2 URI Codec: Encoding and Decoding URIs
The net/uri-codec module provides utilities for encoding and decoding strings using the URI encoding rules given in RFC 2396 [RFC2396], and to encode and decode name/value pairs using the application/x-www-form-urlencoded mimetype given the in HTML 4.0 specification. There are minor differences between the two encodings.
The URI encoding uses allows a few characters to be represented as-is: a through z, A through Z, 0-9, -, _, ., !, ~, *, ', ( and ). The remaining characters are encoded as %⟨xx⟩, where ⟨xx⟩ is the two-character hex representation of the integer value of the character (where the mapping character–integer is determined by US-ASCII if the integer is less than 128).
The encoding, in line with RFC 2396’s recommendation, represents a character as-is, if possible. The decoding allows any characters to be represented by their hex values, and allows characters to be incorrectly represented as-is.
The rules for the application/x-www-form-urlencoded mimetype given in the HTML 4.0 spec are:
Control names and values are escaped. Space characters are replaced by +, and then reserved characters are escaped as described in RFC 1738, section 2.2: Non-alphanumeric characters are replaced by %⟨xx⟩ representing the ASCII code of the character. Line breaks are represented as CRLF pairs: %0D%0A. Note that RFC 2396 supersedes RFC 1738 [RFC1738].
The control names/values are listed in the order they appear in the document. The name is separated from the value by = and name/value pairs are separated from each other by either ; or &. When encoding, ; is used as the separator by default. When decoding, both ; and & are parsed as separators by default.
These rules differs slightly from the straight encoding in RFC 2396 in that + is allowed, and it represents a space. The net/uri-codec library follows this convention, encoding a space as + and decoding + as a space. In addtion, since there appear to be some brain-dead decoders on the web, the library also encodes !, ~, ', (, and ) using their hex representation, which is the same choice as made by the Java’s URLEncoder.
2.1 Functions
(uri-encode str) → string? |
str : string? |
Encode a string using the URI encoding rules.
(uri-decode str) → string? |
str : string? |
Decode a string using the URI decoding rules.
(form-urlencoded-encode str) → string? |
str : string? |
Encode a string using the application/x-www-form-urlencoded encoding rules. The result string contains no non-ASCII characters.
(form-urlencoded-deecode str) → string? |
str : string? |
Decode a string encoded using the application/x-www-form-urlencoded encoding rules.
(alist->form-urlencoded alist) → string? |
Encode an association list using the application/x-www-form-urlencoded encoding rules.
The current-alist-separator-mode parameter determines the separator used in the result.
(form-urlencoded->alist str) |
str : string |
Decode a string encoded using the application/x-www-form-urlencoded encoding rules into an association list. All keys are case-folded for conversion to symbols.
The current-alist-separator-mode parameter determines the way that separators are parsed in the input.
→ (one-of/c 'amp 'semi 'amp-or-semi 'semi-or-amp) |
(current-alist-separator-mode mode) → void? |
mode : (one-of/c 'amp 'semi 'amp-or-semi 'semi-or-amp) |
A parameter that determines the separator used/recognized between associations in form-urlencoded->alist, alist->form-urlencoded, url->string, and string->url.
The default value is 'amp-or-semi, which means that both & and ; are treated as separators when parsing, and & is used as a separator when encoding. The other modes use/recognize only of the separators.
Examples: |
> (define ex '((x . "foo") (y . "bar") (z . "baz"))) |
> (current-alist-separator-mode 'amp) ; try 'amp... |
> (form-urlencoded->alist "x=foo&y=bar&z=baz") |
((x . "foo") (y . "bar") (z . "baz")) |
> (form-urlencoded->alist "x=foo;y=bar;z=baz") |
((x . "foo;y=bar;z=baz")) |
> (alist->form-urlencoded ex) |
"x=foo&y=bar&z=baz" |
> (current-alist-separator-mode 'semi) ; try 'semi... |
> (form-urlencoded->alist "x=foo;y=bar;z=baz") |
((x . "foo") (y . "bar") (z . "baz")) |
> (form-urlencoded->alist "x=foo&y=bar&z=baz") |
((x . "foo&y=bar&z=baz")) |
> (alist->form-urlencoded ex) |
"x=foo;y=bar;z=baz" |
> (current-alist-separator-mode 'amp-or-semi) ; try 'amp-or-semi... |
> (form-urlencoded->alist "x=foo&y=bar&z=baz") |
((x . "foo") (y . "bar") (z . "baz")) |
> (form-urlencoded->alist "x=foo;y=bar;z=baz") |
((x . "foo") (y . "bar") (z . "baz")) |
> (alist->form-urlencoded ex) |
"x=foo&y=bar&z=baz" |
> (current-alist-separator-mode 'semi-or-amp) ; try 'semi-or-amp... |
> (form-urlencoded->alist "x=foo&y=bar&z=baz") |
((x . "foo") (y . "bar") (z . "baz")) |
> (form-urlencoded->alist "x=foo;y=bar;z=baz") |
((x . "foo") (y . "bar") (z . "baz")) |
> (alist->form-urlencoded ex) |
"x=foo;y=bar;z=baz" |