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#include <assert.h>
#include <err.h>
#include <fcntl.h>
#include <linux/fb.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <sysexits.h>
#include <termios.h>
#include <unistd.h>
extern void draw(uint32_t *buf, uint32_t xres, uint32_t yres);
extern void input(char c);
static uint32_t size;
static uint32_t *buf;
static uint32_t *saveBuf;
static void restoreBuf(void) {
memcpy(buf, saveBuf, size);
}
static struct termios saveTerm;
static void restoreTerm(void) {
tcsetattr(STDERR_FILENO, TCSADRAIN, &saveTerm);
}
int main() {
int error;
char *path = getenv("FRAMEBUFFER");
if (!path) path = "/dev/fb0";
int fd = open(path, O_RDWR);
if (fd < 0) err(EX_OSFILE, "%s", path);
struct fb_fix_screeninfo fix;
error = ioctl(fd, FBIOGET_FSCREENINFO, &fix);
if (error) err(EX_IOERR, "%s", path);
struct fb_var_screeninfo var;
error = ioctl(fd, FBIOGET_VSCREENINFO, &var);
if (error) err(EX_IOERR, "%s", path);
assert(!var.xoffset);
assert(!var.yoffset);
assert(var.bits_per_pixel == 32);
assert(!var.grayscale);
assert(var.red.offset == 16);
assert(var.red.length == 8);
assert(var.green.offset == 8);
assert(var.green.length == 8);
assert(var.blue.offset == 0);
assert(var.blue.length == 8);
assert(fix.line_length == var.xres * 4);
size = var.xres * var.yres * 4;
buf = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
if (buf == MAP_FAILED) err(EX_OSERR, "%s", path);
saveBuf = malloc(size);
if (!saveBuf) err(EX_OSERR, "malloc");
memcpy(saveBuf, buf, size);
atexit(restoreBuf);
error = tcgetattr(STDERR_FILENO, &saveTerm);
if (error) err(EX_IOERR, "tcgetattr");
atexit(restoreTerm);
struct termios raw;
cfmakeraw(&raw);
error = tcsetattr(STDERR_FILENO, TCSADRAIN, &raw);
if (error) err(EX_IOERR, "tcsetattr");
for (;;) {
draw(buf, var.xres, var.yres);
char c;
ssize_t len = read(STDIN_FILENO, &c, 1);
if (len < 0) err(EX_IOERR, "read");
if (!len || c == CTRL('C')) return EX_OK;
input(c);
}
}
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