/* fbcopy — copy buffer0 -> buffer1 within /dev/fb0 (mmap both, memcpy).
 * Reproduces the player's "screen-off frame lives in buffer1" state so the
 * launcher's bug condition (yoffset=1 at menu open) can be tested without
 * pressing power (which would also pause the player). */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <stdint.h>

#define GETV 0x4600

int main(void) {
    int fd = open("/dev/fb0", O_RDWR);
    if (fd < 0) { perror("open"); return 1; }
    unsigned char v[160]; memset(v,0,sizeof v);
    if (ioctl(fd, GETV, v) < 0) { perror("getvar"); return 1; }
    uint32_t yres = *(uint32_t*)(v+4);
    uint32_t yv   = *(uint32_t*)(v+12);
    uint32_t bpp  = *(uint32_t*)(v+24);
    if (yv <= yres) { printf("not double-buffered (yv=%u yres=%u)\n", yv, yres); return 2; }
    /* line_length via fix info */
    unsigned char f[68]; memset(f,0,sizeof f);
    if (ioctl(fd, 0x4602, f) < 0) { perror("getfix"); return 1; }
    uint32_t line = *(uint32_t*)(f+44);
    if (!line) line = yres * (bpp/8);
    size_t frame = (size_t)line * yres;
    unsigned char *p = mmap(NULL, frame*2, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
    if (p == MAP_FAILED) { perror("mmap"); return 1; }
    memcpy(p + frame, p, frame);   /* buffer1 <- buffer0 */
    printf("copied %zu bytes buffer0 -> buffer1 (line=%u yres=%u frame=%zu)\n", frame, line, yres, frame);
    munmap(p, frame*2);
    close(fd);
    return 0;
}