Problem converting C/C++ unsigned char to JAVA

Question

The problem with unsigned char. I am reading a PPM image file which has data in ASCII/Extended ASCII.

For a character, eg. '†' , In JAVA, after reading it as char and typecasting into int its value is 8224. In C/C++, after reading it as a unsigned char and typecasting into int its value is 160.

How would i read in JAVA so as to get value 160 ?

The followng C++

unsigned char ch1 ='†';  
char ch2 = '†';  

cout << (int) ch1 << "\n"; // prints 160  
cout << (int) ch2 << "\n"; // prints -96  

In Java,

char ch1 = '^';  
char ch2 = '†';  
System.out.println (" value : " +  (int) ch1); // prints 94  
System.out.println (" value :" +  (byte) ch1); // prints 94  

System.out.println (" value : " +  (int) ch2); // prints 8224  
System.out.println (" value :" +  (byte) ch2); // prints 32 

Following are some exceptions 8224 † 8226 • 8800 ≠ 8482 ™ 8710 ∆ 8211 – 8221 ” 8216 ‘ 9674 ◊ 8260 ⁄ 8249 ‹ 8249 ‹ 8734 ∞ 8747 ∫ 8364 € 8730 √ 8804 ≤

Following are some good ones 94 ^ 102 f 112 p 119 w 126 ~ 196 Ä 122 z 197 Å 197 Å

Any help is appreciated

Answer 1

IIRC Java uses a 16-bit representation for chars (UNICODE?) and C++ normally doesn't unless you use wchars.

I think you'd be better off trying to get C++ to use the UNICODE characters that Java uses rather than the other way around.

Answer 2

In C++ you are using "narrow" characters in some specific encoding that happens to define character '†' as 160. In other encodings 160 may mean something else, and character '†' may be missing altogether.

In Java, you are always dealing with Unicode. 8660 = 0x2020 = U+2020 "DAGGER".

To get "160", you need to convert your string to the same encoding you are using with C++. See String.getBytes(charset).

Answer 3

If you write out the unsigned char 160 in C++ as a single byte, and use InputStream.read() you will get 160. Which character this means depends on the assumed encoding but the value 160 is unchanged.