r2108 + introduce $any_op autotag
[racktables] / inc / code.php
index f6491df87e9f9d0d1b0565fbfe061ebce82f806a..867bc66eb23f4dcb8f5a30bfd0631dfa839682bb 100644 (file)
@@ -1,6 +1,6 @@
 <?php
 /*
- * This file implement lexical scanner and syntax analyzer for the RackCode
+ * This file implements lexical scanner and syntax analyzer for the RackCode
  * access configuration language.
  *
  * The language consists of the following lexems:
  * LEX_PREDICATE
  * LEX_BOOLOP
  *
- * Comments last from the first # to the end of the line and are filtered out
- * automatically.
  */
 
 // Complain about martian char.
-function abortLex1 ($state, $text, $pos)
+function lexError1 ($state, $text, $pos)
 {
-       echo "Error! Could not parse the following text (current state is '${state}'): ";
-       echo substr ($text, 0, $pos);
-       echo '<font color = red>-&gt;' . $text{$pos} . '&lt;-</font>';
-       echo substr ($text, $pos + 1);
-       die;
+       $message = "invalid char with code " . ord (mb_substr ($text, $pos, 1)) . ' (';
+       $message .= mb_substr ($text, $pos, 1) . ") at position ${pos} (FSM state is '${state}')";
+       return array ('result' => 'NAK', 'load' => $message);
 }
 
 // Complain about martian keyword.
-function abortLex2 ($state, $word)
+function lexError2 ($word)
 {
-       echo "Error! Could not parse word (current state is '${state}'): '${word}'.";
-       die;
+       return array
+       (
+               'result' => 'NAK',
+               'load' => "could not parse keyword '${word}'"
+       );
 }
 
 // Complain about wrong FSM state.
-function abortLex3 ($state)
+function lexError3 ($state)
 {
-       echo "Error! Lexical scanner final state is still '${state}' after scanning the last char.";
-       die;
+       return array
+       (
+               'result' => 'NAK',
+               'load' => "FSM state is still '${state}' at end of input"
+       );
 }
 
-function abortSynt ($lexname)
+function lexError4 ($s)
 {
-       echo "Error! Unknown lexeme '${lexname}'.";
-       die;
+       return array
+       (
+               'result' => 'NAK',
+               'load' => "Invalid tag or predicate name '${s}'"
+       );
 }
 
 // Produce a list of lexems from the given text. Possible lexems are:
 function getLexemsFromRackCode ($text)
 {
        $ret = array();
-       $textlen = strlen ($text);
+       $textlen = mb_strlen ($text);
        $state = "ESOTSM";
        for ($i = 0; $i < $textlen; $i++) :
-               $char = $text{$i};
+               $char = mb_substr ($text, $i, 1);
                $newstate = $state;
                switch ($state) :
                        case 'ESOTSM':
@@ -71,11 +76,11 @@ function getLexemsFromRackCode ($text)
                                        case ($char == '#'):
                                                $newstate = 'skipping comment';
                                                break;
-                                       case (preg_match ('/^[a-zA-Z]$/', $char)):
-                                               $newstate = 'reading word';
+                                       case (mb_ereg ('[[:alpha:]]', $char) > 0):
+                                               $newstate = 'reading keyword';
                                                $buffer = $char;
                                                break;
-                                       case (preg_match ('/^[ \t\n]$/', $char)):
+                                       case (preg_match ('/^[ \t\n\r]$/', $char)):
                                                // nom-nom...
