<?php
namespace eMacros;
use eMacros\Exception\ParseException;
class Parser {
/**
* Validated symbols
* @var array
*/
public static $map = array();
/*
* SYMBOL REGEX
*/
const PARENTHESES = '()';
const COMMENT_PREFIX = ';';
const WHITESPACES = " \t\n\r\f\v\0";
/**
* Float validation regex
* @var string
*/
const REAL_PATTERN = '{^[+-]?((\d+|(\d*\.\d+|\d+\.\d*))e[+-]?\d+|\d*\.\d+|\d+\.\d*)}i';
/**
* Integer validation regex
* @var unknown
*/
const INTEGER_PATTERN = '/^([+-]?)(0x([0-9a-f]+)|0([0-7]+)|[1-9]\d*|0)/i';
/**
* String validation regex
* @var string
*/
const STRING_PATTERN = '/^"([^"\\\\]|\\\\.)*"|^\'([^\'\\\\]|\\\\.)*\'/';
/**
* Escape string replacement regex
* @var string
*/
const STRING_ESCAPE_PATTERN = '/\\\\(([0-7]{1,3})|x([0-9A-Fa-f]{1,2})|.)/';
/**
* Symbol validation regex
* @var string
*/
const SYMBOL_PATTERN = '{^[^\s\d(){}\[\]"\';][^\s\'"(){}\[\];]*}';
/**
* Parses a program
* @param string $program
* @throws ParseException
* @return \eMacros\GenericList
*/
public static function parse($program) {
$i = 0;
$len = strlen($program);
$forms = array();
while ($i < $len) {
if (strpos(self::WHITESPACES, $program[$i]) === false) {
try {
$form = self::parseExpression(substr($program, $i), $offset);
if (!is_null($form)) $forms[] = $form;
}
catch (ParseException $e) {
throw new ParseException($program, $e->offset + $i);
}
$i += $offset;
}
else {
++$i;
}
}
return $forms;
}
/**
* Parses an inner expression
* @param string $form
* @param int $offset
* @throws ParseException
* @return mixed
*/
public static function parseExpression($form, &$offset) {
static $parentheses = null;
if (is_null($parentheses)) {
$_parentheses = self::PARENTHESES;
$parentheses = array();
for ($i = 0, $len = strlen($_parentheses); $i < $len; $i += 2) {
$parentheses[$_parentheses[$i]] = $_parentheses[$i + 1];
}
unset($_parentheses);
}
if (isset($form[0], $parentheses[$form[0]])) {
$end = $parentheses[$form[0]];
$values = array();
$i = 1;
$len = strlen($form);
while ($i < $len && $form[$i] != $end) {
if (strpos(self::WHITESPACES, $form[$i]) !== false) {
++$i;
continue;
}
try {
$values[] = self::parseExpression(substr($form, $i), $_offset);
$i += $_offset;
}
catch (ParseException $e) {
throw new ParseException($form, $i + $e->offset);
}
}
if (isset($form[$i]) && $form[$i] == $end) {
$offset = $i + 1;
return new GenericList($values);
}
throw new ParseException($form, $i);
}
elseif (isset($form[0]) && $form[0] == self::COMMENT_PREFIX) {
$offset = strlen(strtok($form, "\n"));
return null;
}
elseif (preg_match(self::REAL_PATTERN, $form, $matches)) {
$offset = strlen($matches[0]);
return new Literal((float) $matches[0]);
}
elseif (preg_match(self::INTEGER_PATTERN, $form, $matches)) {
$offset = strlen($matches[0]);
$sign = $matches[1] == '-' ? -1 : 1;
$value = !empty($matches[3]) ? hexdec($matches[3]) : (!empty($matches[4]) ? octdec($matches[4]) : $matches[2]);
return new Literal($sign * $value);
}
elseif (preg_match(self::STRING_PATTERN, $form, $matches)) {
list($parsed) = $matches;
$offset = strlen($parsed);
return new Literal(preg_replace_callback(self::STRING_ESCAPE_PATTERN, array(__CLASS__, 'unescapeString'), substr($parsed, 1, -1)));
}
elseif (preg_match(self::SYMBOL_PATTERN, $form, $matches)) {
$symbol = $matches[0];
$offset = strlen($matches[0]);
//store validated symbols in order to reduce checks
if (array_key_exists($symbol, self::$map)) {
return self::$map[$symbol];
}
self::$map[$symbol] = new Symbol($symbol);
return self::$map[$symbol];
}
throw new ParseException($form, 0);
}
/**
* Replaces special characters in a string
* @param array $matches
* @return string
*/
protected static function unescapeString($matches) {
static $map = array('n' => "\n", 'r' => "\r", 't' => "\t", 'v' => "\v", 'f' => "\f");
if (!empty($matches[2])) {
return chr(octdec($matches[2]));
}
elseif (!empty($matches[3])) {
return chr(hexdec($matches[3]));
}
elseif (isset($map[$matches[1]])) {
return $map[$matches[1]];
}
return $matches[1];
}
/**
* Flushes validated symbols table
*/
public static function flush() {
self::$map = array();
}
}
?>
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