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Manual Reference Pages  - percent_decode (3m_strings)

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NAME

percent_decode(3f) - [M_strings:ENCODE] percent-decode strings and character arrays (LICENSE:ISC)

CONTENTS

Synopsis
Description
Options
Returns
Examples
Author

SYNOPSIS

function percent_decode(text,exit_code)

     character(len=1),intent(in)  :: text(:)
     integer,optional,intent(out) :: exit_code
     character(len=:),allocatable :: percent_decode

or

function percent_decode(text,exit_code)

     character(len=*),intent(in)  :: text
     integer,optional,intent(out) :: exit_code
     character(len=:),allocatable :: percent_decode

DESCRIPTION

percent_decode(3f) percent-decodes percent-encoded strings or character arrays.

URI containing spaces or most other non-alphanumeric characters must be encoded using percent encoding (aka. URL encoding). This procedure unwinds the encryption.

The characters allowed in a URI are either reserved or unreserved (or a percent character as part of a percent-encoding). Reserved characters are those characters that sometimes have special meaning, while unreserved characters have no such meaning. Using percent-encoding, characters which otherwise would not be allowed are represented using allowed characters. The sets of reserved and unreserved characters and the circumstances under which certain reserved characters have special meaning have changed slightly with each revision of specifications that govern URIs and URI schemes.

According to RFC 3986, the characters in a URL have to be taken from a defined set of unreserved and reserved ASCII characters. Any other characters are not allowed in a URL.

The unreserved characters can be encoded, but should not be. The unreserved characters are:

      > ABCDEFGHIJKLMNOPQRSTUVWXYZ
      > abcdefghijklmnopqrstuvwxyz
      > 0123456789-_.~

The reserved characters have to be encoded only under certain circumstances. The reserved characters are:

      >  * ’ ( ) ; : @ & = + $ , / ? % # [ ]

OPTIONS

SOURCE_STRING
	string or character array to decode
EXIT_CODE
	non-zero if decoding failed

RETURNS

percent_decode
	a string holding a percent-decoded copy of the input

EXAMPLES

Sample program:

      program demo_percent_decode
      use M_strings, only : percent_encode, percent_decode
      implicit none
      character(len=:),allocatable :: input,output
      character(len=*),parameter   :: see=’(g0,*("""",g0,"""":))’
      character(len=*),parameter   :: expected=’&
      &%01%02%03%04%05%06%07%08%09%0A%0B%0C%0D%0E%0F%10%11%12%13%14%15%&
      &16%17%18%19%1A%1B%1C%1D%1E%1F%20%21%22%23%24%25%26%27%28%29%2A%2&
      &B%2C-.%2F0123456789%3A%3B%3C%3D%3E%3F%40ABCDEFGHIJKLMNOPQRSTUVWX&
      &YZ%5B%5C%5D%5E_%60abcdefghijklmnopqrstuvwxyz%7B%7C%7D~%7F%80%81%&
      &82%83%84%85%86%87%88%89%8A%8B%8C%8D%8E%8F%90%91%92%93%94%95%96%9&
      &7%98%99%9A%9B%9C%9D%9E%9F%A0%A1%A2%A3%A4%A5%A6%A7%A8%A9%AA%AB%AC&
      &%AD%AE%AF%B0%B1%B2%B3%B4%B5%B6%B7%B8%B9%BA%BB%BC%BD%BE%BF%C0%C1%&
      &C2%C3%C4%C5%C6%C7%C8%C9%CA%CB%CC%CD%CE%CF%D0%D1%D2%D3%D4%D5%D6%D&
      &7%D8%D9%DA%DB%DC%DD%DE%DF%E0%E1%E2%E3%E4%E5%E6%E7%E8%E9%EA%EB%EC&
      &%ED%EE%EF%F0%F1%F2%F3%F4%F5%F6%F7%F8%F9%FA%FB%FC%FD%FE%FF%20’
      integer                      :: j
         input=’[this is a string]’
         write(*,see)’INPUT=’,input
         output=percent_encode(input)
         write(*,see)’ENCODED=’,output
         output=percent_decode(output)
         write(*,see)’DECODED=’,output
         input=repeat(’ ’,256)
         do j=0,255
               input(j:j)=char(j)
         enddo
         output=percent_encode(input)
         write(*,*)’ENCODING PASSED:’,output==expected
         output=percent_decode(output)
         write(*,*)’DECODING PASSED:’,input == output
      end program demo_percent_decode

Results:

    > INPUT="[this is a string]"
    > ENCODED="%5Bthis%20is%20a%20string%5D"
    > DECODED="[this is a string]"
    >  ENCODING PASSED: T
    >  DECODING PASSED: T

AUTHOR

o	based on dm_cgi_encode.f90, Copyright (c) 2023, Philipp Engel
o	Modified to be more aligned with percent_encode(3f), John S. Urban, 2024

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Nemo Release 3.1

percent_decode (3m_strings)

January 10, 2025

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