                                                break;
                                        case ($char == '{'):
@@ -85,13 +90,13 @@ function getLexemsFromRackCode ($text)
                                                $newstate = 'reading predicate 1';
                                                break;
                                        default:
-                                               abortLex1 ($state, $text, $i);
+                                               return lexError1 ($state, $text, $i);
                                }
                                break;
-                       case 'reading word':
+                       case 'reading keyword':
                                switch (TRUE)
                                {
-                                       case (preg_match ('/^[a-zA-Z]$/', $char)):
+                                       case (mb_ereg ('[[:alpha:]]', $char) > 0):
                                                $buffer .= $char;
                                                break;
                                        case (preg_match ('/^[ \t\n]$/', $char)):
@@ -117,72 +122,78 @@ function getLexemsFromRackCode ($text)
                                                                $ret[] = array ('type' => 'LEX_BOOLCONST', 'load' => $buffer);
                                                                break;
                                                        default:
-                                                               abortLex2 ($state, $buffer);
+                                                               return lexError2 ($buffer);
                                                }
                                                $newstate = 'ESOTSM';
                                                break;
                                        default:
-                                               abortLex1 ($state, $text, $i);
+                                               return lexError1 ($state, $text, $i);
                                }
                                break;
                        case 'reading tag 1':
                                switch (TRUE)
                                {
-                                       case (preg_match ('/^[ \t\n]$/', $char)):
+                                       case (preg_match ('/^[ \t\n\r]$/', $char)):
                                                // nom-nom...
                                                break;
-                                       case (preg_match ('/^[a-zA-Z\$]$/', $char)):
+                                       case (mb_ereg ('[[:alnum:]\$]', $char) > 0):
                                                $buffer = $char;
                                                $newstate = 'reading tag 2';
                                                break;
                                        default:
-                                               abortLex1 ($state, $text, $i);
+                                               return lexError1 ($state, $text, $i);
                                }
                                break;
                        case 'reading tag 2':
                                switch (TRUE)
                                {
                                        case ($char == '}'):
-                                               $ret[] = array ('type' => 'LEX_TAG', 'load' => rtrim ($buffer));
+                                               $buffer = rtrim ($buffer);
+                                               if (!validTagName ($buffer, TRUE))
+                                                       return lexError4 ($buffer);
+                                               $ret[] = array ('type' => 'LEX_TAG', 'load' => $buffer);
                                                $newstate = 'ESOTSM';
                                                break;
-                                       case (preg_match ('/^[a-zA-Z0-9 _-]$/', $char)):
+                                       case (mb_ereg ('[[:alnum:]\. _~-]', $char) > 0):
                                                $buffer .= $char;
                                                break;
                                        default:
-                                               abortLex1 ($state, $text, $i);
+                                               return lexError1 ($state, $text, $i);
                                }
                                break;
                        case 'reading predicate 1':
                                switch (TRUE)
                                {
-                                       case (preg_match ('/^[ \t\n]$/', $char)):
+                                       case (preg_match ('/^[ \t\n\r]$/', $char)):
                                                // nom-nom...
                                                break;
-                                       case (preg_match ('/^[a-zA-Z]$/', $char)):
+                                       case (mb_ereg ('[[:alnum:]]', $char) > 0):
                                                $buffer = $char;
                                                $newstate = 'reading predicate 2';
                                                break;
                                        default:
-                                               abortLex1 ($state, $text, $i);
+                                               return lexError1 ($state, $text, $i);
                                }
                                break;
                        case 'reading predicate 2':
                                switch (TRUE)
                                {
                                        case ($char == ']'):
-                                               $ret[] = array ('type' => 'LEX_PREDICATE', 'load' => rtrim ($buffer));
+                                               $buffer = rtrim ($buffer);
+                                               if (!validTagName ($buffer))
+                                                       return lexError4 ($buffer);
+                                               $ret[] = array ('type' => 'LEX_PREDICATE', 'load' => $buffer);
                                                $newstate = 'ESOTSM';
                                                break;
-                                       case (preg_match ('/^[a-zA-Z0-9 _-]$/', $char)):
+                                       case (mb_ereg ('[[:alnum:]\. _~-]', $char) > 0):
                                                $buffer .= $char;
                                                break;
                                        default:
-                                               abortLex1 ($state, $text, $i);
+                                               return lexError1 ($state, $text, $i);
                                }
                                break;
                        case 'skipping comment':
-                               switch ($text{$i})
+                               switch ($char)
                                {
                                        case "\n":
                                                $newstate = 'ESOTSM';
@@ -195,49 +206,35 @@ function getLexemsFromRackCode ($text)
                endswitch;
                $state = $newstate;
        endfor;
-       if ($state != 'ESOTSM')
-               abortLex3 ($state);
-       return $ret;
-}
-
-function syntReduce_BOOLCONST (&$stack)
-{
-       if (count ($stack) < 1)
-               return FALSE;
-       $top = array_pop ($stack);
-       if ($top['type'] == 'LEX_BOOLCONST')
-       {
-               $s = array
-               (
-                       'type' => 'SYNT_EXPRESSION',
-                       'kids' => array ($top)
-               );
-               array_push ($stack, $s);
-               return TRUE;
-       }
-       // No luck, push it back.
