Moving ConfEditor class from switch-master to core
authorRoan Kattouw <catrope@users.mediawiki.org>
Wed, 17 Jun 2009 17:20:01 +0000 (17:20 +0000)
committerRoan Kattouw <catrope@users.mediawiki.org>
Wed, 17 Jun 2009 17:20:01 +0000 (17:20 +0000)
includes/AutoLoader.php
includes/ConfEditor.php [new file with mode: 0644]

index 4ccfe5f..b1552de 100644 (file)
@@ -32,6 +32,7 @@ $wgAutoloadLocalClasses = array(
        'ChangeTags' => 'includes/ChangeTags.php',
        'ChannelFeed' => 'includes/Feed.php',
        'ConcatenatedGzipHistoryBlob' => 'includes/HistoryBlob.php',
+       'ConfEditor' => 'includes/ConfEditor.php',
        'ConstantDependency' => 'includes/CacheDependency.php',
        'CreativeCommonsRdf' => 'includes/Metadata.php',
        'Credits' => 'includes/Credits.php',
diff --git a/includes/ConfEditor.php b/includes/ConfEditor.php
new file mode 100644 (file)
index 0000000..5ac1d7f
--- /dev/null
@@ -0,0 +1,1053 @@
+<?php
+
+/** 
+ * This is a state machine style parser with two internal stacks:
+ *   * A next state stack, which determines the state the machine will progress to next
+ *   * A path stack, which keeps track of the logical location in the file.
+ *
+ * Reference grammar:
+ *
+ * file = T_OPEN_TAG *statement
+ * statement = T_VARIABLE "=" expression ";"
+ * expression = array / scalar / T_VARIABLE
+ * array = T_ARRAY "(" [ element *( "," element ) [ "," ] ] ")"
+ * element = assoc-element / expression
+ * assoc-element = scalar T_DOUBLE_ARROW expression
+ * scalar = T_LNUMBER / T_DNUMBER / T_STRING / T_CONSTANT_ENCAPSED_STRING
+ */
+class ConfEditor {
+       /** The text to parse */
+       var $text;
+
+       /** The token array from token_get_all() */
+       var $tokens;
+
+       /** The current position in the token array */
+       var $pos;
+
+       /** The current 1-based line number */
+       var $lineNum;
+
+       /** The current 1-based column number */
+       var $colNum;
+
+       /** The current 0-based byte number */
+       var $byteNum;
+
+       /** The current ConfEditorToken object */
+       var $currentToken;
+
+       /** The previous ConfEditorToken object */
+       var $prevToken;
+
+       /** 
+        * The state machine stack. This is an array of strings where the topmost 
+        * element will be popped off and become the next parser state.
+        */
+       var $stateStack;
+
+
+       /**
+        * The path stack is a stack of associative arrays with the following elements:
+        *    name              The name of top level of the path
+        *    level             The level (number of elements) of the path
+        *    startByte         The byte offset of the start of the path
+        *    startToken        The token offset of the start
+        *    endByte           The byte offset of thee
+        *    endToken          The token offset of the end, plus one
+        *    valueStartToken   The start token offset of the value part
+        *    valueStartByte    The start byte offset of the value part
+        *    valueEndToken     The end token offset of the value part, plus one
+        *    valueEndByte      The end byte offset of the value part, plus one
+        *    nextArrayIndex    The next numeric array index at this level
+        *    hasComma          True if the array element ends with a comma
+        *    arrowByte         The byte offset of the "=>", or false if there isn't one
+        */
+       var $pathStack;
+
+       /**
+        * The elements of the top of the pathStack for every path encountered, indexed 
+        * by slash-separated path.
+        */
+       var $pathInfo;
+
+       /**
+        * Next serial number for whitespace placeholder paths (@extra-N)
+        */
+       var $serial;
+
+       /**
+        * Editor state. This consists of the internal copy/insert operations which 
+        * are applied to the source string to obtain the destination string.
+        */
+       var $edits;
+
+       /**
+        * Simple entry point for command-line testing
+        */
+       static function test( $text ) {
+               try {
+                       $ce = new self( $text );
+                       $ce->parse();
+               } catch ( ConfEditorParseError $e ) {
+                       return $e->getMessage() . "\n" . $e->highlight( $text );
+               }
+               return "OK";
+       }
+
+       /**
+        * Construct a new parser
+        */
+       public function __construct( $text ) {
+               $this->text = $text;
+       }
+
+       /**
+        * Edit the text. Returns the edited text. 
+        * @param array $ops Array of operations.
+        *
+        * Operations are given as an associative array, with members:
+        *    type:     One of delete, set, append or insert (required)
+        *    path:     The path to operate on (required)
+        *    key:      The array key to insert/append, with PHP quotes
+        *    value:    The value, with PHP quotes
+        *
+        * delete
+        *    Deletes an array element or statement with the specified path.
