
-
-
-2:
-	popl	%ebx
-	popl	%esi
-	popl	%edi
-	leave
-	ret

src/add-ons/screen_savers/nebula/makefile

@@ -6,7 +6,7 @@ CFLAGS	= -O3 -ffast-math -funroll-loops -fomit-frame-pointer -fexpensive-optimiz
 LIBS	= -lbe -lscreensaver
 NAME	= Nebula
 FILES 	= Nebula
-ASMFILES = draw
+ASMFILES =
 STARFILE = draw_stars
 STARWIDTHS = 320 512 576 640 800 1024 1152 1280 1400 1600
 OBJDIR	= obj.x86