-       array_push ($stack, $top);
-       return FALSE;
+       if ($state != 'ESOTSM' and $state != 'skipping comment')
+               return lexError3 ($state);
+       return array ('result' => 'ACK', 'load' => $ret);
 }
 
 // Parse the given lexems stream into a list of RackCode sentences. Each such
-// sentence is a syntax tree, suitable for tag sequence evaluation. It may
-// contain all of the lexems plus the following syntax contructs:
-// SYNT_NOT
-// SYNT_EXPRESSION
-// SYNT_DEFINITION
-// SYNT_GRANT
-// SYNT_SENTENCE
-// SYNT_CODE
+// sentence is a syntax tree, suitable for tag sequence evaluation. The final
+// parse tree may contain the following nodes:
+// LEX_TAG
+// LEX_PREDICATE
+// LEX_BOOLCONST
+// SYNT_NOT (1 argument, holding SYNT_EXPR)
+// SYNT_BOOLOP (2 arguments, each holding SYNT_EXPR)
+// SYNT_DEFINITION (2 arguments: term and definition)
+// SYNT_GRANT (2 arguments: decision and condition)
+// SYNT_CODETEXT (sequence of sentences)
+//
+// After parsing the input successfully a list of SYNT_GRANT and SYNT_DEFINITION
+// trees is returned.
 function getSentencesFromLexems ($lexems)
 {
-       $ret = array(); // This is going to be the tree.
        $stack = array(); // subject to array_push() and array_pop()
        $done = 0; // $lexems[$done] is the next item in the tape
        $todo = count ($lexems);
 
-       // Perform shift-reduce parsing.
-       while ($done < $todo)
+       // Perform shift-reduce processing. The "accept" actions occurs with an
+       // empty input tape and the stack holding only one symbol (the start
+       // symbol, SYNT_CODETEXT).
+       while (TRUE)
        {
                $stacktop = $stacksecondtop = $stackthirdtop = array ('type' => 'null');
                $stacksize = count ($stack);
@@ -248,7 +245,12 @@ function getSentencesFromLexems ($lexems)
                        // correct sentence base on the stack and some "and {something}" items
                        // on the input tape, hence let's detect this specific case and insist
                        // on "shift" action to make EXPR parsing hungry one.
-                       if ($stacktop['type'] == 'SYNT_EXPR' and $lexems[$done]['type'] == 'LEX_BOOLOP')
+                       if
+                       (
+                               $stacktop['type'] == 'SYNT_EXPR' and
+                               ($done < $todo) and 
+                               $lexems[$done]['type'] == 'LEX_BOOLOP'
+                       )
                        {
                                // shift!
                                array_push ($stack, $stacktop);
@@ -266,6 +268,27 @@ function getSentencesFromLexems ($lexems)
                                array_push ($stack, $stacksecondtop);
                        }
                        array_push ($stack, $stacktop);
+                       // First detect definition start to save the predicate from being reduced into
+                       // expression.
