From 155c39a9495a17bcfe02aa2f20ba161145ab4601 Mon Sep 17 00:00:00 2001 From: Burdette Lamar Date: Tue, 7 Nov 2023 00:59:41 -0600 Subject: [PATCH] Enhanced Rdoc for Base64 (#7) * Enhanced Rdoc for Base64 * Enhanced RDoc for Base64 --- lib/base64.rb | 370 ++++++++++++++++++++++++++++++++++++++++++-------- 1 file changed, 310 insertions(+), 60 deletions(-) diff --git a/lib/base64.rb b/lib/base64.rb index 15c0b29..59f66f8 100644 --- a/lib/base64.rb +++ b/lib/base64.rb @@ -1,88 +1,330 @@ # frozen_string_literal: true # -# = base64.rb: methods for base64-encoding and -decoding strings +# \Module \Base64 provides methods for: # - -# The Base64 module provides for the encoding (#encode64, #strict_encode64, -# #urlsafe_encode64) and decoding (#decode64, #strict_decode64, -# #urlsafe_decode64) of binary data using a Base64 representation. +# - Encoding a binary string (containing non-ASCII characters) +# as a string of printable ASCII characters. +# - Decoding such an encoded string. # -# == Example +# \Base64 is commonly used in contexts where binary data +# is not allowed or supported: # -# A simple encoding and decoding. +# - Images in HTML or CSS files, or in URLs. +# - Email attachments. # -# require "base64" +# A \Base64-encoded string is about one-third larger that its source. +# See the {Wikipedia article}[https://en.wikipedia.org/wiki/Base64] +# for more information. # -# enc = Base64.encode64('Send reinforcements') -# # -> "U2VuZCByZWluZm9yY2VtZW50cw==\n" -# plain = Base64.decode64(enc) -# # -> "Send reinforcements" +# This module provides three pairs of encode/decode methods. +# Your choices among these methods should depend on: +# +# - Which character set is to be used for encoding and decoding. +# - Whether "padding" is to be used. +# - Whether encoded strings are to contain newlines. +# +# Note: Examples on this page assume that the including program has executed: +# +# require 'base64' +# +# == Encoding Character Sets +# +# A \Base64-encoded string consists only of characters from a 64-character set: +# +# - ('A'..'Z'). +# - ('a'..'z'). +# - ('0'..'9'). +# - =, the 'padding' character. +# - Either: +# - %w[+ /]: +# {RFC-2045-compliant}[https://datatracker.ietf.org/doc/html/rfc2045]; +# _not_ safe for URLs. +# - %w[- _]: +# {RFC-4648-compliant}[https://datatracker.ietf.org/doc/html/rfc4648]; +# safe for URLs. +# +# If you are working with \Base64-encoded strings that will come from +# or be put into URLs, you should choose this encoder-decoder pair +# of RFC-4648-compliant methods: +# +# - Base64.urlsafe_encode64 and Base64.urlsafe_decode64. +# +# Otherwise, you may choose any of the pairs in this module, +# including the pair above, or the RFC-2045-compliant pairs: +# +# - Base64.encode64 and Base64.decode64. +# - Base64.strict_encode64 and Base64.strict_decode64. +# +# == Padding +# +# \Base64-encoding changes a triplet of input bytes +# into a quartet of output characters. +# +# Padding in Encode Methods +# +# Padding -- extending an encoded string with zero, one, or two trailing +# = characters -- is performed by methods Base64.encode64, +# Base64.strict_encode64, and, by default, Base64.urlsafe_encode64: +# +# Base64.encode64('s') # => "cw==\n" +# Base64.strict_encode64('s') # => "cw==" +# Base64.urlsafe_encode64('s') # => "cw==" +# Base64.urlsafe_encode64('s', padding: false) # => "cw" +# +# When padding is performed, the encoded string is always of length 4n, +# where +n+ is a non-negative integer: +# +# - Input bytes of length 3n generate unpadded output characters +# of length 4n: +# +# # n = 1: 3 bytes => 4 characters. +# Base64.strict_encode64('123') # => "MDEy" +# # n = 2: 6 bytes => 8 characters. +# Base64.strict_encode64('123456') # => "MDEyMzQ1" +# +# - Input bytes of length 3n+1 generate padded output characters +# of length 4(n+1), with two padding characters at the end: +# +# # n = 1: 4 bytes => 8 