In this stage, I think I used the hash calculation correctly. However, when I try to test it, I get errors saying that the hash is not correct, even though it is. In another test, the hash is not correct.
correct hash:
[tester::#RB2] Running tests for Stage #RB2 (Calculate info hash)
[tester::#RB2] Running ./your_bittorrent.sh info /tmp/torrents245747744/itsworking.gif.torrent
[your_program] Tracker URL: http://bittorrent-test-tracker.codecrafters.io/announce
[your_program] Length: 2549700
[your_program] Info hash: 70edcac2611a8829ebf467a6849f5d8408d9d8f4
[tester::#RB2] Expected stdout to contain "Info Hash: 70edcac2611a8829ebf467a6849f5d8408d9d8f4", got: "Tracker URL: http://bittorrent-test-tracker.codecrafters.io/announce\nLength: 2549700\nInfo hash: 70edcac2611a8829ebf467a6849f5d8408d9d8f4\n"
[tester::#RB2] Test failed
incorrect hash:
[tester::#RB2] Running tests for Stage #RB2 (Calculate info hash)
[tester::#RB2] Running ./your_bittorrent.sh info /tmp/torrents2180998007/codercat.gif.torrent
[your_program] Tracker URL: http://bittorrent-test-tracker.codecrafters.io/announce
[your_program] Length: 2994120
[your_program] Info hash: b2e418942622262a433ceda7b2e6e154a112318e
[tester::#RB2] Expected stdout to contain "Info Hash: c77829d2a77d6516f88cd7a3de1a26abcbfab0db", got: "Tracker URL: http://bittorrent-test-tracker.codecrafters.io/announce\nLength: 2994120\nInfo hash: b2e418942622262a433ceda7b2e6e154a112318e\n"
[tester::#RB2] Test failed
edit: forgot to mention that the info hash for the sample.torrent is correct. i checked with the example on the website’s instructions.
For the first case, I think it’s just a case of capitalization (expected: “Info Hash”, actual: “Info hash”).
For the second case, one common issue we’ve observed is related to sorting keys: if the keys in the dictionary aren’t sorted before encoding, you’ll end up with a different hash. Could you confirm whether this is the case?
about the second case, i think this may be the problem. i wasn’t aware the use of sorting.
i checked the specification and didn’t find anything about sorting the keys.
can you please provide sources so i can reference to?
I appreciate your answer, but even though the dictionary is sorted, it still doesn’t give the correct hash. I’m including the logs and the order of the dictionary here to show you that, although the order is correct, the hash isn’t, even though it passed other tests.
the order “length”, “name”, “piece length”, “pieces” is the correct order as raw string.
“length”
l: 108
e: 101
n: 110
g: 103
t: 116
h: 104
“name”
n: 110
a: 97
m: 109
e: 101
“piece length”
p: 112
i: 105
e: 101
c: 99
e: 101
(space): 32
l: 108
e: 101
n: 110
g: 103
t: 116
h: 104
“pieces”
p: 112
i: 105
e: 101
c: 99
e: 101
s: 115
i even included functions to ensure that the strings are sorted:
// Comparison function to be used with qsort
int compare_keyval_pairs(const void *a, const void *b) {
KeyValPair *pairA = (KeyValPair *)a;
KeyValPair *pairB = (KeyValPair *)b;
return strcmp(pairA->key, pairB->key);
}
// Function to sort a dictionary by its keys
void sort_dict(KeyValPair *dict, size_t size) {
qsort(dict, size, sizeof(KeyValPair), compare_keyval_pairs);
}
Can you try running your code against these locally, and see if the hashes match what you get by uploading the same files here? https://torrent.parts/
For context, hash mismatch cases are really hard to help out with since we can’t reverse the hash to figure out what the bug with the input is. The best we can do is share common mistakes + prove that the hash is indeed wrong.
Aha, nice find. Cool! So it looks like you have a file to locally test with - the fact that it doesn’t render on GitHub likely means that it contains a lot of binary content compared to the others.
Please let us know if you figure out what the bug was here!
FINALLY A SOULTION!!!
the problem was that in that file were a \x00 character, which most of the string.h functions, consider this EOF but in that case it wasn’t, like strlen(), strcat() and so on.
I stopped using functions like those started safely and carfully handle binary strings.
