 WOT: ARRGGHHH, i hate fixing someone elses code!, F%^$SH*&@@@ |
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| SirAndy |
 Aug 15 2005, 07:33 PM
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#1
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Resident German  Group: Admin Posts: 41,618 Joined: 21-January 03 From: Oakland, Kalifornia Member No.: 179 Region Association: Northern California  |
this was supposed to be a simple stripped down BASE64 decoder done in java.
i don't (can't) use a lot of standard libraries because this App will be run on PDAs and java enabled cellphones, so SIZE does matter. no problem, i get one of my contractors the BASE64 specs and some sample implementations ... he's been fighting with this for 3 days now so i get his sourcefile and have a look at it this morning. looks OK at first glance, but when you run it, it sporadically spits out wrong bytevalues while some decode just fine. wtf? so i spend all day going through his code (which is not that much) and i just can't figure out what's wrong. then finally, about 15 minutes ago it dawns on me, have a look at this: bReturn2[nn+2] = (byte)(iRes % 0xFF); bReturn2[nn+1] = (byte)((iRes >> 8) % 0xFF); bReturn2[nn+0] = (byte)((iRes >> 16) % 0xFF); bReturn2 is a byte array, iRes a integer, the purpose is to roll the lower 3 bytes of the integer into 3 sequential fields in the byte array. i had been staring at this for 6 hours and couldn't figure out what was wrong. all the while it was right in front of me, plain sight, right there ... (IMG:http://www.914world.com/bbs2/html/emoticons/headbang.gif) can you find the error? (IMG:http://www.914world.com/bbs2/html/emoticons/idea.gif) Andy PS: did i mention that i HATE going through someone else code? |
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| SpecialK |
Aug 15 2005, 08:02 PM
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#2
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aircraft surgeon Group: Benefactors Posts: 3,211 Joined: 15-March 04 From: Pacific, MO Member No.: 1,797  |
I have NFI, but I'd guess you're missing a parenthesis in the first line........but then again....I have NFI. (IMG:http://www.914world.com/bbs2/html/emoticons/confused24.gif)
Get your broken off allen wrench out? |
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| Midtowner |
Aug 15 2005, 08:15 PM
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#3
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Ooooo! Group: Members Posts: 652 Joined: 21-December 04 From: Sunnyvale, CA Member No.: 3,316 Region Association: None |
Sounds all Japanese to me! (IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif)
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| Joe Bob |
Aug 15 2005, 08:27 PM
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#4
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Retired admin, banned a few times Group: Members Posts: 17,427 Joined: 24-December 02 From: Boulder CO Member No.: 5 Region Association: None |
Or ya got extra ones....parenthesis that is....
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| Foxman |
Aug 15 2005, 08:29 PM
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#5
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Member Group: Members Posts: 57 Joined: 17-March 05 From: Fort Worth, TX Member No.: 3,778 |
bReturn2[nn+2] = (byte)(iRes % 0xFF);
What are you calculating the remainder of? Are you dividing iRes and 0XFF somewhere else? It is hard to say without seeing the rest of the function. |
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| johnmhudson111 |
Aug 15 2005, 08:29 PM
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#6
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Member Group: Members Posts: 491 Joined: 29-November 04 From: Nesbit, MS Member No.: 3,191 |
(IMG:http://www.914world.com/bbs2/html/emoticons/agree.gif) Just a WAG since I have no coding ability, just an analyst by nature and that seems to be the missing pattern. |
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| SirAndy |
Aug 15 2005, 08:32 PM
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#7
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Resident German Group: Admin Posts: 41,618 Joined: 21-January 03 From: Oakland, Kalifornia Member No.: 179 Region Association: Northern California |
nope, nothing missing, syntax is just fine, compiles and runs without an error ... (IMG:http://www.914world.com/bbs2/html/emoticons/wink.gif) Andy |
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| SirAndy |
Aug 15 2005, 08:35 PM
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#8
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Resident German Group: Admin Posts: 41,618 Joined: 21-January 03 From: Oakland, Kalifornia Member No.: 179 Region Association: Northern California |
this takes a 4 byte integer and zeros out all bits except the lowest 8 (0xff) and then stores those 8 bit in an byte-array. 1st line has no shift to get 1st byte 2nd line has 8 bit shift to get 2nd byte 3rd line has 16 bit shift to get 3rd byte that all is correct, but he still managed to f&%$ it up ... (IMG:http://www.914world.com/bbs2/html/emoticons/dry.gif) Andy |
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| johnmhudson111 |
Aug 15 2005, 08:36 PM
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#9
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Member Group: Members Posts: 491 Joined: 29-November 04 From: Nesbit, MS Member No.: 3,191 |
bReturn2[nn+2] = (byte)((iRes >> 4) % 0xFF); bReturn2[nn+1] = (byte)((iRes >> 8) % 0xFF); bReturn2[nn+0] = (byte)((iRes >> 16) % 0xFF); Nother WAG, I give up after this one (IMG:http://www.914world.com/bbs2/html/emoticons/happy11.gif) |
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| jonwatts |
Aug 15 2005, 08:37 PM
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#10
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no rules, just wrong Group: Benefactors Posts: 2,321 Joined: 13-January 03 From: San Jose, CA Member No.: 141 |
I would have used the '&' operator instead of the '%' operator, but that's just me.
