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rockbox/apps/plugins/lib/gray_pixelfuncs.c
Jens Arnold 85890b88df Const policed the grayscale lib & plugin 
git-svn-id: svn://svn.rockbox.org/rockbox/trunk@4985 a1c6a512-1295-4272-9138-f99709370657
2004-08-03 20:57:06 +00:00

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C
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/***************************************************************************
* __________ __ ___.
* Open \______ \ ____ ____ | | _\_ |__ _______ ___
* Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ /
* Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < <
* Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \
* \/ \/ \/ \/ \/
* $Id$
*
* Grayscale framework
* Low level pixel drawing functions
*
* This is a generic framework to use grayscale display within Rockbox
* plugins. It obviously does not work for the player.
*
* Copyright (C) 2004 Jens Arnold
*
* All files in this archive are subject to the GNU General Public License.
* See the file COPYING in the source tree root for full license agreement.
*
* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
* KIND, either express or implied.
*
****************************************************************************/
#ifndef SIMULATOR /* not for simulator by now */
#include "plugin.h"
#ifdef HAVE_LCD_BITMAP /* and also not for the Player */
#include "gray.h"
/* Prototypes */
static void _writepixel(int x, int y, unsigned long pattern);
static void _invertpixel(int x, int y, unsigned long pattern);
/* function pointer array */
void (* const _gray_pixelfuncs[4])(int x, int y, unsigned long pattern) = {
_invertpixel, _writepixel, _writepixel, _writepixel
};
/* Set a pixel to a specific bit pattern (low level routine) */
static void _writepixel(int x, int y, unsigned long pattern)
{
register unsigned mask, random;
register unsigned char *address;
/* Some (pseudo-)random function must be used here to shift the bit
* pattern randomly, otherwise you would get flicker and/or moire.
* Since rand() is relatively slow, I've implemented a simple, but very
* fast pseudo-random generator based on linear congruency in assembler.
* It delivers max. 16 pseudo-random bits in each iteration. */
/* simple but fast pseudo-random generator */
asm (
"mov #75,r1 \n"
"mulu %1,r1 \n" /* multiply by 75 */
"sts macl,%1 \n" /* get result */
"add #74,%1 \n" /* add another 74 */
/* Since the lower bits are not very random: */
"swap.b %1,%0 \n" /* get bits 8..15 (need max. 5) */
"and %2,%0 \n" /* mask out unneeded bits */
: /* outputs */
/* %0 */ "=&r"(random),
/* %1, in & out */ "+r"(_gray_random_buffer)
: /* inputs */
/* %2 */ "r"(_graybuf->randmask)
: /* clobbers */
"r1", "macl"
);
/* precalculate mask and byte address in first bitplane */
asm (
"mov %3,%0 \n" /* take y as base for address offset */
"shlr2 %0 \n" /* shift right by 3 (= divide by 8) */
"shlr %0 \n"
"mulu %0,%2 \n" /* multiply with width */
"and #7,%3 \n" /* get lower 3 bits of y */
"sts macl,%0 \n" /* get mulu result */
"add %4,%0 \n" /* add base + x to get final address */
"mov %3,%1 \n" /* move lower 3 bits of y out of r0 */
"mova .wp_masktable,%3\n" /* get address of mask table in r0 */
"bra .wp_predone \n" /* skip the table */
"mov.b @(%3,%1),%1 \n" /* get entry from mask table */
".align 2 \n"
".wp_masktable: \n" /* mask table */
".byte 0x01 \n"
".byte 0x02 \n"
".byte 0x04 \n"
".byte 0x08 \n"
".byte 0x10 \n"
".byte 0x20 \n"
".byte 0x40 \n"
".byte 0x80 \n"
".wp_predone: \n"
: /* outputs */
/* %0 */ "=&r"(address),
/* %1 */ "=&r"(mask)
: /* inputs */
/* %2 */ "r"(_graybuf->width),
/* %3 = r0 */ "z"(y),
/* %4 */ "r"(_graybuf->data + x)
: /* clobbers */
"macl"
);
/* the hard part: set bits in all bitplanes according to pattern */
asm volatile (