+        *    e.g. 
+        *        array('type' => 'delete', 'path' => '$foo/bar/baz' )
+        *    is equivalent to the runtime PHP code:
+        *        unset( $foo['bar']['baz'] );
+        *
+        * set
+        *    Sets the value of an array element. If the element doesn't exist, it 
+        *    is appended to the array. If it does exist, the value is set, with 
+        *    comments and indenting preserved.
+        *
+        * append
+        *    Appends a new element to the end of the array. Adds a trailing comma.
+        *    e.g.
+        *        array( 'type' => 'append', 'path', '$foo/bar', 
+        *            'key' => 'baz', 'value' => "'x'" )
+        *    is like the PHP code:
+        *        $foo['bar']['baz'] = 'x';
+        *
+        * insert
+        *    Insert a new element at the start of the array.
+        *
+        */
+       public function edit( $ops ) {
+               $this->parse();
+
+               $this->edits = array(
+                       array( 'copy', 0, strlen( $this->text ) )
+               );
+               foreach ( $ops as $op ) {
+                       $type = $op['type'];
+                       $path = $op['path'];
+                       $value = isset( $op['value'] ) ? $op['value'] : null;
+                       $key = isset( $op['key'] ) ? $op['key'] : null;
+
+                       switch ( $type ) {
+                       case 'delete':
+                               list( $start, $end ) = $this->findDeletionRegion( $path );
+                               $this->replaceSourceRegion( $start, $end, false );
+                               break;
+                       case 'set':
+                               if ( isset( $this->pathInfo[$path] ) ) {
+                                       list( $start, $end ) = $this->findValueRegion( $path );
+                                       $encValue = $value; // var_export( $value, true );
+                                       $this->replaceSourceRegion( $start, $end, $encValue );
+                                       break;
+                               }
+                               // No existing path, fall through to append
+                               $slashPos = strrpos( $path, '/' );
+                               $key = var_export( substr( $path, $slashPos + 1 ), true );
+                               $path = substr( $path, 0, $slashPos );
+                               // Fall through
+                       case 'append':
+                               // Find the last array element
+                               $lastEltPath = $this->findLastArrayElement( $path );
+                               if ( $lastEltPath === false ) {
+                                       throw new MWException( "Can't find any element of array \"$path\"" );
+                               }
+                               $lastEltInfo = $this->pathInfo[$lastEltPath];
+
+                               // Has it got a comma already?
+                               if ( strpos( $lastEltPath, '@extra' ) === false && !$lastEltInfo['hasComma'] ) {
+                                       // No comma, insert one after the value region
+                                       list( $start, $end ) = $this->findValueRegion( $lastEltPath );
+                                       $this->replaceSourceRegion( $end - 1, $end - 1, ',' );
+                               }
+
+                               // Make the text to insert
+                               list( $start, $end ) = $this->findDeletionRegion( $lastEltPath );
+
+                               if ( $key === null ) {
+                                       list( $indent, $arrowIndent ) = $this->getIndent( $start );
+                                       $textToInsert = "$indent$value,";
+                               } else {
+                                       list( $indent, $arrowIndent ) = 
+                                               $this->getIndent( $start, $key, $lastEltInfo['arrowByte'] );
+                                       $textToInsert = "$indent$key$arrowIndent=> $value,";
+                               }
+                               $textToInsert .= ( $indent === false ? ' ' : "\n" );
+
+                               // Insert the item
+                               $this->replaceSourceRegion( $end, $end, $textToInsert );
+                               break;
+                       case 'insert':
+                               // Find first array element
+                               $firstEltPath = $this->findFirstArrayElement( $path );
+                               if ( $firstEltPath === false ) {
+                                       throw new MWException( "Can't find array element of \"$path\"" );
+                               }
+                               list( $start, $end ) = $this->findDeletionRegion( $firstEltPath );
+                               $info = $this->pathInfo[$firstEltPath];
+
+                               // Make the text to insert
+                               if ( $key === null ) {
+                                       list( $indent, $arrowIndent ) = $this->getIndent( $start );
+                                       $textToInsert = "$indent$value,";
+                               } else {
+                                       list( $indent, $arrowIndent ) = 
+                                               $this->getIndent( $start, $key, $info['arrowByte'] );
+                                       $textToInsert = "$indent$key$arrowIndent=> $value,";
+                               }
+                               $textToInsert .= ( $indent === false ? ' ' : "\n" );
+
+                               // Insert the item
+                               $this->replaceSourceRegion( $start, $start, $textToInsert );
+                               break;
+                       default:
+                               throw new MWException( "Unrecognised operation: \"$type\"" );
+                       }
+               }
+
+               // Do the edits
+               $out = '';
+               foreach ( $this->edits as $edit ) {
+                       if ( $edit[0] == 'copy' ) {
+                               $out .= substr( $this->text, $edit[1], $edit[2] - $edit[1] );
+                       } else { // if ( $edit[0] == 'insert' )
+                               $out .= $edit[1];
+                       }
+               }
+
+               // Do a second parse as a sanity check
+               $this->text = $out;
+               try {
+                       $this->parse();
+               } catch ( ConfEditorParseError $e ) {
+                       throw new MWException( 
+                               "Sorry, ConfEditor broke the file during editing and it won't parse anymore: " .
