3 Purell is a tiny Go library to normalize URLs. It returns a pure URL. Pure-ell. Sanitizer and all. Yeah, I know...
5 Based on the [wikipedia paper][wiki] and the [RFC 3986 document][rfc].
7 [![build status](https://travis-ci.org/PuerkitoBio/purell.svg?branch=master)](http://travis-ci.org/PuerkitoBio/purell)
11 `go get github.com/PuerkitoBio/purell`
15 * **v1.1.1** : Fix failing test due to Go1.12 changes (thanks to @ianlancetaylor).
16 * **2016-11-14 (v1.1.0)** : IDN: Conform to RFC 5895: Fold character width (thanks to @beeker1121).
17 * **2016-07-27 (v1.0.0)** : Normalize IDN to ASCII (thanks to @zenovich).
18 * **2015-02-08** : Add fix for relative paths issue ([PR #5][pr5]) and add fix for unnecessary encoding of reserved characters ([see issue #7][iss7]).
19 * **v0.2.0** : Add benchmarks, Attempt IDN support.
20 * **v0.1.0** : Initial release.
24 From `example_test.go` (note that in your code, you would import "github.com/PuerkitoBio/purell", and would prefix references to its methods and constants with "purell."):
34 func ExampleNormalizeURLString() {
35 if normalized, err := NormalizeURLString("hTTp://someWEBsite.com:80/Amazing%3f/url/",
36 FlagLowercaseScheme|FlagLowercaseHost|FlagUppercaseEscapes); err != nil {
41 // Output: http://somewebsite.com:80/Amazing%3F/url/
44 func ExampleMustNormalizeURLString() {
45 normalized := MustNormalizeURLString("hTTpS://someWEBsite.com:443/Amazing%fa/url/",
49 // Output: http://somewebsite.com/Amazing%FA/url
52 func ExampleNormalizeURL() {
53 if u, err := url.Parse("Http://SomeUrl.com:8080/a/b/.././c///g?c=3&a=1&b=9&c=0#target"); err != nil {
56 normalized := NormalizeURL(u, FlagsUsuallySafeGreedy|FlagRemoveDuplicateSlashes|FlagRemoveFragment)
60 // Output: http://someurl.com:8080/a/c/g?c=3&a=1&b=9&c=0
66 As seen in the examples above, purell offers three methods, `NormalizeURLString(string, NormalizationFlags) (string, error)`, `MustNormalizeURLString(string, NormalizationFlags) (string)` and `NormalizeURL(*url.URL, NormalizationFlags) (string)`. They all normalize the provided URL based on the specified flags. Here are the available flags:
70 // Safe normalizations
71 FlagLowercaseScheme NormalizationFlags = 1 << iota // HTTP://host -> http://host, applied by default in Go1.1
72 FlagLowercaseHost // http://HOST -> http://host
73 FlagUppercaseEscapes // http://host/t%ef -> http://host/t%EF
74 FlagDecodeUnnecessaryEscapes // http://host/t%41 -> http://host/tA
75 FlagEncodeNecessaryEscapes // http://host/!"#$ -> http://host/%21%22#$
76 FlagRemoveDefaultPort // http://host:80 -> http://host
77 FlagRemoveEmptyQuerySeparator // http://host/path? -> http://host/path
79 // Usually safe normalizations
80 FlagRemoveTrailingSlash // http://host/path/ -> http://host/path
81 FlagAddTrailingSlash // http://host/path -> http://host/path/ (should choose only one of these add/remove trailing slash flags)
82 FlagRemoveDotSegments // http://host/path/./a/b/../c -> http://host/path/a/c
84 // Unsafe normalizations
85 FlagRemoveDirectoryIndex // http://host/path/index.html -> http://host/path/
86 FlagRemoveFragment // http://host/path#fragment -> http://host/path
87 FlagForceHTTP // https://host -> http://host
88 FlagRemoveDuplicateSlashes // http://host/path//a///b -> http://host/path/a/b
89 FlagRemoveWWW // http://www.host/ -> http://host/
90 FlagAddWWW // http://host/ -> http://www.host/ (should choose only one of these add/remove WWW flags)
91 FlagSortQuery // http://host/path?c=3&b=2&a=1&b=1 -> http://host/path?a=1&b=1&b=2&c=3
93 // Normalizations not in the wikipedia article, required to cover tests cases
94 // submitted by jehiah
95 FlagDecodeDWORDHost // http://1113982867 -> http://66.102.7.147
96 FlagDecodeOctalHost // http://0102.0146.07.0223 -> http://66.102.7.147
97 FlagDecodeHexHost // http://0x42660793 -> http://66.102.7.147
98 FlagRemoveUnnecessaryHostDots // http://.host../path -> http://host/path
99 FlagRemoveEmptyPortSeparator // http://host:/path -> http://host/path
101 // Convenience set of safe normalizations
102 FlagsSafe NormalizationFlags = FlagLowercaseHost | FlagLowercaseScheme | FlagUppercaseEscapes | FlagDecodeUnnecessaryEscapes | FlagEncodeNecessaryEscapes | FlagRemoveDefaultPort | FlagRemoveEmptyQuerySeparator
104 // For convenience sets, "greedy" uses the "remove trailing slash" and "remove www. prefix" flags,
105 // while "non-greedy" uses the "add (or keep) the trailing slash" and "add www. prefix".