+                       if
+                       (
+                               $stacktop['type'] == 'LEX_PREDICATE' and
+                               $stacksecondtop['type'] == 'LEX_DEFINE'
+                       )
+                       {
+                               array_pop ($stack);
+                               array_pop ($stack);
+                               array_push
+                               (
+                                       $stack,
+                                       array
+                                       (
+                                               'type' => 'SYNT_DEFINE',
+                                               'load' => $stacktop['load']
+                                       )
+                               );
+                               continue;
+                       }
                        // Try "replace" action only on a non-empty stack.
                        // If a handle is found for reversing a production rule, do it and start a new
                        // cycle instead of advancing further on rule list. This will preserve rule priority
@@ -277,6 +300,7 @@ function getSentencesFromLexems ($lexems)
                                $stacktop['type'] == 'LEX_PREDICATE'
                        )
                        {
+                               // reduce!
                                array_pop ($stack);
                                array_push
                                (
@@ -295,6 +319,7 @@ function getSentencesFromLexems ($lexems)
                                $stacksecondtop['type'] == 'LEX_NOT'
                        )
                        {
+                               // reduce!
                                array_pop ($stack);
                                array_pop ($stack);
                                array_push
@@ -306,7 +331,7 @@ function getSentencesFromLexems ($lexems)
                                                'load' => array
                                                (
                                                        'type' => 'SYNT_NOTEXPR',
-                                                       'arg' => $stacktop
+                                                       'load' => $stacktop['load']
                                                )
                                        )
                                );
@@ -319,6 +344,7 @@ function getSentencesFromLexems ($lexems)
                                $stackthirdtop['type'] == 'LEX_LBRACE'
                        )
                        {
+                               // reduce!
                                array_pop ($stack);
                                array_pop ($stack);
                                array_pop ($stack);
@@ -336,6 +362,7 @@ function getSentencesFromLexems ($lexems)
                                $stackthirdtop['type'] == 'SYNT_EXPR'
                        )
                        {
+                               // reduce!
                                array_pop ($stack);
                                array_pop ($stack);
                                array_pop ($stack);
@@ -349,18 +376,264 @@ function getSentencesFromLexems ($lexems)
                                                (
                                                        'type' => 'SYNT_BOOLOP',
                                                        'subtype' => $stacksecondtop['load'],
-                                                       'left' => $stackthirdtop,
-                                                       'right' => $stacktop
+                                                       'left' => $stackthirdtop['load'],
+                                                       'right' => $stacktop['load']
                                                )
                                        )
                                );
                                continue;
                        }
+                       if
+                       (
+                               $stacktop['type'] == 'SYNT_EXPR' and
+                               $stacksecondtop['type'] == 'LEX_DECISION'
+                       )
+                       {
+                               // reduce!
+                               array_pop ($stack);
+                               array_pop ($stack);
+                               array_push
+                               (
+                                       $stack,
+                                       array
+                                       (
+                                               'type' => 'SYNT_GRANT',
+                                               'decision' => $stacksecondtop['load'],
+                                               'condition' => $stacktop['load']
+                                       )
+                               );
+                               continue;
+                       }
+                       if
+                       (
+                               $stacktop['type'] == 'SYNT_EXPR' and
+                               $stacksecondtop['type'] == 'SYNT_DEFINE'
+                       )
+                       {
+                               // reduce!
+                               array_pop ($stack);
+                               array_pop ($stack);
+                               array_push
+                               (
+                                       $stack,
+                                       array
+                                       (
+                                               'type' => 'SYNT_DEFINITION',
+                                               'term' => $stacksecondtop['load'],
+                                               'definition' => $stacktop['load']
+                                       )
+                               );
+                               continue;
+                       }
+                       if
+                       (
+                               ($stacktop['type'] == 'SYNT_GRANT' or $stacktop['type'] == 'SYNT_DEFINITION') and
+                               $stacksecondtop['type'] == 'SYNT_CODETEXT'
+                       )
+                       {
+                               // reduce!
