Buu Nguyen

[C#] On Modify relative urls in a css file

2009-11-01T06:52:47-08:00

@Ants: that's an interesting observation. I am not aware of any source saying "../" is not allowed in the middle/end either. I'm thinking whether this is typical enough to tackle it in the code though.

Thanks for the link, it's a super cool technique.

[C#] On Modify relative urls in a css file

2009-10-31T09:52:21-07:00

@Ants: Thanks. You're right about the bug in line 21. Re. 22-29, I don't think "path/to/../to/image.gif" is a valid CSS URL. How do you come up with that in the first place :)?

The newly refactored code is below.

private static string FixUrl(string cssPath, Match match)
{
	try
	{
		const string template = "url(\"{0}\")";
		var url = match.Groups["url"].Value.Trim('\"', '\'');
		if (url.StartsWith("/"))
			return string.Format(template, url);

		var cssFolder = cssPath.Substring(0, cssPath.LastIndexOf("/"));
		var backFolderCount = Regex.Matches(url, @"\.\./").Count;
		for (int i = 0; i < backFolderCount; i++)
		{
			url = url.Substring(3); // skip 1 '../'
			cssFolder = cssFolder.Substring(0, cssFolder.LastIndexOf("/")); // move back 1 folder
		}
		return string.Format(template, cssFolder + "/" + url);
	}
	catch (Exception ex)
	{
		return match.Value;
	}
}

[C#] Modify relative urls in a css file

2009-10-30T16:39:57-07:00

This function changes all URLs inside a CSS file which are relative to the path of that CSS file into URLs which are relative to the web application. For instance, if the CSS file path is /content/site.css, then:
- Any occurence of url(path/to/image.gif) will become url(/content/path/to/image.gif)
- Any occurence of url(../path/to/image.gif) will become url(/path/to/image.gif)
- ...

public string Transform(string cssPath, string cssContent)
{
        return Regex.Replace(cssContent, @"url\((?<url>.*?)\)", 
			match => FixUrl(cssPath, match),
			RegexOptions.IgnoreCase | RegexOptions.Singleline | RegexOptions.ExplicitCapture);
}

/// <summary>
/// Assume cssPath is /content/site.css:
///     * in: path/to/image.gif     -> out: /content/path/to/image.gif
///     * in: ../path/to/image.gif  -> out: /path/to/image.gif
///     * in: /path/to/image.gif    -> out: /path/to/image.gif
/// </summary>
private static string FixUrl(string cssPath, Match match)
{
	try
	{
		var url = match.Groups["url"].Value;
		const string template = "url({0})";
		if (url.StartsWith("/"))
			return url;
		var adjustedResourceFolder = cssPath.Substring(0, resourcePath.LastIndexOf("/"));
		var backFolderCount = Regex.Matches(url, @"\.\./").Count;
		for (int i = 0; i < backFolderCount; i++)
		{
			url = url.Substring(3);
			adjustedResourceFolder = adjustedResourceFolder.Substring(0,
				adjustedResourceFolder.LastIndexOf("/"));
		}
		return string.Format(template, (adjustedResourceFolder + "/" + url));
	}
	catch (Exception ex)
	{
		return match.Value;
	}
}