how to decrypt xxtea? - c++

Question

I am trying to se if I can use XXTEA in my application.
The code that I found on Wikipedia code is only for encryption and there is no code for decryption.
How can I decrypt with XXTEA?
I am developing c++ in windows (visual studio 2012)

Answer 1

The code snippet in the article apparently uses negative values of n to mean decoding.
#include <stdio.h>
#include <stdint.h>
void btea(uint32_t *v, int n, uint32_t const key[4]); /* ... */
int main(void) {
char s[128] = "hello world bla bla bla bla bla bla";
uint32_t key[4] = {1,2,3,4};
int n = 128 / sizeof(uint32_t);
printf("%s\n",s);
btea((uint32_t*)s, n, key);
printf("%s\n",s);
btea((uint32_t*)s, -n, key);
printf("%s\n",s);
}
prints:
$ ./a.out | hexdump -C
00000000 68 65 6c 6c 6f 20 77 6f 72 6c 64 20 62 6c 61 20 |hello world bla |
00000010 62 6c 61 20 62 6c 61 20 62 6c 61 20 62 6c 61 20 |bla bla bla bla |
00000020 62 6c 61 0a 2f 44 86 75 d5 16 83 bd 5d 20 af f3 |bla./D.u....] ..|
00000030 a7 dd bf 9f 3a cd a0 13 ef 2b 89 48 2e f6 89 20 |....:....+.H... |
00000040 e2 ba e4 9f ed 38 d1 86 43 82 9e a6 47 6c e4 6d |.....8..C...Gl.m|
00000050 a8 82 22 9e cb 5b d1 a1 18 14 ef 18 ca 23 26 cc |.."..[.......#&.|
00000060 18 1d 4f ba 1b d5 f5 d0 45 72 1c 69 b9 22 a3 08 |..O.....Er.i."..|
00000070 44 71 1f 3b 8f a9 9d 5b 14 93 7b 59 b4 6b e8 1b |Dq.;...[..{Y.k..|
00000080 18 97 1b 74 61 d6 e9 e9 60 96 8e 4c 26 be 21 fc |...ta...`..L&.!.|
00000090 75 9f 4a 18 67 46 f0 95 2b ca 90 d9 f4 ce 3f 2f |u.J.gF..+.....?/|
000000a0 44 82 56 44 c0 0a 39 57 ff 7f 0a 68 65 6c 6c 6f |D.VD..9W...hello|
000000b0 20 77 6f 72 6c 64 20 62 6c 61 20 62 6c 61 20 62 | world bla bla b|
000000c0 6c 61 20 62 6c 61 20 62 6c 61 20 62 6c 61 0a |la bla bla bla.|
000000cf