+                               $e->getMessage() );
+               }
+               return $out;
+       }
+       
+       /**
+        * Get the variables defined in the text
+        * @return array( varname => value )
+        */
+       function getVars() {
+               $vars = array();
+               $this->parse();
+               foreach( $this->pathInfo as $path => $data ) {
+                       if ( $path[0] != '$' )
+                               continue;
+                       $trimmedPath = substr( $path, 1 );
+                       $name = $data['name'];
+                       if ( $name[0] == '@' )
+                               continue;
+                       if ( $name[0] == '$' )
+                               $name = substr( $name, 1 );
+                       $parentPath = substr( $trimmedPath, 0,
+                               strlen( $trimmedPath ) - strlen( $name ) );
+                       if( substr( $parentPath, -1 ) == '/' )
+                               $parentPath = substr( $parentPath, 0, -1 );
+                       
+                       $value = substr( $this->text, $data['valueStartByte'],
+                               $data['valueEndByte'] - $data['valueStartByte']
+                       );
+                       $this->setVar( $vars, $parentPath, $name,
+                               $this->parseScalar( $value ) );
+               }
+               return $vars;
+       }
+       
+       /**
+        * Set a value in an array, unless it's set already. For instance,
+        * setVar( $arr, 'foo/bar', 'baz', 3 ); will set
+        * $arr['foo']['bar']['baz'] = 3;
+        * @param $array array
+        * @param $path string slash-delimited path
+        * @param $key mixed Key
+        * @param $value mixed Value
+        */
+       function setVar( &$array, $path, $key, $value ) {
+               $pathArr = explode( '/', $path );
+               $target =& $array;
+               if ( $path !== '' ) {
+                       foreach ( $pathArr as $p ) {
+                               if( !isset( $target[$p] ) )
+                                       $target[$p] = array();
+                               $target =& $target[$p];
+                       }
+               }
+               if ( !isset( $target[$key] ) )
+                       $target[$key] = $value;
+       }
+       
+       /**
+        * Parse a scalar value in PHP
+        * @return mixed Parsed value
+        */
+       function parseScalar( $str ) {
+               if ( $str !== '' && $str[0] == '\'' )
+                       // Single-quoted string
+                       return strtr( substr( $str, 1, -1 ),
+                               array( '\\\'' => '\'', '\\\\' => '\\' ) );
+               if ( $str !== '' && @$str[0] == '"' )
+                       // Double-quoted string
+                       return strtr( stripcslashes( substr( $str, 1, -1 ) ),
+                                array( '\'' => '\\\'' ) );
+               if ( substr( $str, 0, 4 ) == 'true' )
+                       return true;
+               if ( substr( $str, 0, 5 ) == 'false' )
+                       return false;
+               if ( substr( $str, 0, 4 ) == 'null' )
+                       return null;
+               // Must be some kind of numeric value, so let PHP's weak typing
+               // be useful for a change
+               return $str;
+       }
+
+       /**
+        * Replace the byte offset region of the source with $newText.
+        * Works by adding elements to the $this->edits array.
+        */
+       function replaceSourceRegion( $start, $end, $newText = false ) {
+               // Split all copy operations with a source corresponding to the region
+               // in question.
+               $newEdits = array();
+               foreach ( $this->edits as $i => $edit ) {
+                       if ( $edit[0] !== 'copy' ) {
+                               $newEdits[] = $edit;
+                               continue;
+                       }
+                       $copyStart = $edit[1];
+                       $copyEnd = $edit[2];
+                       if ( $start >= $copyEnd || $end <= $copyStart ) {
+                               // Outside this region
+                               $newEdits[] = $edit;
+                               continue;
+                       }
+                       if ( ( $start < $copyStart && $end > $copyStart )
+                               || ( $start < $copyEnd && $end > $copyEnd )
+                       ) {
+                               throw new MWException( "Overlapping regions found, can't do the edit" );
+                       }
+                       // Split the copy
+                       $newEdits[] = array( 'copy', $copyStart, $start );
+                       if ( $newText !== false ) {
+                               $newEdits[] = array( 'insert', $newText );
+                       }
+                       $newEdits[] = array( 'copy', $end, $copyEnd );
+               }
+               $this->edits = $newEdits;
+       }
+
+       /**
+        * Finds the source byte region which you would want to delete, if $pathName 
+        * was to be deleted. Includes the leading spaces and tabs, the trailing line 
+        * break, and any comments in between.