+                               array_pop ($stack);
+                               array_pop ($stack);
+                               $stacksecondtop['load'][] = $stacktop;
+                               array_push
+                               (
+                                       $stack,
+                                       $stacksecondtop
+                               );
+                               continue;
+                       }
+                       if
+                       (
+                               $stacktop['type'] == 'SYNT_GRANT' or
+                               $stacktop['type'] == 'SYNT_DEFINITION'
+                       )
+                       {
+                               // reduce!
+                               array_pop ($stack);
+                               array_push
+                               (
+                                       $stack,
+                                       array
+                                       (
+                                               'type' => 'SYNT_CODETEXT',
+                                               'load' => array ($stacktop)
+                                       )
+                               );
+                               continue;
+                       }
+               }
+               // The fact we execute here means, that no reduction or early shift
+               // has been done. The only way to enter another iteration is to "shift"
+               // more, if possible. If the tape is empty, we are facing the
+               // "accept"/"reject" dilemma. The only possible way to "accept" is to
+               // have sole starting nonterminal on the stack (SYNT_CODETEXT).
+               if ($done < $todo)
+               {
+                       array_push ($stack, $lexems[$done++]);
+                       continue;
                }
-               // We are here because of either an empty stack or none reduction succeeded. Shift!
-               array_push ($stack, $lexems[$done++]);
+               // The moment of truth.
+               if (count ($stack) == 1 and $stack[0]['type'] == 'SYNT_CODETEXT')
+                       return array ('result' => 'ACK', 'load' => $stack[0]['load']);
+               return array ('result' => 'NAK', 'load' => 'Syntax error!');
        }
-       return $stack;
+}
+
+function eval_expression ($expr, $tagchain, $ptable)
+{
+       switch ($expr['type'])
+       {
+               case 'LEX_TAG': // Return true, if given tag is present on the tag chain.
+                       foreach ($tagchain as $tagInfo)
+                               if ($expr['load'] == $tagInfo['tag'])
+                                       return TRUE;
+                       return FALSE;
+               case 'LEX_PREDICATE': // Find given predicate in the symbol table and evaluate it.
+                       $pname = $expr['load'];
+                       if (!isset ($ptable[$pname]))
+                       {
+                               showError ("Predicate '${pname}' is referenced before declaration", __FUNCTION__);
+                               return;
+                       }
+                       return eval_expression ($ptable[$pname], $tagchain, $ptable);
+               case 'LEX_BOOLCONST': // Evaluate a boolean constant.
+                       switch ($expr['load'])
+                       {
+                               case 'true':
+                                       return TRUE;
+                               case 'false':
+                                       return FALSE;
+                               default:
+                                       showError ("Could not parse a boolean constant with value '${expr['load']}'", __FUNCTION__);
+                                       return; // should failure be harder?
