fbsim

main.c (6905B)

---

 /***********************************************************
 Copyright 2020 Morel Bérenger
 
 Permission is hereby granted, free of charge, to any person
 obtaining a copy of this software and associated
 documentation files (the "Software"), to deal in the Software
 without restriction, including without limitation the rights
 to use, copy, modify, merge, publish, distribute, sublicense,
 and/or sell copies of the Software, and to permit persons to
 whom the Software is furnished to do so, subject to the
 following conditions:
 
 The above copyright notice and this permission notice shall
 be included in all copies or substantial portions of the
 Software.
 
 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY
 KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
 WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
 PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS
 OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
 OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
 OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 ***********************************************************/
 
 #include <stdlib.h>
 #include <stdio.h>
 #include <stdint.h>
 #include <errno.h>
 #include <string.h>
 
 #include <unistd.h>
 #include <fcntl.h>
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <sys/mman.h>
 #include <time.h>
 
 #include <SDL/SDL.h>
 
 void usage_and_quit( int argc, char** argv );
 void shmem_deinit( void );
 uint16_t get_u16( int argc, char** argv, char const* const str, char const* const label );
 
 struct shared_mem_t
 {
 	void* mem;
 	size_t size;
 	char const* path;
 	int fd;
 };
 
 static struct shared_mem_t fbsim;
 
 void usage_and_quit( int argc, char** argv )
 {
 	fprintf( stderr,
 			"Usage: %s path width height bpp freq\n"
 			"\tpath: (%s) where to share memory\n"
 			"\twidth: (%s)\n"
 			"\theight: (%s)\n"
 			"\tbpp: (%s) bits per pixel\n"
 			"\tfreq: (%s) refresh frequency, in Hertz\n"
 			, argv[0]
 			, argc < 1 ? "NEEDED" : argv[1]
 			, argc < 2 ? "NEEDED" : argv[2]
 			, argc < 3 ? "NEEDED" : argv[3]
 			, argc < 4 ? "NEEDED" : argv[4]
 			, argc < 5 ? "NEEDED" : argv[5]
 	);
 	exit( EXIT_FAILURE );
 }
 
 void shmem_deinit( void )
 {
 	if( MAP_FAILED != fbsim.mem && 0 != fbsim.size )
 	{
 		if( -1 == munmap( fbsim.mem, fbsim.size ) )
 		{
 			fprintf( stderr, "munmap( %p, %lu ): %s (%d)\n",
 					fbsim.mem, fbsim.size,
 					strerror( errno ), errno );
 		}
 	}
 	close( fbsim.fd );
 	if( -1 == unlink( fbsim.path ) )
 	{
 		fprintf( stderr, "unlink( %s ): %s (%d)\n",
 				fbsim.path, strerror( errno ), errno );
 	}
 }
 
 uint16_t get_u16( int argc, char** argv, char const* const str, char const* const label )
 {
 	unsigned long tmp_ul;
 	char *tmp_ptr;
 	tmp_ul = strtoul( str, &tmp_ptr, 10 );
 	if( errno )
 	{
 		fprintf( stderr, "%s error: %s (%d)\n",
 				label, strerror( errno ), errno );
 		usage_and_quit( argc, argv );
 	}
 	if( tmp_ul > UINT16_MAX || *tmp_ptr )
 	{
 		fprintf( stderr, "%s error: invalid value\n",
 				label );
 		usage_and_quit( argc, argv );
 	}
 	return (uint16_t) tmp_ul;
 }
 
 int main(int argc, char *argv[])
 {
 	uint16_t xres, yres, bpp, freq;
 	char *file_name;
 	SDL_Surface* screen;
 
 	if( argc < 6 )
 	{
 		usage_and_quit( argc, argv );
 	}
 
 	file_name = argv[1];
 	xres = get_u16( argc, argv, argv[2], "X_RESOLUTION" );
 	yres = get_u16( argc, argv, argv[3], "Y_RESOLUTION" );
 	bpp  = get_u16( argc, argv, argv[4], "BITS_PER_PIXEL" );
 	freq = get_u16( argc, argv, argv[5], "REFRESH_RATE" );
 
 	fprintf( stdout,
 			"width: %u height: %u, depth: %u, frequency: %u, shared_on: %s\n",
 			xres, yres, bpp,
 			freq, file_name
 	);
 
 	if( 0 == freq )
 	{
 		fprintf( stderr, "frequencies of 0Hz are not supported\n" );
 		exit( EXIT_FAILURE );
 	}
 