+        */
+       function findDeletionRegion( $pathName ) {
+               if ( !isset( $this->pathInfo[$pathName] ) ) {
+                       throw new MWException( "Can't find path \"$pathName\"" );
+               }
+               $path = $this->pathInfo[$pathName];
+               // Find the start
+               $this->firstToken();
+               while ( $this->pos != $path['startToken'] ) {
+                       $this->nextToken();
+               }
+               $regionStart = $path['startByte'];
+               for ( $offset = -1; $offset >= -$this->pos; $offset-- ) {
+                       $token = $this->getTokenAhead( $offset );
+                       if ( !$token->isSkip() ) {
+                               // If there is other content on the same line, don't move the start point
+                               // back, because that will cause the regions to overlap.
+                               $regionStart = $path['startByte'];
+                               break;
+                       }
+                       $lfPos = strrpos( $token->text, "\n" );
+                       if ( $lfPos === false ) {
+                               $regionStart -= strlen( $token->text );
+                       } else {
+                               // The line start does not include the LF
+                               $regionStart -= strlen( $token->text ) - $lfPos - 1;
+                               break;
+                       }
+               }
+               // Find the end
+               while ( $this->pos != $path['endToken'] ) {
+                       $this->nextToken();
+               }
+               $regionEnd = $path['endByte']; // past the end
+               for ( $offset = 0; $offset < count( $this->tokens ) - $this->pos; $offset++ ) {
+                       $token = $this->getTokenAhead( $offset );
+                       if ( !$token->isSkip() ) {
+                               break;
+                       }
+                       $lfPos = strpos( $token->text, "\n" );
+                       if ( $lfPos === false ) {
+                               $regionEnd += strlen( $token->text );
+                       } else {
+                               // This should point past the LF
+                               $regionEnd += $lfPos + 1;
+                               break;
+                       }
+               }
+               return array( $regionStart, $regionEnd );
+       }
+
+       /**
+        * Find the byte region in the source corresponding to the value part. 
+        * This includes the quotes, but does not include the trailing comma 
+        * or semicolon. 
+        *
+        * The end position is the past-the-end (end + 1) value as per convention.
+        */
+       function findValueRegion( $pathName ) {
+               if ( !isset( $this->pathInfo[$pathName] ) ) {
+                       throw new MWEXception( "Can't find path \"$pathName\"" );
+               }
+               $path = $this->pathInfo[$pathName];
+               if ( $path['valueStartByte'] === false || $path['valueEndByte'] === false ) {
+                       throw new MWException( "Can't find value region for path \"$pathName\"" );
+               }
+               return array( $path['valueStartByte'], $path['valueEndByte'] );
+       }
+
+       /**
+        * Find the path name of the last element in the array.
+        * If the array is empty, this will return the @extra interstitial element.
+        * If the specified path is not found or is not an array, it will return false.
+        */
+       function findLastArrayElement( $path ) {
+               // Try for a real element
+               $lastEltPath = false;
+               foreach ( $this->pathInfo as $candidatePath => $info ) {
+                       $part1 = substr( $candidatePath, 0, strlen( $path ) + 1 );
+                       $part2 = substr( $candidatePath, strlen( $path ) + 1, 1 );
+                       if ( $part2 == '@' ) {
+                               // Do nothing
+                       } elseif ( $part1 == "$path/" ) {
+                               $lastEltPath = $candidatePath;
+                       } elseif ( $lastEltPath !== false ) {
+                               break;
+                       }
+               }
+               if ( $lastEltPath !== false ) {
+                       return $lastEltPath;
+               }
+
+               // Try for an interstitial element
+               $extraPath = false;
+               foreach ( $this->pathInfo as $candidatePath => $info ) {
+                       $part1 = substr( $candidatePath, 0, strlen( $path ) + 1 );
+                       if ( $part1 == "$path/" ) {
+                               $extraPath = $candidatePath;
+                       } elseif ( $extraPath !== false ) {
+                               break;
+                       }
+               }
+               return $extraPath;
+       }
+
+       /*
+        * Find the path name of first element in the array.
+        * If the array is empty, this will return the @extra interstitial element.
+        * If the specified path is not found or is not an array, it will return false.
