Browse code
Import from the old rivettracker git repository at sourceforge (amisaph/amisapphire branch)
Clarissa Walker (ami-sapphire) authored on 2014/01/24 14:02:23
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+<?php |
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+/* |
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+ |
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+ Programming info |
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+ |
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+All functions output a small array, which we'll call $return for now. |
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+ |
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+$return[0] is the data expected of the function |
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+$return[1] is the offset over the whole bencoded data of the next |
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+ piece of data. |
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+ |
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+numberdecode returns [0] as the integer read, and [1]-1 points to the |
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+symbol that was interprented as the end of the interger (either "e" or |
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+":"). |
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+numberdecode is used for integer decodes both for i11e and 11:hello there |
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+so it is tolerant of the ending symbol. |
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+ |
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+decodelist returns $return[0] as an integer indexed array like you would use in C |
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+for all the entries. $return[1]-1 is the "e" that ends the list, so [1] is the next |
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+useful byte. |
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+ |
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+decodeDict returns $return[0] as an array of text-indexed entries. For example, |
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+$return[0]["announce"] = "http://www.whatever.com:6969/announce"; |
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+$return[1]-1 again points to the "e" that ends the dictionary. |
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+ |
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+decodeEntry returns [0] as an integer in the case $offset points to |
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+i12345e or a string if $offset points to 11:hello there style strings. |
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+It also calls decodeDict or decodeList if it encounters a d or an l. |
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+ |
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+ |
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+Known bugs: |
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+- The program doesn't pay attention to the string it's working on. |
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+ A zero-sized or truncated data block will cause string offset errors |
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+ before they get rejected by the decoder. This is worked around by |
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+ suppressing errors. |
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+ |
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+*/ |
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+ |
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+// Protect our namespace using a class |
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+class BDecode |
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+{
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+ |
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+function numberdecode($wholefile, $start) |
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+{
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+ $ret[0] = 0; |
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+ $offset = $start; |
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+ |
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+ // Funky handling of negative numbers and zero |
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+ $negative = false; |
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+ if ($wholefile[$offset] == '-') |
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+ {
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+ $negative = true; |
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+ $offset++; |
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+ } |
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+ if ($wholefile[$offset] == '0') |
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+ {
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+ $offset++; |
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+ if ($negative) |
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+ return array(false); |
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+ if ($wholefile[$offset] == ':' || $wholefile[$offset] == 'e') |
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+ {
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+ $offset++; |
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+ $ret[0] = 0; |
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+ $ret[1] = $offset; |
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+ return $ret; |
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+ } |
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+ return array(false); |
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+ } |
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+ while (true) |
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+ {
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+ |
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+ if ($wholefile[$offset] >= '0' && $wholefile[$offset] <= '9') |
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+ {
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+ |
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+ $ret[0] *= 10; |
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+ $ret[0] += ord($wholefile[$offset]) - ord("0");
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+ $offset++; |
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+ } |
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+ // Tolerate : or e because this is a multiuse function |
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+ else if ($wholefile[$offset] == 'e' || $wholefile[$offset] == ':') |
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+ {
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+ $ret[1] = $offset+1; |
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+ if ($negative) |
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+ {
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+ if ($ret[0] == 0) |
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+ return array(false); |
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+ $ret[0] = - $ret[0]; |
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+ } |
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+ return $ret; |
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+ } |
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+ else |
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+ return array(false); |
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+ } |
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+ |
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+} |
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+ |
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+function decodeEntry($wholefile, $offset=0) |
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+{
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+ if ($wholefile[$offset] == 'd') |
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+ return $this->decodeDict($wholefile, $offset); |
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+ if ($wholefile[$offset] == 'l') |
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+ return $this->decodelist($wholefile, $offset); |
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+ if ($wholefile[$offset] == "i") |
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+ {
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+ $offset++; |
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+ return $this->numberdecode($wholefile, $offset); |
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+ } |
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+ // String value: decode number, then grab substring |
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+ $info = $this->numberdecode($wholefile, $offset); |
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+ if ($info[0] === false) |
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+ return array(false); |
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+ $ret[0] = substr($wholefile, $info[1], $info[0]); |
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+ $ret[1] = $info[1]+strlen($ret[0]); |
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+ return $ret; |
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+} |
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+ |
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+function decodeList($wholefile, $start) |
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+{
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+ $offset = $start+1; |
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+ $i = 0; |
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+ if ($wholefile[$start] != 'l') |
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+ return array(false); |
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+ $ret = array(); |
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+ while (true) |
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+ {
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+ if ($wholefile[$offset] == 'e') |
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+ break; |
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+ $value = $this->decodeEntry($wholefile, $offset); |
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+ if ($value[0] === false) |
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+ return array(false); |
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+ $ret[$i] = $value[0]; |
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+ $offset = $value[1]; |
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+ $i ++; |
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+ } |
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+ |
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+ // The empy list is an empty array. Seems fine. |
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+ $final[0] = $ret; |
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+ $final[1] = $offset+1; |
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+ return $final; |
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+ |
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+ |
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+ |
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+} |
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+ |
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+// Tries to construct an array |
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+function decodeDict($wholefile, $start=0) |
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+{
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+ $offset = $start; |
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+ if ($wholefile[$offset] == 'l') |
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+ return $this->decodeList($wholefile, $start); |
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+ if ($wholefile[$offset] != 'd') |
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+ return false; |
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+ $ret = array(); |
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+ $offset++; |
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+ while (true) |
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+ {
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+ if ($wholefile[$offset] == 'e') |
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+ {
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+ $offset++; |
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+ break; |
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+ } |
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+ $left = $this->decodeEntry($wholefile, $offset); |
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+ if (!$left[0]) |
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+ return false; |
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+ $offset = $left[1]; |
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+ if ($wholefile[$offset] == 'd') |
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+ {
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+ // Recurse |
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+ $value = $this->decodedict($wholefile, $offset); |
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+ if (!$value[0]) |
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+ return false; |
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+ $ret[addslashes($left[0])] = $value[0]; |
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+ $offset= $value[1]; |
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+ continue; |
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+ } |
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+ else if ($wholefile[$offset] == 'l') |
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+ {
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+ $value = $this->decodeList($wholefile, $offset); |
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+ if (!$value[0] && is_bool($value[0])) |
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+ return false; |
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+ $ret[addslashes($left[0])] = $value[0]; |
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+ $offset = $value[1]; |
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+ } |
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+ else |
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+ {
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+ $value = $this->decodeEntry($wholefile, $offset); |
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+ if ($value[0] === false) |
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+ return false; |
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+ $ret[addslashes($left[0])] = $value[0]; |
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+ $offset = $value[1]; |
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+ } |
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+ } |
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+ if (empty($ret)) |
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+ $final[0] = true; |
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+ else |
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+ $final[0] = $ret; |
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+ $final[1] = $offset; |
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+ return $final; |
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+ |
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+ |
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+} |
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+ |
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+ |
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+} // End of class declaration. |
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+ |
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+ |
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+ |
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+// Use this function. eg: BDecode("d8:announce44:http://www. ... e");
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+function BDecode($wholefile) |
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+{
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+ $decoder = new BDecode; |
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+ $return = $decoder->decodeEntry($wholefile); |
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+ return $return[0]; |
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+} |
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+ |
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+ |
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+?> |
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\ No newline at end of file |