 	switch( bpp )
 	{
 		case 24:
 			fprintf( stdout, "Using RGB colors\n" );
 			break;
 		case 32:
 			fprintf( stdout, "Using RGBn colors, with n not used\n" );
 			break;
 		case 8:
 			fprintf( stdout, "Using 256 colors\n" );
 			//pass through
 		case 16:
 			fprintf( stdout, "Using 65536 colors\n" );
 			//pass through
 		default:
 			fprintf( stderr, "Using bpp=%d is not supported (yet?).\n", bpp );
 			exit( EXIT_FAILURE );
 	}
 
 	fbsim.mem  = MAP_FAILED;
 	fbsim.size = xres * yres * bpp / 8;
 	fbsim.path = file_name;
 	if( -1 == ( fbsim.fd = open( fbsim.path, O_RDWR | O_CREAT, S_IWUSR | S_IRUSR ) ) )
 	{
 		fprintf( stderr, "open( %s, O_RDWR ): %s (%d)\n",
 				fbsim.path, strerror( errno ), errno );
 		exit( EXIT_FAILURE );
 	}
 	atexit( shmem_deinit );
 	if( -1 == ftruncate( fbsim.fd, (off_t) fbsim.size ) )
 	{
 		fprintf( stderr, "ftruncate( %s, %zu ): %s (%d)\n",
 				fbsim.path, fbsim.size, strerror( errno ), errno );
 		exit( EXIT_FAILURE );
 	}
 	fprintf( stderr, "Using %zu of shared memory\n", fbsim.size );
 	fbsim.mem = mmap( NULL, fbsim.size, PROT_READ | PROT_WRITE, MAP_SHARED, fbsim.fd, 0 );
 	if( MAP_FAILED == fbsim.mem )
 	{
 		fprintf( stderr, "mmap( 0, %zu, flags ): %s (%d)\n",
 				fbsim.size, strerror( errno ), errno );
 		exit( EXIT_FAILURE );
 	}
 
 	if( SDL_Init( SDL_INIT_VIDEO ) == -1 )
 	{
 		fprintf( stderr, "Could not initialize SDL: %s.\n", SDL_GetError() );
 		exit( EXIT_FAILURE );
 	}
 	atexit( SDL_Quit );
 
 	//Notes:
 	//not using SDL_DOUBLEBUF: goal is to mmap the window after all
 	//not using SDL_FULLSCREEN: goal is to "emulate" rendering on different devices
 	//not using SDL_OPENGL: goal is to "emulate" a framebuffer
 	//not using SDL_RESIZABLE: goal is to "emulate" a framebuffer
 	//using SDL_NOFRAME: goal is to "emulate" a framebuffer (no decoration)
 	//       ^ this was done originally, but is more annoying than useful
 	screen = SDL_SetVideoMode( xres, yres, bpp, 0 /*SDL_NOFRAME*/ );
 	if( NULL == screen )
 	{
 		fprintf( stderr, "Failed to initialize window: %s.\n", SDL_GetError() );
 		usage_and_quit( argc, argv );
 	}
 
 	struct timespec timer;
 	timer.tv_sec = 0;
 	timer.tv_nsec = 1000000000 / freq;
 
 	const uint16_t scanline = screen->pitch;
 	const uint8_t * const endsrcy = (uint8_t*) fbsim.mem + fbsim.size;
 	const size_t srcw = xres * bpp / 8;
 
 	fprintf( stdout, "updates screen every %zu nano seconds (10^-9)\n", timer.tv_nsec );
 
 	//unlikely case
 	if( SDL_MUSTLOCK( screen ) )
 	{
 		fprintf( stdout, "using locks\n" );
 		while( -1 != nanosleep( &timer, NULL ) )
 		{
 			if( -1 == SDL_LockSurface( screen ) )
 			{
 				fprintf( stderr, "lock screen: %s.\n", SDL_GetError() );
 				exit( EXIT_FAILURE );
 			}
 
 			uint8_t const* srcy = fbsim.mem;
 			uint8_t * dsty = screen->pixels;
 			for( ; srcy < endsrcy; srcy += srcw, dsty += scanline )
 			{
 				memcpy( dsty, srcy, srcw );
 			}
 
 			SDL_UnlockSurface( screen );
 			SDL_Flip( screen );
 		}
 		exit( EXIT_SUCCESS );
 	}
 
 	//most likely case
 	while( -1 != nanosleep( &timer, NULL ) )
 	{
 		uint8_t const* srcy = fbsim.mem;
 		uint8_t * dsty = screen->pixels;
 		for( ; srcy < endsrcy; srcy += srcw, dsty += scanline )
 		{
 			memcpy( dsty, srcy, srcw );
 		}
 
 		SDL_Flip( screen );
 	}
 	exit( EXIT_SUCCESS );
 }