+        */
+       function findFirstArrayElement( $path ) {
+               // Try for an ordinary element
+               foreach ( $this->pathInfo as $candidatePath => $info ) {
+                       $part1 = substr( $candidatePath, 0, strlen( $path ) + 1 );
+                       $part2 = substr( $candidatePath, strlen( $path ) + 1, 1 );
+                       if ( $part1 == "$path/" && $part2 != '@' ) {
+                               return $candidatePath;
+                       }
+               }
+
+               // Try for an interstitial element
+               foreach ( $this->pathInfo as $candidatePath => $info ) {
+                       $part1 = substr( $candidatePath, 0, strlen( $path ) + 1 );
+                       if ( $part1 == "$path/" ) {
+                               return $candidatePath;
+                       }
+               }
+               return false;
+       }
+
+       /**
+        * Get the indent string which sits after a given start position.
+        * Returns false if the position is not at the start of the line.
+        */
+       function getIndent( $pos, $key = false, $arrowPos = false ) {
+               $arrowIndent = ' ';
+               if ( $pos == 0 || $this->text[$pos-1] == "\n" ) {
+                       $indentLength = strspn( $this->text, " \t", $pos );
+                       $indent = substr( $this->text, $pos, $indentLength );
+               } else {
+                       $indent = false;
+               }
+               if ( $indent !== false && $arrowPos !== false ) {
+                       $textToInsert = "$indent$key ";
+                       $arrowIndentLength = $arrowPos - $pos - $indentLength - strlen( $key );
+                       if ( $arrowIndentLength > 0 ) {
+                               $arrowIndent = str_repeat( ' ', $arrowIndentLength );
+                       }
+               }
+               return array( $indent, $arrowIndent );
+       }
+
+       /**
+        * Run the parser on the text. Throws an exception if the string does not 
+        * match our defined subset of PHP syntax.
+        */
+       public function parse() {
+               $this->initParse();
+               $this->pushState( 'file' );
+               $this->pushPath( '@extra-' . ($this->serial++) );
+               $token = $this->firstToken();
+
+               while ( !$token->isEnd() ) {
+                       $state = $this->popState();
+                       if ( !$state ) {
+                               $this->error( 'internal error: empty state stack' );
+                       }
+
+                       switch ( $state ) {
+                       case 'file':
+                               $token = $this->expect( T_OPEN_TAG );
+                               $token = $this->skipSpace();
+                               if ( $token->isEnd() ) {
+                                       break 2;
+                               }
+                               $this->pushState( 'statement', 'file 2' );
+                               break;
+                       case 'file 2':
+                               $token = $this->skipSpace();
+                               if ( $token->isEnd() ) {
+                                       break 2;
+                               }
+                               $this->pushState( 'statement', 'file 2' );
+                               break;
+                       case 'statement':
+                               $token = $this->skipSpace();
+                               if ( !$this->validatePath( $token->text ) ) {
+                                       $this->error( "Invalid variable name \"{$token->text}\"" );
+                               }
+                               $this->nextPath( $token->text );
+                               $this->expect( T_VARIABLE );
+                               $this->skipSpace();
+                               $arrayAssign = false;
+                               if ( $this->currentToken()->type == '[' ) {
+                                       $this->nextToken();
+                                       $token = $this->skipSpace();
+                                       if ( !$token->isScalar() ) {
+                                               $this->error( "expected a string or number for the array key" );
+                                       }
+                                       if ( $token->type == T_CONSTANT_ENCAPSED_STRING ) {
+                                               $text = $this->parseScalar( $token->text );
+                                       } else {
+                                               $text = $token->text;
+                                       }
+                                       if ( !$this->validatePath( $text ) ) {
+                                               $this->error( "Invalid associative array name \"$text\"" );
+                                       }
+                                       $this->pushPath( $text );
+                                       $this->nextToken();
+                                       $this->skipSpace();
+                                       $this->expect( ']' );
+                                       $this->skipSpace();
+                                       $arrayAssign = true;
+                               }
+                               $this->expect( '=' );
+                               $this->skipSpace();
+                               $this->startPathValue();
+                               if ( $arrayAssign )
+                                       $this->pushState( 'expression', 'array assign end' );
+                               else
+                                       $this->pushState( 'expression', 'statement end' );
+                               break;
+                       case 'array assign end':
+                       case 'statement end':
+                               $this->endPathValue();
+                               if ( $state == 'array assign end' )
+                                       $this->popPath();
+                               $this->skipSpace();
+                               $this->expect( ';' );
+                               $this->nextPath( '@extra-' . ($this->serial++) );
+                               break;
+                       case 'expression':
+                               $token = $this->skipSpace();
+                               if ( $token->type == T_ARRAY ) {
+                                       $this->pushState( 'array' );
+                               } elseif ( $token->isScalar() ) {
+                                       $this->nextToken();
+                               } elseif ( $token->type == T_VARIABLE ) {
+                                       $this->nextToken();
+                               } else {
+                                       $this->error( "expected simple expression" );
+                               }
+                               break;
+                       case 'array':
+                               $this->skipSpace();
+                               $this->expect( T_ARRAY );
+                               $this->skipSpace();
+                               $this->expect( '(' );
+                               $this->skipSpace();
