1. Writing and Reading Raw Data
Binary IO
Writing and Reading Raw Data

2. Files
Two major flavors of file:
Text Binary

3. Text Files Text files Easier to read by hand
Easier to reverse engineer
Easier to hand edit
More portable

4. Binary Files Binary files More compact Faster
" " = 12 ascii chars = 96 bytes
1 double = 8 bytes
Faster
No conversions from strings to numbers
Easier random access
Known size for numerics

5. Working in Binary Mode Can specify binary more when opening a file
//Open an output filestream binary mode
ofstream file("info.dat", ios::binary);
//Open a filestream using both output mode and binary
fstream file2("info.dat", ios::out | ios::binary);
//Open a filestream using allowing output, input both in binary
fstream file3("info.dat", ios::out | ios::in | ios::binary);

6. Working in Binary Mode Binary IO : n bytes starting at address s
Address expressed as char * char = 1 byte

7. Writing
Write c-string:

8. Results
Outputting ascii chars…
Hex editor:
Good text editor: Notepad:

9. Writing Non-Chars Write other types: Get pointer to data
Cast as a char*
Use sizeof( ) to calculate number of bytes

10. Cast Types Static_cast sanity checks types
Reinterpret_cast sanity checks size
C-Style cast picks whichever
int x = 15;
//Ask to do conversion if compiler knows rule to change type
double y = static_cast<double>(x);
//Tell compiler to ignore logic and treat bits as new type
// Has to be same size
double y2 = reinterpret_cast<double>(x);
//C-Style : might do static, might do reinterpret
double y3 = (double)(x);

11. Cast Types Static_cast sanity checks types
Reinterpret_cast sanity checks size
C-Style cast picks whichever
int x = 15;
//Ask to do conversion if compiler knows rule to change type
char* dataPointer = static_cast<char*>(&x);
//Tell compiler to ignore logic and treat bits as new type
char* dataPointer2 = reinterpret_cast<char*>(&x);
//C-Style : might do static, might do reinterpret
char* dataPointer3 = (char*)(&x);

12. Results Outputting ascii followed by bits for 15 (F) Hex editor:
Good text editor: Notepad:

13. Size
Int = 4 bytes

14. Results
Outputting 15 (F16) followed by 258 (10216)

15. Endianess
Endianess : bytes order of a word in main memory

16. Little vs Big Endian Big is "Normal": Little weird Words in order
Bytes in a word backwards

17. Little Endian Arrangement Little Endian Arrangement
Results
Outputting 15 (F16) followed by 258 (10216)
Little Endian Arrangement
Meaning 0F 00
Little Endian Arrangement
Meaning 02 01 00

18. Reading
Need to read string, 2 ints
String unknown length

19. Reading
Read string char by char:

20. Reading
Same, using c-string

21. Reading
Reading two ints:

22. Complex Files
Graphic/Sound/etc… files have defined structure:

23. Other Option Structured text : XML Less efficient than text
Machine parseable
Wide collection of tools