c - How to parse raw "disk" data? -


the output below belongs fat32 disk file. want display files , corresponding allocated sectors each file, c program.

i'm unable find root directory following guide. (example 1 - find root directory in http://www.tavi.co.uk/phobos/fat.html) seems 0x16 , 0x17 00. don't point anything?

i'm reading document again , again , i'm exhausted. can explain i'm doing wrong, or how right simple steps?

any appreciated! thank you.

alternative resource: http://wiki.osdev.org/fat#fat_32_2

0000000: eb58 906d 6b66 732e 6661 7400 0201 2000  .x.mkfs.fat... . 0000010: 0200 0000 00f8 0000 2000 4000 0000 0000  ........ .@..... 0000020: 400d 0300 0306 0000 0000 0000 0200 0000  @............... 0000030: 0100 0600 0000 0000 0000 0000 0000 0000  ................ 0000040: 8000 29c8 a726 5e4e 4f20 4e41 4d45 2020  ..)..&^no name   0000050: 2020 4641 5433 3220 2020 0e1f be77 7cac    fat32   ...w|. 0000060: 22c0 740b 56b4 0ebb 0700 cd10 5eeb f032  ".t.v.......^..2 0000070: e4cd 16cd 19eb fe54 6869 7320 6973 206e  .......this n 0000080: 6f74 2061 2062 6f6f 7461 626c 6520 6469  ot bootable di 0000090: 736b 2e20 2050 6c65 6173 6520 696e 7365  sk.  please inse 00000a0: 7274 2061 2062 6f6f 7461 626c 6520 666c  rt bootable fl 00000b0: 6f70 7079 2061 6e64 0d0a 7072 6573 7320  oppy and..press  00000c0: 616e 7920 6b65 7920 746f 2074 7279 2061  key try 00000d0: 6761 696e 202e 2e2e 200d 0a00 0000 0000  gain ... ....... 00000e0: 0000 0000 0000 0000 0000 0000 0000 0000  ................ 00000f0: 0000 0000 0000 0000 0000 0000 0000 0000  ................ 0000100: 0000 0000 0000 0000 0000 0000 0000 0000  ................ 0000110: 0000 0000 0000 0000 0000 0000 0000 0000  ................ 0000120: 0000 0000 0000 0000 0000 0000 0000 0000  ................ 0000130: 0000 0000 0000 0000 0000 0000 0000 0000  ................ 0000140: 0000 0000 0000 0000 0000 0000 0000 0000  ................ 0000150: 0000 0000 0000 0000 0000 0000 0000 0000  ................ 0000160: 0000 0000 0000 0000 0000 0000 0000 0000  ................ 0000170: 0000 0000 0000 0000 0000 0000 0000 0000  ................ 0000180: 0000 0000 0000 0000 0000 0000 0000 0000  ................ 0000190: 0000 0000 0000 0000 0000 0000 0000 0000  ................ 00001a0: 0000 0000 0000 0000 0000 0000 0000 0000  ................ 00001b0: 0000 0000 0000 0000 0000 0000 0000 0000  ................ 00001c0: 0000 0000 0000 0000 0000 0000 0000 0000  ................ 00001d0: 0000 0000 0000 0000 0000 0000 0000 0000  ................ 00001e0: 0000 0000 0000 0000 0000 0000 0000 0000  ................ 00001f0: 0000 0000 0000 0000 0000 0000 0000 55aa  ..............u. 0000200: 5252 6141 0000 0000 0000 0000 0000 0000  rraa............ 0000210: 0000 0000 0000 0000 0000 0000 0000 0000  ................ 0000220: 0000 0000 0000 0000 0000 0000 0000 0000  ................ 0000230: 0000 0000 0000 0000 0000 0000 0000 0000  ................ 0000240: 0000 0000 0000 0000 0000 0000 0000 0000  ................ 0000250: 0000 0000 0000 0000 0000 0000 0000 0000  ................ 0000260: 0000 0000 0000 0000 0000 0000 0000 0000  ................ ....

i used these create file:

dd if=/dev/zero of=disk.img bs=1k count=100000 losetup /dev/loop0 disk.img mkdosfs -s 1 -f 32 /dev/loop0 100000

i'm unable find root directory following guide. (example 1 - find root directory in http://www.tavi.co.uk/phobos/fat.html) seems 0x16 , 0x17 00. don't point anything?

the mentioned document talks fat16, doesn't apply fat32 file system; refer alternative resource instead.
according that, size of fat in sectors @ offset 36 (= 0x24, start of standard boot record) length 4 (in bytes); in c, access (assuming there's unsigned char *fat32fs pointing boot record, , you're on little-endian system) e. g.

#include <stdint.h>     uint32_t fatsectors = *(uint32_t *)&fat32fs[36];

in example file, size 0x00000603 (= 1539).


Comments

Post a Comment

Popular posts from this blog

Email notification in google apps script -

https://support.google.com/docs/answer/91588?hl=en i have sheet the cells filled in data pulled via apps script, website. pull in exact same data, not. on old sheets version use able emails when data "changes" different value. new sheets, email when new data pasted cells, though exact same data......and, can't set @ ranges anymore, entire document. there easy way watch cells when data changes, , email myself? this looks lot you're trying do. for checking whether value has changed after edit, this gives necessary information it. hence, know whether new value same 1 or not. implementing "workaround" talked in second link, able compare , send email myself if value changed. initiate onedit trigger goes off onedit function uses these lines after checks in place have passed. var email = "xyz@whatever.com"; mailapp.sendemail(email, "triggermail", "a change has occurred in sheet"); note: sends "notification...
Read more

c++ - Difference between pre and post decrement in recursive function argument -

i have following sample code used pre-decrement void function(int c) { if(c == 0) { return; } else { cout << "dp" << c << endl; function(--c); cout << c << endl; return; } } this function give output input 4 : dp3 dp2 dp1 dp0 0 1 2 3 but when use post decrement void function(int c) { if(c == 0) { return; } else { cout << "dp" << c << endl; function(c--); cout << c << endl; return; } } output goes in infinite loop dp4 can explain me in detail why happens ? this happens because function(c--) called same value of c , when finishes c decremented. recursively called, hence called same value no chance of return , hit stack overflow error. assume this, int x = 1, y = 0; y = x++ result y == 1 , x == 2. if y = ++x , bot x , y 2.
Read more

javascript - IE11 incompatibility with jQuery's 'readonly'? -

the code i'm running has no issues in firefox, or chrome. user typing 1 textbox, tabs next , can continue typing that. when run webpage on ie11, user tabs next textbox , can't type in. textbox has double-clicked before user can insert anything. i've googled , seems ie give problems when using older jquery (i.e. prefers 'prop' 'attr' ). in code below jquery's readonly keyword being used in way ie11 no longer recognise/accept? i assume issue readonly , removeclass('ignore') working expected. //when focus on textbox 1 $("#field1").focus(function() { //remove readonly property textbox 1 $('#field1').prop('readonly', false).removeclass('ignore'); //add readonly property other textboxes $('#field2, #field3, #field4') .prop('readonly', 'readonly').addclass('ignore').val(''); }); i'm using jquery 2.1.3 ...
Read more