+                               $this->pushPath( '@extra-' . ($this->serial++) );
+                               if ( $this->isAhead( ')' ) ) {
+                                       // Empty array
+                                       $this->pushState( 'array end' );
+                               } else {
+                                       $this->pushState( 'element', 'array end' );
+                               }
+                               break;
+                       case 'array end':
+                               $this->skipSpace();
+                               $this->popPath();
+                               $this->expect( ')' );
+                               break;
+                       case 'element':
+                               $token = $this->skipSpace();
+                               // Look ahead to find the double arrow
+                               if ( $token->isScalar() && $this->isAhead( T_DOUBLE_ARROW, 1 ) ) {
+                                       // Found associative element
+                                       $this->pushState( 'assoc-element', 'element end' );
+                               } else {
+                                       // Not associative
+                                       $this->nextPath( '@next' );
+                                       $this->startPathValue();
+                                       $this->pushState( 'expression', 'element end' );
+                               }
+                               break;
+                       case 'element end':
+                               $token = $this->skipSpace();
+                               if ( $token->type == ',' ) {
+                                       $this->endPathValue();
+                                       $this->markComma();
+                                       $this->nextToken();
+                                       $this->nextPath( '@extra-' . ($this->serial++) );
+                                       // Look ahead to find ending bracket
+                                       if ( $this->isAhead( ")" ) ) {
+                                               // Found ending bracket, no continuation
+                                               $this->skipSpace();
+                                       } else {
+                                               // No ending bracket, continue to next element
+                                               $this->pushState( 'element' );
+                                       }
+                               } elseif ( $token->type == ')' ) {
+                                       // End array
+                                       $this->endPathValue();
+                               } else {
+                                       $this->error( "expected the next array element or the end of the array" );
+                               }
+                               break;
+                       case 'assoc-element':
+                               $token = $this->skipSpace();
+                               if ( !$token->isScalar() ) {
+                                       $this->error( "expected a string or number for the array key" );
+                               }
+                               if ( $token->type == T_CONSTANT_ENCAPSED_STRING ) {
+                                       $text = $this->parseScalar( $token->text );
+                               } else {
+                                       $text = $token->text;
+                               }
+                               if ( !$this->validatePath( $text ) ) {
+                                       $this->error( "Invalid associative array name \"$text\"" );
+                               }
+                               $this->nextPath( $text );
+                               $this->nextToken();
+                               $this->skipSpace();
+                               $this->markArrow();
+                               $this->expect( T_DOUBLE_ARROW );
+                               $this->skipSpace();
+                               $this->startPathValue();
+                               $this->pushState( 'expression' );
+                               break;
+                       }
+               }
+               if ( count( $this->stateStack ) ) {
+                       $this->error( 'unexpected end of file' );
+               }
+               $this->popPath();
+       }
+
+       /**
+        * Initialise a parse.
+        */
+       protected function initParse() {
+               $this->tokens = token_get_all( $this->text );
+               $this->stateStack = array();
+               $this->pathStack = array();
+               $this->firstToken();
+               $this->pathInfo = array();
+               $this->serial = 1;
+       }
+
+       /**
+        * Set the parse position. Do not call this except from firstToken() and 
+        * nextToken(), there is more to update than just the position.
+        */
+       protected function setPos( $pos ) {
+               $this->pos = $pos;
+               if ( $this->pos >= count( $this->tokens ) ) {
+                       $this->currentToken = ConfEditorToken::newEnd();
+               } else {
+                       $this->currentToken = $this->newTokenObj( $this->tokens[$this->pos] );
+               }
+               return $this->currentToken;
+       }
+
+       /**
+        * Create a ConfEditorToken from an element of token_get_all()
+        */
+       function newTokenObj( $internalToken ) {
+               if ( is_array( $internalToken ) ) {
+                       return new ConfEditorToken( $internalToken[0], $internalToken[1] );
+               } else {
+                       return new ConfEditorToken( $internalToken, $internalToken );
+               }
+       }
+
+       /**
+        * Reset the parse position
+        */
+       function firstToken() {
+               $this->setPos( 0 );
+               $this->prevToken = ConfEditorToken::newEnd();
+               $this->lineNum = 1;
+               $this->colNum = 1;
+               $this->byteNum = 0;
+               return $this->currentToken;
+       }
+
+       /**
+        * Get the current token
+        */
+       function currentToken() {
+               return $this->currentToken;
+       }
+
+       /**
+        * Advance the current position and return the resulting next token
+        */
+       function nextToken() {
+               if ( $this->currentToken ) {
+                       $text = $this->currentToken->text;
+                       $lfCount = substr_count( $text, "\n" );
+                       if ( $lfCount ) {
+                               $this->lineNum += $lfCount;
+                               $this->colNum = strlen( $text ) - strrpos( $text, "\n" );
+                       } else {
+                               $this->colNum += strlen( $text );
+                       }
+                       $this->byteNum += strlen( $text );
+               }
+               $this->prevToken = $this->currentToken;
+               $this->setPos( $this->pos + 1 );
+               return $this->currentToken;
+       }
+
+       /**
+        * Get the token $offset steps ahead of the current position.