characters. +# Base64.strict_encode64('1234') # => "MDEyMw==" +# # n = 2: 7 bytes => 12 characters. +# Base64.strict_encode64('1234567') # => "MDEyMzQ1Ng==" +# +# - Input bytes of length 3n+2 generate padded output characters +# of length 4(n+1), with one padding character at the end: +# +# # n = 1: 5 bytes => 8 characters. +# Base64.strict_encode64('12345') # => "MDEyMzQ=" +# # n = 2: 8 bytes => 12 characters. +# Base64.strict_encode64('12345678') # => "MDEyMzQ1Njc=" +# +# When padding is suppressed, for a positive integer n: +# +# - Input bytes of length 3n generate unpadded output characters +# of length 4n: +# +# # n = 1: 3 bytes => 4 characters. +# Base64.urlsafe_encode64('123', padding: false) # => "MDEy" +# # n = 2: 6 bytes => 8 characters. +# Base64.urlsafe_encode64('123456', padding: false) # => "MDEyMzQ1" +# +# - Input bytes of length 3n+1 generate unpadded output characters +# of length 4n+2, with two padding characters at the end: +# +# # n = 1: 4 bytes => 6 characters. +# Base64.urlsafe_encode64('1234', padding: false) # => "MDEyMw" +# # n = 2: 7 bytes => 10 characters. +# Base64.urlsafe_encode64('1234567', padding: false) # => "MDEyMzQ1Ng" +# +# - Input bytes of length 3n+2 generate unpadded output characters +# of length 4n+3, with one padding character at the end: +# +# # n = 1: 5 bytes => 7 characters. +# Base64.urlsafe_encode64('12345', padding: false) # => "MDEyMzQ" +# # m = 2: 8 bytes => 11 characters. +# Base64.urlsafe_encode64('12345678', padding: false) # => "MDEyMzQ1Njc" +# +# Padding in Decode Methods +# +# All of the \Base64 decode methods support (but do not require) padding. +# +# \Method Base64.decode64 does not check the size of the padding: +# +# Base64.decode64("MDEyMzQ1Njc") # => "01234567" +# Base64.decode64("MDEyMzQ1Njc=") # => "01234567" +# Base64.decode64("MDEyMzQ1Njc==") # => "01234567" +# +# \Method Base64.strict_decode64 strictly enforces padding size: +# +# Base64.strict_decode64("MDEyMzQ1Njc") # Raises ArgumentError +# Base64.strict_decode64("MDEyMzQ1Njc=") # => "01234567" +# Base64.strict_decode64("MDEyMzQ1Njc==") # Raises ArgumentError +# +# \Method Base64.urlsafe_decode64 allows padding in +str+, +# which if present, must be correct: +# see {Padding}[Base64.html#module-Base64-label-Padding], above: +# +# Base64.urlsafe_decode64("MDEyMzQ1Njc") # => "01234567" +# Base64.urlsafe_decode64("MDEyMzQ1Njc=") # => "01234567" +# Base64.urlsafe_decode64("MDEyMzQ1Njc==") # Raises ArgumentError. +# +# == Newlines +# +# An encoded string returned by Base64.encode64 or Base64.urlsafe_encode64 +# has an embedded newline character +# after each 60-character sequence, and, if non-empty, at the end: +# +# # No newline if empty. +# encoded = Base64.encode64("\x00" * 0) +# encoded.index("\n") # => nil +# +# # Newline at end of short output. +# encoded = Base64.encode64("\x00" * 1) +# encoded.size # => 4 +# encoded.index("\n") # => 4 +# +# # Newline at end of longer output. +# encoded = Base64.encode64("\x00" * 45) +# encoded.size # => 60 +# encoded.index("\n") # => 60 +# +# # Newlines embedded and at end of still longer output. +# encoded = Base64.encode64("\x00" * 46) +# encoded.size # => 65 +# encoded.rindex("\n") # => 65 +# encoded.split("\n").map {|s| s.size } # => [60, 4] +# +# The string to be encoded may itself contain newlines, +# which are encoded as \Base64: +# +# # Base64.encode64("\n\n\n") # => "CgoK\n" +# s = "This is line 1\nThis is line 2\n" +# Base64.encode64(s) # => "VGhpcyBpcyBsaW5lIDEKVGhpcyBpcyBsaW5lIDIK\n" # -# The purpose of using base64 to encode data is that it translates any -# binary data into purely printable characters. - module Base64 VERSION = "0.1.1" module_function - # Returns the Base64-encoded version of +bin+. - # This method complies with RFC 2045. - # Line feeds are added to every 60 encoded characters. + # Returns a string containing the RFC-2045-compliant \Base64-encoding of +bin+. + # + # Per RFC 2045, the returned string may contain the URL-unsafe characters + # + or /; + # see {Encoding Character Set}[Base64.html#module-Base64-label-Encoding+Character+Sets] above: + # + # Base64.encode64("\xFB\xEF\xBE") # => "++++\n" + # Base64.encode64("\xFF\xFF\xFF") # => "////\n" + # + # The returned string may include padding; + # see {Padding}[Base64.html#module-Base64-label-Padding] above. # - # require 'base64' - # Base64.encode64("Now is the time for all good coders\nto learn Ruby") + # Base64.encode64('*') # => "Kg==\n" # - # Generates: + # The returned string ends with a newline character, and if sufficiently long + # will have one or more embedded newline characters; + # see {Newlines}[Base64.html#module-Base64-label-Newlines] above: + # + # Base64.encode64('*') # => "Kg==\n" + # Base64.encode64('*' * 46) + # # => "KioqKioqKioqKioqKioqKioqKioqKioqKioqKioqKioqKioqKioqKioqKioq\nKg==\n" + # + # The string to be encoded may itself contain newlines, + # which will be encoded as ordinary \Base64: + # + # Base64.encode64("\n\n\n") # => "CgoK\n" + # s = "This is line 1\nThis is line 2\n" + # Base64.encode64(s) # => "VGhpcyBpcyBsaW5lIDEKVGhpcyBpcyBsaW5lIDIK\n" # - # Tm93IGlzIHRoZSB0aW1lIGZvciBhbGwgZ29vZCBjb2RlcnMKdG8gbGVhcm4g - # UnVieQ== def encode64(bin) [bin].pack("m") end - # Returns the Base64-decoded version of +str+. - # This method complies with RFC 2045. - # Characters outside the base alphabet are ignored. - # - # require 'base64' - # str = 'VGhpcyBpcyBsaW5lIG9uZQpUaGlzIG' + - # 'lzIGxpbmUgdHdvClRoaXMgaXMgbGlu' + - # 'ZSB0aHJlZQpBbmQgc28gb24uLi4K' - # puts Base64.decode64(str) - # - # Generates: - # - # This is line one - # This is line two - # This is line three - # And so on... + # Returns a string containing the decoding of an RFC-2045-compliant + # \Base64-encoded string +str+: + # + # s = "VGhpcyBpcyBsaW5lIDEKVGhpcyBpcyBsaW5lIDIK\n" + # Base64.decode64(s) # => "This is line 1\nThis is line 2\n" + # + # Non-\Base64 characters in +str+ are ignored; + # see {Encoding Character Set}[Base64.html#module-Base64-label-Encoding+Character+Sets] above: + # these include newline characters and characters - and /: + # + # Base64.decode64("\x00\n-_") # => "" + # + # Padding in +str+ (even if incorrect) is ignored: + # + # Base64.decode64("MDEyMzQ1Njc") # => "01234567" + # Base64.decode64("MDEyMzQ1Njc=") # => "01234567" + # Base64.decode64("MDEyMzQ1Njc==") # => "01234567" + # def decode64(str) str.unpack1("m") end - # Returns the Base64-encoded version of +bin+. - # This method complies with RFC 4648. - # No line feeds are added. + # Returns a string containing the RFC-2045-compliant \Base64-encoding of +bin+. + # + # Per RFC 2045, the returned string may contain the URL-unsafe characters + # + or /; + # see {Encoding Character Set}[Base64.html#module-Base64-label-Encoding+Character+Sets] above: + # + # Base64.strict_encode64("\xFB\xEF\xBE") # => "++++\n" + # Base64.strict_encode64("\xFF\xFF\xFF") # => "////\n" + # + # The returned string may include padding; + # see {Padding}[Base64.html#module-Base64-label-Padding] above. + # + # Base64.strict_encode64('*') # => "Kg==\n" + # + # The returned string will have no newline characters, regardless of its length; + # see {Newlines}[Base64.html#module-Base64-label-Newlines] above: + # + # Base64.strict_encode64('*') # => "Kg==" + # Base64.strict_encode64('*' * 46) + # # => "KioqKioqKioqKioqKioqKioqKioqKioqKioqKioqKioqKioqKioqKioqKioqKg==" + # + # The string to be encoded may itself contain newlines, + # which will be encoded as ordinary \Base64: + # + # Base64.strict_encode64("\n\n\n") # => "CgoK" + # s = "This is line 1\nThis is line 2\n" + # Base64.strict_encode64(s) # => "VGhpcyBpcyBsaW5lIDEKVGhpcyBpcyBsaW5lIDIK" + # def strict_encode64(bin) [bin].pack("m0") end - # Returns the Base64-decoded version of +str+. - # This method complies with RFC 