<?php
// css_util.php - Cascading Style Sheets utilities
// Version 0.2  Sat, 25 Nov 2006 18:09:33 -0600
//
// Copyright (C) 2006  Dwayne C. Litzenberger <dlitz@dlitz.net>
// 
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

// This file provides some utilities for dealing with Cascading Style Sheets.
// See http://www.w3.org/TR/CSS2/

// css_encode -- Encode arbitrary character string for use as a CSS identifier.
//
// string css_encode ( string string )
//
// Encodes an arbitrary character string for use in a CSS identifier.
//
// See http://www.w3.org/TR/CSS2/syndata.html#q4
//
// This function assumes the latin1 character set.
//
function css_encode($string)
{
    // Replace all chars that are not alphanumeric and are not U+00A1 and above
    $string = preg_replace_callback('#([^A-Za-z0-9\xA1-\xFF])#s',
        '_css_encode__latin1_cb', $string);

    // Replace leading digit
    $string = preg_replace_callback('#^([0-9])#s',
        '_css_encode__latin1_cb', $string);

    return $string;
}

function _css_encode__latin1_cb($m)
{
    $charval = ord($m[1]);
    if (($charval >= 0x21 and $charval <= 0x2f) or
        ($charval >= 0x3a and $charval <= 0x40) or
        ($charval >= 0x5b and $charval <= 0x60) or
        ($charval >= 0x7b and $charval <= 0x7e))
    {
        return "\\".chr($charval);
    } else {
        return "\\".str_pad(dechex($charval), 2, '0', STR_PAD_LEFT).' ';
    }
}


// css_decode -- Decode a CSS-encoded identifier string.
//
// string css_decode ( string string )
//
// Decodes a character string that has been encoded according to CSS2
// conventions.
//
// See http://www.w3.org/TR/CSS2/syndata.html#q4
//
// This function assumes the latin1 character set.
//
function css_decode($string)
{
    $cbo = new _css_decode__callbacks();
    $cb = array($cbo, 'latin1_cb');
    $retval = preg_replace_callback(
        '#(\\\\\n)|\\\\([0-9A-Fa-f]{1,5})\s?|\\\\([0-9A-Fa-f]{6})|\\\\([^0-9A-Fa-f])#s',
        $cb, $string);
    if ($cb->error) {
        return false;
    }
    return $retval;
}

class _css_decode__callbacks
{
    var $error;
    function latin1_cb($m)
    {
        $this->error = false;
        if (!empty($m[1])) {
            // Inside a string, a backslash followed by a newline is ignored.
            return '';
        } else if (!empty($m[4])) {
            // "\C", where C is a non-hexadecimal character, returns C.
            return $m[4];
        } else if (!empty($m[2]) or !empty($m[3])) {
            if (!empty($m[2])) {
                $codepoint = hexdec($m[2]);
            } else {
                $codepoint = hexdec($m[3]);
            }
            if ($codepoint < 0 or $codepoint > 255) {
                trigger_error("css_decode: illegal character", E_USER_WARNING);
                $this->error = true;
                return FALSE;
            }
            return chr($codepoint);
        }
        die(__FILE__.":".__LINE__.": BUG: This should never happen.");
    }
}

// css_uri_specialchars -- Escape special characters in a CSS URI.
//
// string css_uri_specialchars ( string uri )
//
// css_encode() SHOULD be enough, at least according to my reading of the CSS2
// spec, but instead of treating backslashes as escape characters in "url(...)"
// values, MSIE 6 converts backslashes ("\") into path separators ("/"). Argh.
//
// So, we create a new function that doesn't use backslash-escaping, but
// instead just percent-encodes a few known special characters and leaves
// everything else alone.
//
// See http://www.w3.org/TR/CSS2/syndata.html#uri
//
function css_uri_specialchars($uri)
{
    // Percent-encode all characters except those expected to be in URIs
    // (Based on code from uri_util.php 0.7)
    $uri = preg_replace_callback('#([^A-Za-z0-9\-._~:/?\#\[\]@!$&\'()*+,;=%])#s', '_css_uri_specialchars__cb', $uri);

    // Percent-encode CSS URI special characters:
    //   DQUOTE / "'" / "\" / "(" / ")"
    $uri = preg_replace_callback("#([\"'\\\\()])#s", '_css_uri_specialchars__cb', $uri);

    return $uri;
}

function _css_uri_specialchars__cb($m)
{
    return '%'.strtoupper(bin2hex($m[1]));
}

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