+        * $offset may be negative, to get tokens behind the current position.
+        */
+       function getTokenAhead( $offset ) {
+               $pos = $this->pos + $offset;
+               if ( $pos >= count( $this->tokens ) || $pos < 0 ) {
+                       return ConfEditorToken::newEnd();
+               } else {
+                       return $this->newTokenObj( $this->tokens[$pos] );
+               }
+       }
+
+       /**
+        * Advances the current position past any whitespace or comments
+        */
+       function skipSpace() {
+               while ( $this->currentToken && $this->currentToken->isSkip() ) {
+                       $this->nextToken();
+               }
+               return $this->currentToken;
+       }
+
+       /**
+        * Throws an error if the current token is not of the given type, and
+        * then advances to the next position.
+        */
+       function expect( $type ) {
+               if ( $this->currentToken && $this->currentToken->type == $type ) {
+                       return $this->nextToken();
+               } else {
+                       $this->error( "expected " . $this->getTypeName( $type ) . 
+                               ", got " . $this->getTypeName( $this->currentToken->type ) );
+               }
+       }
+
+       /**
+        * Push a state or two on to the state stack.
+        */
+       function pushState( $nextState, $stateAfterThat = null ) {
+               if ( $stateAfterThat !== null ) {
+                       $this->stateStack[] = $stateAfterThat;
+               }
+               $this->stateStack[] = $nextState;
+       }
+
+       /**
+        * Pop a state from the state stack.
+        */
+       function popState() {
+               return array_pop( $this->stateStack );
+       }
+
+       /**
+        * Returns true if the user input path is valid.
+        * This exists to allow "/" and "@" to be reserved for string path keys
+        */
+       function validatePath( $path ) {
+               return strpos( $path, '/' ) === false && substr( $path, 0, 1 ) != '@';
+       }
+
+       /**
+        * Internal function to update some things at the end of a path region. Do
+        * not call except from popPath() or nextPath().
+        */
+       function endPath() {
+               $i = count( $this->pathStack ) - 1;
+               $key = '';
+               foreach ( $this->pathStack as $pathInfo ) {
+                       if ( $key !== '' ) {
+                               $key .= '/';
+                       }
+                       $key .= $pathInfo['name'];
+               }
+               $pathInfo['endByte'] = $this->byteNum;
+               $pathInfo['endToken'] = $this->pos;
+               $this->pathInfo[$key] = $pathInfo;
+       }
+
+       /**
+        * Go up to a new path level, for example at the start of an array.
+        */
+       function pushPath( $path ) {
+               $this->pathStack[] = array(
+                       'name' => $path,
+                       'level' => count( $this->pathStack ) + 1,
+                       'startByte' => $this->byteNum,
+                       'startToken' => $this->pos,
+                       'valueStartToken' => false,
+                       'valueStartByte' => false,
+                       'valueEndToken' => false,
+                       'valueEndByte' => false,
+                       'nextArrayIndex' => 0,
+                       'hasComma' => false,
+                       'arrowByte' => false
+               );
+       }
+
+       /**
+        * Go down a path level, for example at the end of an array.
+        */
+       function popPath() {
+               $this->endPath();
+               array_pop( $this->pathStack );
+       }
+
+       /**
+        * Go to the next path on the same level. This ends the current path and 
+        * starts a new one. If $path is @next, the new path is set to the next
+        * numeric array element.
+        */
+       function nextPath( $path ) {
+               $this->endPath();
+               $i = count( $this->pathStack ) - 1;
+               if ( $path == '@next' ) {
+                       $nextArrayIndex =& $this->pathStack[$i]['nextArrayIndex'];
+                       $this->pathStack[$i]['name'] = $nextArrayIndex;
+                       $nextArrayIndex++;
+               } else {
+                       $this->pathStack[$i]['name'] = $path;
+               }
+               $this->pathStack[$i] = 
+                       array(
+                               'startByte' => $this->byteNum,
+                               'startToken' => $this->pos,
+                               'valueStartToken' => false,
+                               'valueStartByte' => false,
+                               'valueEndToken' => false,
+                               'valueEndByte' => false,
+                               'hasComma' => false,
+                               'arrowByte' => false,
+                       ) + $this->pathStack[$i];
+       }
+
+       /**
+        * Mark the start of the value part of a path.
