Android教程：開機Logo

Android系統開機第一個程序的進程是init，它的源碼位於system/core/init/init.c，其中函數load_565rle_image負責logo的顯示，如果讀取成功，就在/dev/graphics/fb0顯示圖片，如果讀取失敗，則將/dev/tty0設為文本模式，並打開/dev/tty0並輸出android字樣。之後會顯示android開機動畫(其實兩張圖片做成的效果)，logo圖片由INIT_IMAGE_FILE(在init.h中)指定。

1. int load_565rle_image(char *fn)
   
2. {
   
3.     struct FB fb;
   
4.     struct stat s;
   
5.     unsigned short *data, *bits, *ptr;
   
6.     unsigned count, max;
   
7.     int fd;
   
8. 
   
9.     if (vt_set_mode(1))
   
10.         return -1;
    
11. 
    
12.     fd = open(fn, O_RDONLY);
    
13.     if (fd < 0) {
    
14.         ERROR("cannot open '%s'\n", fn);
    
15.         goto fail_restore_text;
    
16.     }
    
17. 
    
18.     if (fstat(fd, &s) < 0) {
    
19.         goto fail_close_file;
    
20.     }
    
21. 
    
22.     data = mmap(0, s.st_size, PROT_READ, MAP_SHARED, fd, 0);
    
23.     if (data == MAP_FAILED)
    
24.         goto fail_close_file;
    
25. 
    
26.     if (fb_open(&fb))
    
27.         goto fail_unmap_data;
    
28. 
    
29.     max = fb_width(&fb) * fb_height(&fb);
    
30.     ptr = data;
    
31.     count = s.st_size;
    
32.     bits = fb.bits;
    
33.     while (count > 3) {
    
34.         unsigned n = ptr[0];
    
35.         if (n > max)
    
36.             break;
    
37.         android_memset16(bits, ptr[1], n << 1);
    
38.         bits += n;
    
39.         max -= n;
    
40.         ptr += 2;
    
41.         count -= 4;
    
42.     }
    
43. 
    
44.     munmap(data, s.st_size);
    
45.     fb_update(&fb);
    
46.     fb_close(&fb);
    
47.     close(fd);
    
48.     unlink(fn);
    
49.     return 0;
    
50. 
    
51. fail_unmap_data:
    
52.     munmap(data, s.st_size);
    
53. fail_close_file:
    
54.     close(fd);
    
55. fail_restore_text:
    
56.     vt_set_mode(0);
    
57.     return -1;
    
58. }