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. }