mirror of
https://github.com/renbaoshuo/S2OJ.git
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96d4a3ecf7
Due to historical reasons, the code is in subfolder "1". With SVN removal, we place the code back and remove the annoying "1" folder.
220 lines
9.2 KiB
PHP
220 lines
9.2 KiB
PHP
<?php
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/**
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* Validates a font family list according to CSS spec
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*/
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class HTMLPurifier_AttrDef_CSS_FontFamily extends HTMLPurifier_AttrDef
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{
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protected $mask = null;
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public function __construct()
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{
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$this->mask = '_- ';
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for ($c = 'a'; $c <= 'z'; $c++) {
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$this->mask .= $c;
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}
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for ($c = 'A'; $c <= 'Z'; $c++) {
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$this->mask .= $c;
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}
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for ($c = '0'; $c <= '9'; $c++) {
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$this->mask .= $c;
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} // cast-y, but should be fine
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// special bytes used by UTF-8
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for ($i = 0x80; $i <= 0xFF; $i++) {
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// We don't bother excluding invalid bytes in this range,
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// because the our restriction of well-formed UTF-8 will
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// prevent these from ever occurring.
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$this->mask .= chr($i);
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}
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/*
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PHP's internal strcspn implementation is
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O(length of string * length of mask), making it inefficient
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for large masks. However, it's still faster than
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preg_match 8)
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for (p = s1;;) {
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spanp = s2;
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do {
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if (*spanp == c || p == s1_end) {
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return p - s1;
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}
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} while (spanp++ < (s2_end - 1));
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c = *++p;
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}
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*/
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// possible optimization: invert the mask.
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}
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/**
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* @param string $string
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* @param HTMLPurifier_Config $config
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* @param HTMLPurifier_Context $context
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* @return bool|string
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*/
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public function validate($string, $config, $context)
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{
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static $generic_names = array(
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'serif' => true,
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'sans-serif' => true,
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'monospace' => true,
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'fantasy' => true,
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'cursive' => true
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);
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$allowed_fonts = $config->get('CSS.AllowedFonts');
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// assume that no font names contain commas in them
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$fonts = explode(',', $string);
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$final = '';
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foreach ($fonts as $font) {
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$font = trim($font);
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if ($font === '') {
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continue;
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}
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// match a generic name
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if (isset($generic_names[$font])) {
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if ($allowed_fonts === null || isset($allowed_fonts[$font])) {
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$final .= $font . ', ';
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}
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continue;
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}
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// match a quoted name
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if ($font[0] === '"' || $font[0] === "'") {
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$length = strlen($font);
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if ($length <= 2) {
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continue;
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}
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$quote = $font[0];
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if ($font[$length - 1] !== $quote) {
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continue;
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}
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$font = substr($font, 1, $length - 2);
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}
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$font = $this->expandCSSEscape($font);
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// $font is a pure representation of the font name
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if ($allowed_fonts !== null && !isset($allowed_fonts[$font])) {
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continue;
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}
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if (ctype_alnum($font) && $font !== '') {
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// very simple font, allow it in unharmed
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$final .= $font . ', ';
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continue;
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}
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// bugger out on whitespace. form feed (0C) really
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// shouldn't show up regardless
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$font = str_replace(array("\n", "\t", "\r", "\x0C"), ' ', $font);
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// Here, there are various classes of characters which need
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// to be treated differently:
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// - Alphanumeric characters are essentially safe. We
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// handled these above.
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// - Spaces require quoting, though most parsers will do
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// the right thing if there aren't any characters that
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// can be misinterpreted
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// - Dashes rarely occur, but they fairly unproblematic
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// for parsing/rendering purposes.
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// The above characters cover the majority of Western font
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// names.
