error('LZW flavour not supported.'); } $this->initsTable(); $this->data = $data; $this->dataLength = strlen($data); // Initialize pointers $this->bytePointer = 0; $this->bitPointer = 0; $this->nextData = 0; $this->nextBits = 0; $oldCode = 0; $string = ''; $uncompData = ''; while (($code = $this->getNextCode()) != 257) { if ($code == 256) { $this->initsTable(); $code = $this->getNextCode(); if ($code == 257) { break; } $uncompData .= $this->sTable[$code]; $oldCode = $code; } else { if ($code < $this->tIdx) { $string = $this->sTable[$code]; $uncompData .= $string; $this->addStringToTable($this->sTable[$oldCode], $string[0]); $oldCode = $code; } else { $string = $this->sTable[$oldCode]; $string = $string.$string[0]; $uncompData .= $string; $this->addStringToTable($string); $oldCode = $code; } } } return $uncompData; } /** * Initialize the string table. */ public function initsTable() { $this->sTable = array(); for ($i = 0; $i < 256; $i++) { $this->sTable[$i] = chr($i); } $this->tIdx = 258; $this->bitsToGet = 9; } /** * Add a new string to the string table. */ public function addStringToTable($oldString, $newString='') { $string = $oldString.$newString; // Add this new String to the table $this->sTable[$this->tIdx++] = $string; if ($this->tIdx == 511) { $this->bitsToGet = 10; } elseif ($this->tIdx == 1023) { $this->bitsToGet = 11; } elseif ($this->tIdx == 2047) { $this->bitsToGet = 12; } } // Returns the next 9, 10, 11 or 12 bits public function getNextCode() { if ($this->bytePointer == $this->dataLength) { return 257; } $this->nextData = ($this->nextData << 8) | (ord($this->data[$this->bytePointer++]) & 0xff); $this->nextBits += 8; if ($this->nextBits < $this->bitsToGet) { $this->nextData = ($this->nextData << 8) | (ord($this->data[$this->bytePointer++]) & 0xff); $this->nextBits += 8; } $code = ($this->nextData >> ($this->nextBits - $this->bitsToGet)) & $this->andTable[$this->bitsToGet-9]; $this->nextBits -= $this->bitsToGet; return $code; } public function encode($in) { $this->error("LZW encoding not implemented."); } } }