Add support for base64url variant of base-64 encoding/decoding

Implement the RFC4648 variant of base64 encoding used by URLs.
* doc/lispref/text.texi (base64url-encode-region,
base64url-encode-string): Document new functions.
(base64-decode-region, base64-decode-string): Document new optional
parameter 'base64url' used to use url variant when decoding data.

* src/fns.c (base64url-encode-region, base64url-encode-region): New
functions to manage url variant.
(base64-decode-region, base64-decode-string): Add optional
parameter to indicate use of url-variant.
(base64_encode_region_1, base64_encode_string_1): Internal functions
with extracted code from 'base64_encode_region' and
'base64_encode_string' and optional parameters to manage padding and
url variant.
(base64-encode-region, base64-encode-string) : Use
base64_encode_region_1 and base64_encode_string_1.
(base64-encode-1): Add parameters to manage padding and url variant.
(base64-decode-1): Add parameter to manage url variant.

* test/src/fns-tests.el (fns-tests--with-region): New helper macro to
test region variant of base64 encode / decode functions.
(fns-tests--string-repeat): Helper function used in base64 tests.
(fns-tests-base64-encode-region, fns-tests-base64-encode-string):
Tests for standard base64 function.
(fns-test-base64url-encode-region,
fns-test-base64url-encode-string): Tests for url variant.
(fns-tests-base64-decode-string): Tests for decoding part.

1 files changed, 39 insertions, 3 deletions

diff --git a/doc/lispref/text.texi b/doc/lispref/text.texi
index 278bc3c2680..3e0cf4c06f6 100644
--- a/doc/lispref/text.texi
+++ b/doc/lispref/text.texi
@@ -4541,7 +4541,7 @@ Internet informational document describing a standard.  RFCs are
 usually written by technical experts acting on their own initiative,
 and are traditionally written in a pragmatic, experience-driven
 manner.
-}2045.  This section describes the functions for
+}2045 and also in RFC4648.  This section describes the functions for
 converting to and from this code.
 
 @deffn Command base64-encode-region beg end &optional no-line-break
@@ -4558,6 +4558,22 @@ text, to avoid overlong lines.  However, if the optional argument
 the output is just one long line.
 @end deffn
 
+@deffn Command base64url-encode-region beg end &optional no-pad
+This function converts the region from @var{beg} to @var{end} into base
+64 code.  It returns the length of the encoded text.  An error is
+signaled if a character in the region is multibyte, i.e., in a
+multibyte buffer the region must contain only characters from the
+charsets @code{ascii}, @code{eight-bit-control} and
+@code{eight-bit-graphic}.
+
+Contrary to the function @code{base64-encode-region}, this function
+doesnt inserts newline characters into the encoded text, so the output
+is just one long line.
+
+If the optional argument @var{no-pad} is non-@code{nil} then padding
+(@code{=}) isn't generated.
+@end deffn
+
 @defun base64-encode-string string &optional no-line-break
 This function converts the string @var{string} into base 64 code.  It
 returns a string containing the encoded text.  As for
@@ -4570,20 +4586,40 @@ text, to avoid overlong lines.  However, if the optional argument
 the result string is just one long line.
 @end defun
 
-@deffn Command base64-decode-region beg end
+@defun base64url-encode-string string &optional no-pad
+This function converts the string @var{string} into base 64 url code
+(see RFC4648).  It returns a string containing the encoded text.  As
+for @code{base64url-encode-region}, an error is signaled if a
+character in the string is multibyte.
+
+Contrary to @code{base64-encode-string}, this function doesnt inserts
+newline characters into the encoded text, so the result string is just
+one long line.
+
+If the optional argument @var{no-pad} is non-@code{nil} then padding
+(@code{=}) isn't generated.
+@end defun
+
+@deffn Command base64-decode-region beg end &optional base64url
 This function converts the region from @var{beg} to @var{end} from base
 64 code into the corresponding decoded text.  It returns the length of
 the decoded text.
 
 The decoding functions ignore newline characters in the encoded text.
+
+If optional argument @var{base64url} is is non-@code{nil} then padding
+become optionnal and url variant is used (see RFC4648).
 @end deffn
 
-@defun base64-decode-string string
+@defun base64-decode-string string &optional base64url
 This function converts the string @var{string} from base 64 code into
 the corresponding decoded text.  It returns a unibyte string containing the
 decoded text.
 
 The decoding functions ignore newline characters in the encoded text.
+
+If optional argument @var{base64url} is is non-@code{nil} then padding
+become optionnal and url variant is used (see RFC4648).
 @end defun
 
 @node Checksum/Hash