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// - Arbitrary Unicode characters not in ASCII. Because
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// most parsers give little thought to Unicode, treatment
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// of these codepoints is basically uniform, even for
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// punctuation-like codepoints. These characters can
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// show up in non-Western pages and are supported by most
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// major browsers, for example: "ＭＳ 明朝" is a
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// legitimate font-name
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// <http://ja.wikipedia.org/wiki/MS_明朝>. See
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// the CSS3 spec for more examples:
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// <http://www.w3.org/TR/2011/WD-css3-fonts-20110324/localizedfamilynames.png>
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// You can see live samples of these on the Internet:
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// <http://www.google.co.jp/search?q=font-family+ＭＳ+明朝|ゴシック>
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// However, most of these fonts have ASCII equivalents:
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// for example, 'MS Mincho', and it's considered
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// professional to use ASCII font names instead of
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// Unicode font names. Thanks Takeshi Terada for
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// providing this information.
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// The following characters, to my knowledge, have not been
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// used to name font names.
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// - Single quote. While theoretically you might find a
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// font name that has a single quote in its name (serving
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// as an apostrophe, e.g. Dave's Scribble), I haven't
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// been able to find any actual examples of this.
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// Internet Explorer's cssText translation (which I
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// believe is invoked by innerHTML) normalizes any
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// quoting to single quotes, and fails to escape single
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// quotes. (Note that this is not IE's behavior for all
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// CSS properties, just some sort of special casing for
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// font-family). So a single quote *cannot* be used
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// safely in the font-family context if there will be an
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// innerHTML/cssText translation. Note that Firefox 3.x
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// does this too.
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// - Double quote. In IE, these get normalized to
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// single-quotes, no matter what the encoding. (Fun
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// fact, in IE8, the 'content' CSS property gained
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// support, where they special cased to preserve encoded
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// double quotes, but still translate unadorned double
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// quotes into single quotes.) So, because their
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// fixpoint behavior is identical to single quotes, they
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// cannot be allowed either. Firefox 3.x displays
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// single-quote style behavior.
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// - Backslashes are reduced by one (so \\ -> \) every
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// iteration, so they cannot be used safely. This shows
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// up in IE7, IE8 and FF3
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// - Semicolons, commas and backticks are handled properly.
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// - The rest of the ASCII punctuation is handled properly.
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// We haven't checked what browsers do to unadorned
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// versions, but this is not important as long as the
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// browser doesn't /remove/ surrounding quotes (as IE does
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// for HTML).
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//
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// With these results in hand, we conclude that there are
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// various levels of safety:
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// - Paranoid: alphanumeric, spaces and dashes(?)
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// - International: Paranoid + non-ASCII Unicode
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// - Edgy: Everything except quotes, backslashes
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// - NoJS: Standards compliance, e.g. sod IE. Note that
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// with some judicious character escaping (since certain
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// types of escaping doesn't work) this is theoretically
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// OK as long as innerHTML/cssText is not called.
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// We believe that international is a reasonable default
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// (that we will implement now), and once we do more
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// extensive research, we may feel comfortable with dropping
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// it down to edgy.
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// Edgy: alphanumeric, spaces, dashes, underscores and Unicode. Use of
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// str(c)spn assumes that the string was already well formed
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// Unicode (which of course it is).
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if (strspn($font, $this->mask) !== strlen($font)) {
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continue;
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}
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// Historical:
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// In the absence of innerHTML/cssText, these ugly
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// transforms don't pose a security risk (as \\ and \"
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// might--these escapes are not supported by most browsers).
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// We could try to be clever and use single-quote wrapping
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// when there is a double quote present, but I have choosen
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// not to implement that. (NOTE: you can reduce the amount
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// of escapes by one depending on what quoting style you use)
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// $font = str_replace('\\', '\\5C ', $font);
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// $font = str_replace('"', '\\22 ', $font);
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// $font = str_replace("'", '\\27 ', $font);
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// font possibly with spaces, requires quoting
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$final .= "'$font', ";
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}
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$final = rtrim($final, ', ');
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if ($final === '') {
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return false;
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}
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return $final;
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}
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}
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// vim: et sw=4 sts=4
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