4648. - # ArgumentError is raised if +str+ is incorrectly padded or contains - # non-alphabet characters. Note that CR or LF are also rejected. + # Returns a string containing the decoding of an RFC-2045-compliant + # \Base64-encoded string +str+: + # + # s = "VGhpcyBpcyBsaW5lIDEKVGhpcyBpcyBsaW5lIDIK" + # Base64.strict_decode64(s) # => "This is line 1\nThis is line 2\n" + # + # Non-\Base64 characters in +str+ not allowed; + # see {Encoding Character Set}[Base64.html#module-Base64-label-Encoding+Character+Sets] above: + # these include newline characters and characters - and /: + # + # Base64.strict_decode64("\n") # Raises ArgumentError + # Base64.strict_decode64('-') # Raises ArgumentError + # Base64.strict_decode64('_') # Raises ArgumentError + # + # Padding in +str+, if present, must be correct: + # + # Base64.strict_decode64("MDEyMzQ1Njc") # Raises ArgumentError + # Base64.strict_decode64("MDEyMzQ1Njc=") # => "01234567" + # Base64.strict_decode64("MDEyMzQ1Njc==") # Raises ArgumentError + # def strict_decode64(str) str.unpack1("m0") end - # Returns the Base64-encoded version of +bin+. - # This method complies with ``Base 64 Encoding with URL and Filename Safe - # Alphabet'' in RFC 4648. - # The alphabet uses '-' instead of '+' and '_' instead of '/'. - # Note that the result can still contain '='. - # You can remove the padding by setting +padding+ as false. + # Returns the RFC-4648-compliant \Base64-encoding of +bin+. + # + # Per RFC 4648, the returned string will not contain the URL-unsafe characters + # + or /, + # but instead may contain the URL-safe characters + # - and _; + # see {Encoding Character Set}[Base64.html#module-Base64-label-Encoding+Character+Sets] above: + # + # Base64.urlsafe_encode64("\xFB\xEF\xBE") # => "----" + # Base64.urlsafe_encode64("\xFF\xFF\xFF") # => "____" + # + # By default, the returned string may have padding; + # see {Padding}[Base64.html#module-Base64-label-Padding], above: + # + # Base64.urlsafe_encode64('*') # => "Kg==" + # + # Optionally, you can suppress padding: + # + # Base64.urlsafe_encode64('*', padding: false) # => "Kg" + # + # The returned string will have no newline characters, regardless of its length; + # see {Newlines}[Base64.html#module-Base64-label-Newlines] above: + # + # Base64.urlsafe_encode64('*') # => "Kg==" + # Base64.urlsafe_encode64('*' * 46) + # # => "KioqKioqKioqKioqKioqKioqKioqKioqKioqKioqKioqKioqKioqKioqKioqKg==" + # def urlsafe_encode64(bin, padding: true) str = strict_encode64(bin) str.chomp!("==") or str.chomp!("=") unless padding @@ -90,14 +332,22 @@ def urlsafe_encode64(bin, padding: true) str end - # Returns the Base64-decoded version of +str+. - # This method complies with ``Base 64 Encoding with URL and Filename Safe - # Alphabet'' in RFC 4648. - # The alphabet uses '-' instead of '+' and '_' instead of '/'. - # - # The padding character is optional. - # This method accepts both correctly-padded and unpadded input. - # Note that it still rejects incorrectly-padded input. + # Returns the decoding of an RFC-4648-compliant \Base64-encoded string +str+: + # + # +str+ may not contain non-Base64 characters; + # see {Encoding Character Set}[Base64.html#module-Base64-label-Encoding+Character+Sets] above: + # + # Base64.urlsafe_decode64('+') # Raises ArgumentError. + # Base64.urlsafe_decode64('/') # Raises ArgumentError. + # Base64.urlsafe_decode64("\n") # Raises ArgumentError. + # + # Padding in +str+, if present, must be correct: + # see {Padding}[Base64.html#module-Base64-label-Padding], above: + # + # Base64.urlsafe_decode64("MDEyMzQ1Njc") # => "01234567" + # Base64.urlsafe_decode64("MDEyMzQ1Njc=") # => "01234567" + # Base64.urlsafe_decode64("MDEyMzQ1Njc==") # Raises ArgumentError. + # def urlsafe_decode64(str) # NOTE: RFC 4648 does say nothing about unpadded input, but says that # "the excess pad characters MAY also be ignored", so it is inferred that