107 // Convenience set of usually safe normalizations (includes FlagsSafe)
108 FlagsUsuallySafeGreedy NormalizationFlags = FlagsSafe | FlagRemoveTrailingSlash | FlagRemoveDotSegments
109 FlagsUsuallySafeNonGreedy NormalizationFlags = FlagsSafe | FlagAddTrailingSlash | FlagRemoveDotSegments
111 // Convenience set of unsafe normalizations (includes FlagsUsuallySafe)
112 FlagsUnsafeGreedy NormalizationFlags = FlagsUsuallySafeGreedy | FlagRemoveDirectoryIndex | FlagRemoveFragment | FlagForceHTTP | FlagRemoveDuplicateSlashes | FlagRemoveWWW | FlagSortQuery
113 FlagsUnsafeNonGreedy NormalizationFlags = FlagsUsuallySafeNonGreedy | FlagRemoveDirectoryIndex | FlagRemoveFragment | FlagForceHTTP | FlagRemoveDuplicateSlashes | FlagAddWWW | FlagSortQuery
115 // Convenience set of all available flags
116 FlagsAllGreedy = FlagsUnsafeGreedy | FlagDecodeDWORDHost | FlagDecodeOctalHost | FlagDecodeHexHost | FlagRemoveUnnecessaryHostDots | FlagRemoveEmptyPortSeparator
117 FlagsAllNonGreedy = FlagsUnsafeNonGreedy | FlagDecodeDWORDHost | FlagDecodeOctalHost | FlagDecodeHexHost | FlagRemoveUnnecessaryHostDots | FlagRemoveEmptyPortSeparator
121 For convenience, the set of flags `FlagsSafe`, `FlagsUsuallySafe[Greedy|NonGreedy]`, `FlagsUnsafe[Greedy|NonGreedy]` and `FlagsAll[Greedy|NonGreedy]` are provided for the similarly grouped normalizations on [wikipedia's URL normalization page][wiki]. You can add (using the bitwise OR `|` operator) or remove (using the bitwise AND NOT `&^` operator) individual flags from the sets if required, to build your own custom set.
123 The [full godoc reference is available on gopkgdoc][godoc].
127 * `FlagDecodeUnnecessaryEscapes`, `FlagEncodeNecessaryEscapes`, `FlagUppercaseEscapes` and `FlagRemoveEmptyQuerySeparator` are always implicitly set, because internally, the URL string is parsed as an URL object, which automatically decodes unnecessary escapes, uppercases and encodes necessary ones, and removes empty query separators (an unnecessary `?` at the end of the url). So this operation cannot **not** be done. For this reason, `FlagRemoveEmptyQuerySeparator` (as well as the other three) has been included in the `FlagsSafe` convenience set, instead of `FlagsUnsafe`, where Wikipedia puts it.
129 * The `FlagDecodeUnnecessaryEscapes` decodes the following escapes (*from -> to*):
132 - %2B-%3B -> +,-./0123456789:;
134 - %40-%5A -> @ABCDEFGHIJKLMNOPQRSTUVWXYZ
136 - %61-%7A -> abcdefghijklmnopqrstuvwxyz
140 * When the `NormalizeURL` function is used (passing an URL object), this source URL object is modified (that is, after the call, the URL object will be modified to reflect the normalization).
142 * The *replace IP with domain name* normalization (`http://208.77.188.166/ → http://www.example.com/`) is obviously not possible for a library without making some network requests. This is not implemented in purell.
144 * The *remove unused query string parameters* and *remove default query parameters* are also not implemented, since this is a very case-specific normalization, and it is quite trivial to do with an URL object.
146 ### Safe vs Usually Safe vs Unsafe
148 Purell allows you to control the level of risk you take while normalizing an URL. You can aggressively normalize, play it totally safe, or anything in between.
150 Consider the following URL:
152 `HTTPS://www.RooT.com/toto/t%45%1f///a/./b/../c/?z=3&w=2&a=4&w=1#invalid`
154 Normalizing with the `FlagsSafe` gives:
156 `https://www.root.com/toto/tE%1F///a/./b/../c/?z=3&w=2&a=4&w=1#invalid`
158 With the `FlagsUsuallySafeGreedy`:
160 `https://www.root.com/toto/tE%1F///a/c?z=3&w=2&a=4&w=1#invalid`
162 And with `FlagsUnsafeGreedy`:
164 `http://root.com/toto/tE%1F/a/c?a=4&w=1&w=2&z=3`
168 * Add a class/default instance to allow specifying custom directory index names? At the moment, removing directory index removes `(^|/)((?:default|index)\.\w{1,4})$`.
170 ## Thanks / Contributions
181 The [BSD 3-Clause license][bsd].
183 [bsd]: http://opensource.org/licenses/BSD-3-Clause
184 [wiki]: http://en.wikipedia.org/wiki/URL_normalization
185 [rfc]: http://tools.ietf.org/html/rfc3986#section-6
186 [godoc]: http://go.pkgdoc.org/github.com/PuerkitoBio/purell
187 [pr5]: https://github.com/PuerkitoBio/purell/pull/5
188 [iss7]: https://github.com/PuerkitoBio/purell/issues/7