+        */
+       function startPathValue() {
+               $path =& $this->pathStack[count( $this->pathStack ) - 1];
+               $path['valueStartToken'] = $this->pos;
+               $path['valueStartByte'] = $this->byteNum;
+       }
+
+       /**
+        * Mark the end of the value part of a path.
+        */
+       function endPathValue() {
+               $path =& $this->pathStack[count( $this->pathStack ) - 1];
+               $path['valueEndToken'] = $this->pos;
+               $path['valueEndByte'] = $this->byteNum;
+       }
+
+       /**
+        * Mark the comma separator in an array element
+        */
+       function markComma() {
+               $path =& $this->pathStack[count( $this->pathStack ) - 1];
+               $path['hasComma'] = true;
+       }
+
+       /**
+        * Mark the arrow separator in an associative array element
+        */
+       function markArrow() {
+               $path =& $this->pathStack[count( $this->pathStack ) - 1];
+               $path['arrowByte'] = $this->byteNum;
+       }
+
+       /**
+        * Generate a parse error
+        */
+       function error( $msg ) {
+               throw new ConfEditorParseError( $this, $msg );
+       }
+
+       /**
+        * Get a readable name for the given token type.
+        */
+       function getTypeName( $type ) {
+               if ( is_int( $type ) ) {
+                       return token_name( $type );
+               } else {
+                       return "\"$type\"";
+               }
+       }
+
+       /**
+        * Looks ahead to see if the given type is the next token type, starting 
+        * from the current position plus the given offset. Skips any intervening 
+        * whitespace.
+        */
+       function isAhead( $type, $offset = 0 ) {
+               $ahead = $offset;
+               $token = $this->getTokenAhead( $offset );
+               while ( !$token->isEnd() ) {
+                       if ( $token->isSkip() ) {
+                               $ahead++;
+                               $token = $this->getTokenAhead( $ahead );
+                               continue;
+                       } elseif ( $token->type == $type ) {
+                               // Found the type
+                               return true;
+                       } else {
+                               // Not found
+                               return false;
+                       }
+               }
+               return false;
+       }
+
+       /**
+        * Get the previous token object
+        */
+       function prevToken() {
+               return $this->prevToken;
+       }
+
+       /**
+        * Echo a reasonably readable representation of the tokenizer array.
+        */
+       function dumpTokens() {
+               $out = '';
+               foreach ( $this->tokens as $token ) {
+                       $obj = $this->newTokenObj( $token );
+                       $out .= sprintf( "%-28s %s\n", 
+                               $this->getTypeName( $obj->type ), 
+                               addcslashes( $obj->text, "\0..\37" ) );
+               }
+               echo "<pre>" . htmlspecialchars( $out ) . "</pre>";
+       }
+}
+
+/**
+ * Exception class for parse errors
+ */
+class ConfEditorParseError extends MWException {
+       var $lineNum, $colNum;
+       function __construct( $editor, $msg ) {
+               $this->lineNum = $editor->lineNum;
+               $this->colNum = $editor->colNum;
+               parent::__construct( "Parse error on line {$editor->lineNum} " . 
+                       "col {$editor->colNum}: $msg" );
+       }
+
+       function highlight( $text ) {
+               $lines = StringUtils::explode( "\n", $text );
+               foreach ( $lines as $lineNum => $line ) {
+                       if ( $lineNum == $this->lineNum - 1 ) {
+                               return "$line\n" .str_repeat( ' ', $this->colNum - 1 ) . "^\n";
+                       }
+               }
+       }
+
+}
+
+/**
+ * Class to wrap a token from the tokenizer.
+ */
+class ConfEditorToken {
+       var $type, $text;
+       
+       static $scalarTypes = array( T_LNUMBER, T_DNUMBER, T_STRING, T_CONSTANT_ENCAPSED_STRING );
+       static $skipTypes = array( T_WHITESPACE, T_COMMENT, T_DOC_COMMENT );
+
+       static function newEnd() {
+               return new self( 'END', '' );
+       }
+
+       function __construct( $type, $text ) {
+               $this->type = $type;
+               $this->text = $text;
+       }
+
+       function isSkip() {
+               return in_array( $this->type, self::$skipTypes );
+       }
+
+       function isScalar() {
+               return in_array( $this->type, self::$scalarTypes );
+       }
+
+       function isEnd() {
+               return $this->type == 'END';
+       }
+}
+