+                       }
+               case 'SYNT_NOTEXPR':
+                       return !eval_expression ($expr['load'], $tagchain, $ptable);
+               case 'SYNT_BOOLOP':
+                       $leftresult = eval_expression ($expr['left'], $tagchain, $ptable);
+                       switch ($expr['subtype'])
+                       {
+                               case 'or':
+                                       if ($leftresult)
+                                               return TRUE; // early success
+                                       return eval_expression ($expr['right'], $tagchain, $ptable);
+                               case 'and':
+                                       if (!$leftresult)
+                                               return FALSE; // early failure
+                                       return eval_expression ($expr['right'], $tagchain, $ptable);
+                               default:
+                                       showError ("Cannot evaluate unknown boolean operation '${boolop['subtype']}'");
+                                       return;
+                       }
+               default:
+                       showError ("Evaluation error, cannot process expression type '${expr['type']}'", __FUNCTION__);
+                       break;
+       }
+}
+
+function gotClearanceForTagChain ($tagchain)
+{
+       global $rackCode;
+       $ptable = array();
+       foreach ($rackCode as $sentence)
+       {
+               switch ($sentence['type'])
+               {
+                       case 'SYNT_DEFINITION':
+                               $ptable[$sentence['term']] = $sentence['definition'];
+                               break;
+                       case 'SYNT_GRANT':
+                               if (eval_expression ($sentence['condition'], $tagchain, $ptable))
+                                       switch ($sentence['decision'])
+                                       {
+                                               case 'allow':
+                                                       return TRUE;
+                                               case 'deny':
+                                                       return FALSE;
+                                               default:
+                                                       showError ("Condition match for unknown grant decision '${sentence['decision']}'", __FUNCTION__);
+                                                       break;
+                                       }
+                               break;
+                       default:
+                               showError ("Can't process sentence of unknown type '${sentence['type']}'", __FUNCTION__);
+                               break;
+               }
+       }
+       return FALSE;
+}
+
+function getRackCode ($text)
+{
+       if (!mb_strlen ($text))
+               return array ('result' => 'NAK', 'load' => 'The RackCode text was found empty in ' . __FUNCTION__);
+       $text = str_replace ("\r", '', $text) . "\n";
+       $lex = getLexemsFromRackCode ($text);
+       if ($lex['result'] != 'ACK')
+               return $lex;
+       $synt = getSentencesFromLexems ($lex['load']);
+       if ($synt['result'] != 'ACK')
+               return $synt;
+       // An empty sentence list is semantically valid, yet senseless,
+       // so checking intermediate result once more won't hurt.
+       if (!count ($synt['load']))
+               return array ('result' => 'NAK', 'load' => 'Empty parse tree found in ' . __FUNCTION__);
+       return semanticFilter ($synt['load']);
+}
+
+// Return NULL, if the given expression can be evaluated against the given
+// predicate list. Return the name of the first show stopper otherwise.
+function firstUnrefPredicate ($plist, $expr)
+{
+       switch ($expr['type'])
+       {
+               case 'LEX_BOOLCONST':
+               case 'LEX_TAG':
+                       return NULL;
+               case 'LEX_PREDICATE':
+                       return in_array ($expr['load'], $plist) ? NULL : $expr['load'];
+               case 'SYNT_NOTEXPR':
+                       return firstUnrefPredicate ($plist, $expr['load']);
+               case 'SYNT_BOOLOP':
+                       if (($tmp = firstUnrefPredicate ($plist, $expr['left'])) !== NULL)
+                               return $tmp;
+                       if (($tmp = firstUnrefPredicate ($plist, $expr['right'])) !== NULL)
+                               return $tmp;
+                       return NULL;
+               default:
+                       return NULL;
+       }
+}
+
+function semanticFilter ($code)
+{
+       $predicatelist = array();
+       foreach ($code as $sentence)
+               switch ($sentence['type'])
+               {
+                       case 'SYNT_DEFINITION':
+                               $up = firstUnrefPredicate ($predicatelist, $sentence['definition']);
+                               if ($up !== NULL)
+                                       return array
+                                       (
+                                               'result' => 'NAK',
+                                               'load' => "definition [${sentence['term']}] uses unknown predicate [${up}]"
+                                       );
+                               $predicatelist[] = $sentence['term'];
+                               break;
+                       case 'SYNT_GRANT':
+                               $up = firstUnrefPredicate ($predicatelist, $sentence['condition']);
+                               if ($up !== NULL)
+                                       return array
+                                       (
+                                               'result' => 'NAK',
+                                               'load' => "grant sentence uses unknown predicate [${up}]"
+                                       );
+                               break;
+                       default:
+                               return array ('result' => 'NAK', 'load' => 'unknown sentence type');
+               }
+       return array ('result' => 'ACK', 'load' => $code);
 }
 
 ?>