"cmp/hs %1,%5 \n" /* random >= depth ? */
"bf .wp_ntrim \n"
"sub %1,%5 \n" /* yes: random -= depth */
/* it's sufficient to do this once, since the mask guarantees
* random < 2 * depth */
".wp_ntrim: \n"
/* calculate some addresses */
"mulu %4,%1 \n" /* end address offset */
"not %3,r1 \n" /* get inverse mask (for "and") */
"sts macl,%1 \n" /* result of mulu */
"mulu %4,%5 \n" /* address offset of <random>'th plane */
"add %2,%1 \n" /* end offset -> end address */
"sts macl,%5 \n" /* result of mulu */
"add %2,%5 \n" /* address of <random>'th plane */
"bra .wp_start1 \n"
"mov %5,r2 \n" /* copy address */
/* first loop: set bits from <random>'th bitplane to last */
".wp_loop1: \n"
"mov.b @r2,r3 \n" /* get data byte */
"shlr %0 \n" /* shift bit mask, sets t bit */
"and r1,r3 \n" /* reset bit (-> "white") */
"bf .wp_white1 \n" /* t=0? -> "white" bit */
"or %3,r3 \n" /* set bit ("black" bit) */
".wp_white1: \n"
"mov.b r3,@r2 \n" /* store data byte */
"add %4,r2 \n" /* advance address to next bitplane */
".wp_start1: \n"
"cmp/hi r2,%1 \n" /* address < end address ? */
"bt .wp_loop1 \n"
"bra .wp_start2 \n"
"nop \n"
/* second loop: set bits from first to <random-1>'th bitplane
* Bit setting works the other way round here to equalize average
* execution times for bright and dark pixels */
".wp_loop2: \n"
"mov.b @%2,r3 \n" /* get data byte */
"shlr %0 \n" /* shift bit mask, sets t bit */
"or %3,r3 \n" /* set bit (-> "black") */
"bt .wp_black2 \n" /* t=1? -> "black" bit */
"and r1,r3 \n" /* reset bit ("white" bit) */
".wp_black2: \n"
"mov.b r3,@%2 \n" /* store data byte */
"add %4,%2 \n" /* advance address to next bitplane */
".wp_start2: \n"
"cmp/hi %2,%5 \n" /* address < <random>'th address ? */
"bt .wp_loop2 \n"
: /* outputs */
: /* inputs */
/* %0 */ "r"(pattern),
/* %1 */ "r"(_graybuf->depth),
/* %2 */ "r"(address),
/* %3 */ "r"(mask),
/* %4 */ "r"(_graybuf->plane_size),
/* %5 */ "r"(random)
: /* clobbers */
"r1", "r2", "r3", "macl"
);
}
/* invert all bits for one pixel (low level routine) */
static void _invertpixel(int x, int y, unsigned long pattern)
{
register unsigned mask;
register unsigned char *address;
(void) pattern; /* not used for invert */
/* precalculate mask and byte address in first bitplane */
asm (
"mov %3,%0 \n" /* take y as base for address offset */
"shlr2 %0 \n" /* shift right by 3 (= divide by 8) */
"shlr %0 \n"
"mulu %0,%2 \n" /* multiply with width */
"and #7,%3 \n" /* get lower 3 bits of y */
"sts macl,%0 \n" /* get mulu result */
"add %4,%0 \n" /* add base + x to get final address */
"mov %3,%1 \n" /* move lower 3 bits of y out of r0 */
"mova .ip_masktable,%3\n" /* get address of mask table in r0 */
"bra .ip_predone \n" /* skip the table */
"mov.b @(%3,%1),%1 \n" /* get entry from mask table */
".align 2 \n"
".ip_masktable: \n" /* mask table */
".byte 0x01 \n"
".byte 0x02 \n"
".byte 0x04 \n"
".byte 0x08 \n"
".byte 0x10 \n"
".byte 0x20 \n"
".byte 0x40 \n"
".byte 0x80 \n"
".ip_predone: \n"
: /* outputs */
/* %0 */ "=&r"(address),
/* %1 */ "=&r"(mask)
: /* inputs */
/* %2 */ "r"(_graybuf->width),
/* %3 = r0 */ "z"(y),
/* %4 */ "r"(_graybuf->data + x)
: /* clobbers */
"macl"
);
/* invert bits in all bitplanes */
asm volatile (
"mov #0,r1 \n" /* current_plane = 0 */
".ip_loop: \n"
"mov.b @%1,r2 \n" /* get data byte */
"add #1,r1 \n" /* current_plane++; */
"xor %2,r2 \n" /* invert bits */
"mov.b r2,@%1 \n" /* store data byte */
"add %3,%1 \n" /* advance address to next bitplane */
"cmp/hi r1,%0 \n" /* current_plane < depth ? */
"bt .ip_loop \n"
: /* outputs */
: /* inputs */
/* %0 */ "r"(_graybuf->depth),
/* %1 */ "r"(address),
/* %2 */ "r"(mask),
/* %3 */ "r"(_graybuf->plane_size)
: /* clobbers */
"r1", "r2"
);
}
#endif // #ifdef HAVE_LCD_BITMAP
#endif // #ifndef SIMULATOR
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