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.\" ========================================================================
.\"
.IX Title "URI::Escape 3pm"
.TH URI::Escape 3pm "2012-02-11" "perl v5.14.2" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
URI::Escape \- Percent\-encode and percent\-decode unsafe characters
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 4
\& use URI::Escape;
\& $safe = uri_escape("10% is enough\en");
\& $verysafe = uri_escape("foo", "\e0\-\e377");
\& $str  = uri_unescape($safe);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
This module provides functions to percent-encode and percent-decode \s-1URI\s0 strings as
defined by \s-1RFC\s0 3986. Percent-encoding \s-1URI\s0's is informally called \*(L"\s-1URI\s0 escaping\*(R".
This is the terminology used by this module, which predates the formalization of the
terms by the \s-1RFC\s0 by several years.
.PP
A \s-1URI\s0 consists of a restricted set of characters.  The restricted set
of characters consists of digits, letters, and a few graphic symbols
chosen from those common to most of the character encodings and input
facilities available to Internet users.  They are made up of the
\&\*(L"unreserved\*(R" and \*(L"reserved\*(R" character sets as defined in \s-1RFC\s0 3986.
.PP
.Vb 4
\&   unreserved    = ALPHA / DIGIT / "\-" / "." / "_" / "~"
\&   reserved      = ":" / "/" / "?" / "#" / "[" / "]" / "@"
\&                   "!" / "$" / "&" / "\*(Aq" / "(" / ")"
\&                 / "*" / "+" / "," / ";" / "="
.Ve
.PP
In addition, any byte (octet) can be represented in a \s-1URI\s0 by an escape
sequence: a triplet consisting of the character \*(L"%\*(R" followed by two
hexadecimal digits.  A byte can also be represented directly by a
character, using the US-ASCII character for that octet.
.PP
Some of the characters are \fIreserved\fR for use as delimiters or as
part of certain \s-1URI\s0 components.  These must be escaped if they are to
be treated as ordinary data.  Read \s-1RFC\s0 3986 for further details.
.PP
The functions provided (and exported by default) from this module are:
.ie n .IP "uri_escape( $string )" 4
.el .IP "uri_escape( \f(CW$string\fR )" 4
.IX Item "uri_escape( $string )"
.PD 0
.ie n .IP "uri_escape( $string, $unsafe )" 4
.el .IP "uri_escape( \f(CW$string\fR, \f(CW$unsafe\fR )" 4
.IX Item "uri_escape( $string, $unsafe )"
.PD
Replaces each unsafe character in the \f(CW$string\fR with the corresponding
escape sequence and returns the result.  The \f(CW$string\fR argument should
be a string of bytes.  The \fIuri_escape()\fR function will croak if given a
characters with code above 255.  Use \fIuri_escape_utf8()\fR if you know you
have such chars or/and want chars in the 128 .. 255 range treated as
\&\s-1UTF\-8\s0.
.Sp
The \fIuri_escape()\fR function takes an optional second argument that
overrides the set of characters that are to be escaped.  The set is
specified as a string that can be used in a regular expression
character class (between [ ]).  E.g.:
.Sp
.Vb 3
\&  "\ex00\-\ex1f\ex7f\-\exff"          # all control and hi\-bit characters
\&  "a\-z"                         # all lower case characters
\&  "^A\-Za\-z"                     # everything not a letter
.Ve
.Sp
The default set of characters to be escaped is all those which are
\&\fInot\fR part of the \f(CW\*(C`unreserved\*(C'\fR character class shown above as well
as the reserved characters.  I.e. the default is:
.Sp
.Vb 1
\&    "^A\-Za\-z0\-9\e\-\e._~"
.Ve
.ie n .IP "uri_escape_utf8( $string )" 4
.el .IP "uri_escape_utf8( \f(CW$string\fR )" 4
.IX Item "uri_escape_utf8( $string )"
.PD 0
.ie n .IP "uri_escape_utf8( $string, $unsafe )" 4
.el .IP "uri_escape_utf8( \f(CW$string\fR, \f(CW$unsafe\fR )" 4
.IX Item "uri_escape_utf8( $string, $unsafe )"
.PD
Works like \fIuri_escape()\fR, but will encode chars as \s-1UTF\-8\s0 before
escaping them.  This makes this function able to deal with characters
with code above 255 in \f(CW$string\fR.  Note that chars in the 128 .. 255
range will be escaped differently by this function compared to what
\&\fIuri_escape()\fR would.  For chars in the 0 .. 127 range there is no
difference.
.Sp
Equivalent to:
.Sp
.Vb 2
\&    utf8::encode($string);
\&    my $uri = uri_escape($string);
.Ve
.Sp
Note: JavaScript has a function called \fIescape()\fR that produces the
sequence \*(L"%uXXXX\*(R" for chars in the 256 .. 65535 range.  This function
has really nothing to do with \s-1URI\s0 escaping but some folks got confused
since it \*(L"does the right thing\*(R" in the 0 .. 255 range.  Because of
this you sometimes see \*(L"URIs\*(R" with these kind of escapes.  The
JavaScript \fIencodeURIComponent()\fR function is similar to \fIuri_escape_utf8()\fR.
.IP "uri_unescape($string,...)" 4
.IX Item "uri_unescape($string,...)"
Returns a string with each \f(CW%XX\fR sequence replaced with the actual byte
(octet).
.Sp
This does the same as:
.Sp
.Vb 1
\&   $string =~ s/%([0\-9A\-Fa\-f]{2})/chr(hex($1))/eg;
.Ve
.Sp
but does not modify the string in-place as this \s-1RE\s0 would.  Using the
\&\fIuri_unescape()\fR function instead of the \s-1RE\s0 might make the code look
cleaner and is a few characters less to type.
.Sp
In a simple benchmark test I did,
calling the function (instead of the inline \s-1RE\s0 above) if a few chars
were unescaped was something like 40% slower, and something like 700% slower if none were.  If
you are going to unescape a lot of times it might be a good idea to
inline the \s-1RE\s0.
.Sp
If the \fIuri_unescape()\fR function is passed multiple strings, then each
one is returned unescaped.
.PP
The module can also export the \f(CW%escapes\fR hash, which contains the
mapping from all 256 bytes to the corresponding escape codes.  Lookup
in this hash is faster than evaluating \f(CW\*(C`sprintf("%%%02X", ord($byte))\*(C'\fR
each time.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\s-1URI\s0
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright 1995\-2004 Gisle Aas.
.PP
This program is free software; you can redistribute it and/or modify
it under the same terms as Perl itself.