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| r_towle |
Aug 15 2005, 08:58 PM
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#11
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Custom Member Group: Members Posts: 24,572 Joined: 9-January 03 From: Taxachusetts Member No.: 124 Region Association: North East States 
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bReturn2[nn+0] = (byte)(iRes % 0xFF); bReturn2[nn+1] = (byte)((iRes >> 8) % 0xFF); bReturn2[nn+2] = (byte)((iRes >> 16) % 0xFF); |
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| SirAndy |
Aug 15 2005, 09:07 PM
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#12
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Resident German Group: Admin Posts: 41,618 Joined: 21-January 03 From: Oakland, Kalifornia Member No.: 179 Region Association: Northern California |
we've got a winner! (IMG:http://www.914world.com/bbs2/html/emoticons/smilie_pokal.gif) he used the "%" operator which is MODULO instead of "&" which is bitwise AND ... took me 6 friggin hours to find that one! (IMG:http://www.914world.com/bbs2/html/emoticons/headbang.gif) Andy here's the correct code snippet: bReturn2[nn+2] = (byte)(iRes & 0xFF); bReturn2[nn+1] = (byte)((iRes >> 8) & 0xFF); bReturn2[nn+0] = (byte)((iRes >> 16) & 0xFF); |
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| jonwatts |
Aug 15 2005, 09:07 PM
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#13
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no rules, just wrong Group: Benefactors Posts: 2,321 Joined: 13-January 03 From: San Jose, CA Member No.: 141 |
Dumb question. Is your input base10 or base16? It doesn't matter to the compiler but it makes a difference to us humans.
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| ematulac |
Aug 15 2005, 09:08 PM
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#14
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914 addict Group: Members Posts: 540 Joined: 24-November 03 From: Palmdale, CA Member No.: 1,382 |
edit: nevermind ... modulus looked strange to me there, but it didn't register.
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| jonwatts |
Aug 15 2005, 09:09 PM
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#15
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no rules, just wrong Group: Benefactors Posts: 2,321 Joined: 13-January 03 From: San Jose, CA Member No.: 141 |
WOW, and I am such a suck-ass programmer too, but I do have to live in byte-stream land on a daily basis so maybe that helps.
I'd like to thank the Academy, my agent, and Andy for the beautiful 944 CV's, axles, and powder coated trailing arms (or do I just win an attaboy?). |
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| SirAndy |
Aug 15 2005, 09:10 PM
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#16
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Resident German Group: Admin Posts: 41,618 Joined: 21-January 03 From: Oakland, Kalifornia Member No.: 179 Region Association: Northern California |
nope, java integer is reverse byte order, so that part was correct ... jon nailed it, see post above! (IMG:http://www.914world.com/bbs2/html/emoticons/type.gif) Andy |
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| Foxman |
Aug 15 2005, 09:12 PM
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#17
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Member Group: Members Posts: 57 Joined: 17-March 05 From: Fort Worth, TX Member No.: 3,778 |
damn, I never thought about the input.
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